Glossary of technical terms for the use of metallurgical engineers Terms starting with alphabet ‘P’
Glossary of technical terms for the use of metallurgical engineers
Terms starting with alphabet ‘P’
Package – It is a bundle of things packed and wrapped. In case of composites, package consists of yarn, roving, and so on in the form of units capable of being unwound and suitable for handling, storing, shipping, and use.
Packaged boiler – It is a boiler supplied with all of its components i.e., burner, controls and auxiliary equipment, designed as a single engineered package, and ready for on-site installation.
Package flow conveyor – It is a conveyor system installed within racking, featuring either a wheel bed or roller configuration.
Package stop – It consists of different devices, whether manual or mechanical which are utilized to halt the movement on a conveyor.
Packaging – It can be described as a coordinated system of preparing goods for transport, warehousing, logistics, sale, and end use. Packaging contains, protects, preserves, transports, informs, and sells.
Packaging, nuclear fuel – It is a special way of processing spent fuel for temporary storage or final disposal.
Packaging radioactive waste – It is an operation whereby waste is converted into a form suitable for transportation and/or storage and/or final disposal. Very low-level radioactive waste (vinyl, cleaning rags, etc.) is placed in steel drums. Low-level wasted and intermediate-level waste is first compacted to reduce its volume as far as possible, then encapsulated in a special material (concrete, bitumen or resin matrix) to form solid blocks capable of withstanding all environmental conditions. High-level waste is placed in a glass mixture (vitrification process). Once vitrified, the waste is placed in stainless steel canisters.
Pack carburizing – It is a method of surface hardening of steel in which parts are packed in a steel box with a carburizing compound and heated to high temperatures. Common carburizing compounds contain 10 % to 20 % alkali or alkaline earth metal carbonates (for example, barium carbonate, BaCO3) bound to hardwood charcoal or to coke by oil, tar, or molasses. This process has been largely supplanted by gas and liquid carburizing processes.
Pack cementation – It is a coating process akin to pack carburizing which involves packing the parts to be coated into a retort with a carefully blended mixture of powders and then exposing the pack under hermetically sealed conditions or an inert atmosphere to elevated temperatures. Pack cementation is principally used for the application of aluminum diffusion coatings and ceramic coatings.
Packed-bed scrubbers –They consist of a chamber containing layers of variously-shaped packing material, such as Raschig rings, spiral rings, or Berl saddles, that provide a large surface area for liquid-particle contact.
Packed density – It is the density of a powder when the volume receptacle is tapped or vibrated under specified conditions while being loaded.
Packing – It is the process of placing items into the packaging container. In case of a valve, packing is the deformable sealing material inserted into a valve stem stuffing box, which, when compressed by a gland, provides a tight seal about the stem.
Packing box (assembly) – It is the part of the bonnet assembly used to seal against leakage around the closure member stem. Included in the complete packing box assembly are various combinations of some or all of the component parts such as packing, packing follower, packing nut, lantern ring, packing spring, packing flange, packing flange studs or bolts, packing flange nuts, packing ring, packing wiper ring, felt wiper ring, Belleville springs, and anti-extrusion ring.
Packing density – It is the weight of a unit volume of powder, normally expressed as grams per cubic meter, determined by a specified method.
Packing material – It is a material in which compacts are embedded during the pre-sintering or sintering operations. The material can act as a getter to protect the compacts from contamination.
Pack nitriding – It is a method of surface hardening of steel in which parts are packed in a steel box with a nitriding compound and heated to high temperatures.
Pack rolling – It is the hot rolling a pack of two or more sheets of metal. Scale prevents their being welded together.
Pad – It is the general term which is used for that part of a die which delivers holding pressure to the metal being worked.
Padding – It is the process of adding metal to the cross section of a casting wall, normally extending from a riser, to ensure adequate feed metal to a localized area during solidification where a shrink occurs if the added metal is not present.
Paddle mixture – It is a mixer which uses paddles mounted on a rotating shaft or disk to move and mix the powder.
Pad lubrication – It is a system of lubrication in which the lubricant is delivered to a bearing surface by a pad of felt or similar material.
Padmount transformer – It is a kind of metal enclosed distribution transformer which is suitable for mounting on grade.
Paint – It is a material or mixture which, when applied as a liquid to a surface forms a solid film for the purpose of decoration and / or protection. As art, this is used to create an image or images known as a painting. Normally, a paint contains a binder(s), solvent(s), and a pigment(s). Frequently other materials are present to give special properties to the paint film. Examples of such additives are rust inhibitors, light stabilizers, and softening agents (plasticizers). Paint can be made in several colours and types. Majority of the paints are either oil-based or water-based, and each has distinct characteristics.
Painting – It is defined as the process of applying paint, or another medium, to a solid surface. Paints or other forms of colour are normally applied to using a paintbrush.
Paired electron – It is one of two electrons which together form a valence bond between two atoms.
Paired t test – It is a test for the difference between means for two groups when the groups are not independently sampled.
Palladium – It is a chemical element, with symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal. Palladium, platinum, rhodium, ruthenium, iridium and osmium form a group of elements referred to as the platinum group metals (PGMs). They have similar chemical properties, but palladium has the lowest melting point and is the least dense of them.
Palladium barrier leak detector – It is a leak detector using hydrogen as the tracer gas and using the principle of hydrogen diffusing rapidly through a hot palladium barrier into an evacuated vacuum gauge.
Pallet boxes – These are large industrial boxes fixed to or on top of pallets, which can be used to transport products in bulk.
Pallet flow conveyor – It is a conveyor specifically designed for the smooth movement of pallets, containers, and heavy loads, typically within a rack structure.
Pallet lifters – They use forks to lift pallets from underneath.
Pallets – It consists of a flat transport structure which supports goods stably, frequently in the form of wood. It allows for easy lifting and movement by forklifts.
Pan – It is used to wash gravel, sand or crushed rock samples in order to isolate gold or other valuable metals by their higher density. The typical pan is a light but rugged circular metal dish with a flat bottom and sides which slope out at about 45-degree. Its inner surface is required to be smooth and free from grease and rust.
Pan-cake forging – It is a rough forged shape, normally flat, which can be got quickly with minimal tooling. Considerable machining is normally needed to achieve the finish size.
Pan-cake grain structure – It is a metallic structure in which the lengths and widths of individual grains are large compared to their thicknesses.
Pan or apron conveyor – This is the most common type of chain conveyor. It consists of one or more strands of endless chain, normally link plate roller type, running in steel guides. Rollers ensure minimum pulling effort in the chain, while roller guides supported on the super-structure of the conveyor, carry the entire load of the materials and chains. The carrying surface of the conveyor is composed of a series of plates or shapes called ‘apron’, which are attached to the links of the chains through cleats. The bed created by the aprons is used for carrying bulk materials as well as unit loads. When the conveyor aprons have vertical flanges on all sides to form a pan like shape, if is specifically called a ‘pan conveyor’. Material carried by the apron is discharged over the sprockets at the driven end, and the conveyor chain with aprons comes back empty on its return journey. These are normally slow speed conveyors with a speed range of 20 meters per minute to 35 meters per minute.
Panel buildings – These ca refer to buildings which are (i) built of structural insulated panels, and (ii) built of pre-fabricated concrete blocks. Panel buildings can be either frameless (column-less), or the panels can be fitted to (i) timber-framed, steel-framed, or reinforced concrete-framed buildings, (ii) over common blockwork, or (iii) over existing masonry products.
Panning – It is one of the principal techniques of the individual prospector for recovering gold and diamonds in placer (alluvial) deposits.
Pantograph – It is a linkage which supports the current collector of an electric locomotive.
Paper – It is produced from moist fibres of cellulose pulp and dried into flexible sheets with a variety of uses.
Paper coatings – These consist of coatings which are applied during the manufacturing process of paper to improve its finish and printability. The coating is designed to improve certain characteristics of the paper so that the finished paper product has the properties needed for its intended application, which includes its opacity, brightness, whiteness, colour, surface smoothness, gloss, and ink receptivity.
Paradigm shift – It is frequently a change in the perception of how things are to be thought about, done, or made. A paradigm shift can replace old processes, technologies, and products with new ones eliminating industry connected with the old processes, technologies, and products. Reacting well in time to key paradigm shifts have a lot to do with the long-term success. Paradigm shift is a popular, or perhaps, not so popular shift transformation of the way the humans perceive events, people, environment, and life altogether. It can be a national or international shift, and can have dramatic effects, which can be whether positive or negative, on the way the things are being done today and in the future.
Paraffin – It is a trivial name for an alkane. It is another name for kerosene which is a combustible hydrocarbon liquid. It is derived from petroleum.
Paraffin wax – It is a soft colourless solid derived from petroleum, coal, or oil shale which consists of a mixture of hydrocarbon molecules containing between 20 and 40 carbon atoms. It is solid at room temperature and begins to melt above around 37 deg C, and its boiling point is above 370 deg C. Common applications for paraffin wax include lubrication, electrical insulation, and candles. Dyed paraffin wax can be made into crayons.
Paraformer – It is a device similar to a transformer which couples energy between two circuits by varying magnetic parameters.
Parallel – Parallel lines are coplanar infinite straight lines which do not intersect at any point. Parallel planes are planes in the same three-dimensional space that never meet. Parallel curves are curves that do not touch each other or intersect and keep a fixed minimum distance.
Parallel circuits – If two or more components are connected in parallel, they have the same difference of potential (voltage) across their ends. The potential differences across the components are the same in magnitude, and they also have identical polarities. The same voltage is applied to all circuit components connected in parallel. The total current is the sum of the currents through the individual components, in accordance with Kirchhoff’s current law.
Paralleling three-phase transformers – Two or more three-phase transformers, or two or more banks made up of three single-phase units, can be connected in parallel for additional capacity. In addition to requirements for parallel operation of single-phase transformers, phase angular displacements (phase rotation) between high voltages and low voltages are to be the same for both. The requirement for identical angular displacement is required to be met for paralleling any combination of three-phase units and / or any combination of banks made up of three single-phase units.
Parallelism – It is a term encountered in geometric dimensioning and tolerancing (GD&T) / geometrical product specifications (GPS). It controls a requirement for two features to be geometrically parallel, within a certain acceptable tolerance. As such it is a relative control i.e., no one feature in isolation can be parallel.
Parallelism gauge – It is a dial gauge or a coordinate measuring machine for the measurement of parallelism.
Parallel laminate – It is a laminate of woven fabric in which the plies are aligned in the same position as originally aligned in the fabric roll. It is also a series of flat or curved cloth-resin layers stacked uniformly on top of each other.
Parallel offset – It means that the axes of connected shafts are parallel but not in the same straight line. It is also called radial misalignment.
Parallel operation of single-phase transformers – This is done for additional capacity. In perfect parallel operation of two or more transformers, current in each transformer is directly proportional to the transformer capacity, and the arithmetic sum is equal to one-half of the total current. In practice, this is seldom achieved because of small variations in transformers. However, there are conditions for operating transformers in parallel. In the first condition, any combination of positive and negative polarity transformers can be used. However, in all cases, numerical notations are to be followed on both primary connection and secondary connection. It is to be noted that each subscript number on a transformer is to be connected to the same subscript number on the other transformer. With positive and negative polarity transformers, the location of connections on the tanks are reversed. Hence, care is to be exercised for ensuring that terminals are connected. The second condition is that the tap settings is to be identical. The third condition is that the voltage ratings are to be identical, which, of course, makes the turns ratios also identical. The fourth condition is that the percent impedance of one transformer is to be between 92.5 % and 107.5 % of the other. Otherwise, circulating currents between the two transformers are excessive. The fifth condition is that the frequencies are to be identical. Standard frequency of 50 hertz or 60 hertz which are normally used in several countries do not present a problem. It can be noticed from the above requirements, that paralleled transformers do not have to be the same size. However, to meet the percent impedance requirement, they are to be nearly of the same size. Majority of the utilities do not parallel transformers if they are more than one standard kVA size rating different from each other, since otherwise circulating currents are excessive.
Parallel roller conveyor – It is a type of conveyor system which is characterized by multiple rollers aligned parallel to each other, requiring regular checks for roller health, alignment, and efficient material flow.
Parallel slide valve or parallel gate valve – Parallel slide valve or parallel gate valve is a slide valve with a parallel-faced gate-like closure member. This closure member can consist of a single disk or twin disks with a spreading mechanism in between. Parallel slid gate valve is ideal for high temperature and pressure line to prevent thermal binding.
Parallel welding – It is a resistance welding secondary circuit variation in which the secondary current is divided and conducted through the work-pieces and electrodes in parallel electrical paths to simultaneously form multiple resistance spot, seam, or projection welds.
Para-magnet – It is a body or substance which, placed in a magnetic field, possesses magnetization in direct proportion to the field strength. It is a substance in which the magnetic moments of the atoms are not aligned.
Para-magnetic material – It is a material whose specific permeability is higher than unity and is practically independent of the magnetizing force. It is also a material with a small positive susceptibility because of the interaction and independent alignment of permanent atomic and electronic magnetic moments with the applied field.
Para-magnetism – It is a property shown by substances which, when placed in a magnetic field, are magnetized parallel to the field to an extent proportional to the field (except at very low temperatures or in extremely large magnetic fields).
Parameter – It is a characteristic which can help in defining or classifying a particular system (meaning a process, event, project, object, and situation, etc.). That is, a parameter is an element of a system that is useful, or critical, when identifying the system, or when evaluating its performance, status, condition, etc. Parameter has more specific meanings within various disciplines. In statistics, parameter is a summary measure of some characteristic for the population, such as the population mean or proportion. This word occurs in its customary mathematical meaning of an unknown quantity which varies over a certain set of inputs. In statistical modelling, it most normally occurs in expressions defining frequency or probability distributions in terms of their relevant parameters (such as mean and variance of normal distribution), or in statistical models describing the estimated effect of a variable or variables on a response. Of utmost importance is the notion that statistical parameters are merely estimates, computed from the sample data, which are meant to provide insight as to what the true population parameter value is, although the true population parameter always remains unknown to the analyst. The population values are frequently modelled from a distribution. Then the shape of the distribution depends on its parameters. For example, the parameters of the normal distribution are the mean, and the standard deviation. For the binomial distribution, the parameters are the number of trials, and the probability of success. Parameter in crystal is the length of any side of a unit cell of a given crystal structure. The term is also used for the fractional coordinates, ‘x’, ‘y’, ‘z’ of lattice points when these are variable.
Parameter design – It is the second stage of the robust design process in which a robust design is achieved by optimizing performance of the system through experimentation which minimizes variation in the presence of uncontrolled user and environmental factors (noise).
Parameter estimation – In estimation theory, it is the practice of assigning values to a process model so it accurately predicts the process’s behaviour.
Parametric design – It is the third stage of the engineering design process, normally called detail design. In this stage of design, detailed analysis determines the final shape, dimensions, and properties of parts. Optimization methods, especially those employed in robust design are used to enhance quality. Final decisions are made on materials and manufacturing processes, and the part cost is determined.
Parameterization: In climate models, this term refers to the technique of representing processes which cannot be explicitly resolved at the spatial or temporal resolution of the model (sub-grid scale processes) by relationships between the area or time-averaged effect of such sub-grid-scale processes and the larger scale flow.
Paratoluosulfonic acid (PTS) – It is used in foundries as a hardening catalyst for sand.
Para-xylene, p-xylene – It is an aromatic hydrocarbon. It is one of the three isomers of di-methyl-benzene known collectively as xylenes. The p– stands for para–, indicating that the two methyl groups in p-xylene occupy the diametrically opposite substituent positions 1 and 4. It is in the positions of the two methyl groups, their arene substitution pattern, that it differs from the other isomers, o-xylene and m-xylene. All have the same chemical formula C6H4(CH3)2. All xylene isomers are colourless and highly flammable. The odour threshold of p-xylene is 0.62 parts per million.
Parent coil – It is a coil which has been processed to final temper as a single unit. The parent coil can subsequently be cut into two or more smaller coils or into individual sheets or plates to provide the needed width and length.
Parent metal – It is a non-standard term for base metal.
Parent plate – It is a plate which has been processed to final temper as a single unit. The parent plate can subsequently be cut into two or more smaller plates to provide the needed width and length.
Paris Convention – It is the main international convention on third party nuclear liability alongside the Brussels Convention. The Paris Convention provides for compensation for injury to or loss of life of any person, and for damage to, or loss of any property caused by a nuclear accident in a nuclear installation or during the transport of nuclear substances to and from installations. It does not cover damage to the nuclear installation itself.
Parison – It is the hollow plastic tube from which a plastic component is blow molded.
Parity – It normally refers to the state of equality or equivalence between two or more things, such as people, prices, purchasing power and mathematical functions. In mathematics, parity is the property of an integer of whether it is even or odd. An integer is even if it is divisible by 2, and odd if it is not. For example, −4, 0, and 82 are even numbers, while −3, 5, 7, and 21 are odd numbers. The above definition of parity applies only to integer numbers; hence, it cannot be applied to numbers like 1/2 or 4.201.
Parkes process – It is a process which is used to recover precious metals from lead and based on the principle that if 1 % zinc to 2 % zinc is stirred into the molten lead, a compound of zinc with gold and silver separates out and can be skimmed off.
Park transform – It is a mathematical technique which is useful in the analysis of three-phase systems.
Part – It is the designed object which has no assembly operations in its manufacture. Parts can be either standard or special purpose. A standard part, like a screw or spring, has a generic function and is manufactured in quantity without the intention of being used in a particular product. A special purpose part is designed and manufactured for a specific purpose in a specific product.
Part drawing – It is a detailed drawing of a component to facilitate its production. All the principles of orthographic projection and the technique of graphic representation are followed to communicate the details in a part drawing. A part drawing with production details is rightly called as a production drawing or working drawing.
Partial annealing – It is an imprecise term which is used to denote a treatment given cold-worked metallic material to reduce its strength to a controlled level or to effect stress relief. To be meaningful, the type of material, the degree of cold work, and the time-temperature schedule is to be stated.
Partial de-oxidation – It takes place because of insufficient additions of ferro-alloys and other deoxidizing agents in liquid steel. This results into incomplete removal of dissolved oxygen from liquid steel.
Partial discharge – It is the breakdown of insulating gas or solid material by an electric field, but without formation of an arc.
Partial joint preparation – It means joint penetration which is intentionally less than complete.
Partial (journal) bearing – It is a bearing in which the bore extends not more than half the circumference of the journal.
Partial hydrodynamic lubrication – It is a loosely defined regime of lubrication, especially in metal-working, where thin-film lubrication predominates.
Partial likelihood estimation – It is the estimation method for the Cox regression model. It uses only the part of the likelihood function which is based exclusively on the regression coefficients.
Partially premixed burners – In these burners a portion of the fuel is mixed with the oxidizer. This is normally done for stability and safety reasons. The partial premixing helps anchor the flame, but not fully premixing lessens the chance for flashback. This type of burner normally has a flame length and temperature and heat flux distribution which is between the fully premixed and diffusion flames.
Partially stabilized zirconia (PSZ) – It is a type of zirconium oxide (ZrO2) ceramic material which has been stabilized with an additive material, typically yttrium oxide (Y2O3), magnesium oxide (MgO), or calcium oxide (CaO). The addition of these additive materials prevents the transformation of zirconia from its tetragonal to its monoclinic phase, which can cause cracking and failure of the material. The properties of partially stabilized zirconia make it an attractive material for various industrial applications. Some of its key properties include high strength and toughness, good wear resistance, low thermal conductivity, and high thermal shock resistance.
Partial oxidation (POX) – It is a type of chemical reaction. It occurs when a sub-stoichiometric fuel-air mixture is partially combusted in a reformer, creating a hydrogen-rich syngas which can then be put to further use, for example in a fuel cell.
Partial pressure – In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal gas mixture is the sum of the partial pressures of the gases in the mixture. The partial pressure of a gas is a measure of thermodynamic activity of the molecules of the gas. Gases dissolve, diffuse, and react as per their partial pressures but not as per their concentrations in gas mixtures or liquids.
Partial regression coefficient (also known as partial slope) – It is the coefficient for a predictor in a regression model which contains more than one explanatory variable. It represents the effect of that predictor controlling for all other predictors in the model.
Particle – It is a minute portion of matter. A metal powder particle can consist of one or more crystals.
Particle accelerator – It is a device which raises the velocities of charged atomic or sub-atomic particles to high values.
Particle impact noise detection (PIND) – It is a test which is designed to identify the presence of loose particles inside a device cavity that can impact the functionality, reliability or even personal safety. The particle impact noise detection test provides a non-destructive means of identifying those devices containing unattached particles with sufficient mass which, upon impact with the device case or enclosure, excite the transducer and produce a signal for detection.
Particle growth – It take place in three stages namely nucleation, coalescent coagulation, and agglomeration.
Particle hardness – It is the hardness of an individual particle as measured by a Knoop or Vickers type micro-hardness indentation test.
Particle-induced X-ray emission – It is a method of trace elemental analysis in which a beam of ions (normally protons) is directed at a thin foil on which the sample to be analyzed has been deposited. The energy spectrum of the resulting x-rays is measured.
Particle-reinforced metal-matrix composite – It consists of the materials produced which are produced by adding reinforcement in the form of particles (ceramic or metal), fibres, whiskers or even a sheet metal to a metal or alloy matrix. It is a material where small particles of a reinforcing material are dispersed within a metallic matrix, creating a composite material with improved mechanical properties like increased strength, stiffness, and wear resistance compared to the base metal alone. It is essentially a metal matrix composite where the reinforcing phase is in the form of discrete particles.
Particle morphology – It is the form and structure of an individual particle.
Particle shape – It is the appearance of a metal particle, such as spherical, rounded, angular, acicular, dendritic, irregular, porous, fragmented, blocky, rod, flake, nodular, or plate.
Particle size – It is the controlling lineal dimension of an individual particle as determined by analysis with screens or other suitable instruments. Particle size is also a measure of dust size, expressed in micro-meters or per cent passing through a standard mesh screen.
Particle size analysis – It consists of particle size distribution, normally expressed as the weight percentage retained on each of a series of standard screens of decreasing mesh size and the percentage passed by the screen of finest size. It is also called screen classification or sieve analysis.
Particle size distribution – It is the percentage, by weight or by number, of each fraction into which a powder or sand sample has been classified with respect to sieve number or particle size.
Particle size range – It consists of the limits between which a variation in particle size is allowed.
Particle sizing – It means segregation of granular material into specified particle size ranges.
Particle spacing – It is the distance between the surfaces of two or more adjacent particles in a loose powder or a compact.
Particle strengthening – It is a common form of strengthening in metals, in which small second-phase particles are distributed in a ductile matrix. Examples are precipitation-hardening (age-hardening) systems and dispersion-hardened alloys.
Particulate composite – It is the material which consist of one or more constituents suspended in a matrix of another material. These particles are either metallic or non-metallic.
Particulate reinforced ceramic-matrix composite – It is a ceramic-matrix composite in which the reinforcing components are particles of equiaxed or platelet geometry (in contrast to whiskers or short fibres).
Particulate loading – It is the quantity of particles in a given volume of air or water. It is normally measured in milligrams per litre.
Particulate matter (PM) – Particulate matter is also known as aerosols and is a term used to describe very small solids. Smoke, ash, soot, dust, metals, and other particles from burning fuels are examples of some of the materials which make up particulate matter. It can consist of hundreds of different chemicals, including carbon, sulphur, nitrogen, and metal compounds. In fact, it refers to everything emitted in the form of a condensed (liquid or solid) phase. Particulate matter originates from several different sources, including construction sites, vehicle exhausts, industrial plants, unpaved roads, and come in many shapes and sizes. Some are large enough to be seen with the naked eye, whereas others can only be seen through powerful microscopes. Particulate matter in the atmosphere typically measures between 0.01 micrometers to 10 micrometers in diameter. Majority of the particulate matter is found in the lower troposphere, where it has a residence time of a few days. The particulate matter is removed when rain or snow carries it out of the atmosphere or when larger particles settle out of suspension because of the gravity. Large particulate matter particles (normally 1 micrometer to 10 micrometers in diameter) are generated when winds blow sea salt, dust, and other debris into the atmosphere. Fine particulate matter particles with diameters less than 1 micrometer are mainly produced when precursor gases condense in the atmosphere. Major components of fine particulate matter are sulphate, nitrate, organic carbon, and elemental carbon.
Particulate matter-10 (PM10) – It is that particulate matter which measures 10 micrometers or less.
Particulate matter-2.5 (PM2.5) – It is the particulate matter which measures 2.5 micrometers or less. It is a major pollutant source which is generated by smoke from wildfires, prescribed burns and fireplace activity.
Particulate removal – It consists of the removal of particulate air pollutants from their gaseous media by using gravitational, centrifugal, electro-static and magnetic forces, thermal diffusion, or other techniques.
Particulates – These are microscopic particles of solid or liquid matter suspended in the air. The term aerosol refers to the particulate / air mixture, as opposed to the particulate matter alone, though it is sometimes defined as a subset of aerosol terminology. Sources of particulate matter can be natural or anthropogenic. They have impacts on climate and precipitation which adversely affect human health, in ways additional to direct inhalation.
Parting – In the recovery of precious metals, it is the separation of silver from gold. It also the zone of separation between cope and drag portions of the mould or flask in sand casting. It is a composition sometimes used in sand moulding to facilitate the removal of the pattern. It is the cutting simultaneously along two parallel lines or along two lines that balance each other in side thrust. It is also a shearing operation used to produce two or more parts from a stamping.
Parting agent – It is a lubricant, liquid, or powder (frequently silicone oils and waxes) which is used to prevent sticking of moulded articles in the cavity.
Parting compound – It is a material dusted or sprayed on foundry (casting) patterns to prevent adherence of sand and to promote easy separation of cope and drag parting surfaces when the cope is lifted from the drag.
Parting line – It is a mark on a moulded piece where the sections of a mould have met in closing. It is the intersection of the parting plane of a casting or plastic mould or the parting plane between forging dies with the mould or die cavity. It is a raised line or projection on the surface of a casting, plastic part, or forging that corresponds to said intersection.
Parting plane – In forging, it is the dividing line between dies. It is the plane which includes the principal die face and is perpendicular to the direction of ram travel. When parting surfaces of the dies are flat, the parting plane coincides with the parting line. In casting, it is the dividing line between mould halves.
Parting sand – In foundry practice, it is a fine sand for dusting on sand mould surfaces which are to be separated.
Partition coefficient – It is the ratio of concentrations of a compound in a mixture of two immiscible solvents at equilibrium. This ratio is hence a comparison of the solubilities of the solute in these two liquids. The partition coefficient normally refers to the concentration ratio of un-ionized species of compound, whereas the distribution coefficient refers to the concentration ratio of all species of the compound (ionized plus un-ionized).
Partitions – Partition consist of a sectioning device within a container. Partitions can be corrugated, scored or interlocking. They provide cushioning as well as separation.
Partnership – It is a relationship in which individuals or organizations share resources and responsibility to achieve a common objective, as well as any resulting rewards or recognition. It frequently includes a formal contract, new resources and shared risks and rewards. The structure includes a central body of decision-makers whose roles are defined. The links are formalized. Communication is frequent, the leadership is autonomous and the focus is on specific issues. Partnerships are a form of collaboration.
Parts accumulator – It is a component in a conveyor system which temporarily holds and accumulates products or materials, necessitating periodic inspections for proper functioning and capacity management.
Parts conveyor – It is the conveyor system which is used to catch and gather smaller parts and debris away from the production areas in a warehouse.
Parts list – It is also called bill of materials. It is a document which is used to track the parts in an assembly. It consists of the part number, part name, and quantity needed for the complete assembly. It can also contain information on procurement tracking or special assembly instructions.
Parts per billion – It is a measure of proportion by weight, equivalent to one unit weight of a material per billion (10 to the power 9) unit weights of compound. One part per billion is equivalent to 1 nanogram per gram.
Parts per million – It is a measure of proportion by weight, equivalent to one unit weight of a material per million (10 to the power 6) unit weights of compound. One part per million is equivalent to 1 milligram per kilograms. Parts per million means that how many parts a certain molecule or compound makes up within the one million parts of the whole solution. It is typically used to describe concentrations of chemicals dissolved in a solvent (typically water) or compounds in soil.
Pascal – It is the unit of pressure in the International System of Units (SI). It is also used to quantify internal pressure, stress, Young’s modulus, and ultimate tensile strength. The unit is an SI coherent derived unit defined as one newton per square metre.[
Pascal’s law – It is a principle in fluid mechanics which states that a pressure change at any point in a confined incompressible fluid is transmitted throughout the fluid such that the same change occurs everywhere.
Pascal’s principle – It is defined as ‘a change in pressure at any point in an enclosed incompressible fluid at rest is transmitted equally and undiminished to all points in all directions throughout the fluid, and the force due to the pressure acts at right angles to the enclosing walls.
Pass – It is a single transfer of metal through a stand of rolls. It is also the open space between two grooved rolls through which metal is processed. It is also the weld metal deposited in one trip along the axis of a weld. In boiler terminology, pass is a confined passage-way, containing heating surface, through which a fluid flows in essentially one direction.
Passivation – It is a reduction of the anodic reaction rate of an electrode involved in corrosion. It is also the process in metal corrosion by which metals become passive. It is the changing of a chemically active surface of a metal to a much less reactive state. It is also the formation of an insulating layer directly over a semiconductor surface to protect the surface from contaminants, moisture, and so forth.
Passivator – It is a type of corrosion inhibitor which appreciably changes the potential of a metal to a more noble (positive) value.
Passive – It is a metal corroding under the control of a surface reaction product. It is also the state of the metal surface characterized by low corrosion rates in a potential region which is strongly oxidizing for the metal.
Passive-active cell – It is a corrosion cell in which the anode is a metal in the active state and the cathode is the same metal in the passive state.
Passive air preheaters – These preheaters are gas to gas heat recovery devices for low to medium temperature applications where cross contamination between gas streams are required to be prevented. Passive preheaters are usually of two types namely (i) the plate type and (ii) the heat pipe type. The plate type preheater consists of multiple parallel plates which create separate channels for hot and cold gas streams. Hot and cold flows alternate between the plates and allow significant areas for heat transfer. The heat pipe heat exchanger consists of several pipes with sealed ends. Each pipe contains a capillary wick structure which facilitates movement of the working fluid between the hot and cold ends of the pipe. Hot gases pass over one end of the heat pipe causing the working fluid inside the pipe to evaporate. Pressure gradients along the pipe cause the hot vapour to move to the other end of the pipe, where the vapour condenses and transfers heat to the cold gas. The condensate then cycles back to the hot side of the pipe through capillary action.
Passive extreme pressure – These are extreme pressure additives which function by adsorbing a film of carbonate particles at the tool-work-piece interface in metalworking operations. These films have low shear strengths and high melting points. They reduce friction and minimize metal transfer from the work-piece to the tool. Passive extreme pressure additives do not contain phosphorus, sulphur, or chlorine, but are synergistic with sulphur containing extreme pressure additives. They offer advantages over conventional extreme pressure additives in that they are less corrosive, are more easily disposed of after use, are low foaming, and are easily cleaned from the work-piece surface. They can be used with both ferrous and non-ferrous metals.
Passively safe – It is a passively safe facility can be safely shut down automatically, without any operator intervention and without any external power supply from the grid or from backup generators to drive instruments or equipment.
Passive roller – It consists of a conveyor system where rollers are arranged perpendicular to the direction of material flow, needing routine checks for roller health, alignment, and efficient material movement.
Passivity – It is a condition in which a piece of metal, because of an impervious covering of oxide or other compound, has a potential much more positive than that of the metal in the active state.
Paste compound – It is a metal powder mixed with a thin binder for use as a brush-on brazing filler metal.
Pasteurization – It is a method in which the micro-organisms are killed by heat treatment, and usually involves the application of temperature below 100 deg C. The heating can be generated by hot water, dry heat, or electric current, and products are rapidly cooled at 4 deg C just after the heat treatment. Industrial methods using pasteurization utilize two approaches namely (i) utilization of a high temperature for a short time, or (ii) a low temperature for a longer time.
Patent – It is a grant made by a government to inventors which permits them the sole right to make, sell, and use the invention for a period of time.
Patent drawing – When new equipments or devices are invented, patent drawings come into existence, to illustrate and explain the invention. These are normally axonometric drawings and are to be self-explanatory. It is necessary that the patent drawings are mechanically correct and include complete information of every detail of the invention. However, these drawings are not useful for production purposes. The salient features on the drawing are numbered for identification and complete description
Patenting – In wire-making, it is a heat treatment applied to medium-carbon or high-carbon steel before drawing of wire or between drafts. This process consists of heating to a temperature above the transformation range and then cooling to a temperature below Ae1 temperature in air or in a bath of molten lead or salt.
Patent leveling – It is the leveling of a piece of sheet metal (i.e., removing warp and distortion) by gripping it at both ends and subjecting it to a stress higher than its yield strength.
Patch cables – These are short cables with connectors, which are used to make connections between outlets of a patch panel or for temporary connections to a system under test.
Path – It is a sequence of activities which follows a set of arcs from the start node to the finish node of a network. It is a route through a project network. The length of the path is defined as the sum of the durations of the activities of the path.
Pathogens – These are micro-organisms which cause, or can cause, disease. Communicable diseases can be transmitted by the pathogenic organisms in wastewater.
Pathway – It a line of communication over interconnecting two places or terminals. It is also a way or a course of action for achieving a specified result.
Patina – It is the coating, normally green, which forms on the surface of metals such as copper and copper alloys exposed to the atmosphere. The term is also used to describe the appearance of a weathered surface of any metal.
Pattern – It is a form of wood, metal, or other material around which moulding material is placed to make a mould for casting metals. It is also a form of wax-base or plastic-base material around which refractory material is placed to make a mould for casting metals. It is a full-scale reproduction of a part used as a guide in cutting. In statistics, pattern is a characteristic of data. A good statistical analysis is one which takes account of all the ‘pattern’ in the data. In inference this can be expressed or ‘modelled’ as data = pattern + residual. The idea is that the data has variability, i.e., the values differ from each other. Some of the variability can be understood, and hence, it is part of the ‘pattern’ or ‘signal’ in the data. What is left over is not understood and is called the residual, (or ‘noise’ or ‘error’). A good analysis is one which explains as much as possible. Hence if one can still see any patterns in the residual part, then consider how it can be moved over into the pattern (or model). Even with a descriptive-statistics, it is important that the analysis reflects the possible patterns in the data. At least the obvious patterns in the data are to be considered when doing the analysis. In case of X-rays, pattern is the spatial arrangement and relative intensities of diffracted beams.
Pattern draft – It is the taper allowed on the vertical faces of a pattern to permit easy withdrawal of the pattern from the mould or die.
Patterned sheet – It consists of raising a design in relief against a surface.
Pattern layout – It is a full-size drawing of a pattern showing its arrangement and structural features.
Patternmaker’s shrinkage – It is the contraction allowance made on patterns to compensate for the decrease in dimensions as the solidified casting cools in the mould from the freezing temperature of the metal to room temperature. The pattern is made larger by the quantity of contraction which is characteristic of the particular metal to be used.
Payment – A payment is the transfer of wealth from one party (such as a person or organization) to another. A payment is normally made in exchange for the provision of goods, services or both or to fulfill a legal obligation.
p-chart – In statistical quality control, p-chart is a type of control chart which used to monitor the proportion of non-conforming units in a sample, where the sample proportion non-conforming is defined as the ratio of the number of non-conforming units to the sample size ‘n’. The p-chart only accommodates pass / fail type inspection as determined by one or more go-no go gauges or tests, effectively applying the specifications to the data before they are plotted on the chart. Other types of control charts display the magnitude of the quality characteristic under study, making troubleshooting possible directly from those charts.
PDES / STEP – It is a standard data protocol for the transfer of digital data between different software and machines. PDES is more comprehensive than the Initial Graphics Exchange Standard (IGES) in that it
includes product attributes such as material type and form features in addition to solid model topology.
Peak demand – It is the maximum rate at which energy is consumed from an electrical grid. It can be either an instantaneous measure or the maximum energy transferred in some interval such as 15 minutes.
Peak overlap – It is the formation of a single peak when two closely spaced X-ray peaks cannot be resolved; the energy (or wave-length) of the peak is some average of the characteristic energies (or wave-lengths) of the original two peaks.
Pearlite – Pearlite is a mixture of ferrite and cementite in which the two phases are formed from austenite in an alternating lamellar pattern. It is a metastable lamellar aggregate of ferrite and cementite resulting from the transformation of austenite at temperatures above the bainite range. Formation of pearlite needs relatively slow cooling from the austenite region and depends on the steel composition. Pearlite forms at temperatures below the lower critical temperature of the steel in question and can be formed isothermally or by continuous cooling. As the hardenability of the steel decreases, the cooling rate can be increased without the formation of other constituents. As isothermal reaction temperature decreases or the cooling rate increases, the inter-lamellar spacing decreases. The strength and toughness of pearlitic steels increase as the inter-lamellar spacing decreases.
Pearlitic malleable – It is a cast iron made by prolonged annealing of white iron in which decarburization, graphitization, or both take place to eliminate some or all of the cementite. The graphite is in the form of temper carbon. If decarburization is the predominant reaction, the product shows a light fracture surface, hence whiteheart malleable. Otherwise, the fracture surface is dark, hence blackheart malleable. Ferritic malleable has a predominantly ferritic matrix. Pearlitic malleable can contain pearlite, spheroidite, or tempered martensite, depending on heat treatment and desired hardness.
Pearlitic structure – It is a micro-structure which is resembling that of the pearlite constituent in steel. Hence, it is a lamellar structure of varying degrees of coarseness.
Pearson correlation coefficient (r) – This is a measure of the correlation or linear relationship between two variables ‘x’ and ‘y’, giving a value between +1 and −1 inclusive. It is widely used in the sciences as a measure of the strength of linear dependence between two variables.
Pearson’s product moment correlation coefficient – It is denoted as ‘r’ij, where i and j refer to two variables, Pearson’s product moment correlation coefficient reflects the degree of linear association between two continuous (ratio or interval scale) variables, and is bounded between +1 for perfect positive correlation and –1 for perfect negative correlation.
Peat – It occurs in waterlogged areas, such as swamps or bogs, where plant matter is accumulated and buried by sediment, then compacted.
Peat-land – It is permanent wetlands characterized by a bed made of highly organic soil (higher than 50 % combustible) composed of partially decayed plant material.
Peat soil – It refers to a type of soil which is formed through the accumulation and decomposition of organic materials under waterlogged conditions with a lack of oxygen. It has a high organic content, typically above 75 %, and shows a dark brown to black colour with a spongy consistency.
Pebbles – The preferred term is orange peel which means a surface roughening in the form of a pebble-grained pattern where a metal of unusually coarse grain is stressed beyond its elastic limit.
Peclet number (Pe) – It is a class of dimensionless numbers relevant in the study of transport phenomena in a continuum. It is defined to be the ratio of the rate of advection of a physical quantity by the flow to the rate of diffusion of the same quantity driven by an appropriate gradient. In the context of species or mass transfer, the Peclet number is the product of the Reynolds number and the Schmidt number (Re × Sc). In the context of the thermal fluids, the thermal Peclet number is equivalent to the product of the Reynolds number and the Prandtl number (Re × Pr).
Pedestal bearing – It is a bearing that is supported on a column or pedestal rather than on the main body of the machine.
Peeling – It is the detaching of one layer of a coating from another, or from the substrate, because of poor adherence. Peeling is one of the abnormalities in the rolls. During rolling, a thin layer of oxide is formed on the roll surface within the rolling width. Partial removal of just this oxide layer is known as peeling. This peeling can be easily identified when observed as silvery circumferential streaks of parent roll material, intermingled with blue / black oxide streaks still adhering to the roll surface.
Peel ply – It is a layer of open-weave material, normally fibre-glass or heat-set nylon, applied directly to the surface of a prepreg lay-up. The peel ply is removed from the cured laminate immediately before bonding operations, leaving a clean, resin-rich surface which needs no further preparation for bonding, other than application of a primer where one is needed.
Peel strength – It is the adhesive bond strength, as in kilograms per square centimeter of width, got by a stress applied in a peeling mode.
Peel test – It is a destructive method of inspection which mechanically separates a lap joint by peeling.
Peening – It is the mechanical working of metal by hammer blows or shot impingement.
Peening wear– It consists of removal of material from a solid surface caused by repeated impacts on very small areas.
Peep-hole – It is a small hole in the furnace refractories which can be looked through for observation of inside of the furnace.
Pegmatite – It is a coarse-grained, igneous rock, normally coarse, but irregular in texture, and similar to a granite in composition. It normally occurs in dykes or veins and sometimes contains valuable minerals.
Pellet – It is similar to a shotted particle. It is generally, a small rounded or spherical solid body. In case of ironmaking, it is a type of agglomerated iron ore fines which has better tumbler index when compared with that of the parent iron ore. Pellets are widely used as a substitute of lump ore for the production of direct reduced iron and in the blast furnace for the production of hot metal.
Pelletization processes – There are several iron ore pelletizing processes/technologies which are available for the production of the pellets. Some of these are (i) shaft furnace process, (ii) straight travelling grate process, (iii) grate kiln process, (iv) cement bonded processes (Grangcold process, MIS Grangcold Process, and char process etc.), and (v) hydrothermal processes, (COBO process, MTU process, and INDESCO process etc.). However, at present, only the straight travelling grate (STG) process and the grate kiln (GK) process are more popular processes.
Peltier–Seebeck effect – It is the thermoelectric effect, movement of heat because of the electric current flow.
Pencil glide -It is the glide on multiple slip planes in a common direction in all of the planes.
Pendant group – It is an offshoot or side chain of the backbone of a polymeric molecule, especially one which is itself neither oligomeric or polymeric.
Pendants – These are the operator’s connection to the crane. They provide the controls to make the crane do the job. A pendant control hangs down from the hoist or off of a separate festoon track and allows the operator to control the crane. Although pendant controls can be used on almost any type of overhead crane, they are ideal for cranes that are in lower duty cycle classes. Because it is hardwired into the electrification system, the crane controls will always have power, so the operator doesn’t have to worry about replacing or charging batteries for a crane that doesn’t get used too often. Often, pendant controls are the preferred control method for explosion proof cranes.
Pendulum – It is a device made of a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring force because of gravity which accelerates it back toward the equilibrium position. When released, the restoring force acting on the pendulum’s mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period. The period depends on the length of the pendulum and also to a slight degree on the amplitude, the width of the pendulum’s swing. The regular motion of pendulums has been used for timekeeping and has been the world’s most accurate timekeeping technology until the 1930s.
Pendulum shears – These shears consist of cutting systems suspended in an ‘oscillating’ configuration. The cut can be performed for material which is travelling or stopped. These shears are used for cropping head end or tail end or dividing the hot input material conveyed to the rolling mill.
Penetrant – It is a liquid with low surface tension used in liquid penetrant inspection to flow into surface openings of parts being inspected.
Penetrant inspection – It is a type of non-destructive inspection which locates discontinuities that are open to the surface of a metal by first allowing a penetrating dye or fluorescent liquid to infiltrate the discontinuity, removing the excess penetrant, and then applying a developing agent which causes the penetrant to seep back out of the discontinuity and register as an indication. It is suitable for both ferrous and non-ferrous materials, but is limited to the detection of open surface discontinuities in non-porous solids.
Penetration – In founding, it is an imperfection on a casting surface caused by metal running into voids between sand grains. It is normally referred to as metal penetration. In welding, it is the distance from the original surface of the base metal to that point at which fusion ceased. In case of piles, penetration is the downward movement of the pile per blow.
Penetration drawing – It is designed for structural, mechanical, electrical, plumbing, and fire protection systems. This drawing is dimensionally locating all sleeve / cores and shaft penetration through floors and walls including the size of the actual opening and rough-in dimensions.
Penetration hardness – It is the resistance of a material to indentation. This is the normal type of hardness test, in which a pointed or rounded indenter is pressed into a surface under a substantially static load. It is also the resistance of a solid surface to the penetration of a second, normally harder, body under prescribed conditions. Numerical values used to express indentation hardness are not absolute physical quantities, but depend on the hardness scale used to express hardness.
Penetration hardness number – It is the numerical value expressing the resistance of a body to the penetration of a second, normally harder, body.
Penetration of a grease – It is the depth in 1/10 millimeter that a standard cone penetrates the sample in a standard cup under prescribed conditions of weight, time (5 second), and temperature (25 deg C). The result depends on whether or not the grease has been subjected to shear. In unworked penetration, the grease is transferred with as little deformation as possible or is tested in its container. In worked
penetration, the grease is subjected to 60 double strokes in a standard device. In prolonged worked penetration, the grease is worked for a specified period before the 60 strokes. The results can be quoted as penetration number or penetration value.
Penetrometer – In grease technology, it is an instrument for measuring the consistency of a grease by allowing a cone to penetrate into the grease under controlled conditions.
Penning gauge – It is a type of vacuum gauge comprising a means of ionizing the gas molecules, electrodes to facilitate the collection of the positive ions formed, and means of indicating the magnitude of the collected ion current.
Penta-basic – It means having five hydrogen atoms which can be replaced by metals or bases.
Pentoxide – It is a binary compound containing five atoms of oxygen, e.g., iodine pentoxide (I2O5).
Pentyl – It is an alkyl functional group containing five carbon atoms, with the generic chemical formula C5H11. It is the substituent form of the alkane pentane
Pentagrid converter – It is a type of self-oscillating vacuum tube (radio receiving valve) with five grids used as the frequency mixer stage of a superheterodyne radio receiver.
Penta-erythritol tetra-nitrate (PENT) – It is an explosive material. It is the nitrate ester of penta-erythritol, and is structurally very similar to nitro-glycerin. Penta refers to the five carbon atoms of the neopentane skeleton.
Pentlandite – It is nickel iron sulphide which is the most common nickel ore.
Pentode – It is an electronic device having five electrodes. The term normally applies to a three-grid amplifying vacuum tube or thermionic valve.
People strategy – Proper people strategy helps the management to know how people feel, behave and perform in the organization. This knowledge provides the basis to increase productivity, solve issues and celebrate achievements.
Per- – It is a prefix in IUPAC (International Union of Pure and Applied Chemistry) chemical nomenclature meaning complete, exhaustive, or extreme, as in a completely substituted hydrocarbon, or indicating the presence of a peroxy group.
Peracid – It is an acid containing an acidic peroxy group (–O–O–) e.g., periodic acid.
Percentage (pct) – It is a number or ratio expressed as a fraction of 100. It is frequently denoted using the ‘percent sign’ (%). It is a dimensionless number (pure number) which is mainly used for expressing proportions, but percent is nonetheless a unit of measurement in its orthography and usage. In statistics, percentage means that for a variable with ‘n’ observations, of which the frequency of a particular characteristic is ‘r’, the percentage is 100*r/n. For example, if the frequency of an activity is 11 times in 55 years, then the percentage is 100*11/55 = 20 % of the years. Percentages are widely used (and misused). Whenever percentages are used it is to be made clear what is the 100 %. In the example above it is the value 55.
Percentage elongation after fracture (A) – It is the gauge length elongation after fracture expressed as a percentage of the original gauge length.
Percent error – For testing machines, it is the ratio, expressed as a percentage, of the error to the correct value of the applied load.
Percentile – It is the value in a distribution such that a certain percentage of cases are lower than that value. For example, the 75th percentile is the value such that 75 % of cases have lower values. The ‘p’th percentile of a list is the number such that at least ‘p’ % of the values in the list are no larger than it. So, the lower quartile is the 25th percentile and the median is the 50th percentile. One definition used to give percentiles, is that the ‘p’th is the 100/p*(n+1)’th observation. For example, with 7 observations, the 25th percentile is the 100/25*8 = 2nd observation in the sorted list. Similarly, the 20th percentile = 100/20*8 = 1.6th observation. An approximate value for the ‘p’th percentile can be read from a cumulative frequency graph as the value of the variable corresponding to a cumulative frequency of ‘r’ %. So, the lower quartile is the 25th percentile and the median is the 50th percentile. The term ‘percentile’ was introduced by Galton in 1885.
Percent theoretical density – It is also known as density ratio. It is the ratio of the determined density of a compact to the absolute density of metal of the same composition. It is normally expressed as a percentage.
Perchlorate – It is a chemical compound containing the perchlorate ion, ClO4-, the conjugate base of perchloric acid. As counterions, there can be metal cations, quaternary ammonium cations or other ions, for example, nitronium cation (NO2)+. The term perchlorate can also describe perchlorate esters or covalent perchlorates. These are organic compounds which are alkyl or aryl esters of perchloric acid. Perchlorate contamination of water endangers human health.
Perchloroethylene – It is also known as tetrachloroethylene, or under the systematic name tetrachloroethene, and abbreviations such as perc, and PCE. It is a chlorocarbon with the formula Cl2C=CCl2. It is a colorless, nonflammable liquid solvent with a sweet, ether-like odour. It is mainly used in industrial settings and for dry cleaning fabrics and degreasing metals.
Percolate – It means to cause (a solvent) to pass through a permeable substance in order to extract a soluble constituent.
Percolation – It is the process of a liquid slowly passing through a filter or porous material. It can also refer to the movement of water through soil and rock.
Percolating filter – It is also called trickling filter is a type of waste-water treatment system. It consists of a fixed bed of some material, such as rocks, coke, gravel, slag, poly-urethane foam, sphagnum peat moss, ceramic, or plastic media, over which sewage or other waste-water flows downward and causes a layer of microbial slime (bio-film) to grow, covering the bed of media. Aerobic conditions are maintained by splashing, diffusion, and either by forced-air flowing through the bed or natural convection of air if the filter medium is porous. The treatment of sewage or other waste-water with percolating filters is among the oldest and most well characterized treatment technologies.
Percussion cone – It is the damage produced by contact stresses generated by mechanical contact of a hard, blunt object with a glass surface. Typically, it has the appearance of a semicircular or circular crack on the damaged surface, propagating into the glass, flaring out with increasing depth into a cone-shaped crack. It is also called impact bruise, butterfly bruise, bump check, and Hertzian crack.
Percussion welding – It is a resistance welding process which produces coalescence of abutting surfaces using heat from an arc produced by a rapid discharge of electrical energy. Pressure is applied percussively during or immediately following the electrical discharge.
PERED technology for direct reduced iron production -PERED technology is also known as ‘Persian Reduction’ technology. It is the direct reduction technology invented and patented by ‘Mines and Metals Engineering GmbH’. The PERED direct reduction process converts iron oxides, in the form of pellets or lump ore, to highly reduced product suitable for steel making. The reduction of iron oxide takes place without its melting with the help of reducing gases in solid state in a vertical shaft furnace. This technology improves the process of direct reduction for the production of direct reduced iron (DRI).
The process is a gas based direct reduction process which has been developed by a team of specialists having experience in different areas of the direct reduction process to ensure that all the flows of different processes are taken care in the main process to obtain optimum and efficient results. The most popular gas used for reduction is reformed natural gas though other gases such as Corex gas and coke oven gas etc. can also be used. PERED technology lowers capital cost, water consumption, maintenance cost, and energy consumption. In PERED, the reduction process takes place at a lesser temperature due to the improved cooling methods and reduced pollutant gas emissions. With less heat, more homogeneous reducing gas, more controllable pellet feed and use of centrifugal compressors, PERED requires less water, electricity and gas to operate, alongside less operational and maintenance expenditure.
Perennial water body – It normally refers to mainly liquid fresh water, as opposed to sea and glaciers or other ice. Most frequently the term refers to running water as in perennial streams and large rivers. Simplistically a perennial water body is one which keeps full or flowing throughout the year.
Perfect combustion– It is the complete oxidation of all the combustible constituents of a fuel, utilizing all the oxygen supplied.
Perfect gas – It is a gas which obeys Boyle’s law, Charle’s law and has zero heat of free expansion. It is also known as an ideal gas.
Per-fluoro-carbons (PFCs) – They are man-made compounds containing just fluorine and carbon. They are normally colourless, odourless non-flammable gases at environmental temperatures and for the most part chemically unreactive. They are among the six greenhouse gases to be abated under the Kyoto Protocol. These are by-products of aluminum smelting and uranium enrichment. They also replace chloro-fluoro-carbons in manufacturing semi-conductors. The Global Warming Potential of PFCs is 6,500 – 9,200 times that of carbon di-oxide.
Perfluoro-poly-ethers (PFPEs) – These are a class of organofluorine compound. The main properties of perfluoro-poly-ethers are being temperature resistant between −58 deg C (215 K) and 257 deg C (530 K) (depending on specific composites), having very low outgassing compared to other fluids (vapour pressure of 0.000008 pascal) and having a dielectric strength of around 15.7 millivolt per meter. The thermal and chemical stability of perfluoro-poly-ethers along with a vapor–liquid equilibrium of 230 deg C when mixed with the right composites make it a suitable candidate for vapour phase soldering technologies.
Perforating – It is the punching of several holes, normally identical and arranged in a regular pattern, in a sheet, work-piece blank, or previously formed part. The holes are normally round, but can be of any shape. The operation is also called multiple punching.
Perforations – These are small holes in a material which are organized in a fashion making it easier for consumers to open.
Performance – It is defined as the action or process of carrying out or accomplishing an action, task, or function. It is the act of performing, of doing something successfully, and the use of knowledge as distinguished from merely possessing it. Performance involves several factors, such as task performance and contextual performance. Task performance is evaluated based on the objectives, contextual performance reveals the softer skills, such as relationship with coworkers, with customers or ability to solve problems.
Performance assessment – It is the linkage of inputs (e.g., funding, manpower, equipment, and supplies), actions (e.g., advice, projects, programmes, and services) and outputs (e.g., reports, plans, policies, and products) to outcomes or results (e.g., an increase in awareness, a change in behaviour, or the achievement of an outcome or end result, such as a healthy environment).
Performance based incentive – It refers to performance-based pay programmes where an employee is incentivized and rewarded for achieving higher goals and objectives. Organizations have several incentives with some tying pay to individual performance and some pay to organization wide performance.
Performance indices – These indices are derived based on the trade-off between a constraint and the free variable; they characterize the performance of a particular geometry as a function of material properties. Each combination of function, objective and constraint leads to a particular performance index defined by a material property or a combination of material properties.
Performance management – It includes activities in the organization which ensure that goals are consistently being met in an effective and efficient manner. It focuses on the performance of the organization, department, employees, or even the production processes which produces the product or service, as well as many other areas. It is also known as a process by which the organization aligns the resources, systems and employees to strategic objectives and priorities. An organization aspiring for success needs in place the process of performance management. Aims of the performance management in the organization are (i) to make the performance of the organization visible, (ii) to drive the management and the employees to take actions, and (iii) to provide timely feedback on the effect of the actions for taking corrective measures.
Performance measure – It is a qualitative or quantitative measure of an outcome, intended to gauge the performance of the organization, its initiatives, policies, and / or activities. A performance measure tracks the degree to which the organization’s performance can influence change (i.e., the progress towards a target).
Performance rating scale – It is a tool which evaluates the job performance of the employees. It is a systematic way to assess how well an employee is meeting their job responsibilities.
Performance standards – These are standards which state design requirements but not the methods that are to be used to achieve the objective.
Periclase – It is a magnesium mineral which occurs naturally in contact metamorphic rocks and is a major component of most basic refractory bricks. It is a cubic form of magnesium oxide (MgO). In nature it normally forms a solid solution with wustite (FeO) and is then referred to as ferro-periclase or magnesio-wustite.
Periclase grain – It is a crystalline magnesium oxide in granular form. It contains at least 85 % by weight magnesia.
Period – It is a horizontal row of the periodic table of the elements and the elements which share it.
Periodic reverse plating – It is a method of plating in which the current is reversed periodically. The cycles are normally no longer than a few minutes and may be much less.
Periodic table of the elements – It is also simply known as the periodic table. It is a tabular arrangement of the chemical elements organized by their atomic number, electron configuration, and other chemical properties, whose adopted structure shows periodic trends and is used by people to derive relationships between different elements as well as to predict the properties and behaviours of undiscovered or newly synthesized elements. In the periodic table of the elements, the horizontal rows are called periods and the vertical columns are called groups or families.
Peripheral coarse grain, peripheral grain band – It is an effect shown in extruded products and also forgings made from extruded stock. It is an area of recrystallized grains at the periphery which has lower properties than the non-recrystallized core.
Peripheral milling – It consists of milling a surface parallel to the axis of the cutter.
Peripheral segregation – It is a casting defect which is normally found in the peripheral zone of the casting. It is characterized by an above-average high concentration of alloying elements and a sharp concentration jump to the adjacent structure. There are also frequently alloying element impoverished zones below the peripheral segregation zones. The occurrence of peripheral segregations has to be considered in relationship to the solidification of the peripheral shell. Peripheral segregation forms during the dwell of the peripheral shell in the air gap region. Transport of residual melt regions enriched in the alloying elements towards the surface of the cast log takes place. The main transport mechanism is the metallo-static pressure of the melt before the peripheral shell. This is referred to as air gap segregation. A further mechanism for the formation of peripheral segregation is the residual melt enriched with alloying elements overflowing the meniscus curvature of the peripheral shell. This is referred to as meniscus segregation. Different segregation formation shapes can be differentiated in peripheral segregation.
Peripheral velocity – It refers to the velocity of a point located on the outer edge of a rotating circle or disc. It is the speed at which the outermost point of the object moves in a circular path.
Peritectic – It is an isothermal reversible reaction in metals in which a liquid phase reacts with a solid phase to produce a single (and different) solid phase on cooling.
Peritectic equilibrium – It is a reversible univariant transformation in which a solid phase stable only at lower temperature decomposes into a liquid and a solid phase that are conjugate at higher temperature, or conversely.
Peritectic point – It is the point on a phase diagram where a reaction takes place between a previously precipitated phase and the liquid to produce a new solid phase. When this point is reached, the temperature remains constant until the reaction has run to completion. A peritectic point is also an invariant point.
Peritectoid – It is an isothermal reversible reaction in which a solid phase reacts with a second solid phase to produce a single (and different) solid phase on cooling.
Peritectoid equilibrium – It is a reversible univariant transformation in which a solid phase stable only at low temperature decomposes with rising temperature into two or more conjugate solid phases.
Peritectoid point – It is similar in appearance to a peritectic, being an inverted ‘V’ corresponding to an upper limit of formation of a single solid phase. But the difference is that the two-phase field above is formed of two solid phases (whereas in a peritectic, one is liquid).
Permafrost – It is the ground (soil or rock and included ice and organic material) which remains
at or below 0 deg C for at least 2 consecutive years.
Permanence – It is the property of a plastic which describes its resistance to appreciable changes in characteristics with time and environment.
Permanent hardness – It is non-carbonate hardness. It is because of the presence of dissolved chlorides, sulphates, and nitrates of calcium and magnesium. Unlike temporary hardness, permanent hardness is not destroyed on boiling. It is removed by special methods. it can be removed by the use of chemical agents.
Permanent linear change (PLC) – It consists of dimensional expansion or contraction which remains in a refractory which is heated with no externally applied force to a specified temperature for a specified time and then cooled to ambient temperature.
Permanent magnet – It is an object made from a material which is magnetized and which creates its own persistent magnetic field. It is a magnet which retains its polarization after an external field is removed.
Permanent magnet material – It is a ferro-magnetic metal or alloy capable of being magnetized permanently because of its ability to retain induced magnetization and magnetic poles after removal of externally applied fields, i.e., a metal or alloy with high coercive force. The name is based on the fact that the quality of the early permanent magnets has been related to their hardness. The ferro-magnetic metal or alloy include the elements iron, nickel and cobalt and their alloys, some alloys of rare-earth metals, and some naturally occurring minerals such as lodestone. Although ferro-magnetic materials are the only ones attracted to a magnet strongly enough to be normally considered magnetic, all other substances respond weakly to a magnetic field, by one of several other types of magnetism.
Permanent magnet synchronous generator – It is an alternating current generator which uses a permanent field magnet instead of an electro-magnet.
Permanent mould – It is a metal, graphite, or ceramic mould (other than an ingot mould) of two or more parts which is used repeatedly for the production of several castings of the same form. Liquid metal is normally poured in by gravity.
Permanent mould casting – Here, the two halves of the mould are made of metal, normally cast iron, steel, or refractory alloys. The cavity, including the runners and gating system are machined into the mould halves. For hollow parts, either permanent cores (made of metal) or sand-bonded ones can be used, depending on whether the core can be extracted from the part without damage after casting. The surface of the mould is coated with clay or other hard refractory material. This improves the life of the mould. Before moulding, the surface is covered with a spray of graphite or silica, which acts as a lubricant. This has two purposes namely (i) it improves the flow of the liquid metal, and (ii) it allows the cast part to be withdrawn from the mould more easily. The process can be automated, and hence yields high through-put rates. Also, it produces very good tolerance and surface finish. It is normally used for producing pistons used in car engines, gear blanks, cylinder heads, and other parts made of low melting point metals, e.g., copper, bronze, aluminum, and magnesium etc.
Permanent set – It is the deformation remaining after a sample has been stressed a prescribed quantity in tension, compression, or shear for a specified time period and released for a specified time period. For creep tests, it is the residual unrecoverable deformation after the load causing the creep has been removed for a substantial and specified period of time. It is also the increase in length, expressed as a percentage of the original length, by which an elastic material fails to return to its original length after being stressed for a standard period of time.
Permeability – It is the passage or diffusion (or rate of passage) of a gas, vapour, liquid, or solid through a material (frequently porous) without physically or chemically affecting it, i.e., the measure of fluid flow (gas or liquid) through a material. It is also a general term used to express different relationships between magnetic induction and magnetizing force. These relationships are either ‘absolute permeability’, which is a change in magnetic induction divided by the corresponding change in the magnetizing, or ‘specific (relative) permeability’, which is the ratio of the absolute permeability to the permeability of free space. In metal casting, it is the characteristics of moulding materials which permit gases to pass through them. In case of refractories, it is the capacity of a refractory for transmitting a fluid (gas or liquid)’ ‘Permeability number’ is determined by a standard test.
Permeability coefficient – It is the steady-state rate of flow of gas through unit area and thickness of a solid barrier per unit pressure differential at a given temperature.
Permeable surface – It is the surface which allow rain water to soak into the surface. The water is stored temporarily under the surface in the sub-base layer which is located below the surfacing (a storage layer). It is then allowed to slowly seep into the ground, or if the ground is unsuitable for this it flows to the drains. Even when connected to the drains, the permeable surfaces act as a buffer to slow the rate of water flow and reduce the volume of water entering the drainage system. Permeable surfaces reduce the total volume, the frequency, and the peak flow rate of rainwater which enters drains and water courses. Hence, they can help to reduce the impact of rainfall on the drainage system. If sufficient area is covered by permeable surfaces it can help to reduce the risk of flooding from sewers and water courses.
Permissible stress design – It is a design philosophy used by engineers. The designer ensures which the stresses developed in a structure because of the service loads do not exceed the elastic limit. This limit is normally determined by ensuring that stresses remain within the limits through the use of factors of safety. In structural engineering, the permissible stress design approach has normally been replaced internationally by limit state design (also known as ultimate stress design) as far as structural engineering is considered, except for some isolated cases.
Permissible variation – For testing machines, it is the maximum allowable error in the value of the quantity indicated. It is convenient to express permissible variation in terms of the percent error.
Permit – It is an authorization, license, or equivalent control document issued by a regulatory authority to implement the requirements of a regulation or to operate a facility. For example, in case of environment regulation, it is normally to limit the quantity of pollutants discharged into the environment. Other example is permit to operate a wastewater treatment plant.
Permit to work – It is a formal written or verbal authority to operate a planned procedure, which is designed to protect personnel, working in hazardous areas or activities, or when performing maintenance on a safety-related system. It is authority for a safe system of work.
Peroxide – It is a class of compounds which contain a peroxy group, having the generic structural formula R–O–O–R, where ‘R’ is any element or functional group, e.g., hydrogen peroxide (empirically H2O2, structurally H–O–O–H). It is another name for the peroxy group itself. It is also a salt of the anion (O2)2-
Peroxy – It is also known as peroxide and sometimes peroxo. It is a functional group consisting of two oxygen atoms directly connected to each other by a single bond and each also connected to one other atom. Peroxides have the general structural formula –O–O–.
Peroxyacetyl nitrate (PAN) – It is a secondary pollutant present in photochemical smog. It is thermally unstable and decomposes into peroxyethanoyl radicals and nitrogen di-oxide gas. It is an oxidant which is more stable than ozone. Hence, it is more capable of long-range transport than ozone. It serves as a carrier for oxides of nitrogen (NOx) and causes ozone formation in the global troposphere. It is a toxic air pollutant which can cause eye irritation, lung damage, and genetic damage. It is also considered a potential contributor to skin cancer.
Perpendicular section – It is a section cut perpendicular to a surface of interest in a sample.
Perseveration – It is defined as the tendency to continue a particular behaviour, even when it ceases to be effective or rewarding.
Persistence – It is defined as the ability to keep going with a behaviour to reach a goal, even when the task is difficult or takes a long time.
Persistent organic pollutants (POPs) – These are organic compounds which are resistant to degradation through chemical, biological, and photolytic processes. These pollutants are toxic and adversely affect human health and the environment. Since these pollutants can be transported by wind and water, majority of these pollutants generated at one place can and do affect people and wild-life far from where they are used and released.
Persistent slip lines – These are small steps contained within a grain and visible at the microscale on free surfaces or in metallographic cross sections of parts which have been subject to a number of cyclic loads slightly below the number needed to initiate a crack. The precursor to a fatigue crack.
Personal computer (PC) – It is a computer designed for individual use. It is typically used for tasks such as word processing, internet browsing, email, multimedia playback, and gaming. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or technician.
Personal protective equipment (PPE) – It is the equipment or a device which is intended to be worn or otherwise used by an employee at work and which protects the employee against one or more risks arising from the operation to the employee’s safety or health. It includes any addition or accessory to the equipment designed to meet a similar objective. It protects the employee from hazards and any harmful conditions (existing and potential) which may result in injury, illness, or possibly fatal injury. PPE can be an item worn on the body, such as gloves, or a device, such as a protective shield or barrier. Besides face shields, safety glasses, helmets, and safety shoes, personal protective equipment also includes a variety of devices and garments such as goggles, coveralls, gloves, vests, earplugs, and respirators.
Person-period data format – It is a type of dataset for statistical analysis in which each subject contributes to the dataset as many records as there are occasions on which that subject is measured. Datasets in this format are frequently necessary in survival analysis and growth-curve analysis.
Personnel – These are a group of people who are employed in an organization or engaged in an organized undertaking.
Personnel training – It is the process of teaching employees the knowledge and skills they need to perform their jobs. It can also refer to the ongoing process of improving their skills and competencies.
Perspective drawing – A perspective drawing highlights the spatial aspects of a building along with showing its three-dimensional volumes. It is the realistic image of the project which is under construction. In addition to this, there are different types of perspectives based on vanishing points. Perspective drawing is a technique for depicting three-dimensional volumes and spatial relationships based on the eye level and vanishing point (or points) of the viewer. It can give a realistic impression of what a volume or space is going to look like in reality. Constructing perspective drawings of projects is extremely complicated, but has been much simplified recently because of the development of computer aided design (CAD), building information modelling (BIM), and other forms of computer-generated imagery (CGI).
Pessimistic time – It is the time needed to complete an activity under the most unfavourable conditions.
Pesticide – It is a chemical compound which is used to control unwanted species which attack crops, animals, or people. This diverse group of chemicals includes herbicides, fungicides, and insecticides.
Petrography – It is a branch of petrology which focuses on detailed descriptions of rocks. Someone who studies petrography is called a petrographer. The mineral content and the textural relationships within the rock are described in detail. The classification of rocks is based on the information acquired during the petrographic analysis. Petrographic descriptions start with the field notes at the outcrop and include macroscopic description of hand-sized specimens. The most important petrographer’s tool is the petrographic microscope. The detailed analysis of minerals by optical mineralogy in thin section and the micro-texture and structure are critical to understanding the origin of the rock.
Petroleum – It is also called crude oil. It is a naturally occurring liquid found beneath the earth’s surface which can be refined into fuel. A fossil fuel, petroleum is created by the decomposition of organic matter over time and used as fuel in furnaces and to power vehicles, heating units, and machines, and can be converted into plastics.
Petroleum-based metal working lubricants -This family of metal working lubricants provides the users with broadest range of choices of various lubricant properties both chemical and physical in nature. The primary vehicle in the make-up of this family of lubricants is the blending oil (which can be of varying viscosities). For obtaining additional physical properties additives such as fats, polymers, and wetting agents can also be added. If necessary, chemical extreme pressure agents such as sulphur, chlorine, and phosphorous can be added to the formulation. In special cases, additives can be added for the rust prevention. Also, cleaning inducers can be included to provide for easier cleaning. Petroleum-based lubricants are used in metal working processes on a selective basis. Cosmetic-type piece parts of stainless steel and some heavy-duty formed sections can require petroleum-based lubricants.
Petroleum coke – It is also called pet coke. Itis a final carbon-rich solid material which is derived from oil refining, and is one type of the group of fuels referred to as cokes. Pet coke is the coke which, in particular, derives from a final cracking process, a thermo-based chemical engineering process which splits long chain hydro-carbons of petroleum into shorter chains. The process takes place in units termed coker units. Other types of coke are derived from coal. Stated briefly, petroleum coke is the carbonization product of high-boiling hydro-carbon fractions obtained in petroleum processing (heavy residues.
Petroleum-coke-base carbon refractory – It is a manufactured refractory comprised substantially of calcined petroleum coke.
Petroleum engineering – It is a field of engineering which is concerned with the activities related to the production of hydrocarbons, which can be either crude oil or natural gas. Exploration and production are deemed to fall within the upstream sector of the oil and gas industry. Exploration, by earth scientists, and petroleum engineering are the oil and gas industry’s two main subsurface disciplines, which focus on maximizing economic recovery of hydrocarbons from subsurface reservoirs. Petroleum geology and geophysics focus on provision of a static description of the hydrocarbon reservoir rock, while petroleum engineering focuses on estimation of the recoverable volume of this resource using a detailed understanding of the physical behaviour of oil, water and gas within porous rock at very high pressure.
Petroleum oil – It is a refined hydro-carbon oil without animal or vegetable additives.
Petroff equation – It is an equation describing the viscous power loss in a concentric bearing full of lubricant. The resisting torque on the shaft (To = shear stress × shaft radius × bearing area) is given by ‘To = (pi square x n x N x L x D square)/2c’ where pi = 3.1416, ‘n’ is the dynamic viscosity, ‘N’ is the shaft speed, ‘L’ is the bearing length, ‘D’ is the shaft diameter, and ‘2c’ is the diametral clearance.
Pewter – It is a tin-base white metal containing antimony and copper. Originally, pewter has been defined as an alloy of tin and lead, but to avoid toxicity and dullness of finish, lead is excluded from modern pewter. These modern compositions contain 1 % to 8 % antimony and 0.25 % to 3 % copper.
PFD – it is ‘Probability of Failure on Demand’ which is applied normally to a plant protection system.
pH – It is the hydrogen ion concentration of a water to denote acidity or alkalinity. This pH number is the negative exponent of 10 representing hydrogen ion concentration in grams per litre. For example, a pH of 7 represent (10)-7 grams per litre. It is the negative logarithm of the hydrogen-ion activity. It denotes the degree of acidity or basicity of a solution. At 25 deg C, a pH of 7 is the neutral value. Decreasing values below 7 indicates increasing acidity, while increasing values above 7 indicates increasing basicity. The pH values range from 0 to 14.
Phaneritic – It is a term used to describe the coarse-grained texture of some igneous rocks.
PHAR (Pickliq hydrochloric acid regeneration) – It is a process for regeneration of spent hydrochloric acid from steel pickling. The process is applicable to any size pickling operation. PHAR technology eliminates the disposal problem, creating considerable reductions in operating, environmental, and capital costs. The process uses sulphuric acid to restore hydrochloric acid for reuse. PHAR produces ferrous sulphate crystals (sulphate hepta-hydrate), an economically viable by-product, which can be sold for the industrial purposes. By eliminating transportation and / or treatment of spent pickling liquor, along with costs associated with generating hydrochloric acid to replace the spent liquor solution, PHAR produces energy savings of 95 %, cost savings of 52 %, and a 91 % reduction in CO2 emissions, compared to the existing technology.
Phase – It is a physically homogeneous and distinct portion of a material system. It is a region of material which is chemically uniform, physically distinct, and (frequently) mechanically separable. In a system consisting of ice and water in a glass jar, the ice cubes are one phase, the water is a second phase, and the humid air is a third phase over the ice and water. The glass of the jar is a different material, in its own separate phase. More precisely, a phase is a region of space (a thermodynamic system), throughout which all physical properties of a material are essentially uniform. Examples of physical properties include density, refraction index, magnetization, and chemical composition. In electricity, phase refers to the distribution of alternating current electric power. It describes the position of a point in time on a wave-form cycle. It is defined by the electric load distribution corresponding to the type of unit, which could be a single-phase or a three-phase electrical system. Single-phase has less power, requiring two wires, whereas three-phase (3-phase) requires more, such as three or four.
Phase change – It is the transition from one physical state to another, such as gas to liquid, liquid to solid, gas to solid, or vice versa. It is defined as a change in the arrangement of atoms, molecules, or particles of a substance with a fixed chemical composition, induced from the outside, resulting in the presence of new properties of matter. This physical phenomenon is reversible and manifests through the emergence of distinct material properties
Phase change / bi-state sensors – These low-cost non-electric sensors are made from heat-sensitive fusible crystalline solids which change decisively from a solid to a liquid with a different colour at a fixed temperature depending on the blend of ingredients. They are available as crayons, lacquers, pellets, or labels over a wide range of temperatures from 38 deg C to 1,650 deg C. They offer a very inexpensive method for surface temperature visual verification within around 0.5 deg C. Monitoring minimum and maximum temperatures during shipment of perishable goods is a common application.
Phase change lubrication – It is the lubrication provided by steady melting of a lubricating species. It is also known as melt lubrication.
Phase contrast – It is the contrast in high-resolution transmission electron microscopy (TEM) images arising from interference effects between the transmitted beam and one or more diffracted beams.
Phase contrast illumination – It is a special method of controlled illumination ideally suited to observing thin, transparent objects whose structural details vary only slightly in thickness or refractive index. This can also be applied to the examination of opaque materials to determine surface elevation changes.
Phase converter – It is an electrical apparatus which converts power from a system of phases to another system, for example, converting single-phase power to three-phase.
Phase diagram – It is a graphical representation of the temperature and composition limits of phase fields in an alloy or ceramic system as they actually exist under the specific conditions of heating or cooling. A phase diagram can be an equilibrium diagram, an approximation to an equilibrium diagram, or a representation of metastable conditions or phases. It is synonymous with constitution diagram.
Phase-field model – is a mathematical model for solving interfacial problems. It has mainly been applied to solidification dynamics, but it has also been applied to other situations such as hydrogen embrittlement. It needs information on the structures and properties of individual structural features in a microstructure as input and predicts the microstructure evolution based on fundamental thermodynamic and kinetic principles.
Phase-fired controllers – It is an alternating current power controller which adjusts the effective value of output by switching on at a variable time phase in the alternating current cycle.
Phase locked loop – It is an oscillator circuit which produces an output signal that is in a fixed timing relation to a reference input.
Phase modulation – It means impressing information on a carrier wave by advancing or delaying the waveform slightly. It is related to frequency modulation.
Phase rule – It is a general principle governing multi-component, multi-phase systems in thermodynamic equilibrium. For a system without chemical reactions, it relates the number of freely varying intensive properties (F) to the number of components (C), the number of phases (P), and number of ways of performing work on the system (N) i.e., F = N + C – P + 1. F=N+C−P+1Examples of intensive properties which count toward ‘F’ are the temperature and pressure. For simple liquids and gases, pressure-volume work is the only type of work, in which case N = 1. The number of degrees of freedom ‘F’ (also called the variance) is the number of independent intensive properties, i.e., the largest number of thermodynamic parameters such as temperature or pressure that can be varied simultaneously and independently of each other. An example of a one-component system (C = 1) is a pure chemical. A two-component system (C = 2) has two chemically independent components, like a mixture of water and ethanol. Examples of phases which count toward ‘P’ are solids, liquids and gases.
Phase transformations – These transformations occur through a two-stage process of nucleation and growth, in which nucleation can be spontaneous (homogeneous), or take place on some kind of interface (heterogeneous).
Phase transition – It is a transformation of a chemical substance between solid, liquid, and gaseous states of matter and, in rare cases, plasma. It is also the measurable values of the external conditions at which such a transformation occurs.
Phasor – It is a vector representing a signal of a given frequency in phase space.
Phasor measurement unit – It is a system which measures the timing and amplitude of voltages and currents on an electrical grid, synchronized over a wide geographic area. The resulting measurements can be used to manage power flow on the grid.
Phenols – Phenols are organic compounds which have a hydroxyl group attached to one or more aromatic rings in their chemical structure.
Phenolic compounds – These compounds are among the major contaminants of the environment and water sources. Their origin can be from natural or anthropogenic activities.
Phenolic esters cold box systems – Ester-cured phenolic cold box process uses two components namely a resin and a curing agent. The resin (beta-set) is an alkaline phenolic resole in water, and the curing agent is the vapour of a volatile ester, methyl formate. The beta-set resin offers higher strength development and excellent dimensional stability, both highly desirable traits in making high valued castings.
Phenolic resins – Phenolics are thermosetting resins produced by the reaction of phenol or substituted phenol with an aldehyde, normally formaldehyde, in the presence of a catalyst. Phenolic resin composites offer superior fire resistance, excellent high-temperature performance, long-term durability, and resistance to hydro-carbon and chlorinated solvents.
Phenolic urethane cold box systems – The phenolic urethane cold box process utilizes an amine gas to catalyze the reaction between a phenolic resin and an isocyanate resin to produce a urethane bond. Phenolic urethane cold box resins are good for high core strengths, long mixed sand bench life, humidity resistance, and release characteristics.
Phenolic water – It is generated in the by- product plant of coke oven battery and has substantial quantity of dissolved phenol in it. In the steel plant with wet quenching, this water is used for quenching of hot coke. In plant with dry quenching, this water is treated in mechanical, biological, chemical treatment plants before its discharge.
Phenol–formaldehyde – It is one of the oldest commercial synthetic polymers. The polymer is the result of a step-growth polymerization of two simple chemicals: phenol or a mixture of phenols and formaldehyde using an acidic or basic catalyst. Phenol is reactive towards formaldehyde at the ortho and para sites, allowing up to three units of formaldehyde to attach to the aromatic ring. The main product of the reaction between them is the production of methylene bridges between aromatic rings.
Phenol formaldehyde resins – These are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde. These are used as the basis for Bakelite. Phenolic formaldehyde has been the first commercial synthetic resins. They have been widely used for the production of moulded products such as billiard balls, laboratory countertops, and as coatings and adhesives. They have been at one time the primary material used for the production of circuit boards but have been largely replaced with epoxy resins and fibre glass cloth, as with fire-resistant FR-4 circuit board materials.
Phenol-resorcinol-formaldehyde – It a type of adhesive which is known for its strength and durability. It is mainly used in the structural application area. The dark glue line is strong and resistant to both weather and water.
Phenyl – It is a functional group consisting of a cyclic ring of six carbon atoms with the chemical formula –C6H5. It is the substituent form of the cyclo-alkane benzene.
Phenyl ether polymers – These are a class of polymers that contain a phenoxy or a thiophenoxy group as the repeating group in ether linkages. Commercial phenyl ether polymers belong to two chemical classes namely polyphenyl ethers (PPEs) and polyphenylene oxides (PPOs). The phenoxy groups in the former class of polymers do not contain any substituents whereas those in the latter class contain 2 to 4 alkyl groups on the phenyl ring.
Phenyl-silane resins – These are thermosetting copolymers of silicone and phenolic resins. These resins are furnished in solution form.
Phi bonds – These are normally covalent chemical bonds, where six lobes of one involved atomic orbital overlap six lobes of the other involved atomic orbital. This overlap leads to the formation of a bonding molecular orbital with three nodal planes which contain the inter-nuclear axis and go through both atoms.
Phonograph – It is a record player which is a device that converts the mechanical movements of a stylus in a disk or cylinder recording groove into sound.
Phosam process – It is a process for ammonia removal from coke oven gas. This process absorbs the ammonia from the coke oven gas using a solution of mono-ammonium phosphate (NH4H2PO4). The process produces saleable anhydrous ammonia. In the Phosam process, ammonia is selectively absorbed from the coke oven gas by direct contact with an aqueous solution of ammonium phosphate in a two-stage spray absorption vessel. Phosam process selectively absorbs ammonia from the coke oven gas through direct contact with an aqueous solution of phosphate, which is added only in minimal quantities. The absorption solution actually contains a mixture of (i) phosphoric acid (H3PO4), (ii) mono ammonium phosphate, (iii) di-ammonium phosphate [(NH4)2HPO4], and (iv) tri-ammonium phosphate [(NH4)3PO4]. The reversible absorption reactions which take place are (i) H3PO4 + NH3 = NH4H2PO4, (ii) NH4H2PO4 + NH3 = (ΝΗ4)2HPO4, and (iii) (NH4)2HPO4 + NH3 = (ΝΗ4)3PO4. The ammonia absorbed is recovered by steam stripping. This regenerates the absorption solution which is returned to the spray absorber. The steam stripping is performed at high pressure of around 1.3 mega pascals. The reason for this is that the reversible reactions which liberate the ammonia from solution are favoured by higher temperatures. Hence, by operating at high pressure (and hence higher temperature), the consumption of stripping steam is minimized. The overhead vapours from the stripper are virtually only water vapour and ammonia. These vapours are condensed and then fed to a fractionating column where anhydrous ammonia is recovered as the condensed overhead product. The fractionator bottoms product, mainly water, leaves the system as effluent.
Phosphate coating – It means forming an adherent phosphate coating on a metal by immersion in a suitable aqueous phosphate solution. It is also called phosphatizing.
Phosphate conversion coating – It is a chemical treatment which is applied to steel parts that creates a thin adhering layer of iron, zinc, or manganese phosphates to improve corrosion resistance or lubrication or a foundation for subsequent coatings or painting. It is one of the most common types of conversion coating. The process is also called phosphate coating, phosphatization, phosphatizing, or phosphating. It is also known by the trade name Parkerizing.
Phosphate ester – It is an ester derived from an alcohol and phosphoric acid. It is also called organo-phosphate compounds since these molecules have a phosphate group bonded to carbon.
Phosphating – It is the forming an adherent phosphate coating on a metal by immersion in a suitable aqueous phosphate solution. It is also called phosphatizing.
Phosphor bronze, leaded phosphor bronze – It is a hard and strong cast and wrought copper / tin alloys with small, deliberate, phosphorus additions. Wrought alloys contain 4 % to 8 % tin, whilst cast alloys contain 9 % to 12 % tin. Leaded phosphor bronzes, with lead contents up to 20 %, are normally available only as castings. Phosphor bronzes are used for bearing applications. Two common types of bearing bronzes are copper-base alloys containing 5 % to 20 % tin and a small quantity of phosphorus (phosphor bronzes) and copper-base alloys containing up to 10 % tin and up to 30 % lead (leaded bronzes).
Phosphorescence – Phosphorescence is a type of photoluminescence related to fluorescence. When exposed to light (radiation) of a shorter wavelength, a phosphorescent substance glows, absorbing the light and reemitting it at a longer wave-length. It is a type of photo-luminescence in which the time period between the absorption and re-emission of light is relatively long (of the order of 10 to the power -4 to 10 seconds or longer).
Phosphoric acid It is also known as orthophosphoric acid, or mono-phosphoric acid It is a colourless, odourless phosphorus-containing solid, and inorganic compound with the chemical formula H3PO4. It is normally come across as an 85 % aqueous solution, which is a colourless, odourless, and non-volatile syrupy liquid. It is a major industrial chemical, being a component of several fertilizers.
Phosphorized copper – It is the general term applied to copper deoxidized with phosphorus. The normally used term is deoxidized copper.
Phosphorus (P) – It has atomic number 15 and atomic weight 30.974. It has density of 1.82 per cubic centimeters. It has a melting point of 44.1 deg C and boiling point of 280 deg C. It is normally considered an undesirable impurity in steels. It is present in varying concentrations in iron ore, is retained in hot metal, but is eliminated early in the steelmaking process. Phosphorus oxidizes readily and is removed from steel as P2O5, which is taken up by the oxidizing slag, before the oxidation of carbon takes place. Phosphorus has embrittlement effects. It increases machinability. It is an undesirable element. It increases strength and hardness and decreases ductility and notch impact toughness of steel. The adverse effects on ductility and toughness are greater in quenched and tempered high carbon steels. Phosphorus levels are normally controlled to low levels. Higher phosphorus is specified in low carbon free-machining steels to improve machinability.
Phosphorus reversion – It is the reversion of phosphorus from slag to steel which can take place when heating to the aimed temperature, close to the end of the steelmaking process. Phosphorus reversion phenomenon also occurs during slag foaming if the high phosphorus slag has not been removed prior to this operation.
Photo-cell – It is a light sensor which produces or alters a voltage when light is present.
Photo-chemical machining (PCM) – It is a chemical milling process which is used to fabricate sheet metal components using a photoresist and etchants to corrosively machine away selected areas. This process emerged as an offshoot of the printed circuit board industry. Photo etching can produce highly complex parts with very fine detail accurately and economically. This process offers economical alternatives to stamping, punching, laser or water jet cutting, or wire electrical discharge machining (EDM) for thin gauge precision parts. The tooling is inexpensive and quickly produced. It maintains dimensional tolerances and does not create burrs or sharp edges. It can make a part in hours after receiving the drawing.
Photo-chemical pollution – It refers to the formation of smog, particularly in urban areas, because of the reaction of volatile organic compounds from liquid fuels with sunlight, leading to the production of nitrogen dioxide and high ozone concentrations.
Photochemical smog – It is a brownish-gray haze caused by the action of solar ultraviolet radiation on atmosphere polluted with hydrocarbons and oxides of nitrogen. It contains anthropogenic air pollutants, mainly ozone, nitric acid, and organic compounds, which are trapped near the ground by temperature inversion. These pollutants and also some others can affect human health and cause damage to plants. Photochemical smog often has an unpleasant odor due to some of its gaseous components.
Photo-detector – It is a device which detects visible light.
Photo-diode – It is a two-terminal device whose terminal voltage or current changes in response to light.
Photodiode array – It consists of an array of photodiodes of microscopic dimensions, each capable of being coupled to a signal line in turn through an associated transistor circuit adjacent to it on the chip.
Photo-elasticity – It is an optical method for evaluating the magnitude and distribution of stresses, using a transparent model of a part, or a thick film of photoelastic material bonded to a real part.
Photo-elastic modulator (PEM) – It is an optical device used to modulate the polarization of a light source. The photoelastic effect is used to change the birefringence of the optical element in the photoelastic modulator. The basic design of a photoelastic modulator consists of a piezoelectric transducer and a half wave resonant bar; the bar being a transparent material (now most commonly fused silica). The transducer is tuned to the natural frequency of the bar. This resonance modulation results in highly sensitive polarization measurements. The fundamental vibration of the optic is along its longest dimension.
Photo-electric effect – It is the emission of electrons from a material caused by electro-magnetic radiation such as ultra-violet light. Electrons emitted in this manner are called photo-electrons. The phenomenon is studied to draw inferences about the properties of atoms, molecules and solids. The effect has found use in electronic devices specialized for light detection and precisely timed electron emission.
Photo-electric sensor – It is a sensor in a conveyor system which uses light beams for material detection, demanding regular inspections for accurate sensing and preventing false readings.
Photo-electric electron-multiplier tube – – It is a device in which incident electromagnetic radiation creates electrons by the photoelectric effect. These electrons are accelerated by a series of electrodes called dynodes, with secondary emission adding electrons to the stream at each dynode. It is also called photomultiplier tube.
Photo-emission electron microscopy (PEEM) – It is also called photo-electron microscopy (PEM). It is a type of electron microscopy which utilizes local variations in electron emission to generate image contrast. The excitation is normally produced by ultraviolet light, synchrotron radiation or X-ray sources. Photo-emission electron microscopy measures the coefficient indirectly by collecting the emitted secondary electrons generated in the electron cascade which follows the creation of the primary core hole in the absorption process. Photo-emission electron microscopy is a surface sensitive technique since the emitted electrons originate from a shallow layer.
Photo eye – It is a sensor which is designed to identify the presence of a load within a conveyor system.
Photography – It is the application and practice of creating images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is used in several fields. Typically, a lens is used to focus the light reflected or emitted from objects into a real image on the light-sensitive surface inside a camera during a timed exposure. With an electronic image sensor, this produces an electrical charge at each pixel, which is electronically processed and stored in a digital image file for subsequent display or processing.
Photo-luminescence – It is the re-emission of light absorbed by an atom or molecule. The light is emitted in random directions. There are two types of photo-luminescence namely fluorescence and phosphorescence.
Photo-macrograph – It is a macrograph produced by photographic means.
Photo-meter – It is a device so designed that it measures the ratio of the radiant power of two electro-magnetic beams. It is an instrument which measures light.
Photo-micrograph – It is a micrograph made by photographic means.
Photo-microscopy – Prior to the development of photographic attachments, microstructures were to be sketched. Although the need for such documentation is no more there, sketching remains useful as a teaching method. Photo-microscopy is important in metallography, since the photo-micrograph can faithfully reproduce the detail observed for others to view. With the equipment presently available, high-quality micrographs are easily produced. However, this needs careful attention to sample preparation, etching, and use of the microscope. Reproduction of false microstructures is all too common and has caused inaccurate interpretations, rejection of good materials, and faulty conclusions in failure analyses.
Photo-multiplier tube – It is a device in which incident electromagnetic radiation creates electrons by the photoelectric effect. These electrons are accelerated by a series of electrodes called dynodes, with secondary emission adding electrons to the stream at each dynode. It is also known as multiplier phototube, electron multiplier phototube, and photoelectric electron-multiplier tube.
Photon – It is a carrier of electro-magnetic radiation of all wave-lengths (such as gamma rays and radio waves).
Photonics – It is the technology of conveying information through light or infrared radiation.
Photon scanning tunneling micro-scope (PSTM) – It is analogous to the operation of an electron scanning tunneling microscope, with the primary distinction being that photon scanning tunneling micro-scope involves tunneling of photons instead of electrons from the sample surface to the probe tip. A beam of light is focused on a prism at an angle higher than the critical angle of the refractive medium in order to induce total internal reflection within the prism. Although the beam of light is not propagated through the surface of the refractive prism under total internal reflection, an evanescent field of light is still present at the surface.
Photo-resist – It is a radiation-sensitive material which, when properly applied to a variety of substrates and then properly exposed and developed, masks portions of the substrate with a high degree of integrity. It is also a photo-sensitive coating which is applied to a laminate and subsequently exposed through a photo tool (film) and developed to create a pattern that can be either plated or etched.
Photo-resistor – It is a resistor whose resistance varies when light strikes it.
Photosynthesis – It is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabolism. Photosynthesis normally refers to oxygenic photosynthesis, a process which produces oxygen. Photosynthetic organisms store the chemical energy so produced within intracellular organic compounds (compounds containing carbon) like sugars, glycogen, cellulose, and starches. For use this stored chemical energy, an organism’s cells metabolize the organic compounds through cellular respiration. Photosynthesis plays a critical role in producing and maintaining the oxygen content of the earth’s atmosphere, and it supplies most of the biological energy necessary for complex life on earth.
Photo-transistor – It is a transistor which is sensitive to light.
Photovoltaic cell (PV cell) – It is also known as solar cell. It is an electronic device which converts the energy of light directly into electricity by means of the photovoltaic effect. It is a form of photoelectric cell, a device whose electrical characteristics (such as current, voltage, or resistance) vary when it is exposed to light. Individual photovoltaic cell devices are frequently the electrical building blocks of photovoltaic modules, known as solar panels. Photovoltaic cells consist of crystalline silicon, or cadmium telluride thin-film solar cells. The common single-junction silicon solar cell can produce a maximum open-circuit voltage of around 0.5 volts to 0.6 volts. Photovoltaic cells can operate under sunlight or artificial light. In addition to producing energy, they can be used as a photodetector (for example infrared detectors), detecting light or other electromagnetic radiation near the visible range, or measuring light intensity.
Photovoltaic effect – It is the generation of voltage and electric current in a material upon exposure to light. It is a physical phenomenon. The photovoltaic effect is closely related to the photoelectric effect. For both phenomena, light is absorbed, causing excitation of an electron or other charge carrier to a higher-energy state. The main distinction is that the term photoelectric effect is now normally used when the electron is ejected out of the material (normally into a vacuum) and photovoltaic effect used when the excited charge carrier is still contained within the material. In either case, an electric potential (or voltage) is produced by the separation of charges, and the light has to have a sufficient energy to overcome the potential barrier for excitation.
Photovoltaic (PV) junction box – It is also known as the solar panel junction box. It is a box which enables electrical connections to be made between the solar cell array and the solar charge control device composed of solar cell modules. The Photovoltaic junction box is a specific structural form which combines electrical design, mechanical design, and material science into one complete design. It connects the power generated by solar cells to the external line.
Photovoltaics (PV) – It is the conversion of light into electricity using semi-conducting materials which show the photovoltaic effect.
Photovoltaic system – It uses solar modules, each comprising a number of solar cells, which generate electrical power. Photovoltaic installations can be ground-mounted, rooftop-mounted, wall-mounted or floating. The mount can be fixed or use a solar tracker to follow the sun across the sky.
Physical absorption – For physical absorption, carbon di-oxide is physically absorbed in a solvent as per Henry’s Law. The absorption capacity of organic or inorganic solvents for carbon di-oxide increases with increasing pressure and with decreasing temperatures. Absorption of carbon di-oxide occurs at high partial pressures of carbon di-oxide and low temperatures. The solvents are then regenerated by either heating or pressure reduction. The advantage of this method is that it needs relatively little energy, but the carbon di-oxide is to be at high partial pressure.
Physical accounting – It is the practice of accounting for natural resources and the environment using physical units like weight, area, or number. It is used to assess the environmental impact of economic activities.
Physical adsorption – It is also called physisorption. It is the binding of an adsorbate to the surface of a solid by forces whose energy levels approximate those of condensation.
Physical assets – These are tangible items which can be seen, touched, and used. They are a necessary part of the operations of the organization. They include buildings, plant and equipment, facilities, vehicles, and land.
Physical catalyst – It is the radiant energy capable of promoting or modifying a chemical reaction.
Physical chemistry – It is the study of macroscopic and microscopic phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistical mechanics, analytical dynamics and chemical equilibria. Physical chemistry, in contrast to chemical physics, is predominantly (but not always) a supra-molecular science, as the majority of the principles on which it was founded relate to the bulk rather than the molecular or atomic structure alone (for example, chemical equilibrium and colloids).
Physical crack size (ap) – In fracture mechanics, it is the distance from a reference plane to the observed crack front. This distance can represent an average of several measurements along the crack front. The reference plane depends on the sample form, and it is normally taken to be either the boundary or a plane containing either the load line or the centre-line of a sample or plate.
Physical etching – It is the development of microstructure through removal of atoms from the surface or lowering the grain surface potential.
Physical law – It is also called scientific law, or law of nature. It is a scientific generalization based on empirical observations of physical behaviour. Empirical laws are typically conclusions based on repeated scientific experiments over several years, and which have become accepted universally within the scientific community. The production of a summary description of nature in the form of such laws is a fundamental aim of science. Physical laws are distinct from the law, either religious or civil, and are not to be confused with the concept of natural law. Nor are the ‘physical law’ be confused with ‘law of physics’ – the term ‘physical law’ normally covers laws in other sciences (e.g., biology) as well.
Physical metallurgy – It is the science and technology dealing with the properties of metals and alloys, and of the effects of composition, processing, and environment on those properties.
Physical modelling – Physical modelling of the continuous casting process such as using water to simulate liquid steel enables considerable insight into the flow behaviour of the liquid steel during the continuous casting process. Previous understanding of fluid flow in the continuous casting process has come about mainly through experiments using physical water models. This technique is a useful way to test and understand the effects of new configurations before implementing them in the process. A full-scale model has the important additional benefit of providing operator training and understanding.
Physical objective aperture – In electron microscopy, it is a metal diaphragm centrally pierced with a small hole used to limit the cone of electrons accepted by the objective lens. This improves image contrast, since highly scattered electrons are prevented from arriving at the Gaussian image plane and hence cannot contribute to background fog.
Physical parameters – These are numerical values which describe the size, energy output, and other characteristics of an object or system. These parameters can be used to measure the strength of magnetic fields, temperatures, and densities.
Physical phenomenon – It refers to observable events or occurrences in the nature which cannot be explained by classical theory. As an example, heat is a physical phenomenon, which is defined as the transfer of thermal energy across a well-defined boundary around a thermodynamic system.
Physical pollution – It consists of the introduction or presence of harmful substances or forces in the environment which cause damage to the environment and its processes because of their material actions, as through vibration, thermal alteration, or electro-magnetic radiation.
Physical properties – It is the properties of a metal or alloy which are relatively insensitive to micro-structure and can be measured without the application of force, e.g., density, electrical conductivity, coefficient of thermal expansion, magnetic permeability, and lattice parameter. It does not include chemical reactivity. It does not include chemical reactivity. The modulus of elasticity can be considered a physical property, since it is structure-insensitive at the engineering scale of measurement. The modulus of elasticity is controlled by interatomic binding forces, and it can be determined from physical testing (e.g., by the speed of sound and density of a material).
Physical quality – It is also called structural quality, which is applicable when specified strength and elongation values are needed in addition to bend tests.
Physical quantity – It is a property of a material or system that can be quantified by measurement. A physical quantity can be expressed as a value, which is the algebraic multiplication of a numerical value and a unit of measurement. For example, the physical quantity mass, symbol ‘m’, can be quantified as ‘m=n’ kilogram, where ‘n’ is the numerical value and kilogram is the unit symbol. Quantities which are vectors have, besides numerical value and unit, direction, or orientation in space.
Physical testing It consists of methods which are used to determine the entire range of the material’s physical properties of a material. In addition to density and thermal, electrical, and magnetic properties, physical testing methods can be used to assess simple fundamental physical properties such as colour, crystalline form, and melting point.
Physical vapour deposition (PVD) – It is a coating process whereby the deposition species are transferred and deposited in the form of individual atoms or molecules. The most common physical vapour deposition methods are sputtering and evaporation. Sputtering, which is the principal physical vapour deposition process, involves the transport of a material from a source(target) to a substrate by means of the bombardment of the target by gas ions which have been accelerated by a high voltage. Atoms from the target are ejected by momentum transfer between the incident ions and the target. These ejected particles move across the vacuum chamber to be deposited on the substrate. Evaporation, which has been the first physical vapour deposition process used, involves the transfer of material to form a coating by physical means alone, essentially vapourization. The streaming vapour is generated by melting and evaporating a coating material source bar, by an electron beam in a vacuum chamber. Since
both of these methods are line-of-sight processes, it is necessary to use specially shaped targets or multiple evaporation sources and to rotate or move the substrate uniformly to expose all areas. Physical vapour deposition coatings are used to improve the wear, friction, and hardness properties of cutting tools and as corrosion-resistant coatings.
Physical work environment – It is the part of the work-place facility which can be detected by human senses or by physical, chemical, biological, or ergonomic assessment including the structure, air, machines, furniture, products, chemicals, materials and processes which are present or which occur in the workplace, and which can affect the physical or mental safety, health, and well-being of workers. If the workers perform their tasks outdoors or in a vehicle then that location is their physical work environment.
Physics – It is the scientific study of matter, its fundamental constituents, its motion and behaviour through space and time, and the related entities of energy and force. It is one of the most fundamental scientific disciplines.
Physisorption – It is the binding of an adsorbate to the surface of a solid by forces whose energy levels approximate those of condensation.
Pi – It is a mathematical constant which is approximately equal to 3.14159, i.e., the ratio of a circle’s circumference to its diameter. It appears in several formulae, and some of these formulae are normally used for defining pi, to avoid relying on the definition of the length of a curve.
Pi bonding – It consists of covalent bonding in which the atomic orbitals overlap along a plane perpendicular to the sigma bond(s) joining the nuclei of two or more atoms.
Pi bonds – These are covalent chemical bonds, in each of which two lobes of an orbital on one atom overlap with two lobes of an orbital on another atom, and in which this overlap occurs laterally. Each of these atomic orbitals has an electron density of zero at a shared nodal plane which passes through the two bonded nuclei. This plane also is a nodal plane for the molecular orbital of the pi bond. Pi bonds can form in double and triple bonds but do not form in single bonds in most cases.
Pi electron – It is an electron that participates in pi bonding.
Pick – It is an individual filling yarn, running the width of a woven fabric at right angles to the warp. It is also called fill, woof, and weft.
Pick count – It consists of the number of filling yarns per centimeter of woven fabric.
Picket line – A reference line, marked by pickets or stakes, established on a land for mapping and survey purposes.
Pickle – It means the chemical removal of surface oxides (scale) and other contaminants such as dirt from iron and steel by immersion in an aqueous acid solution. The most common pickling solutions are sulphuric acid and hydrochloric acid.
Pickle liquor – It is a spent acid-pickling bath.
Pickle stain – It is the discolouration of metal because of the chemical cleaning without adequate washing and drying.
Pickling – It is the chemical removal of surface oxides (scale) and other contaminants such as dirt from iron and steel by immersion in an aqueous acid solution. The most common pickling solutions are sulphuric acid and hydrochloric acid.
Pickling cracks – Pickling is chemical surface cleaning operation (using acids) used to remove unwanted scale. Picking cracks are hydrogen induced cracks caused by the diffusion of the hydrogen generated at the surface into the base metal. Such cracks mostly occur in materials having high residual stresses such as hardened or cold worked metals.
Pick-off – It is an automatic device for removing a finished part from the press die after it has been stripped.
Pick-up – It is the transfer of metal from tools to part or from part to tools during a forming operation. It also consists of small particles of oxidized metal adhering to the surface of a mill product. It is also irregular surface roughness or damage caused by adhesion and subsequent fracture or tearing between the forming tools and the work-piece.
Pick-up, repeating – It is repeating depression caused by a particle adhering to a rotating roll over which the metal has passed.
Pick-up, roll – It consist of small particles of metal and metal oxide generated in the roll bite, which subsequently transfer to the rolled product. It can be distributed uniformly and / or in streaks.
Picogram – It is one trillionth of a gram.
Pidgeon process – It is a process for production of magnesium by reduction of magnesium oxide with ferro-silicon.
Pie chart – It is used to represent nominal data (in other words, data classified in different categories). It visually represents a distribution of categories. A pie chart needs a list of categorical variables and the numerical variables. Here, the term ‘pie’ represents the whole and the ‘slices’ represents the parts of the whole. The pie chart is also is known as ‘circle graph’ since it divides the circular statistical graphic into sectors or slices in order to illustrate the numerical data.
The pie chart is normally the most appropriate format for representing information grouped into a small number of categories. It is also used for data which have no other way. The application of 3D effects on a pie chart makes distinguishing the size of each slice difficult. Even if slices are of similar sizes, slices farther from the front of the pie chart can appear smaller than the slices closer to the front because of the false perspective. Pie chart contains different segments and sectors in which each sector forms a certain portion of the total (percentage). Each sector denotes a proportionate part of the whole. The total of all the data is equal to 360-degree. The total value of the pie is always 100 %. Fig 3 shows pie charts. It also shows comparison of simple pie chart versus 3D pie chart.
Pier – It is a raised structure which rises above a body of water and normally juts out from its shore, typically supported by piles or pillars, and provides above-water access to offshore areas.
Pierce and pilger process –In this process input rounds are heated in a rotary hearth furnace to a temperature in the range of 1,250 deg C to 1,300 deg C. From the furnace the rounds are descaled by high pressure water jets and fed to the cross-roll piercing mill where they are pierced to produce a thick-walled hollow shell. In this process the material is elongated to between 1.5 times and 2 times and cross section reduces between 33 % and 50 %. The piercing mill features two specially contoured work rolls which are driven in the same direction of rotation. The axes are inclined by approximately 3-degree to 6-degree in relation to the horizontal stock plane. The roll gap is normally closed by a non-driven support roll at the top and a support shoe at the bottom. A piercing point which functions as an internal tool is located at the centre of the roll gap and is held in position by an external thrust block through a mandrel. The thick-walled hollow shell after the cross-roll piercing operation is rolled out further in the pilgering stand to produce the finished pipe. The elongation ratio during the pilgering process lies between 5 and 10, and is accompanied by a reduction in cross section of around 80 % to 90 %. The pilgering stand has two rolls (sometimes called dies because of their forging action) with a tapered pass around their circumference. The rolls rotate counter to the direction of the material flow. The work pass encompasses between 200-degree to 220-degree of the roll circumference and consists of the tapered inlet, an even, cylindrical polishing pass which blends into a larger clearance for releasing the work piece. Pilgering process is a stepwise rolling cum forging process with its recurring backward and forward motion. After the completion of the pilgering process, the finished pipe is stripped from the mandrel. The unworked part of the hollow shell known as pilger head is cut off by a hot saw. The pipe is then fed into a sizing or a reducing mill after reheating it in a furnace. The sizing mill produces a precise outside diameter as well as improves the concentricity of the pipe. It normally consists of three stands with two high or three high roll arrangements. The work rolls form a closed pass, with (in multi stand configurations) each stand pass being off set at an angle to the previous pass.
Piercing – It is the general term for cutting (shearing or punching) openings, such as holes and slots, in sheet material, plate, or parts. This operation is similar to blanking. The difference is that the slug or pierce produced by piercing is scrap, while the blank produced by blanking is the useful part.
Piezo-electric effect – It is the reversible interaction, shown by some crystalline materials, between an elastic strain and an electric field. The direction of the strain depends on the polarity of the field or vice versa. It is the production of a voltage in response to mechanical pressure or mechanical deformation. The piezo-electric effect results from the linear electro-mechanical interaction between the mechanical and electrical states in crystalline materials with no inversion symmetry. The piezoelectric effect is a reversible process, i.e., the materials showing the piezo-electric effect also show the reverse piezo-electric effect, the internal generation of a mechanical strain resulting from an applied electric field. As an example, lead zirconate titanate crystals generate measurable piezo-electricity when their static structure is deformed by around 0.1 % of the original dimension. Conversely, those same crystals change around 0.1 % of their static dimension when an external electric field is applied. The inverse piezo-electric effect is used in the production of ultra-sound waves.
Piezo-electricity – It is the electric charge which accumulates in certain solid materials, such as crystals, certain ceramics, and biological matter, and different proteins in response to applied mechanical stress.
Piezo-electric motor – It is a type of motor which uses piezoelectric elements to generate force.
Piezo-electric pressure measurement – The principle of piezo-electric pressure measurement is based on the physical effect of the same name, only found in some non-conductive crystals, e.g. mono-crystalline quartz. If such a crystal is exposed to pressure or tensile force in a defined direction, certain opposed surfaces of the crystal are charged, positive and negative, respectively. Because of a displacement in the electrically charged lattice elements, an electric dipole moment results which is indicated by the (measurable) surface charges. The charge quantity is proportional to the value of the force. Its polarity depends on the force direction. Electrical voltage created by the surface charges can be measured and amplified. The piezo-electric effect is only suitable for the measurement of dynamic pressures. In practice, piezo-electric pressure measurement is restricted to specialized applications.
Piezo-resistive pressure measurement – The principle of piezo-resistive pressure measurement is similar to the principle of resistive pressure measurement. However, since the strain gauges used for this measuring principle are made of a semi-conductor material, their deflection because of the elongation or compression results primarily in a change in resistivity. As per the equation of the resistance of an electric conductor, the electrical resistance is proportional to the resistivity. While the piezo-resistive effect in metals is negligible and hence effectively insignificant within resistive pressure measurement, in semi-conductors such as silicon it exceeds the effect of the variation of length and cross-section by a factor between 10 and 100. Because of the magnitude of the piezo-resistive effect, piezo-resistive sensors can also be used in very low-pressure ranges. However, due to strong temperature dependency and manufacturing process-related variation, individual temperature compensation of every single sensor is needed.
Piezo-resistive sensor – A piezo-resistive sensor has a far more complex structure. The sensor element is made of a silicon chip. This chip consists of a diaphragm, structured with piezo-resistive resistors, which deflects under pressure. The chip has a surface area of only a few square millimeters and is thus much smaller than, for example, the diaphragms of metal thin-film or ceramic thick film sensors. The piezo chip is very susceptible to environmental influences and, hence, is to be hermetically encased in majority of the cases. For this reason, it is installed into a stainless-steel case which is sealed using a thin flush stainless-steel diaphragm. The free volume between the piezo chip and the external diaphragm is filled with a transmission fluid. Synthetic oil is normally used for this. In an encased piezo-resistive sensor, the pressure medium is only in contact with the stainless-steel diaphragm, which then transmits the pressure through the oil to the internal chip’s diaphragm
Pig – It is a metal casting used in remelting. In nuclear power plant, pig is a container used to ship or store radioactive materials. The thick walls of this shielding device, which are normally made of lead or depleted Uranium, protect the person handling the container from radiation. Large containers used for spent fuel storage are normally called casks. It is also an implement which is used for cleaning rust and alien substances from a piping system.
Pig iron – It is the high-carbon iron made by reduction of iron ore in the blast furnace. It is the cast iron in the form of pigs. It is a high Fe (iron), low residual metallic material which is used for the production of high-quality iron and steel products in a wide variety of furnaces engaged in steelmaking and foundries. The material is not a scrap substitute but rather as a source of clean iron units which can be used to supplement and enhance the scrap charge. Pig iron is an intermediate product and the first product of ironmaking produced during the smelting of iron ore. It is produced when liquid iron (hot metal) is cast in the pig moulds. Pig iron is basically an alloy of iron (Fe), carbon (C), silicon (Si), and manganese (Mn). It also contains some percentage of sulphur (S) and phosphorus (P) as impurity elements, along with some titanium (Ti) and other trace elements. The C content of pig iron is high, typically in the range of 3.5 % to 4.5 %. With its defined and closely controlled specification and the absence of metallic impurities, pig iron is a reliable and consistent charge material for both the electric steelmaking as well as the ferrous castings production. The various grades of pig iron have specific chemical properties designed for their end use. The pig iron also contains valuable alloying elements and reduces the energy consumption of a melt.
Pigment – It consists of small particles which are added to the paint to influence properties such as colour, corrosion resistance, and mechanical strength.
PILC cables – PILC stands for ‘paper insulated lead cover’. For several years, the superior insulation material for power cables from low voltage to high voltages was oil-impregnated paper with lead sheath. Oil-impregnated paper has very good electrical properties and a high degree of thermal overload capacity without excessive deterioration. However, PILC cables have some disadvantages namely (i) they are prone to moisture and damage, (ii) they have low current carrying capacities, (iii) they need low operating temperatures, (iv) they have heavier weight and they are difficult to handle during installation, and (v) there is migration of impregnating compound which do not permit laying cables vertically or on steep slopes. Because of these disadvantages, the use of PILC cables is limited.
Pile – It is relatively long and slender member which is used to transmit the load to deeper soil or rock of high bearing capacity avoiding shallow soil of low bearing capacity. The main types of materials used for piles are wood, steel, and concrete. Piles made from these materials are driven, drilled, or jacked into the ground and connected to pile caps. Depending upon type of soil, pile material and load transmitting characteristic, piles are classified accordingly. Piles are also sometimes used to resist heavy uplift and lateral forces. Piles are normally used for (i) to carry structure loads into or through a soil stratum, (ii) to resist uplift or overturning forces, (iii) to control settlements when spread footings are on marginal or highly compressible soil, (iv) to control scour problems on bridge abutments or piers, (v) in offshore construction to transmit loads through the water and into the underlying soil, and (vi) to control earth movements, such as land-slides.
Pile butt – Pile butt is a member of the pile crew other than the operator and oiler.
Pile cap – It is a thick concrete mat which rests on concrete or timber piles that have been driven into soft or unstable ground to provide a suitable stable foundation. It normally forms part of the deep foundation of a building, typically a multi-story building, structure or support base for heavy equipment, or of a bridge. The cast concrete pile cap distributes the load of the building into the piles. A similar structure to a pile cap is a ‘raft’, which is a concrete foundation floor resting directly onto soft soil which can be liable to subsidence.
Pile driving – It is the operation of forcing a pile into the ground thereby displacing the soil mass across the whole cross section of the pile. Historically, the oldest method of driving a pile, and the method most frequently used today, is by use of an impact type hammer.
Pile foundation – It is defined as a series of columns inserted into the ground to transmit loads to a lower level of sub-soil. A pile is a long cylinder made up of a strong material, such as concrete. Piles are pushed into the ground to act as a steady support for structures built on top of them. Piles transfer the loads from structures to hard strata, rocks, or soil with high bearing capacity. The pile plays an important role as a key component in moving the base load through low-bearing soil strata to strata or rocks with high bearing capacity. In normal soil conditions, pile foundations are used to withstand elevations such as offshore platforms, foundations below groundwater levels, or basic transmission towers. Pile foundations are also used in soft soil to withstand horizontal loads, such as wind power and earth-quake bending forces. Soils which are easy to grow and shrink and which are sensitive to soil moisture change also need a pile foundation. In addition, construction works on water such as jetty and bridge piers, it also needs a pile foundation.
Pile gate – It is a hinged section attached to the pile leads, at the lower end, which acts to keep the pile within the framework of the pile leads.
Pile hammer – It is the unit which develops the energy used to drive piles, the two main parts of which are the ram and the anvil.
Pile monkey – It is a device used to position the pile in the leads beneath the hammer.
Pile rig – It is the crane used to support the leads and pile driving assembly during the driving operation.
Pile splice – It joins two segments of a driven pile, using either a weld (typical for H beams), grout or mechanical means (typical for precast concrete piles). Pile splices enable the use of shorter segments, which allows for driving piles in low-headroom situations such as under bridges or inside buildings. Reducing length of pile segments to under around 20 metres long also means the trailers which haul them to job sites can stay within state length limits.
Pilger tube-reducing process – It is a process of reducing both the diameter and wall thickness of tubing with a mandrel and a pair of rolls.
Piling (sheet piling) – It is a structural steel product with edges designed to interlock. It is used in the construction of cofferdams or riverbank reinforcement. Sheet piling is differentiated according to its cross-sectional shape or its application such as (i) ‘S’, ‘U’, ‘Z’ and omega sheet piling, (ii) flat sheet piling, (iii) fabricated sheet piling (built up from sheet piles, angles and other sections), (iv) lightweight sheet piling (trench sheeting), (v) interlocking ‘H’ sheet piling, and (vi) box and tubular sheet piling.
Piling pipe – It is welded or seamless pipe for use as piles, with the cylinder section acting as a permanent load carrying member or as a shell to form cast-in-place concrete piles. There are normally three grades, which have different minimum tensile strengths, a variety of diameters, ranging from 150 millimeters to 750 millimeters, and a variety of wall thicknesses. Ends can be plain or beveled for welding.
Pillar – It is a block of solid ore or other rock left in place to structurally support the shaft, walls or roof of a mine.
Pilot arc (plasma arc welding) – It is a low current continuous arc between the electrode and the constricting nozzle to ionize the gas and facilitate the start of the welding arc.
Pilot flame – It is a flame which is utilized to ignite the fuel at the main burner or burners.
Pilot survey – It consists of a study, normally on a minor scale, carried out prior to the main survey, primarily to gain information about the appropriateness of the survey instrument, and to improve the efficiency of the main survey. Pilot surveys are an important step in the survey process, specifically for removing unintentional survey question biases, clarifying ambiguous questions, and for identifying gaps and / or inconsistencies in the survey instrument.
Pimples – These are small lumpy inclusions which can sometimes occur in galvanized coatings, caused by dross stirred up from the bottom of the galvanizing pot.
Pin – It is a machine element which secures the position of two or more parts of a machine relative to each other. A large variety of types has been known for a long time; the most commonly used are solid cylindrical pins, solid tapered pins, groove pins, slotted spring pins and spirally coiled spring pins.
Pinchers – It is the surface disturbances on metal sheet or strip which result from rolling processes and which ordinarily appear as fernlike ripples running diagonally to the direction of rolling.
Pinch marks – These are elongated markings, normally running with the grain and resulting from a folding-over of the metal during rolling. Such folds occur at the entry side of the rolling mill and are consequently rolled over and smoothed out in the subsequent rolling. It also consists of a sharp deviation from flat in the sheet which is transferred from processing equipment subsequent to the roll bite.
Pinch pass – It is a pass of sheet metal through rolls to affect a very small reduction in thickness.
Pinch rolls – The function of pinch roll in rolling mills is to drive the bar through dividing shear after it leaves the finishing stand. These are used one each for crop and cobble shears. The pinch rolls assemblies rotate in chocks housed in fabricated frames and are driven through D C Motors through gear box and the Cardan shafts. The roll size varies depending upon the requirement of the mill. The top roll is normally raised pneumatically or lowered with bottom roll in the adjustable to pass-line. The pinch roll housing has sturdy welded construction, which feature wear resistant surface with anti-friction bearing mounting support and the use of sensors that allows precision breaking up to the speed of hot bar material.
Pinch trimming – It is the trimming of the edge of a tubular metal part or shell by pushing or pinching the flange or lip over the cutting edge of a stationary punch or over the cutting edge of a draw punch.
Pinch valves – These valves are mainly used in order to regulate the flow of slurries in certain processes and systems. Pinch valves have flexible bodies which can be shut by pinching them. These valves are frequently used when it is necessary for the slurry to pass straight through when the valve is not pinched. Pinch valves can be controlled mechanically or with fluid pressure.
Pin-cushion distortion – It is the distortion in the image which results when the magnification in the centre of the field is less than that at the edge of the field. It is also termed positive distortion.
PIN diode – It is a multilayer semi-conductor diode with a thin region of intrinsic material between its p-doped and n-doped regions.
Pin expansion test – It is a test for determining the ability of a tube to be expanded or for revealing the presence of cracks or other longitudinal weaknesses, made by forcing a tapered pin into the open end of the tube.
Pin (for bend testing) – It is the plunger or tool used in making semi-guided, guided, or wrap-around bend tests to apply the bending force to the inside surface of the bend. In free bends or semi-guided bends to an angle of 180-degree, a shim or block of the proper thickness can be placed between the legs of the sample as bending is completed. This shim or block is also referred to as a pin or mandrel.
Pinhole – It is small hole left in a weld area which allows low viscosity liquids to enter and become pressurized under the high temperature conditions of the molten zinc bath. It also consists of small cavities that penetrate the surface of a cured part.
Pin-hole porosity – It is the porosity consisting of several small gas holes (pin-holes) distributed throughout the metal. It is found in weld metal, castings, and electro-deposited metal.
Pinion – It is a round gear normally the smaller of two meshed gears which is used in several applications, including drive train and rack and pinion systems.
Pinion shaft – It is a mechanical component that transfers rotational motion and torque. It’s a round rod with teeth that mesh with a larger gear. Pinion shafts are used in several mechanical systems which include industrial equipment and machinery.
Pinned dislocation – It is a dislocation which has been prevented from moving by an obstacle or impurity cluster. This makes the material harder and stronger.
Pin-on-disk machine – It is a tribometer in which one or more relatively moving styli (i.e., the ‘pin’ sample) is loaded against a flat disk sample surface such that the direction of loading is parallel to the axis of rotation of either the disk or the pin-holding shaft, and a circular wear path is described by the pin motion. The typical pin-on-disk arrangement resembles that of a traditional phonograph. Either the disk rotates or the pin sample holder rotates so as to produce a circular path on the disk surface. An arrangement wherein the pin sample is loaded against the curved circumferential surface of a flat disk is not normally considered to be a pin-on-disk machine.
Pin-on-disk tests – These tests are preferably used to determine two-body sliding wear. In pin-on-disk, the pin is attached with the polymeric material which is slid against the metallic disk or the metallic pin is slid against the disk made of polymer material.
Pin shear test – It consists of any of several tests to get shear strength of a metal. Thes common tests which are used on mill products include the double-shear test, single-shear test, the blanking shear test (also known as the punching shear test) and the torsion test.
Piobert lines – These lines are also called Luders lines. These are elongated surface markings or depressions in sheet metal, frequently visible with the unaided eye, caused by discontinuous (inhomogeneous) yielding’.
Pipe – It is the central cavity formed by contraction in metal, especially ingots, during its solidification. It is also an imperfection in wrought or cast products resulting from such a cavity. It is a cast or wrought tubular product of metal or other materials.
Pipe bend drawing – It establishes, by pictorial or tabular description or a combination thereof, end product definition for a single, multi-plane, pipe or pipe assembly along with the identification for the bent pipe or pipe assembly. It is prepared to specify complete requirements and configuration of rigid or semi-rigid piping for direct use in forming on a draw bending machine. It is prepared as a detail, assembly, or detail assembly drawing. It includes (i) pipe material, (ii) end types, (iii) identification and quantity of fittings, (iv) dimensional requirements including bend radii, angles, intersection points, intermediate and overall lengths, and (v) other data necessary to define design requirements.
Pipe classes – Pipe class is a document which specifies the type of the components such as a type of pipe, schedule, material, flange ratings, branch types, valve types and valve trim material, gasket, and all the other components specific requirements to be used for different fluids under different operating conditions in a plant. Pipe class is developed considering operating pressure, operating temperature, and corrosive environment. Piping specifications are technical documents which are generated by organizations for addressing additional requirements applicable to a specific product or application. These specifications provide specific / additional requirements for the materials, components, or services which are beyond requirements specified in standards and codes.
Piped natural gas (PNG) – It is a form of natural gas which is distributed through a network of under-ground pipelines directly to residential, commercial, and industrial consumers. It is a clean-burning fossil fuel composed primarily of methane and is considered a more environmentally friendly alternative to other conventional fuels.
Pipe, drawn – It is the pipe brought to the final dimensions by drawing through a die.
Pipe, extruded -It is a pipe formed by hot extruding.
Pipe fittings – They allow pipes to be joined or installed in the appropriate place and terminated or closed wherever necessary. They can be expensive, need time, and different materials and tools to install. They are an essential part of piping systems. There are thousands of specialized fittings manufactured. Each type of pipe or tube needs its own type of fitting, but usually all pipe fittings share some common features. The basic purpose of using pipe fittings in pipe systems is to connect the bores of two or more pipes or tubes. Pipe fittings are used in piping systems normally (i) to connect straight pipe or tubing sections, (ii) to adapt to different sizes or shapes, (iii) to branch or re-direct the piping system, (iv) if necessary to provide a jointing method if two dissimilar piping materials are used in the one system, and (v) for other purposes, such as regulating, measuring or changing the direction of the fluid flow or to connect up threaded pipe and equipment. They are also used to close or seal a pipe. Fittings for pipe and tubing are very frequently made from the same base material as the pipe or tubing being connected, e.g., stainless steel, steel, copper or plastic. However, any material which is allowed by code can be used, but is to be compatible with the other materials in the system, the fluids being transported, and the temperatures and pressures inside and outside of the system.
Pipe flange – It is a disc, collar or ring that attaches to pipe with the purpose of providing increased support for strength, blocking off a pipeline or implementing the attachment of more items.
Pipe for nipples – It is standard weight, extra strong, or double extra strong welded or seamless pipe, produced for the manufacture of pipe nipples. Pipe for nipples is generally produced in random lengths with plain ends, in nominal sizes from 3 millimeters to 300 millimeters. Close outside diameter tolerances, sound welds, good threading properties, and surface cleanliness are necessary in the pipes used for nipples. Pipe for oil country tubular goods (OCTG) couplings is to be manufactured from seamless pipe. It is normally coated with oil or zinc and is well protected before dispatch.
Pipeline – It is a system of pipes for long-distance transportation of a liquid or gas, typically to a market area for consumption. Pipelines are used to transport materials between equipment. In general, pipelines can be classified in three categories depending on purpose. These categories are (i) gathering pipelines consisting of group of smaller interconnected pipelines forming complex networks, (ii) transportation pipelines consisting mainly of long pipes with large diameters, and (iii) distribution pipelines which are composed of several interconnected pipelines with small diameters.
Pipeline conveyor – Classification of pipeline conveyors is made on the basis of air pressure used. In low pressure system, the operating air pressure is normally limited to 0.1 megapascal gauge. This system is restricted to short distances (up to 500 meters) and small flow rate. This system is further sub-classified into (i) positive pressure system, (ii) negative pressure (or suction) systems, and (iii) combined negative-positive pressure (or combination) system. In medium pressure system the air pressure is in the range of 0.1 megapascal gauge to 0.3 megapascal gauge. In high pressure system the air pressure is in the range of 0.4 megapascal gauge to 0.7 megapascal gauge. Medium-pressure and high-pressure systems are essentially positive pressure type systems.
Pipeline network – Bedsides pipes, tubes, and hoses, it consists of several components which can be categorized into (i) equipments, (ii) pipelines, (iii) fittings, (iv) instruments, and (v) structures. Equipment is a component which provides power, process, and stores materials. Common equipments includes pumps, tanks, vessels, heat exchangers, and towers etc. The individual components necessary to complete a piping system are (i) pipe, (ii) piping flanges and fittings, (iii) valves, (iv) bolts and gaskets (fasteners and sealing), and (v) piping special items, such as steam traps, pipe supports, and valve interlocking etc. Pipes come in different materials and sizes, but steel pipes are the most popular type of pipes. Fittings are components attached to the pipelines and equipments. Pipelines can be of different pipe sizes. They provide means of changing flow directions and allow branches and connections. Fittings include connectors and joints. Instruments and field devices are auxiliary equipment and tools used to measure, monitor and control parameters of piping processes. Instruments include meters and gauges, indicators and recorders, control valves and actuators, and controllers. Meters and gauges are used to measure process variables like flow, temperature, and pressure etc., indicators and recorders are used to monitor process variables, valves and actuators are used to regulate the variables while controllers are used to make appropriate changes in variables for ensuring proper operating conditions and prevent hazards.
Pipe piles – These piles are made of steel pipes and are installed by driving pipes to the desired depth and filling them with concrete. These piles are provided with a driving point or shoe at the lower end. These piles are driven into the ground with their ends open or closed. A pipe can be driven with the lower end closed with a plate or a steel driving point, or the pipe can be driven with the lower end open. Pipes vary in diameter from 150 millimetres to 750 millimetres and the length can reach 60 metres. A closed-end pipe pile is driven in any conventional manner, normally with a pile hammer. If it is necessary to increase the length of a pile, two or more sections can be welded together. An open-end pipe pile is installed by driving the pipe to the needed depth, removing the material from inside, by burst of compressed air, a mixture of water and compressed air, and filling the space with concrete. Since the open-end pipe piles offer lesser driving resistances than closed-end piles, a smaller pile hammer can be used. Epoxy coatings are applied during the pipe manufacture for reducing the pipe corrosion. Sometimes concrete encasement at the construction site is done as a protection against corrosion. An additional thickness of the steel section is normally desired for taking into account the corrosion.
Pipe rolling mills – These mills are used for the production of different types of pipes. Pipe mills can be for the production of welded pipes or for the production of seamless pipes. Welded steel pipes are produced with either a longitudinal seam or a spiral (helical) seam. The starting material for the production of the welded pipes is rolled flat product which depending on the pipe production process, pipe dimensions and application, can be hot rolled or cold rolled steel strip /skelp, and hot rolled wide strip or plate. This starting material can be formed into pipe shape in either hot or cold condition. The forming process can be either a continuous process or a single pipe forming process. In continuous pipe forming process, uncoiled strip material is taken from an accumulator, with the leading end and the trailing end of the consecutive coils being welded together. In single pipe forming process, the pipe forming and welding operation is carried out in single pipe length. There are two types of welding processes which are mainly used for the welded pipe production. These are (i) pressure welding processes, and (ii) fusion welding processes. The commonly used pressure welding processes are (i) pressure welding process e.g. Fretz-Moon process, (ii) direct current electric resistance welding, (iii) low frequency electric resistance welding, (iv) high frequency induction welding, and (v) high frequency conduction welding. The commonly used fusion welding processes are (i) submerged arc welding, and (ii) gas shielded welding. Seamless pipes are made from round billet, which is pierced through the centre to make it a hollow shell and then rolled or extruded and drawn to size. The seamless pipe manufacturing process consists of three stages namely (i) making of a hollow pipe shell in the piercing or extrusion operation, (ii) elongating the hollow pipe shell by reducing its diameter and wall thickness, and (iii) making of a final pipe in the hot or cold rolling process. As the manufacturing process does not include any welding, seamless pipe is perceived to be stronger and more reliable. Seamless pipe is regarded as withstanding pressure better than other types of pipes.
Pipes and tubes – This term is used to cover all hollow products. Although these products are normally produced in cylindrical form, they are frequently subsequently altered by various processing methods to produce square, oval, rectangular, and other symmetrical shapes. Such products have applications which are almost innumerable, but they are most commonly used as conveyors of fluids and as structural members. One of the major applications of the pipe is in the process and the metallurgical industries. The rolling mills for pipes are normally multi stand continuous mills. Pipe is normally produced to several long-standing and broadly applicable industrial standards. While similar standards exist for specific industry application tubing, tube is frequently made to custom sizes and a broader range of diameters and tolerances. Several industrial and government standards exist for the production of pipes and tubes. Tubes are frequently made to custom sizes and can often have a large number of specific sizes and tolerances than pipes. The term ‘tube’ is also normally applied to non-cylindrical sections (square or rectangular tube). Both pipes and tubes are associated with a level of rigidity and permanence while a hose is usually portable and flexible.
Pipe schedule – It is a standard which measures the nominal wall thickness of a pipe. The pipe schedule number is non-dimensional and depends on the nominal pipe size, internal pipe working pressure, and the material used for the pipe wall.
Pipe, seamless – It is the extruded or drawn pipe which does not contain any line junctures resulting from the method of manufacture.
Pipe, structural – It is the pipe which is normally used for structural purposes.
Pipe tap – It is a tap for making internal pipe threads within pipe fittings or holes.
Pipe threads – These are internal or external machine threads, normally tapered, of a design intended for making pressure tight mechanical joints in piping systems.
Pipette – It is also spelled as pipet. It is a type of laboratory tool to transport a measured volume of liquid, frequently as a media dispenser. Pipettes come in several designs for different purposes with differing levels of accuracy and precision, from single piece glass pipettes to more complex adjustable or electronic pipettes. Several pipette types work by creating a partial vacuum above the liquid-holding chamber and selectively releasing this vacuum to draw up and dispense liquid. Measurement accuracy varies greatly depending on the instrument.
Piping – It is a system of pipes which is used to convey fluids (liquids and gases) from one location to another.
Piping and instrument diagram – It is sometimes called process and instrument diagram. It is more technical, describing mechanical details for piping designers, electrical engineers, instrument engineers, and other technical experts who need this detail more than they need process details. Piping and instrument diagrams take the conceptual aspects of a process flow diagram and add detail about the equipment, process sequence, process and utility piping, bypass lines, instruments, valves, vents, drains and other items. Piping and instrument diagrams are the drawings showing piping and communications as schematic (unscaled) lines and control features as symbols. Piping and instrument diagrams show the functional relationship of piping, instrumentation, equipment, and controllers. They are normally a part of the instrumentation drawings in a project drawing set. Piping and instrument diagrams are normally made by process engineers, controls engineers, and electrical engineers. The main purpose of a piping and instrument diagram is to indicate if the equipments are automatically controlled, and if so, how they are inter-locked with instruments. Piping and instrument diagrams convey the inter-connectivity of automated equipments. Piping and instrument diagram is based on the process flow diagram and depicts the technical realization of a process by means of graphical symbols representing equipment and piping, together with graphical symbols for process measurement and control functions. All equipment, valves, and fittings are represented as per ISO 10628-2. The process measuring and control tasks are represented as per IEC 62424. Auxiliary systems can be represented by rectangular frames with references to separate flow diagrams.
Piping design and pipeline engineering – It refers to the creation and documentation of industry standard layout for pipes, equipment, instruments, and controls. Application areas are plumbing, civil, process, and transportation.
Piping drawings – These are scaled graphic representations of piping systems and devices. They include plans (top views), elevations (frontal or profile views) and sections (internal frontal or profile views). Piping drawings can be very complex sometimes as they show all equipment, fittings, instrumentations, dimensions and notes. Data for piping drawings are derived from process flow diagrams, structural, mechanical, instrumentation drawings, and catalogues / manuals of the suppliers. Piping drawings include (i) plot or site plan, (ii) unit plan, (iii) zone plan, (iv) equipment drawings, (v) equipment layout drawings, (vi) piping plans and elevations, and (vii) 3D (three dimensional) plant model.
Piping engineering – It is a discipline which focuses on designing, analyzing, and laying out piping systems. Piping systems are the circulatory pathways for fluids and gases in industrial facilities.
Piping isometric drawing – It is a pseudo-3D diagram of a single pipe run. All fittings and attachments on the pipe are shown.
Piping spool drawings – These are detail section drawings of pipes and fittings used by pipe fitters and welders during construction. A spool diagram is a sub-section of a piping isometric drawing which can be assembled in a shop and shipped to the plant site.
Piping structures – They provide support to all the elements in a piping system and help hold them together. These include foundations, racks and sleepers, platforms, and ladders and different types of local supports and locators. Pipes need supports for rigidity, hence, hangers, clamps, saddles, and anchors etc. are used.
Pips, pip-lines, pip-marks, ident pips – It is a marking on an extrusion (on a non-visible surface) placed there by the extrusion mill’s die to allow the mill to identify extrusions produced by that mill.
Pirani gauge – It is an instrument used to measure the pressure inside a vacuum chamber. The gauge measures electrical resistance in a wire filament which changes in temperature depending on atmospheric pressure.
Piston – It is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from expanding gas in the cylinder to the crankshaft through a piston rod and / or connecting rod. In a pump, the function is reversed and force is transferred from the crankshaft to the piston for the purpose of compressing or ejecting the fluid in the cylinder. In some engines, the piston also acts as a valve by covering and uncovering ports in the cylinder. In case of a valve, a piston is a rigid movable pressure responsive element which transmits force to the piston actuator stem.
Piston-pin bearing – It is a bearing at the smaller (piston) end of a connecting rod in an engine.
Piston press – It is a mechanical press consisting of a ram (piston) and a die and it is driven by either by an electric or a hydraulic drive. The feedstock is punched into a die by a reciprocating ram with a very high compaction pressure to get a briquette. The achieved briquette densities are normally in the range between 1,000 kilograms per cubic meter to 1,200 kilograms per cubic meter.
Piston ring – It is a metallic split ring which is attached to the outer diameter of a piston in an internal combustion engine or steam engine. The main functions of piston rings in engines are (i) sealing the combustion chamber so that there is minimal loss of gases to the crank case, (ii) improving heat transfer from the piston to the cylinder wall, (iii) maintaining the proper quantity of the oil between the piston and the cylinder wall, and (iv) regulating engine oil consumption by scraping oil from the cylinder walls back to the sump. Majority of the piston rings are made from cast iron or steel.
Piston-type actuator – It is a fluid powered device in which the fluid, normally compressed air, acts upon a movable piston to provide motion of the actuator stem and provide seating force upon closure. Piston-type actuators are classified as either double-acting, so that full power can be developed in either direction, or as spring-fail so that upon loss of supply power, the actuator moves the valve in the needed direction of travel.
Piston valves – These valves have a closure member shaped like a piston. When the valve opens, no flow is observed until the piston is fully moved from the seat bore, and when the valve closes, the piston removes any solids which might be deposited on the seat. Hence, piston valves are used with fluids which have solid particles in suspension.
Pit – It is a small, regular or irregular crater in the surface of a material created by exposure to the environment, e.g., corrosion, wear, or thermal cycling. It is also a small, regular or irregular crater in the surface of a plastic, normally of a width approximately the same order of magnitude as its depth.
Pitch – It is a viscoelastic polymer which can be natural or manufactured, derived from petroleum, coal tar, or plants. Pitch produced from petroleum can be called bitumen or asphalt, while plant-derived pitch, a resin, is known as rosin in its solid form. In sound, the sensation of a frequency is normally referred to as the pitch of a sound. A high pitch sound corresponds to a high frequency sound wave and a low pitch sound corresponds to a low frequency sound wave. Pitch is a perceptual property which allows sounds to be ordered on a frequency-related scale, or more commonly, pitch is the quality that makes it possible to judge sounds as ‘higher’ and ‘lower’. Pitch can be quantified as a frequency. The sensation of a frequency is commonly referred to as the pitch of a sound. A high pitch sound corresponds to a high frequency sound wave and a low pitch sound corresponds to a low frequency sound wave. In case of screw gauge, pitch is defined as the linear distance covered by the screw in each rotation. In other words, it can be defined as the axial distance between the two threads of the main scale. In case of fasteners, it is the linear distance from a point on the thread to a corresponding point on the next thread which is measured parallel to the axis of the thread. Pitch in a conveying the distance between the centre points of adjacent components, necessitating periodic assessments to maintain proper pitch dimensions for optimal system performance. Pitches are used as base materials for the manufacture of certain high-modulus carbon fibres and as matrix precursors for carbon-carbon composites.
Pitchblende – It is an important uranium ore mineral. It is black in colour, possesses a characteristic greasy lustre and is highly radioactive.
Pitch-bonded basic brick – It consists of unburned basic refractory shapes which are bonded with pitch. If subsequently heat-treated sufficiently to minimize softening of the bond on reheating, they are referred to as tempered.
Pitch bonding – It is the use of pitch or tar to produce a bond in a pressed unfired refractory.
Pitch circle diameter (PCD) – It is the diameter of that imaginary circle which passes through the centre of all the bolt holes or wheel bolts or wheel rim holes or studs.
Pitch drop experiment – It is a long-term experiment which measures the flow of a piece of pitch over many years. ‘Pitch’ is the name for any of a number of highly viscous liquids which appear solid, most commonly bitumen, also known as asphalt. At room temperature, tar pitch flows at a very low rate, taking several years to form a single drop.
Pitch error – It is the difference between the actual pitch and the nominal pitch on the gear reference circle.
Pitch impregnation – It is the use of liquid pitch or tar to impregnate a refractory after forming or firing.
Pitch-impregnated basic brick – It consists of burned basic refractory shapes impregnated with pitch after firing.
Pit moulding – It is a moulding method in which the drag is made in a pit or hole in the floor.
Pitot tube – It is an instrument which measures the stagnation pressure of a flowing fluid, consisting of an open tube pointing into the fluid and connected to a pressure-indicating device. It is also known as impact tube.
Pitted surfaces – These are the areas of steel where small, sharp cavities exist, normally formed by the corrosion.
Pitting – It is corrosion of a metal surface, confined to a point or small area, which takes the form of cavities. It is the forming small sharp cavities in a surface by corrosion, wear, or other mechanically assisted degradation. It is also localized corrosion of a metal surface, confined to a point or small area, which takes the form of cavities. In tribology, it is a type of wear characterized by the presence of small, sharp surface cavities formed by processes such as fatigue, local adhesion, wear, corrosion, or cavitation.
Pitting corrosion – It is the non-uniform corrosion of the surface which causes small pits or craters to develop. It is a localized form of corrosion which leads to the creation of small holes (pits) in the metal. This form of corrosion is mainly found on passive metals. Passive metals and alloys, such as aluminum, titanium and stainless steel owe their corrosion resistance to a thin oxide layer on the surface with a thickness of only a few nanometers. The corrosion initiating process starts with a local break-down of the passive layer. Local corrosive attack can be initiated on stainless steels, for example, by chloride ions. Pitting corrosion can be quite problematic. Whereas uniform corrosion can be seen clearly on the surface, pitting corrosion often appears only as small pinholes on the surface. The amount of material removed below the pinholes is generally unknown, as hidden cavities may form, making pitting corrosion more difficult to detect and predict. Technically, there is no reasonable way to control pitting corrosion. This form of corrosion is required to be excluded right from the start through proper designing and use of the right material. In addition, pitting corrosion can often be the starting point for more severe forms of corrosion such as stress corrosion cracking (SCC).
Pitting factor – t is the ratio of the depth of the deepest pit resulting from corrosion divided by the average penetration as calculated from weight loss.
Pitting resistance equivalent numbers (PREN) – These are a theoretical way of comparing the pitting corrosion resistance of different types of stainless steels, based on their chemical compositions. Pitting resistance equivalent numbers are useful for ranking and comparing the different grades, but cannot be used to predict whether a particular grade will be suitable for a given application, where pitting corrosion may be a hazard. These are linear formulas, where the molybdenum and nitrogen levels are weighted to take account of their strong influence on pitting corrosion resistance. They typically take the form PREN = Cr + mMo + nN, where ‘m’ and ‘n’ are the factors for molybdenum and nitrogen.
Pivot – It is the point of rotation in a lever system. More generally, it is the centre point of any rotational system.
Pivot bearing – It is an axial-load, radial-load type bearing which supports the end of a rotating shaft or pivot.
Pivoted-pad bearing – It is a pad bearing in which the pads are free to take up a position at an angle to the opposing surface as per the hydrodynamic pressure distribution over its surface.
Pivot plate – It is the gusset which attaches the conveyor to the support leg.
Pixel – It is also called picture element. In digital imaging, a pixel is the smallest addressable element in a raster image, or the smallest addressable element in a dot matrix display device. In majority of the digital display devices, pixels are the smallest element which can be manipulated through software. Each pixel is a sample of an original image, more samples typically provide more accurate representations of the original. The intensity of each pixel is variable. In colour imaging systems, a colour is typically represented by three or four component intensities such as red, green, and blue, or cyan, magenta, yellow, and black.
Placer – It is a deposit of sand and gravel containing valuable metals such as gold, tin, or diamonds.
Plain bearing – It is the simplest type of bearing, comprising just a bearing surface and no rolling elements. Hence, the part of the shaft in contact with the bearing slides over the bearing surface. The simplest example of a plain bearing is a shaft rotating in a hole. A simple linear bearing can be a pair of flat surfaces designed to allow motion, e.g., a drawer and the slides it rests on or the ways on the bed of a lathe. Plain bearings, in general, are the least expensive type of bearing. They are also compact and lightweight, and they have a high load-carrying capacity.
Plain carbon steel – It is steel where the main alloying constituent is carbon. Steel is considered to be plain carbon steel where minimum content is not specified or required for chromium, cobalt, molybdenum, niobium, nickel, tungsten, vanadium, or zirconium, or any other element to be added to get a desired alloying effect or when the specified minimum for copper does not exceed 0.40 % or when the maximum content specified for manganese and silicon does not exceed 1.65 % and 0.60 % respectively. The plain carbon steels are classified based on carbon percentage as (i) ultra low carbon steels which contain very low carbon normally less than 0.005 %, (ii) low carbon steels which contain carbon from 0.005 % up to 0.1 %, (iii) mild steels which contain carbon from 0.1 % up to around 0.3 %, medium carbon steels which contain carbon from 0.35 % to 0.6 %, (iv) high carbon steels which contain carbon from 0.61 % to 1 %, and (v) ultra high carbon steels which contain carbon from 1 % to 1.2 %. Ultra high carbon steels are made by powder metallurgy technique.
Plain journal bearing – It is a plain bearing in which the relatively sliding surfaces are cylindrical and in which there is relative angular motion. One surface is normally stationary and the force acts perpendicularly to the axis of rotation.
Plain thrust bearing – It is a plain bearing of the axial-load type, with or without grooves.
Plain weave – It is a weaving pattern in which the warp and fill fibres alternate, i.e., the repeat pattern is warp / fill / warp / fill, and so on. Both faces of a plain weave are identical. Properties are considerably reduced relative to a weaving pattern with fewer crossovers.
Plan – It consists of a list of steps with details of timing and resources, used to achieve an objective to do something. It is normally understood as a set of intended actions through which one expects to achieve a goal. Plans can be formal or informal. Structured and formal plans, used by multiple people, are more likely to occur in projects, or organizations, or in the conduct of an activity. In most cases, the absence of a well-laid plan can have adverse effects. Informal or ad hoc plans are created by people in all of their pursuits. Plan is also a graphical depiction of characteristics on or under the earth’s surface as portrayed in a horizontal position. Plan is also the overall design of a building. In addition to the design, it offers notes with detailed specifications regarding important components to the plan such as materials which are to be used, area calculations, and more.
Planar – It is a microstructure-related defect. Planar consists of stacking faults, solid–vapour interface, grain and phase boundaries. Because of this defective structure, there is inability of steel to achieve a desired microstructure and hence required microstructure related property during thermo mechanical processing. Planar also means lying essentially in a single plane.
Planar anisotropy – It is a variation in physical and / or mechanical properties with respect to direction within the plane of material in sheet form.
Planar graph – In network theory, it is a set of nodes and interconnecting lines which can be given in one plane without crossing lines.
Planar helix winding -It is a winding in which the filament path on each dome lies on a plane which intersects the dome, while a helical path over the cylindrical section is connected to the dome paths.
Planar magnetron – It is a device which used in the sputtering of thin films, in which a magnet system on the back of the cathode deflects the electrons, lengthening the ionization path. The accelerated ions transfer their momentum to particles of the coating material, which are then deposited on the substrate.
Planar winding – It is a winding in which the filament path lies on a plane which intersects the winding surface.
Planck’s constant (h) – It is a fundamental physical constant, the elementary quantum of action, the ratio of the energy of a photon to its frequency. It is equal to 6.62620 +/- 0.00005 × 10 to the power -34 Joule-seconds or joules per hertz.
Plane grating -It is an optical component which is used to disperse light into its component wave-lengths by diffraction off a series of finely spaced, equidistant ridges. A plane grating has a flat substrate.
Plane of projection – It is an imaginary flat plane upon which the image is projected.
Planers – They are machine tools which develop the cutting action from the straight-line reciprocating motion between the tool and the work-piece. On a planer, the work is reciprocated longitudinally while the tools are fed sideways into the work. The feed in planing is intermittent and represents width of cut. Planer tables are reciprocated by either mechanical or hydraulic drives. Majority of the planers, however, are mechanically driven by such means as variable-voltage, constant-torque drives.
Plane strain – It is the condition in which one of the principal strains is zero. It is the stress condition in linear elastic fracture mechanics in which there is zero strain in direction normal to both the axis of applied tensile stress and the direction of crack growth (i.e., parallel to the crack front)’ It is most nearly achieved in loading thick plates along a direction parallel to the plate surface. Under plane-strain conditions, the plane of fracture instability is normal to the axis of the principal tensile stress.
Plane-strain deformation – It is the deformation because of a two-dimensional strain state. All components of the strain tensor lie in a common plane. Stress-strain constitutive equations then predict a three-dimensional state of stress. The term is used in linear elastic fracture mechanics to indicate a lower value of fracture toughness than plane-stress fracture toughness and a fracture which is macroscale brittle.
Plane-strain fracture toughness (KIc) – It is the crack extension resistance under conditions of crack-tip plane strain. Fracture toughness measured for opening mode loading conditions in which plane-strain conditions exist. Determination of plane-strain fracture toughness is defined as per standards. It is a minimum value of toughness and often identified as KIc.
Plane-strain loading – It is a condition of plastic flow in which there is no normal strain in some direction. In analytical mechanics, it is a statement that there is no displacement in some direction, for example, in the ‘z’ direction, and that displacements in other directions do not depend on ‘z’.
Plane stress – It is the condition in which one of the principal stresses is zero. It is the stress condition in linear elastic fracture mechanics in which the stress in the thickness direction is zero. It is most nearly achieved in loading very thin sheet along a direction parallel to the surface of the sheet. Under plane-stress conditions, the plane of fracture instability is inclined 45-degree to the axis of the principal tensile stress.
Plane-stress fracture toughness (Kc) – In linear elastic fracture mechanics, it is the value of the crack-extension resistance at the instability condition determined from the tangency between the R-curve and the critical crack-extension force curve of the sample.
Plane-stress loading – It is a loading condition in which all force vectors lie in a common plane. The two-dimensional stress state leads to three-dimensional strain.
Planetary mill roll configuration – In this type of roll configuration, there are a pair of heavy back-up rolls surrounded by a large number of planetary rolls. Each planetary roll gives an almost constant reduction to the feed material as it sweeps out of a circular path between the backup roll and the feed material. As each pair of planetary rolls ceases to have contact with the work piece, another pair of rolls makes contact and repeat the reduction. This configuration is used for giving high reduction in a single pass.
Planimetric method – It is a method of measuring grain size in which the grains within a definite area are counted.
Planing – It is a machining process for removing metal from surfaces in horizontal, vertical, or angular planes. It consists of producing flat surfaces by linear reciprocal motion of work and the table to which it is attached, relative to a stationary single-point cutting tool. Although planing is widely used for producing flat, straight surfaces on large work-pieces, the process can also be used to produce contours and a variety of irregular configurations, such as deep slots in large rotors, helical grooves in large rolls, and internal guide surfaces in large valves. It is frequently possible to produce one or two parts on a planer in less time than is needed merely to set up for machining by an alternative method. Hence, planing is frequently used for machining parts to meet production emergencies.
Planishing – It means producing a smooth finish on metal by a rapid succession of blows delivered by highly polished dies or by a hammer designed for the purpose, or by rolling in a planishing mill.
Planned maintenance – It is that maintenance which is organized and carried out with fore-thought, control, and the use of records to a pre-determined plan.
Planning – It means looking ahead and preparing the organization for the future course of actions which need to be followed. It is a preparatory step and consists of chalking out an activity plan for doing the things in an orderly manner for the achievement of the desired targets and objectives. It is a mental predisposition to think before acting and to act in the light of facts rather than guesses. It is a detailed programme regarding future course of action. It is a systematic activity which determines why an action is needed, what is to done, who has to carry out the action, how it is to be done and when to be done. It bridges the gap between where we are, and where we want to go. It makes possible things to occur which would not otherwise occur. Planning takes into consideration of available and prospective human and physical resources so as to get effective co-ordination, contribution as well as perfect adjustment. It includes formulation of one or more detailed plans to achieve optimum balance of needs or demands with the available resources. Through planning, it is possible to make policies, programmes, procedures, budgeting and other related elements. There are several steps involved in the process of planning. These steps include (i) choosing of goals, (ii) identification of actions, (iii) allocation of responsibilities, (iv) reviewing the performance, and (v) making adjustment in the plan.
Plans – Plans are a set of drawings or two-dimensional diagrams which are used to describe a place or object, or to communicate building or fabrication instructions.
Plant – It consists of a building or group of buildings in which different processes or functions are carried out. It is an industrial facility, frequently a complex consisting of several buildings filled with machinery, where workers manufacture items or operate machines which process input raw material into a product.
Plant and equipment – It consists of tangible long-term assets vital to the operations. It means permanent plant, equipment, machinery, apparatus, articles and things of all kinds to be provided and incorporated in the facilities.
Plant commissioning – It refers to the activities from the point in the project when construction is complete (or equipment is installed) until the equipment is placed into service and handed over to the operational team for continued operation and maintenance.
Plant layout – It refers to the arrangement of physical facilities such as machines, equipment, tools, utilities, furnaces, and control rooms etc. in such a manner so as to have quickest flow of material at the lowest cost and with the least quantity of handling in the production of the product from the receipt of the input materials to the dispatch of the finished products. The word ‘plant’ in the plant layout can refer to a production unit of a plant or a complete plant consisting of several production units. Plant layout refers to arrangement of equipments and facilities or plant design. It is a blue print of internal structure and arrangement in a plant. It is a plan for proper and effective utilization of equipments and facilities for the production of the products. It provides smooth flow of materials, and facilitates smooth running of the technological processes in the plant.
Plant utilities – These are provided services which are necessary for the efficient operation of the production units. The requirement of utilities is specific to the process and varies depending on the process. Some important plant utilities are water, gases, steam, condensates, fuel oil, air, drains, and flares. Plant utility piping is designed along with product piping. Colours are used to identify different utilities.
Plan view – It is an orthographic projection of a 3-dimensional object from the position of a horizontal plane through the object. In other words, a plan is a section viewed from the top. In such views, the portion of the object above the plane is omitted to reveal what lies beyond. Basically, a plan view is just another name for the top view of a 3D object.
Plasma – It is one of four fundamental states of matter (the other three being solid, liquid, and gas) characterized by the presence of a considerable portion of charged particles in any combination of ions or electrons. It is the most abundant form of ordinary matter in the universe Plasma can be artificially generated, for example, by heating a neutral gas or subjecting it to a strong electromagnetic field. The presence of charged particles makes plasma electrically conductive, with the dynamics of individual particles and macroscopic plasma motion governed by collective electromagnetic fields and very sensitive to externally applied fields. The response of plasma to electromagnetic fields is used in several modern devices and technologies. Depending on temperature and density, a certain number of neutral particles can also be present, in which case plasma is called partially ionized. Neon signs and lightning are examples of partially ionized plasmas. Unlike the phase transitions between the other three states of matter, the transition to plasma is not well defined and is a matter of interpretation and context. Whether a given degree of ionization suffices to call a substance ‘plasma’ depends on the specific phenomenon being considered.
Plasma arc cutting – It is an arc cutting process which severs metals by melting a localized area with heat from a constricted arc and removing the molten metal with a high-velocity jet of hot, ionized gas issuing from the plasma torch.
Plasma arc welding (PAW) – It is an arc welding process which produces coalescence of metals by heating them with a constricted arc between an electrode and the work-piece (transferred arc) or the electrode and the constricting nozzle (non-transferred arc). Shielding is got from hot, ionized gas issuing from an orifice surrounding the electrode and can be supplemented by an auxiliary source of shielding gas, which can be an inert gas or a mixture of gases. Pressure may or may not be used, and filler metal may or may not be supplied.
Plasma-assisted chemical vapour deposition – It is also known as plasma-enhanced chemical vapour deposition. It is a chemical vapour deposition process which uses low-pressure glow-discharge plasmas to promote the chemical deposition reactions. It is also called plasma-enhanced chemical vapour deposition. It is an important technique used for depositing films of a wide variety of crystalline and non-crystalline materials. Examples of films which are normally deposited using this process are non-crystalline materials such as oxides, nitrides, and oxy-nitrides of silicon, and crystalline materials such as poly-crystalline silicon, epitaxial silicon, and refractory metals and their silicides. All of these materials are extensively used in micro-electronic device fabrication, and plasma-assisted chemical vapour deposition is a critical process step in the fabrication of modern silicon devices. Plasma-assisted chemical vapour deposition is also used in depositing optical coatings and other crystalline compounds such as titanium nitride, which is used in highly wear-resistant coatings on cutting tools. Thermally driven atmospheric-pressure and low-pressure chemical vapour deposition (APCVD and LPCVD respectively) are well understood and established methods for depositing films in integrated circuit (IC) fabrication technology. in a thermally driven chemical vapour deposition process can be quite high (e.g., 700 deg C to 900 deg C, for low pressure chemical vapour deposition silicon nitride deposition) and hence are detrimental to modern silicon devices. Plasma enhancement of the chemical vapour deposition process makes it possible to lower the deposition temperature considerably (e.g., to 250 deg C to 300 deg C for plasma assisted chemical vapour deposition of silicon nitride) while maintaining a reasonable rate of deposition and film quality. Hence, some of the advantages of plasma assisted chemical vapour deposition are (i) films can be deposited on substrates which are be unstable at higher temperatures (e.g., intermetallic dielectric layers deposited on aluminum or the encapsulation of integrated circuits), (ii) lower-temperature film deposition in microelectronic circuits allows precise control of dopant migration. The dimensions of modern microelectronic devices are getting smaller, increasing the importance of this control.
Plasma-assisted physical vapour deposition – It is an advanced thin-film coating technique which combines the principles of physical vapour deposition with plasma activation. This method improves the deposition process by using plasma to ionize and excite the vapourized material, improving adhesion, uniformity, and film quality. Plasma-assisted physical vapour deposition is widely used in industries needing high-performance coatings, such as aerospace, automotive, and electronics, because of its ability to produce durable, corrosion-resistant, and temperature-tolerant films at relatively low temperatures. The process uses a plasma discharge as the source of ions for a sputter process, or the sputter process is driven by ions from an ion source. In both cases the ions are accelerated to a solid target, which is the source of the material to be deposited, the film-forming material.
Plasma carburizing – It is a method of surface hardening in which carbon ions are diffused into a work-piece in a vacuum through the use of high-voltage electrical energy. It is synonymous with ion carburizing or glow discharge carburizing.
Plasma emission monitor (PEM) – It uses the optical emission spectra from the target material to produce a feedback signal to control the reactive gas flow and more directly monitor the conditions at the target surface. The optical emission spectra from the plasma near the target is collected using a collimator connected to a quartz fibre. This signal is fed into a mono-chromator which is linked to a Photo-multiplier. The photo-multiplier outputs an amplified electrical signal to a control unit where the incoming signal level is compared to a preset ‘optimum’ signal level. A control signal is then sent from the control unit to a piezo-electric gas-control valve which is opened or closed in response to a change in the spectral signal. Typically, the optimum reactive gas level is set as some fraction of the spectral peak height of the metallic species. The spectral peak height of pure metal is to be measured for each run just prior to the introduction of the reactive gas, and a thin metallic layer can be deposited before the reactive process attains stoichiometry. In some applications this thin metallic underlayer can create a problem. However, this difficulty can be overcome. The primary advantage of the plasma emission monitor technique is that neither a mass spectrometer nor differential pumping of the sensor is needed, so it is less expensive. This and several similar systems are now commercially available.
Plasma furnaces – Plasma is a partially ionized (up to 50 %) gas which contains electrons, ions, energized molecules, dissociated molecules, neutral molecules, and atoms. The plasma operates at atmospheric pressure and is sufficiently conducting to permit stable transfer of electric power between two or more electrodes. The principal difference between plasma furnaces and arc furnaces is the use of a plasma torch instead of electrodes. In a plasma torch thermionic electrons are emitted from a cathode and accelerated towards the anode. They collide with gas molecules and ionize them. The positively charged gas ions are accelerated in the opposite direction towards the cathode with which they collide, releasing their energy and hence sustaining the thermionic emission. Depending on the type of torch and its construction materials, water cooling can be applied. Several types of alternating current and direct current torches are available. They include transferred arc, non-transferred arc, and superimposed arc. Furnace construction is similar to that of arc resistance and arc furnaces. Refractories and other components are selected to suite the specific application. Plasma furnaces are recent addition into primary and secondary metallurgy.
Plasma ion deposition – It is an ion implantation technique in which ion beams are used to create coatings having special phases, especially ion beam formed carbon coatings in the diamond phase or ion beam formed boron nitride coatings.
Plasma-jet excitation – It is the use of a high-temperature plasma jet to excite an element in a sample, e.g., atomic emission spectroscopy. It is also known as direct current plasma excitation.
Plasma-metal inert gas (MIG) welding – Plasma-metal inert gas welding can be defined as a combination of plasma arc welding (PAW) and gas-metal arc welding (GMAW) within a single torch, where a filler wire is fed through the plasma nozzle orifice. The process can be used for both welding and surfacing. Separate power supplies are used for the plasma arc welding and the gas-metal arc welding elements of the equipment. An arc is struck between the tungsten electrode and the work piece in a similar fashion to that of a PAW system. The filler wire can be fed to the plasma arc, either with or without the gas-metal arc welding arc established. Without power supplied to the filler wire, the system can be operated as a plasma arc welding system with concentric feed of filler wire. Later versions of the system incorporated an annular electrode to replace the offset tungsten electrode in the welding torch.
Plasma metallizing – It is a non-standard term for plasma spraying.
Plasma nitriding – It is a method of surface hardening in which nitrogen ions are diffused into a work-piece in a vacuum through the use of high-voltage electrical energy. It is synonymous with ion nitriding or glow discharge nitriding.
Plasma (ion) nitro-carburizing – It is a surface-hardening process using glow discharge technology to introduce nitrogen and carbon into the surface of a part. As in gaseous nitriding, parts are typically heated to a temperature below Ac1 temperature on the nitrogen–carbon–steel phase diagram.
Plasma processing – It is a plasma-based material processing technology which aims at modifying the chemical and physical properties of a surface.
Plasma rotating electrode process (PREP) – It is a variant on the rotating electrode process (REP). In it, instead of a tungsten electrode, a plasma arc is used to melt the superalloy electrode surface.
Plasma source ion‐implantation (PSII) – It is an ion‐implantation technique which has been optimized for surface modification of materials such as metals, plastics, and ceramics. It departs radically from conventional implantation technology by circumventing the line‐of‐sight restriction inherent in conventional ion implantation. In this technique, targets to be implanted are placed directly in a plasma source and then pulse biased to a high negative potential. A plasma sheath forms around the target and ions bombard the entire target simultaneously. The technique (i) efficiently implants ions to concentrations and depths needed for surface modification, (ii) produces material with improved microhardness and wear properties, and (iii) dramatically improves the life of manufacturing tools in actual industrial applications.
Plasma spray coating – It is a thermal spraying process in which the coating material is melted with the heat of a plasma torch, and the molten melt droplets are propelled against a substrate by the hot, ionized gas of the torch.
Plasma spraying – It is a thermal spraying process in which a non-transferred arc of a plasma torch is utilized to create a gas plasma which acts as the source of heat for melting and propelling the surfacing material to the substrate.
Plasma surface engineering of plastics – Cold gas plasma technology is a preferred industrial process for several applications needing surface chemical modification. Plasma surface treatment, which is conducted in a vacuum environment, affords a wide latitude of possibilities in chemically changing the surface of a plastic to suit a particular application. Three mechanisms which contribute to improvement in the adhesion of two components and the adhesion of coatings are (i) removal of surface contaminants and weakly bound polymer layers. (ii) improvement of wettability through incorporation of polar groups which facilitate spontaneous spreading of adhesive or matrix resin, and (iii) formation of functional groups on the surface which permit covalent bonding. When specialized surface characteristics are needed, coatings with unique chemical and physical characteristics can be deposited by plasma polymerization. Examples include anti-scratch or anti-fog coatings, lubricious coatings, bio-compatible coatings, and chemical and vapour barrier coatings. Since plasma treatment is a process of surface modification, the bulk properties of the material are retained. The nature of the process also allows precise control of the process parameters and ensures repeatability of the process in industrial applications. Also, these surface modifications can be achieved with minimal impact on the environment.
Plasma transferred arc welding – It is a surface welding method, which enables a metallurgical bonding with the base material. It is versatile since it can be used on majority of the alloys. The high-energy plasma transferred arc melts the surface of the base material.
Plasmon – It is a quantum of a collective longitudinal wave in the electron gas of a solid.
Plaster moulding – It is moulding in which a gypsum-bonded aggregate flour in the form of a water slurry is poured over a pattern, permitted to harden, and, after removal of the pattern, thoroughly dried. This technique is used to make smooth non-ferrous castings of accurate size.
Plaster mould casting – Plaster mould casting is a specialized casting process used to produce non-ferrous castings which have high dimensional accuracy, smoother surfaces, and more finely reproduced detail than can be achieved in sand moulds or coated permanent moulds. The four normally recognized plaster mould processes are (i) conventional plaster mould casting, (ii) match plate pattern plaster mould casting, (iii) the Antioch process, and (iv) the foamed plaster process.
Plaster of Paris – It is a fine white powder, which, when mixed with water gets a clay-like consistency and can be shaped around the pattern. The plaster cast can be finished to yield very good surface finish and dimensional accuracy. However, it is relatively soft and not strong enough at temperature above 1,200 deg C, so this method is mainly used to make castings from non-ferrous metals such as zinc, copper, aluminum, and magnesium.
Plastic – It is a material which contains as an essential ingredient an organic polymer of large molecular weight. Plastic is solid in its finished state, and, at some stage in its manufacture or its processing into finished articles, can be shaped by flow. Although materials such as rubber, textiles, adhesives, and paint can also in some cases meet this definition, they are not considered plastics. The terms plastic, resin, and polymer are somewhat synonymous, but the terms resins and polymers very frequently denote the basic material as polymerized, while the term plastic encompasses compounds containing plasticizers, stabilizers, fillers, and other additives.
Plastic deformation – It is the permanent (inelastic) distortion of materials under applied stresses which strain the material beyond its elastic limit. Plastic deformation is observed in most materials, particularly metals and alloys, soils, rocks, concrete, and foams. However, the physical mechanisms which cause plastic deformation can vary widely. At a crystalline scale, plasticity in metals is normally a consequence of dislocations. Such defects are relatively rare in majority of the crystalline materials, but are many in some and part of their crystal structure. In such cases, plastic crystallinity can result. In brittle materials such as rock, and concrete, plasticity is caused predominantly by slip at microcracks. In cellular materials such as liquid foams, plasticity is mainly a result of bubble rearrangements. For several ductile metals, tensile loading applied to a sample causes it to behave in an elastic manner. Each increment of load is accompanied by a proportional increment in extension. When the load is removed, the piece returns to its original size. However, once the load exceeds a threshold, the yield strength, the extension increases more rapidly than in the elastic region, and now when the load is removed, some degree of extension remains.
Plastic fireclay refractory – It is a fireclay refractory material tempered with water and suitable for ramming into place to form a monolithic furnace lining which attains satisfactory physical properties when subjected to the heat of furnace operation.
Plastic flow – It is the phenomenon which takes place when metals are stretched or compressed permanently without rupture.
Plastic hinge – It is the deformation of a section of a beam where plastic bending occurs. In earthquake engineering plastic hinge is also a type of energy damping device allowing plastic rotation (deformation) of an otherwise rigid column connection.
Plastic instability – It is the stage of deformation in a tensile test where the plastic flow becomes nonuniform and necking begins.
Plasticity – It is the property of a material which allows it to be repeatedly deformed without rupture when acted upon by a force sufficient to cause deformation and which allows it to retain its shape after the applied force has been removed. Plasticity is the ability of a solid material to undergo permanent deformation, a non-reversible change of shape in response to applied forces. For example, a solid piece of metal being bent or pounded into a new shape displays plasticity as permanent changes occur within the material itself. In engineering, the transition from elastic behaviour to plastic behaviour is known as yielding.
Plasticity, coal – It refers to the melting and bonding behaviour of the coal. It is the ability for coal to soften and become plastic when heated, and then to re-solidify into a coke. It is an indication of the initial softening, chemical reaction, gas liberation, and re-solidification process within the coke oven. It is an important requirement in the coal blend and is required for the strength of the end product coke. The fluidity of the plastic stage is a major factor in determining what proportions of a coal is used in a blend.
Plasticizer – It is a substance that is added to a material to make it softer and more flexible, to increase its plasticity, to decrease its viscosity, and / or to decrease friction during its handling in manufacture. Plasticizers are also frequently added to concrete formulations to make them more workable and fluid for pouring, hence allowing the water contents to be reduced.
Plastic lubricants – These lubricants are semi-liquids such as grease.
Plastic memory – It is the tendency of a thermoplastic material which has been stretched while hot to return to its unstretched shape upon being reheated.
Plastic or bond fireclay – It is a fireclay of sufficient natural plasticity to bond non-plastic materials.
Plastic pipes – Plastic pipe is widely used for its light weight, chemical resistance, non-corrosive properties, and ease of making connections. Different type of plastic materials can be used for plastic pipes.
Plastic refractory material – It is a refractory material, tempered with water, which can be extruded and which has suitable workability to be pounded into place to form a monolithic structure’
Plastic refractory – It is the unshaped refractory, supplied ready for use, with a high workability, made up of aggregate, bond and liquid, and which hardens after placing by the action of heat. As per the type of product, the main bond can be ceramic, chemical, or organic. Plastic refractory materials are normally supplied in soft, pre-formed blocks or slices and placed by ramming (mechanical or manual).
Plastic replica – In fractography and metallography, a reproduction in plastic of the surface to be studied. It is prepared by evaporation of the solvent from a solution of plastic, polymerization of a monomer, or solidification of a plastic on the surface.
Plastic strain – It consists of dimensional change which does not disappear when the initiating stress is removed. It is normally accompanied by some elastic deformation.
Plastic-strain ratio (r-value) – In formability testing of metals, it is the ratio of the true width strain to the true thickness strain in a sheet tensile test, r = Ew.Et. A formability parameter which relates to drawing, it is also known as the anisotropy factor. A high r-value indicates a material with good drawing properties.
Plastic-zone adjustment, rY – It is an addition to the physical crack size to account for plastic crack-tip deformation enclosed by a linear elastic stress field.
Plastisol – It is a suspension of a finely divided resin in a plasticizer which can be converted to a continuous film by the application of heat. Distinct from baking enamels etc. in that substantially all the original mixture becomes a part of the film; there is no significant evaporation of solvent. The films are normally much thicker than obtainable from coatings that depend on the evaporation of a volatile solvent.
Plastisol coating – It is the polyvinyl chloride (PVC) covering on materials. On roller tubes on a conveying system, it is done to prevent product damage or marking. It is normally green, blue, or red in colour.
Plasto-hydrodynamic lubrication – It is a condition of lubrication in which the friction and film thickness between two bodies in relative motion are determined by plastic deformation of the bodies in combination with the viscous properties of the lubricant at the prevailing pressure, temperature, and rate of shear.
Plate – Plate is a structural element which is characterized by a three-dimensional solid whose thickness is very small when compared with other dimensions. It is a flat-rolled metal product of some minimum thickness and width arbitrarily dependent on the type of metal. Plate thicknesses commonly range from 6 millimeters to 300 millimeters and widths from 200 millimeters to 2,000 millimeters.
Plate, alclad – it is the composite plate composed of an aluminum alloy core having on both surfaces (if on one side only, alclad one-side plate) a metallurgically bonded aluminum or aluminum alloy coating that is anodic to the core, hence electrolytically protecting the core against corrosion.
Plate circle – It is a circle cut from plate.
Platelets – These are also known as plates. These are flat particles of metal powder having considerable thickness. The thickness, however, is smaller when compared to the length and width of the particles.
Platelet shaped inclusions – These are manganese sulphides and oxy-sulphides inclusions in form of thin films (platelets) located along the steel grain boundaries. These inclusions are formed because of deoxidation of steels by aluminum. Such inclusions are formed as a result of eutectic transformation during solidification. Platelet shaped inclusions are not desirable. They considerably weaken the grain boundaries and cause adverse effects on the mechanical properties particularly in hot condition (hot shortness).
Plate martensite – It is the martensite formed partly in steel containing more than around 0.5 % carbon and solely in steel containing more than around 1 % carbon which appears as lenticular-shape plates (crystals).
Platen – It is the mounting plates of a press, to which the entire mould assembly is bolted. It is the sliding member, slide, or ram of a metal forming press. It is a part of a resistance welding, mechanical testing, or other machine with a flat surface to which dies, fixtures, back-ups, or electrode holders are attached and which transmits pressure or force.
Plate tectonics – It is a geological theory which postulates that the earth’s crust is made up of a number of rigid plates which collide, rub up against and spread out from one another.
Plating – It is forming an adherent layer of metal on an object. It is frequently used as a shop term for electroplating.
Plating cracks – Plating cracks are surface discontinuities which can develop due to the penetration of hydrogen or hot plating material into the base metal. Also, some plating materials (such as chromium, copper, or nickel) produce residual tensile stress which can reduce the fatigue strength of a component.
Plating rack – It is a fixture used to hold work and conduct current to it during electro-plating.
Platinum – It is a chemical element, having symbol ‘Pt’ and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. It is a member of the platinum group of elements and group 10 of the periodic table of elements. It has six naturally occurring isotopes. It is one of the rarer elements in earth’s crust. Platinum is one of the least reactive metals. It has remarkable resistance to corrosion, even at high temperatures, and is hence considered a noble metal.
Platinum-group metals (PGMs) – These are six noble, precious metallic elements clustered together in the periodic table. These elements are all transition metals in the d-block. The six platinum-group metals are ruthenium, rhodium, palladium, osmium, iridium, and platinum. They have similar physical and chemical properties, and tend to occur together in the same mineral deposits.
Plenum cable – It is a fire-resistant data communications cable which is permitted to be installed in the air handling spaces of a modern building.
Plenum chamber – In case of plasma arc welding and cutting, and plasma spraying, it is the space between the inside wall of the constricting nozzle and the electrode.
Plied yarn – It is the yarn made by collecting two or more single yarns. Normally, the yarns are twisted together, though sometimes they are collected without twist.
Plow – It is also spelled as plough. It is a mechanism strategically positioned across the conveyor path at the appropriate angle to discharge or divert objects.
Plowing (ploughing) – in tribology, It is the formation of grooves by plastic deformation of the softer of two surfaces in relative motion. The contribution of plowing to frictional resistance is to be distinguished from the contribution of shearing, especially in the classical hemisphere-on-flat model system. In plowing, local solid-phase welding is ignored.
Ploughing component of friction – It originates from the deformation force acting during the ploughing of the softest material in contact by the surface asperities of the harder material and is related to the surface topography. Also, deformation hardened wear particles attached in the interface act in a ploughing way. One additional part to the ploughing component is the asperity deformation which is related to the deformation of the asperities on micro level.
Plug – It is a rod or mandrel over which a pierced tube is forced. It is a rod or mandrel which fills a tube as it is drawn through a die. It is a punch or mandrel over which a cup is drawn. It is a protruding portion of a die impression for forming a corresponding recess in the forging. It is a false bottom in a die. In geology, plug is a common name for a small offshoot from a large body of molten rock. In case of valve, plug is the rotating closure element of a plug valve. It is also, a threaded fitting used to close off and seal an opening into a pressure-containing chamber, e.g., pipe plug.
Plug, eccentric – It is a style of rotary control valve with an eccentrically-rotating plug which cams into and out of the seat, which reduces friction and wear. This style of valve is well suited for erosive applications.
Plugged chute switch – It is a safety device which is integrated into a conveyor system to identify and address material blockages in chutes, necessitating routine inspections for proper functionality and system safety.
Plug rolling process – This rolling process is used for rolling seamless pipes in the diameter range from around 60 millimeters to 406 millimeters with wall thicknesses from around 3 millimeters to 40 millimeters and pipe lengths ranging between 12 meters and 16 meters. In this mill piercing is done in a cross-roll piercing mill to produce a thin wall hollow shell which is elongated to between 3 times and 4.5 times of its original length, corresponding to a deformation level of 65 % to 75 %. The cross-roll piercing mill has two driven work rolls featuring a biconical pass. The axes of the rolls are parallel to the stock and are inclined to the horizontal by between 6-degree and 12-degree. The gap between the work-rolls is adjusted extensively by a top and bottom guide shoe. These guide shoes contribute to the elongation process by acting as stationary rolls, so enabling production of a thin-walled hollow shell. The stock follows a helical line as it passes through the roll gap, so enabling the piercing mandrel, acting as an internal tool, to displace the material more effectively. Owing to the relatively large angle of roll inclination, and higher rolling speeds, stock exit speed is considerably faster. This is necessary owing to the cycle time of the downstream plug strand. In case of large pipe diameters, there is a second piercing mill (also called an elongator) before the plug stand. Recent heavy-duty plug mills have only one cone piercing unit with work rolls featuring a biconical design. They are each angled at around 30-degree to the hollow stock axis and inclined at around 10-degree to 12-degree to the horizontal. The roll gap is closed by means of two side discs which are also driven. The process of forming the hollow shell into the finished pipe is carried out in the downstream plug stand with around two fold elongation (50 % cross sectional reduction), with normally two rolling passes being applied. In the plug stand are mounted the two cylindrical work rolls which are provided with approximately circular grooves, and also the two separately driven stripper rolls. A plug, which is located at the roll pass centre, is held in position by a mandrel supported by a thrust block located downstream of the rolling stand. The resultant annular gap between the rolls and plug correspond to the finished pipe wall thickness.
Plug tap – It is a tap with chamfer extending from three to five threads.
Plug valves – Plug valves are valves with cylindrical or conically-tapered ‘plugs’ which can be rotated inside the valve body to control flow through the valve. The plugs in plug valves have one or more hollow passage ways going sideways through the plug, so that fluid can flow through the plug when the valve is open. Plug valves are simple and often economical. There are two types of plug valves. One has a port through a cylindrical plug which is perpendicular to the pipe and rotates to allow the fluid to proceed through the valve if in an open configuration. In the closed configuration, the cylinder rotates about its axis so that its port is no longer open to the flow of fluid. An advantage of these types of valves is that they are excellent for quick shut-off. The high friction resulting from the design, however, limits their use for accurate modulating / throttling.
Plug weld – It is a weld made in a circular hole in one member of a joint, fusing which member to another member.
Plumbage – It is a special quality of powdered graphite which is used to coat moulds and, in a mixture of clay, to make crucibles.
Plumbing – It deals with piping in buildings which carry water, gas, and wastes in the industrial buildings. Here, pipes sizes are normally small and are made from materials such as copper, steel, cast iron, and plastic.
Plume – It is a vertical body of one fluid moving through another. Several effects control the motion of the fluid, including momentum (inertia), diffusion and buoyancy (density differences). Pure jets and pure plumes define flows which are driven entirely by momentum and buoyancy effects, respectively. Flows between these two limits are normally described as forced plumes or buoyant jets.
Plunge – It is the vertical angle which a linear geological feature makes with the horizontal plane.
Plunge grinding – It is the grinding wherein the only relative motion of the wheel is radially toward the work.
Plunger – It is the ram or piston which forces molten metal into a die in a die casting machine.
Plunger machines – These are those machines which are having a plunger in continuous contact with molten metal.
Plus-mesh – It is the powder sample retained on a screen of stated size, identified by the retaining mesh number.
Plus-sieve – It is the portion of a sample of a granular substance (such as metal powder) which is retained on a standard sieve of specified number. It is contrast with minus sieve.
Plutonic – It refers to rocks of igneous origin which have come from great depth.
Plutonium (Pu) – It is a heavy, radioactive, man-made metallic element with atomic number 94. There are thirteen known isotopes of plutonium, the most important of which in the nuclear industry is isotope Pu-239 which undergoes fission with slow-moving neutrons.
Ply – It is a layer of material which has been combined with other layers in order to provide strength. The number of layers is indicated by prefixing a number, e.g., 4-ply, indicating material composed of 4 layers. In general, fabrics or felts consisting of one or more layers (laminates, and so on). It also consists of the layers which make up a stack. It also consists of yarn resulting from twisting operations (three-ply yarn, and so on). It is a single layer of prepreg. It is also a single pass in filament winding (two plies forming one layer).
Ply-metal – It is the sheet consisting of bonded layers of dissimilar metals.
P/M – It is the acronym for powder metallurgy.
PMR polyimides – It consists of a novel class of high-temperature-resistant polymers. PMR represents in situ polymerization of monomer reactants.
Pneumatic actuator – It is a device which converts energy typically in the form of compressed air into mechanical motion. Within the industry, pneumatic actuators are recognized by several different names including pneumatic cylinders, air cylinders, and air actuators. Consisting of a piston, cylinder, and valves or ports, a pneumatic actuator can convert energy into linear or rotary mechanical motions. This is dependent on whether the application is using a pneumatic rotary actuator or a linear actuator.
Pneumatic conveying systems – Pneumatic conveying is the process of conveying granular / powdered materials by floating the materials in a gas, mainly air, and then allowing it to flow to the destination through a closed pipe. The operating principle common to all types of pneumatic conveying is that motion is imparted to the material by a fast-moving stream of air. Hence, any pneumatic conveyor consists of an air supply equipment (blower or compressor), pipelines, product storages, air lock feeders and dust filters. Pneumatic conveying system is used for delivery of non-sticky, dry materials via pipelines to various storage or process points which are economically inaccessible by conventional conveyors.
Pneumatic conveyor – It is a conveyor system employing air pressure for material transport, needing regular assessments of pneumatic system integrity, pressure levels, and overall efficiency.
Pneumatic cylinder – It is a constituent of a conveyor system utilizing compressed air for generating linear motion, calling for periodic inspections to check for leaks, pressure levels, and overall cylinder performance. It is also known as air cylinder. It is a mechanical device which uses the power of compressed gas to produce a force in a reciprocating linear motion.
Pneumatic hoists – These are also called air hoists. These are powered by pneumatically driven motors. When equipped with a chain as the lifting mechanism, they are called pneumatic chain hoists. Likewise, when equipped with a wire rope as the lifting medium, they are called pneumatic wire rope hoists. These hoists are frequently used in environments which need electric spark avoidance because of a potentially explosive atmosphere.
Pneumatic press – It is a press which uses air or a gas to deliver the pressure to the upper and lower rams.
Pneumatics – It is an application of fluid power. It is the use of gas or pressurized air in mechanical systems. Pneumatic systems used in industry are commonly powered by compressed air or compressed inert gases. A centrally located and electrically-powered compressor powers cylinders, air motors, pneumatic actuators, and other pneumatic devices. A pneumatic system controlled through manual or automatic solenoid valves is selected when it provides a lower cost, more flexible, or safer alternative to electric motors, and hydraulic actuators. Pneumatics also has applications in construction, mining, and other areas.
Pneumatic system – It is a system which uses compressed air to transmit and control energy. Pneumatic systems are used extensively in different industries. Pneumatic system is a collection of interconnected components using compressed air to do work for automated equipment. This work is produced in the form of linear or rotary motion. The compressed air or pressurized gas is normally filtered and dried to protect the cylinders, actuators, tools and bladders performing the work. Some applications need a lubrication device which adds an oil mist to the closed pressurized system. Majority of the pneumatic systems rely on a constant supply of compressed air to make them work. This is provided by an air compressor. The compressor sucks in air from the atmosphere and stores it in a high-pressure tank called a receiver. This compressed air is then supplied to the system through a series of pipes and valves.
Pnictogen – It consists of a chemical element belonging to Group (V) of the periodic table namely nitrogen, phosphorus, arsenic, antimony, bismuth, and moscovium. These elements are united by their common penta-valency, i.e., in their non-ionized states, atoms of these elements all have exactly five valence electrons in their outermost electron shell, three short of a complete octet.
P-N junction – It is a combination of two types of semiconductor materials, p-type and n-type, in a single crystal. The ‘n’ (negative) side contains freely-moving electrons, while the p (positive) side contains freely-moving electron holes. Connecting the two materials causes creation of a depletion region near the boundary, as the free electrons fill the available holes, which in turn allows electric current to pass through the junction only in one direction. p–n junctions represent the simplest case of a semi-conductor electronic device; a p-n junction by itself, when connected on both sides to a circuit, is a diode. More complex circuit components can be created by further combinations of p-type and n-type semi-conductors, e.g., the bipolar junction transistor (BJT) is a semi-conductor in the form n–p–n or p–n–p. Combinations of such semiconductor devices on a single chip allow for the creation of integrated circuits.
Pocket – In a rolling-element bearing, it is the portion of the case which is shaped to receive the rolling element.
Pocket-thrust bearing – It is an externally pressurized thrust bearing having three or more hydrostatic pads with central relieved chambers of pockets supplied with pressurized oil.
Point – It is a microstructure-related defect. Point consists of vacancies both of interstitial and substitutional atoms. Because of this defective structure, there is inability of steel to achieve a desired microstructure and hence required microstructure related property during thermo mechanical processing.
Point angle – In general, it is the angle at the point of a cutting tool. Normally, it is the included angle at the point of a twist drill, the general-purpose angle being 118-degree.
Point estimate – It is the best single estimated value of a parameter. It is the estimate of a parameter given by a single statistic.
Point estimation – In statistics, it involves the use of sample data to calculate a single value (known as a point estimate since it identifies a point in some parameter space) which is to serve as a ‘best guess’ or ‘best estimate’ of an unknown population parameter (e.g., the population mean). More formally, it is the application of a point estimator to the data to obtain a point estimate.
Point-source pollution – It is the pollution which originates from one, easily identifiable cause or location, such as a sewage treatment plant.
Point to point (P2P) – It describes a circuit which connects two points directly, where there are normally no intermediate processing nodes, although there can be switching facilities.
Point to point protocol (PPP) – It is a data link layer (layer 2) communication protocol between two routers directly without any host or any other networking in between It can provide loop direction, authentication, , transmission encryption,https://en.wikipedia.org/wiki/Point-to-Point_Protocol#cite_note-2 and data compression.
Point to point (P2P) topology – It is a network topology which connects two nodes or devices directly using a dedicated line.
Poise (P) – It is the centimeter-gram-second (cgs) unit of dynamic viscosity.
Poisseuille (Pl) – It is the meter-kilogram-second (mks) or International System of Units (SI) unit of dynamic viscosity. 1 Poisseuille is equal to 10 Poise.
Poiseuille flow – It is the particular case of laminar viscous flow through a long pipe of circular cross section.
Poison – It is a chemical substance which is harmful or lethal to living organisms. The term is used in a wide range of industries, where it is frequently specifically defined. Whether something is considered a poison or not can depend on the quantity, the circumstances, and what living things are resent. Poisoning can be accidental or deliberate, and if the cause can be identified there can be ways to neutralize the effects or minimize the symptoms.
Poisson burr – It is a burr which is formed predominantly by the phenomenon that is responsible for Poisson’s ratio. It is sometimes called a flow-type burr.
Poisson distribution – It is a probability distribution for an integer variable representing an event count. The Poisson distribution is frequently referred to as the distribution of rare events. It is typically used to describe the probability of occurrence of an event over time, space, or length. In general, the Poisson distribution is appropriate when such conditions hold as the probability of ‘success’ in any given trial is relatively small, the number of trials is large, and the trials are independent.
Poisson’s ratio – It is the absolute value of the ratio of transverse (lateral) strain to the corresponding axial strain resulting from uniformly distributed axial stress below the proportional limit of the material.
Poisson regression – It is a type of regression analysis in which the study end point is a count of the number of occurrences of an event which has happened to subjects in some fixed period of time.
Polar boss – In filament winding, it is a metal end fitting located in the center of each dome that describes the pole about which winding bands are wrapped.
Polar winding – It is a winding in which the filament path passes tangent to the polar opening at one end of the chamber and tangent to the opposite side of the polar opening at the other end. A one-circuit pattern is inherent in the system.
Polarity – It is a separation of electric charge leading to a molecule or its chemical groups having an electric dipole moment, with a negatively charged end and a positively charged end. In welding, it consists of direct current electrode negative and direct current electrode positive. In case of direct current electrode negative, it is the arrangement of direct current arc welding leads in which the work is the positive pole and the electrode is the negative pole of the welding arc. It is also referred to as straight polarity. In case of direct current electrode positive, it is the arrangement of direct current arc welding leads in which the work is the negative pole and the electrode is the positive pole of the welding arc.
Polarization – It is the change from the open-circuit electrode potential as the result of the passage of current. It is a change in the potential of an electrode during electrolysis, such that the potential of an anode becomes more noble, and that of a cathode more active, than their respective reversiblepotentials. It is equal to the difference between the static electrode potential and the dynamic electrode potential. It is frequently accomplished by formation of a film on the electrode surface.
Polarization admittance – It is the reciprocal of polarization resistance.
Polarization curve – It is a plot of current density against electrode potential for a specific electrode-electrolyte combination.
Polarization density – It is a measure of the increase of the intensity of an electric field over that in free space, owing to the separation of atomic-scale electric dipoles.
Polarization resistance – It is the slope at the corrosion potential of a potential / current density curve. It is also used to describe the method of measuring corrosion rates using these slopes.
Polarized light – Polarized light, as used in metallography, has normally been limited to observation of certain optically anisotropic metals, such as beryllium, alpha-titanium, zirconium, and uranium, which are difficult to etch but respond well to the polarized light when properly polished. Before development of the electron micro-probe analyzer (EMPA) and energy dispersive spectroscopy (EDS), polarized light examination was an integral part of the method for identifying inclusions. Since the development of these instruments, polarized light has been used less frequently for this purpose, since identification with the electron micro-probe analyzer or energy dispersive spectroscopy techniques is more definitive. Majority of the metallurgical microscopes now use synthetic Polaroid filters. The ‘polarizer’ is placed in the light path before the objective, and the ‘analyzer’ is placed in the light path after the objective, normally just below the eyepiece.
Polarized light microscopy – It consists of a number of optical microscopy techniques involving polarized light. Simple techniques include illumination of the sample with polarized light. Directly transmitted light can, optionally, be blocked with a polarizer oriented at 90-degree to the illumination. More complex microscopy techniques which take advantage of polarized light include differential interference contrast microscopy and interference reflection microscopy. Frequently a device called a polarizing plate is used to convert natural light into polarized light. These illumination techniques are normally used on birefringent samples where the polarized light interacts strongly with the sample and so generating contrast with the background. Polarized light microscopy is used extensively in optical mineralogy.
Polarizing element – It is a general term for a device for producing or analyzing plane-polarized light. It can be a Nicol prism, some other form of calcite prism, a reflecting surface, or a polarizing filter.
Polar moment of inertia – It is the moment of inertia where the distance is measured from an axis perpendicular to the plane of the area.
Polarography – It is an electro-analytical technique in which the current between a dropping mercury electrode (DME) and a counter-electrode (both of which are immersed in electrolyte) is measured as a function of the potential difference between the dropping mercury electrode and a reference electrode.
Pole – It is a means of designating the orientation of a crystal plane by stereographically plotting its normal. For example, the north pole defines the equatorial plane. It is either of the two regions of a permanent magnet or electro-magnet where most of the lines of induction enter or leave.
Pole figure – It is a stereoscopic projection of a poly-crystalline aggregate showing the distribution of poles, or plane normal, of a specific crystalline plane, using sample axes as reference axes. Pole figures are used to characterize preferred orientation in poly-crystalline materials.
Policy – It is a governing principle, plan, or consistent course of action developed in order to meet recognized needs and to achieve specific measurable outcomes. Policies are normally broad, conceptual documents which outline approaches and / or considerations to be taken into account by decision makers. Policies do not act as constraints, but provide information. Policy is also a statement of intent which is not legally binding. It sets direction and expectations for activities.
Policy analysis – It is the comparison of the viability and effects of an existing or proposed set of operating rules to the impact of some other option.
Policy development – It is the process of shaping policy, from issue recognition and analysis to implementation and evaluation. Organizational management role is to undertake the necessary steps to develop policy options as well as to decide policy.
Policy instruments – These are the means and tools available to achieve policy goals, including both regulatory and non-regulatory tools.
Polished surface – It is a surface which is prepared for metallographic inspection that reflects a large proportion of the incident light in a specular manner.
Polishing – It is the smoothing of metal surfaces, frequently to a high lustre, by rubbing the surface with a fine abrasive, normally contained in a cloth or other soft lap. It is the results in microscopic flow of some surface metal together with actual removal of a small quantity of surface metal. It is the removal of material by the action of abrasive grains carried to the work by a flexible support, normally either a wheel or a coated abrasive belt. It is also a mechanical, chemical, or electrolytic process or combination thereof used to prepare a smooth, reflective surface suitable for microstructural examination that is free of artifacts or damage introduced during prior sectioning or grinding.
Polishing pond – It is the last in a series of settling ponds through which plant effluent flows before being discharged into the natural environment.
Polishing wear – It is an extremely mild form of wear for which the mechanism has not been clearly identified, but that can involve extremely fine-scale abrasion, plastic smearing of micro-asperities, and / or tribo-chemical material removal.
Pollutant – It is a contaminant in a concentration or quantity which adversely alters the physical, chemical, or biological properties of the natural environment.
Pollutant load – It is the quantity of pollutant entering an environment. Loads are normally expressed in terms of a weight and a time frame, such as kilograms per day.
Pollution – It is the introduction of harmful materials into the environment. These harmful materials are called pollutants. Pollutants can be natural, such as volcanic ash. They can also be created by human activity, such as trash or runoff produced by industrial activities. Pollutants damage the quality of air, water, and land.
Pollution abatement – It consists of the technology applied or measure taken to reduce pollution and / or its impacts on the environment. The normally used technologies are scrubbers, noise mufflers, filters, incinerators, waste-water treatment facilities and composting of wastes.
Pollution control – It refers to the scientific methods and techniques which are used to manage and reduce pollution in the environment, aiming to protect human health and eco-systems.
Pollution prevention – It means working at the source of pollutants to prevent them from being generated or to reduce the amount generated.
Polyacrylates – These are synthetic resins produced by the polymerization of acrylic esters. Forming plastic materials of notable clarity and flexibility under certain methods, the polyacrylates are used mainly in paints and other surface coatings, in adhesives, and in textiles. The most common poly-acrylates are poly-ethyl acrylate and poly-methyl acrylate.
Polyalkylene glycol – It consists of a range of ethylene oxide and propylene oxide derivatives built off different initiators, giving a product family with a wide range of solubility and viscosity properties. Poly-alkylene glycol is versatile polymers which are widely used across a range of industries.
Polyacrylo-nitrile (PAN) – It is a synthetic, semi-crystalline organic polymer resin, with the linear formula (CH2CHCN)n. Almost all poly-acrylo-nitrile resins are copolymers with acrylonitrile as the main monomer. Poly-acrylo-nitrile is used to produce large variety of products including ultra filtration membranes, hollow fibres for reverse osmosis, fibres for textiles, and oxidized poly-acrylo-nitrile fibres. Poly-acrylo-nitrile fibres are the chemical precursor of very high-quality carbon fibre. Poly-acrylo-nitrile is first thermally oxidized in air at 230 deg C to form an oxidized poly-acrylo-nitrile fibre and then carbonized above 1,000 deg C in inert atmosphere to make carbon fibres found in a variety of both high-tech and common daily applications
Polyalpha-olefin (PAO) oil – It is a synthetic oil that is produced by alpha-olefin monomers. It is characterized by its high purity, pour-point characteristics. Poly-alpha-olefins are used in lubricants which have to meet the highest requirements, e.g., in applications with large temperature fluctuations.
Polyamide – It is a thermoplastic polymer in which the structural units are linked by amide or thio-amide groupings (repeated nitrogen and hydrogen groupings). Several polyamides are fibre-forming.
Polyamideimide – It is a polymer containing both amide (nylon) and imide (as in polyimide) groups. Its properties combine the benefits and disadvantages of both.
Polyamide plastic – These are plastics which are based on a resin composed principally of a long-chain synthetic polymeric amide which has recurring amide groups as an integral part of the main polymer chain. Numerical designations (nylon 6, nylon 6/6, and so on) refer to the monomeric amides of which they are made. This plastic is characterized by high toughness and elasticity.
Polyamide resins – Polyamide materials can be categorized by their temperature capabilities into those with an upper limit of 230 deg C for extended time periods, and those capable of extended use up to 315 deg C. Bismaleimides, phenyl-ethynyl-containing polyimides, and some condensation polyimides such as Avimid-K3 belong in the former category, while those materials such as PMR-15, LARC-TPI, Avimid-N and BPDA/TFMB belong in the latter. In terms of chemistry, there are two general types of commercial polyimides namely thermoplastic polyimides, derived from a condensation reaction between anhydrides or anhydride derivatives and diamines, and cross-linked polyimides, derived from an addition reaction between unsaturated groups of a preformed imide monomer or oligomer. The imide monomers or oligomers are also derived from the typical condensation reaction to form the imide group, but polymer formation stems from the addition reaction.
Polyarylsulfone (PAS) – It is a high-temperature-resistant thermoplastic with ‘Tg’ (glass transition temperature) values ranging from 190 reg to 275 deg C. The term is also occasionally used to describe the family of resins which includes polysulfone and polyethersulfone.
Polyatomic – It is composed of two or more atoms, of the same or different elements.
Polyatomic ion – It is a molecule which is composed of two or more covalently bonded atoms which collectively bear a net electric charge and therefore act as an ion.
Polybenzimidazole (PBI) – It is a condensation polymer of diphenyl isophthalate and 3,3’- diaminobenzidine. It is extremely high-temperature resistant. It is available as adhesive and fibre.
Polybutylene terephthalate (PBT) – It is a thermoplastic engineering polymer which is used as an insulator in the electrical and electronics industries. It is a thermoplastic (semi-)crystalline polymer, and a type of polyester. Poly-butylene terephthalate resists solvents, shrinks very little during forming, is mechanically strong, is heat-resistant up to 150 C (or 200 deg C with glass-fibre reinforcement), and can be treated with flame retardants to make it non-combustible. Poly-butylene terephthalate is closely related to other thermoplastic polyesters. Compared to polyethylene terephthalate (PET), poly-butylene terephthalate has slightly lower strength and rigidity, slightly better impact resistance, and a slightly lower glass transition temperature.
Polycarbonate (PC) – It is a thermoplastic polymer which is derived from the direct reaction between aromatic and aliphatic dihydroxy compounds with phosgene, or by the ester exchange reaction with appropriate phosgene-derived precursors. It has highest impact resistance of any transparent plastic.
Polychlorinated bi-phenyls (PCBs) – These are organochlorine compounds with the formula C12H(10-x)Clx. They have been once widely used in the manufacture of carbonless copy paper, as heat transfer fluids, and as dielectric and coolant fluids for electrical equipment. They are highly toxic and carcinogenic chemical compounds, formerly used in industrial and consumer electronic products, whose production has been banned internationally by the Stockholm Convention on Persistent Organic Pollutants in 2001.
Polychromator – It is an optical device which is used to disperse light into different directions to isolate parts of the spectrum of the light. A prism or diffraction grating can be used to disperse the light. Unlike a mono-chromator, it outputs multiple beams over a range of wave-lengths simultaneously. Mono-chromators have one exit slit and one wave-length at a time can pass through that slit. Poly-chromators have multiple exit slits, each of which allows a different wavelength to pass through it. A detector is placed after each slit so that the light at each wave-length is measured by a different detector. Poly-chromators are frequently used in spectroscopy.
Polycondensation – It is a chemical reaction in which two or more molecules combine, with the separation of water or some other simple substance. If a polymer is formed, the process is called polycondensation.
Polycrystalline – It is pertaining to a solid comprised of many crystals or crystallites, intimately bonded together. It can be homogeneous (one substance) or heterogeneous (two or more crystal types or compositions).
Polycrystalline cast superalloys – These are superalloys which are a group of nickel-iron-nickel-, and cobalt-base materials. These superalloys show outstanding strength and surface stability at temperatures up to 85 % of their melting points (0.85 Tm). They are normally used at temperatures above 540 deg C compositions.
Polycrystalline cubic boron nitride (PcBN) – It is the second hardest material after diamond. It is used as a cutting material from which indexable inserts are manufactured for machining. It is produced synthetically and is a composite material made of cubic boron nitride and a mostly ceramic binder phase. The ratio of cubic boron nitride to binder content and the cubic boron nitride grain size determines the application. Polycrystalline cubic boron nitride cutting materials are used in the machining of hard and / or highly abrasive workpiece materials. The high hardness and the extremely high hot hardness (up to temperatures above 1,000 deg C), the edge stability and inertness towards ferrous materials as well as the basically good chemical resistance give cubic boron nitride cutting materials a high potential for use in machining.
Polycrystalline diamond – It is a composite comprising diamond particles, which are formed by sintering together with a metallic binder.
Polycrystal scattering topography (PST) – It is a new kind of X-ray topography which has been devised to observe polycrystalline, amorphous materials. In this method, X-ray is scattered from a poly-crystal produce a topographical image. Poly-crystal scattering topography enables, in principle, to make tomographic observations.
Polycyclic aromatic hydrocarbons (PAHs) – These are hydrocarbons with two or more benzene rings formed by the incomplete combustion of organic materials such as wood, coal, and refuse. They are found in petroleum products and creosote and include such compounds as naphthalene, anthracene, and benzo-a-pyrene. When carried in water, they can pose a threat to human health and aquatic life.
Polyester resins – These are unsaturated polyester resins. These resins are the group of polyesters in which the acid component part of the ester is partially composed of fumaric acid, a 1,2-ethylenically unsaturated material. Maleic anhydride is the predominant source of this fumarate. Maleic anhydride is incorporated into the polyester backbone and then isomerized to provide fumarate esters (commonly referred to as unsaturated polyesters).
Polyesters – Polyesters are macro-molecules which are prepared by the condensation polymerization of difunctional acids or anhydrides with difunctional alcohols or epoxy resins. Polyesters have high strength, exceptionally good abrasion, and fatigue resistance. They have extremely low moisture absorption and hence have good dimensional stability. They are unaffected by mildew.
Polyesters, thermoplastic – These are a class of thermoplastic polymers in which the repeating units are joined by ester groups. The two important types are (i) polyethylene terephthalate (PET), which is widely used as film, fibre, and soda bottles, and (ii) polybutylene terephthalate (PBT), mainly a moulding compound.
Polyesters, thermosetting – These are a class of resins produced by dissolving unsaturated, normally linear, alkyd resins in a vinyl-type active monomer such as styrene, methyl styrene, or diallyl phthalate. Cure is carried out through vinyl polymerization using peroxide catalysts and promoters or heat to accelerate the reaction. The two important commercial types are (i) liquid resins which are cross linked with styrene and used either as impregnants for glass or carbon-fibre reinforcements in laminates, filament-wound structures, and other built-up constructions, or as binders for chopped-fibre reinforcements in moulding compounds, such as sheet moulding compound (SMC), bulk moulding compound (BMC), and thick moulding compound (TMC), and (ii) liquid or solid resins cross linked with other esters in chopped-fiber and mineral-filled moulding compounds, for example, alkyd and diallyl phthalate.
Polyether ether ketone (PEEK) – It is a special polymer material which is composed of repeated units of one ketone bond and two ether bonds in the backbone of the aromatic ring. It is a semi-crystalline, linear, and aliphatic polymer. It is a colourless organic thermoplastic polymer which is used in engineering applications. It has a high melting point of 334 deg C. A composite with a polyether ether ketone matrix can have a continuous use temperature as high as 250 deg C.
Polyether-imide – It is an amorphous engineering thermoplastic. It has a number of desirable properties including a high heat-distortion temperature. Poly-ether-imide has reported ‘Tg’ of 215 deg C and continuous-use temperature of around 170 deg C. Unlike majority of the amorphous resins, poly-ether-imide is resistant to a wide range of chemicals including most hydrocarbons, alcohols, and fully halogenated solvents. Only partially halogenated hydrocarbons such as methylene chloride and tri-chloro-ethane dissolve polyetherimide, and these compounds are not to be used for cleaning.
Polyimide (PI) – It is a polymer produced by reacting an aromatic dianhydride with an aromatic diamine. It is a highly heat-resistant resin. It is similar to a polyamide, differing only in the number of hydrogen molecules contained in the groupings. It is suitable for use as a binder or adhesive. It can be either thermoplastic or thermoset. Polyimide resins are available with a maximum hot / wet in-service temperature of 232 deg C and above (up to 370 deg C for single use short periods). These resins cure by a condensation reaction which releases volatiles during cure at 315 deg C and higher.
Polyether-ketones – These are polymers whose molecular backbone contain alternating ketone (R-CO-R) and Ether (R-O-R) functionalities. The most common are Poly-aryl-ether-ketones, in which there is an aryl group linked in the (1–4)-position between each of the functional groups. The backbone, which is hence very rigid, gives the materials very high glass transition and melting temperatures compared to other plastics.
Polyether-sulfones (PES) – These are a class of engineered polymers with very high thermal oxidative resistance, hydrolytic stability and excellent strength and flexibility. They are amorphous, transparent thermoplastics which can be moulded, extruded, or thermoformed into a wide variety of shapes. The backbone flexibility of this polymer is provided by ether linkages.
Polyethylene – It is the most produced plastic. It is a polymer, mainly used for packaging. Several kinds of poly-ethylene are known, with most having the chemical formula (C2H4)n. Polyethylene is normally a mixture of similar polymers of ethylene, with various values of ‘n’. It can be low-density or high-density and several variations thereof. Its properties can be modified further by cross-linking or co-polymerization. All forms are non-toxic as well as chemically resilient, contributing to polyethylene’s popularity as a multi-use plastic. However, poly-ethylene’s chemical resilience also makes it a long-lived and decomposition-resistant pollutant when disposed of improperly. Being a hydro-carbon, poly-ethylene is colourless to opaque (without impurities or colorants) and combustible.
Polyethylene terephthalate (PET) – It is the most common thermo-plastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods, and thermoforming for manufacturing, and in combination with glass fibre for engineering resins. In the context of textile applications, poly-ethylene terephthalate is referred to by its common name, polyester, whereas the acronym PET is normally used in relation to packaging. Poly-ethylene terephthalate consists of repeating (C10H8O4) units. Poly-ethylene terephthalate is normally recycled.
Poly-generation systems – These are energy generation or conversion systems with multiple input energy sources and multiple output energy produces.
Polyhedral inclusions – These are inclusions whose morphology of dendrite shaped inclusions has been improved by addition (after deep deoxidation by aluminum) of small quantities of rare earth (cerium, lanthanum) or alkaline earth (calcium, magnesium) elements. Since their shape nearing the globular shape, polyhedral inclusions cause less effect on the steel properties than dendrite shape inclusions.
Polymer – It is a high-molecular-weight organic compound, natural or synthetic, with a structure which can be represented by a repeated small unit, the mer. Examples include polyethylene, rubber, and cellulose. Synthetic polymers are formed by addition or condensation polymerization of monomers. Some polymers are elastomers, some are plastics, and some are fibres. When two or more dissimilar monomers are involved, the product is called a copolymer. The chain lengths of commercial thermo-plastics vary from around 1,000 to higher than 100,000 repeating units. Thermo-setting polymers approach infinity after curing, their resin precursors, frequently called prepolymers, can be relatively short (6 to 100 repeating units) before curing. The lengths of polymer chains, normally measured by molecular weight, have very considerable effects on the performance properties of plastics and profound effects on processibility. Polymers, both natural and synthetic, are created through polymerization of several small molecules, known as monomers. Their consequently large molecular mass, relative to small molecule compounds, produces unique physical properties including toughness, high elasticity, viscoelasticity, and a tendency to form amorphous, and semi-crystalline structures rather than crystals.
Polymer blend -It is a mixture of different types of polymer chains. In miscible blends the polymers mix on a molecular level to produce a single phase, as in the blend of poly-phenylene oxide and poly-styrene. In immiscible blends the polymers cannot mix on a molecular level and separate into two phases, as in blends of acrylonitrile butadiene styrene (ABS) and polystyrene.
Polymer casting – To form a ‘plastic’ object by pouring a fluid monomer-polymer solution into an open mould where it finishes polymerizing. Forming plastic film and sheet by pouring the liquid resin onto a moving belt or by precipitation in a chemical bath.
Polymer conveyor chain – It is a conveyor chain made from polymer materials, delivering advantages such as corrosion resistance and reduced noise. Regular evaluations are essential to monitor wear, tension, and overall chain integrity. Polymer derived ceramics – These are the ceramics which are produced from polymers by pyrolysis.
Polymer infiltration and pyrolysis (PIP) – It is the method of fabrication of ceramic matrix composites comprising an infiltration of a low viscosity polymer into the reinforcing ceramic structure (e.g., fabric) followed by pyrolysis i.e., heating the polymer precursor in the absence of oxygen when it decomposes and converts into a ceramic. The ceramics produced from polymers by pyrolysis are called polymer derived ceramics.
Polymer matrix composite – It is a composite material composed of a variety of short or continuous fibres bound together by a matrix of organic polymers. Polymer matrix composites are designed to transfer loads between fibers of a matrix.
Polymeric membrane process for air separation – The process is based on the membrane separation technology. It makes use of the different rates at which air gases diffuse through a polymer membrane. Membrane processes using polymeric materials are based on the difference in rates of diffusion of oxygen and nitrogen through a membrane which separates high-pressure and low-pressure process streams. Membrane separation technology uses tube bundles made of special polymers, frequently configured in a manner similar to a shell and tube heat exchanger. The air separation principle is that different gases have different permeation rates through the polymer film.
Polymeric process – It means the use, injection or application of a polymeric chemical product.
Polymerization – It is the chemical bonding of two or more individual monomer molecules to form a polymer chain or network, or any reaction which produces such a bonding. It is a chemical reaction in which the molecules of a monomer are linked together to form large molecules whose molecular weight is a multiple of that of the original substance. When two or more monomers are involved, the process is called copolymerization.
Polymer matrix – It is the resin portion of a reinforced or filled plastic.
Polymer processing – It involves creating structures using polymers by changing their viscosity and rheological properties and shaping them.
Polymers – They consists of a high molecular weight organic compound, natural or synthetic, with a structure which can be represented by a repeated small unit, the mer. Synthetic polymers are formed by addition or condensation polymerization of monomers. When two or more dissimilar monomers are involved, the product is called a copolymer. The lengths of polymer chains, usually measured by molecular weight, have very significant effects on the performance properties of plastics and profound effects on processability.
Polymethyl methacrylate (PMMA) – It is a synthetic polymer derived from methyl methacrylate. It is a transparent thermoplastic, used as an engineering plastic. It is also known as acrylic, and acrylic glass. It is frequently used in sheet form as a lightweight or shatter-resistant alternative to glass. It can also be used as a casting resin, in inks and coatings, and for several other purposes. It is frequently technically classified as a type of glass, since it is a non-crystalline vitreous substance.
Polymorph – In crystallography, it is one crystal form of a polymorphic material.
Polymorphism – · In crystallography, it is the property of a chemical substance whereby it crystallizes into two or more forms having different crystallographic structures, such as diamond against graphite or face centred cubic iron against body centred cubic iron. It is a general term for the ability of a solid to exist in more than one form. In metals, alloys, and similar substances, this normally means the ability to exist in two or more crystal structures, or in an amorphous state and at least one crystal structure.
Poly-oxy-methylene – It is an engineering thermo-plastic used in precision parts needing high stiffness, low friction, and excellent dimensional stability.
Poly-phase coil – It is a coil intended for connection to a polyphase power supply.
Poly-phase system – It is an alternating current power transmission system using three or more wires, each of which carries a current that is displaced in time with respect to the others. It is a means of distributing alternating-current electrical power which utilizes more than one alternating current phase, which refers to the phase offset value (in degrees) between alternate current in multiple conducting wires. Phases can also refer to the corresponding terminals and conductors, as in colour codes. Poly-phase systems have two or more energized electrical conductors carrying alternating currents with a defined phase between the voltage waves in each conductor. Early systems used 4 wire two-phase with a 90-degree phase angle, but modern systems almost universally use three-phase voltage, with a phase angle of 120-degree (or 2 pi/3 radians). Poly-phase systems are particularly useful for transmitting power to electric motors which rely on alternating current to rotate. Three-phase power is used for industrial applications and for power transmission. Compared to a single-phase, two-wire system, a three-phase three-wire system transmits three times as much power for the same conductor size and voltage, using only 1.5 times as several conductors, making it twice as efficient in conductor utilization.
Polyphenylene sulphide (PPS) – It is an organic polymer consisting of aromatic rings linked by sulphides. Synthetic fibre and textiles derived from this polymer resist chemical and thermal attack.
Polypropylene (PP) – It is a common thermoplastic polymer with excellent properties, including high gas and water permeability resistance, mechanical properties, flame resistance, high heat distortion temperature and others. Polypropylene is widely used in polymer materials in the plastic manufacturing industry to produce various end products, especially plastic packaging.
Polysulphide – It is a synthetic polymer containing sulphur and carbon linkages, produced from organic dihalides and sodium polysulphide. Material is elastomeric in nature, resistant to light, oil, and solvents, and impermeable to gases.
Polystyrene-di-vinyl benzene resin – It is a porous polymer resin which is used in different applications, including chromatography, catalysis, and adsorption. It is used in majority of ion exchange applications. The resin which has ionic sites consisting of mobile charge of ‘SO-H’ radicals and mobile sodium cations (Na+), removes the cations present in water (hence called cation exchange resins). The resin which has tertiary or quaternary ammonium group as mobile cationic radicals and mobile chloride anions (Cl-), removes the anions including silicic and carbonic acids present in water (hence called anion exchange resins).
Polysulphone – It is a high-temperature-resistant thermoplastic polymer with the sulfone linkage, with a ‘Tg’ of 190 deg C.
Poly-tetra-fluoro-ethylene (PTFE) – It is a synthetic fluoropolymer of tetra-fluoro-ethylene, and has several applications since it is chemically inert. Poly-tetra-fluoro-ethylene is a fluorocarbon solid, as it is a high-molecular-weight polymer consisting wholly of carbon and fluorine. It is hydrophobic i.e., neither water nor water-containing substances wet it, since fluoro-carbons show only small London dispersion forces because of the low electric polarizability of fluorine. It has one of the lowest coefficients of friction of any solid. Poly-tetra-fluoro-ethylene is non-reactive, partly because of the strength of carbon–fluorine bonds, so it is frequently used in containers and pipework for reactive and corrosive chemicals. Where used as a lubricant, poly-tetra-fluoro-ethylene reduces friction, wear, and energy consumption of machinery.
Poly-tier support – It consists of adjustable support structures which are designed to accommodate the load and weight of multi-tiered conveyor systems.
Polyurethane – It is a thermosetting resin prepared by the reaction of diisocyanates with polyols, polyamides, alkyd polymers, and polyether polymers.
Polyvinyl alcohol (PVA) – It is a water-soluble synthetic polymer. It has the idealized formula [CH2CH(OH)]n. It is used as a thickener and emulsion stabilizer in polyvinyl acetate adhesive formulations, in a variety of coatings, and 3D printing. It is colourless (white) and odourless. It is normally supplied as beads or as solutions in water.
Polyvinyl chloride (PVC) – Ithttps://en.wikipedia.org/wiki/Polyvinyl_chloride#cite_note-pvc.org_about-8 is a synthetic polymer of plastic. It comes in rigid (sometimes abbreviated as RPVC) and flexible forms. Rigid poly-vinyl chloride is used in construction for pipes, doors and windows. It is also used in making plastic bottles, packaging, and bank or membership cards. Adding plasticizers makes poly-vinyl chloride softer and more flexible. It is used in plumbing, electrical cable insulation, flooring, inflatable products, and in rubber substitutes. With cotton or linen, it is used in the production of canvas. Poly-vinyl chloride is a white, brittle solid. It is soluble in ketones, chlorinated solvents, di-methyl-formamide, tetra-hydro-furan, and di-methyl-acetamide.
Polyvinyl fluoride (PVF) – Its formula is (CH2CHF)n. It is a thermoplastic fluoro-polymer with a repeating vinyl fluoride unit. It is structurally very similar to polyvinyl chloride. It is a polymer material which is mainly used in the flammability-lowering coatings of airplane interiors and photovoltaic module back-sheets. It is also used in metal sheeting.
Polyvinylidene di-fluoride – It is also called poly-vinylidene fluoride. It is a highly non-reactive thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride. Its chemical formula is (C2H2F2)n. Poly-vinylidene di-fluoride is a specialty plastic which is used in applications needing the highest purity, as well as resistance to solvents, acids and hydro-carbons. Poly-vinylidene di-fluoride has low density 1.78 grams per cubic centimeter in comparison to other fluoro-polymers, like poly-tetra-fluoro-ethylene.
Polyvinyl-pyrrolidone (PVP) – It is normally called polyvidone or povidone, is a water-soluble polymer compound made from the monomer N-vinylpyrrolidone. Polyvinyl-pyrrolidone is available in a range of molecular weights and related viscosities, and can be selected as per the desired application properties.
Pontryagin’s minimum principle – It is a mathematical principle which is used in the theory of optimal control.
Pooled point estimate – it is an approximation of a point, normally a mean or variance, which combines information from two or more independent samples believed to have the same characteristics. It is used to assess the effects of treatment samples versus comparative samples.
Pool reactor – It is a reactor in which fuel elements are submerged in an open water pool. The water serves as a moderator, reflector and coolant. It is popularly called a ‘swimming pool reactor’, it is used for research and training, not for electricity generation.
Pop-off – It is the loss of small portions of a porcelain enamel coating. The normal cause is outgassing of hydrogen or other gases from the substrate during firing, but pop-off can also occur because of oxide particles or other debris on the surface of the substrate. Normally, the pits are minute and cone shaped, but when pop-off is the result of severe fish scale the pits can be much larger and irregular.
Pop-out roller – It is a roller is which typically positioned at the ends of a belt conveyor, aiding in transfer, and set in a broad groove to eject if an object intervenes between it and the belt.
Pop, solvent – It consists of blister and / or void in the coating resulting from trapped solvents released during curing process.
Population – It is a group of individuals of the same species living and interbreeding within a given area. Members of a population frequently rely on the same resources, are subject to similar environmental constraints, and depend on the availability of other members to persist over time. In statistics, population is the complete set of all possible elements or objects. Each of the elements is called a piece of data. Population is a collection of units or objects of which some property is defined for every unit or object. Population can consist of finite or infinite number of units. Population is also called universe by some peoples. The number of employees in the organization, number of rolling mills in a plant, length of rail track in the plant, and number of feeders in a sinter plant are a few examples of finite populations. All real numbers, and inclusions in liquid steel are examples of infinite populations. Normally, the population has a large number of animates and inanimates. Moreover, the units or subjects constituting the population can vary from study to study in the same area of activity depending upon the aims and objective of the study. In brief, one is to keep in mind that statistical population of data is not the human population which is normally considered for population in literary sense. It is normally a group or collection of items specified by certain characteristics or defined under certain restrictions. Population is the total collection of cases people wish to generalize the results of their study to. In statistical usage the term population is applied to any finite or infinite collection of individuals. The term population is also used for the infinite population of all possible results of a sequence of statistical trials, for example, tossing a coin. It is important to distinguish between the population, for which statistical parameters are fixed and unknown at any given instant in time, and the sample of the population, from which estimates of the population parameters are computed. Population statistics are normally unknown since the analyst can rarely afford to measure all members of a population, and so a random sample is drawn. Much of statistics is concerned with estimating numerical properties (parameters) of an entire population from a random sample of units from the population. Greek letters are normally used for population parameters. This is to distinguish them from sample statistics.
Population density – It is the size of a population in relation to the quantity of space which it occupies. Density is normally expressed as the number of individuals per unit area or volume. Like all population properties, density is a dynamic characteristic which changes over time since individuals are added to or removed from the population.
Porcelain – It is a glazed or unglazed vitreous ceramic whiteware used for technical purposes. This term designates such products as electrical, chemical, mechanical, structural, and thermal wares when they are vitreous. This term is frequently used as a synonym for china.
Porcelain enamel – It is a substantially vitreous or glassy, inorganic coating (borosilicate glass) bonded to metal by fusion at a temperature above 425 deg C. Porcelain enamels are applied primarily to components made of sheet iron or steel, cast iron, aluminum, or aluminum-coated steels.
Pore – It is a small opening, void, interstice, or channel within a consolidated solid mass or agglomerate, normally larger than atomic or molecular dimensions. It is a minute cavity in a powder metallurgy compact, sometimes added intentionally. It is a minute perforation in an electroplated coating. It is an inherent or induced cavity (void) within a particle or within an object.
Pore area – It is the effective surface porosity of a sintered compact to determine the permeability to a test fluid.
Pore channels – These are the connections between pores in a sintered body.
Pore formation – It consists of the natural formation of pores during compaction and / or sintering.
Pore forming material – It is a substance included in a powder mixture which volatilizes during sintering, and hence produces a desired kind of porosity in a finished compact.
Pore size – It is the width of a pore in a compacted and / or sintered powder or within a particle.
Pore size distribution – It indicates the volume fractions of different pore size categories, which are determined metallographically.
Pore size range – It consists of the limits between which a variation in pore size is allowed.
Pore structure – It consists of pattern of pores in a solid body indicating such characteristics as pore shape, pore size, and pore size distribution.
Pore wall – It is the interface between the pore and the solid.
Porosimeter – It is a test apparatus to measure the interconnected porosity in a sintered compact by means of determining its permeability through the use of a test fluid such as mercury, which wither partially or completely fills the open pore.
Porosity – Porosity is small cavities or bores which are found on the surface of the weld or slightly below surface. Porosity occurs when some constituents of the liquid metal vapourize causing small gas pockets which get entrapped in the liquid metal as it solidifies. These small cavities or bores can have a variety of shapes but mostly they have a spherical shape. The distribution of cavities and bores in weld metal can be linear (linear porosity) or theses can be clustered together (cluster porosity). In general, porosity can result from the presence of dirt, rust or moisture on the surface of base or filler metal. Also, it can result from high sulphur content in the base metal or excessive arc length.
Porous bearing – It is a sintered product whose accessible pore volume is filled with a liquid lubricant which automatically produces a lubricating film on the bearing surface during running of the shaft. This is because of a pumping action of the shaft and frictional heat which lowers the viscosity of the oil. After completion of the running cycle, the oil is reabsorbed into the pore system of the bearing by capillary attraction.
Porphyry – It is an igneous rock in which relatively large crystals, called phenocrysts, are set in a fine-grained ground-mass.
Porphyry copper – It is a deposit of disseminated copper minerals in or around a large body of intrusive rock.
Port – It is an opening through which fluid passes. It is a place at which energy can be observed to enter or leave a system. In case of valve, port is the flow control orifice of a control valve.
Portable conveyors – These are short length flat conveyors which are carried on a wheeled structure. These conveyors are particularly useful for loading and unloading of trucks / transport vehicles. The inclination of the conveyor can normally be adjusted to suit application.
Portable equipments – These are equipments which can be easily transported from job to job or site to site.
Portable instruments – Portable instruments are designed to be moved from one place to another. They are frequently lightweight, compact, and have a portable power source.
Portable optical emission spectrometers – These are important tools for the on-site sorting and identification of metals in the steel scrap. Their analytical precision and accuracy, while not as good as laboratory installed spectrometers, are more than adequate for sorting mixes and most grade verification requirements. A portable spectrometer is capable of separating different types of steel in addition to separating at least 90 % to 95 % of the individual grades which make up each type of steel.
Portable particulate monitor – It is a device which measures the quantity of particulate matter (PM) in the air. It can also measure other pollutants and environmental factors like temperature and humidity.
Portable support – It consists of support mechanisms for portable equipments and conveyors, equipped with castors and wheels to facilitate easy movement.
Portal – It is the surface entrance to a tunnel or adit.
Portal scraper reclaimer – A portal scraper reclaimer is named after the shape of the reclaimer body connecting the two end carriages. This structure is normally similar in shape to an inverted ‘V’ or a portal frame. Since the portal scraper reclaimer reclaims the material from side of a pile, it is principally similar in operation to the side scraper reclaimer. It overcomes the restriction of limited boom length (up to 30 meters pile widths) of a side scraper reclaimer which is due to its cantilever type arrangement, because of having rail bogie on both sides of the stockpile. Hence, wider pile widths can be handled by a portal scraper reclaimer.
Porter’s 5 forces analysis – Porter’s 5 forces analysis model is a tool which analyzes the competitive intensity within a particular market or industry. This analysis consists of 3 forces from the horizontal competition representing (i) threat of new entrants, (ii) threat of established competitors which is also known as competitive rivalry, and (iii) threat of substitute products / services. The balance 2 forces are from vertical competition represented by (i) bargaining power of the buyers, and (ii) bargaining power of the suppliers. Horizontal competition means that these 3 forces are operating in the same manner within the market and in the vertical competition the 2 forces operate within the supply chain. Moreover, the model displays that four forces are connected to the fifth one which is the competitive rivalry.
Portevin–Le Chatelier (PLC) effect – It describes a serrated stress–strain curve or jerky flow, which some materials show as they undergo plastic deformation, specifically inhomogeneous deformation. This effect has been long associated with dynamic strain aging or the competition between diffusing solutes pinning dislocations and dislocations breaking free of this stoppage. The onset of the Portevin–Le Chatelier effect occurs when the strain rate sensitivity becomes negative and inhomogeneous deformation starts. This effect also can appear on the sample’s surface and in bands of plastic deformation. This process starts at a so-called critical strain, which is the minimum strain needed for the onset of the serrations in the stress–strain curve. The critical strain is both temperature and strain rate dependent. The existence of a critical strain is attributed to better solute diffusivity because of the deformation created vacancies and increased mobile dislocation density. Both of these contribute to the instability in substitutional alloys, while interstitial alloys are only affected by the increase in mobile dislocation densities.
Porthole dies – These are dies which produce extruded hollow products from solid extrusion ingots. These dies incorporate a mandrel as an integral part of the die assembly and leave one or two ‘weld’ seams along the extrusions. Bridge, spider, duo and self-stripping dies are particular types of porthole die.
Portland cement – It is the fundamental ingredient in concrete. It is calcium silicate cement made with a combination of calcium, silicon, aluminum, and iron. Different types of portland cement are produced to meet various physical and chemical requirements. The properties of portland cement during hydration vary according to (i) chemical composition, and (ii) degree of fineness. It is possible to produce different types of cements by changing the percentages of the raw materials. There are eight types of portland cements. These are (i) Type I portland cement which is a normal, general purpose cement suitable for all uses and it is used in general construction projects such as buildings, bridges, floors, pavements, and other precast concrete products, (ii) Type IA portland cement which is similar to Type I with the addition of air-entraining properties, (iii) Type II portland cement which generates less heat at a slower rate and has a moderate resistance to sulphate attack, (iv) Type IIA portland cement which is identical to Type II and produces air-entrained concrete, (v) Type III portland cement which is a high early strength cement and causes concrete to set and gain strength rapidly, and it is chemically and physically similar to Type I, except that its particles have been ground finer, (vi) Type IIIA portland cement which is an air-entraining, high early strength cement, (vii) Type IV portland cement which has a low heat of hydration and develops strength at a slower rate than other cement types, making it ideal for use in dams and other massive concrete structures where there is little chance for heat to escape, and (viii) Type V portland cement which is used only in concrete structures which will be exposed to severe sulphate action, principally where concrete is exposed to soil and groundwater with a high sulphate content.
Portland cement concrete – It is the concrete which is made with normal portland cement. This concrete needs around 2 weeks for achieving a sufficient strength to permit the removal of forms and the application of moderate loads. Such concrete reached its design strengths after around 28 days and continue to gain strength at a slower rate thereafter. On several occasions it is desirable to speed up construction by using high-early-strength cements, which, although more expensive, are capable of obtaining the desired strengths in 3 days to 7 days. These cements are particularly useful for the fabrication of precast members, in which the concrete is placed in forms where it quickly gains desired strengths and is then removed from the forms and the forms are used to produce more members.
Portland pozzolana cement – It is produced by inter-grinding ordinary portland cement clinker with 15 % to 40 % of the pozzolana material. Pozzolana is defined as a siliceous or siliceous and aluminous material which in itself possesses little or no cementitious value but in finely divided form and in the presence of moisture, chemically reacts with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties. Natural pozzolanic materials are volcanic ash while the industrial pozzolanic materials are fired clay, rice husk ash etc. It is essential that pozzolana be in finely divided state as it is only then that silica can combine with calcium hydroxide (produced by the hydrating portland cement) in the presence of water to form stable calcium silicates which have cementitious properties. They are similar to those of portland blast furnace cement. Portland pozzolana cement produces low heat of hydration and offer higher resistance to the attack of the aggressive water than ordinary portland cement. It is used in the mass construction works and in marine environments as well as in hydraulic works.
Position sensitive detector (PSD) – It is also called position sensitive device. It is an optical position sensor (OPS) which can measure a position of a light spot in one or two-dimensions on a sensor surface. Position sensitive detectors can be divided into two classes which work according to different principles: In the first class, the sensors have an isotropic sensor surface which supplies continuous position data. The second class has discrete sensors in a raster-like structure on the sensor surface which supply local discrete data.
Position sensor – It is a sensor in a conveyor system which detects the position of materials, demanding regular inspections for accurate sensing and responsiveness.
Position vector – It is a Euclidean vector which represents a point ‘P’ in space. Its length represents the distance in relation to an arbitrary reference origin ‘O’, and its direction represents the angular orientation with respect to given reference axes. It is normally denoted ‘x’, ‘r’, or ‘s’, it corresponds to the straight-line segment from ‘O’ to ‘P’.
Positive-contact bushing – It is a bushing, the inside diameter of which has direct contact with the outside diameter of a shaft or sleeve. Radial or axial clearances are provided in the housing.
Positive-contact seal – It is a seal, the primary function of which is achieved by one surface mating with another. Examples include lip, circumferential, and face-type seals.
Positive crankcase ventilation system – It is used to prevent air pollution caused by gases being emitted from the crankcase. This system supplies fresh filtered air to the crankcase through the air intake hose. The system is positive ventilation type. It can abstract crankcase’s inner mixture gas into engine inlet pipe at proper time by means of engine inlet pipe’s vacuum performance. Hence, the mixture gas can get combustion again, which protects environment. When the engine is operating, the inlet pipe’s vacuum affects positive crankshaft ventilation valve, it makes fresh air come into air cylinder by means of air cleaner and air soft pipe, and then enter into crankcase by means of cylinder shroud. In crankcase, fresh air is mixed in mixture gas, and then the mixed gas will enter into inlet pipe by means of air cylinder shroud and positive crankshaft ventilation valve. At last, the mixed gas is combusted in engine.
Positive crowned pulley – It is a pulley which is designed with an upward curve at both ends converging toward the centre of a conveyor, aiding in the proper alignment and tracking of the conveyor belt.
Positive discharge elevators – These elevators are similar to the centrifugal discharge type excepting that the buckets are side-mounted on two strands of chains (i.e. buckets lie between two strands of chains), and are provided with a pair of two snub sprockets under the head sprockets to invert the buckets for complete discharge. The speed of the elevator can be slow in the range of 0.6 meters per minute to 0.67 meters per minute. These elevators are used for light, fluffy, sluggish and slightly sticky materials. The feeding is through scooping or digging by the buckets. An inclined elevator is particularly suitable for perfect gravity discharge.
Positive eye-piece – It is an eye-piece in which the real image of the object is formed below the lower lens elements of the eye-piece.
Positive feedback – It is feedback from the output of a system which tends to increase the effect of an input. If overdone, leads to instability.
Positive replica – It is a replica whose contours correspond directly to the surface being replicated.
Positive temperature coefficient (PTC) – It refers to the materials which experience an increase in the electrical resistance when their temperature is raised. Materials which have useful engineering applications normally show a relatively rapid increase with temperature, i.e., a higher coefficient.
Possible reserves – It is the valuable mineralization not sampled enough to accurately estimate its tonnage and grade, or even verify its existence. It is also called ‘inferred reserves’.
Post – In structural engineering, it is a main vertical or leaning support in a structure similar to a column or pillar, the term post normally refers to a timber but can be metal, concrete, or stone.
Post cure – It is additional elevated-temperature cure, normally without pressure, to improve final properties and / or complete the cure, or decrease the percentage of volatiles in the compound. In certain resins, complete cure and ultimate mechanical properties are attained only by exposure of the cured resin to higher temperatures than those of curing.
Post forming – It is the forming, bending, or shaping of fully cured, C-staged thermoset laminates which have been heated to make them flexible. On cooling, the formed laminate retains the contours and shape of the mould over which it has been formed.
Post forming heat treatable (PFHT) steel – Post forming heat treatment is a general method to develop an alternative higher strength steel. The major issue holding back widespread implementation of high strength steel (HSS) typically has been maintaining part geometry during and after the heat treatment process. Fixturing the part and then heating (furnace or induction) and immediate quenching appear to be a solution with production applications. In addition, the stamping is formed at a lower strength and then raised to a much higher strength by heat treatment. One process is water quenching of inexpensive steels with chemistries which allow in part strengths in the range of 900 MPa to 1,400 MPa of tensile strength. Another process is air-hardening of alloyed tempering steels which feature very good forming properties in the soft-state (deep-drawing properties) and high strength after heat treatment (air-hardening).
Post-heating – It is the heating weldments immediately after welding, for tempering, for stress relieving, or for providing a controlled rate of cooling to prevent formation of a hard or brittle structure.
Post hoc test – The post hoc test (or post hoc comparison test) is used at the second stage of the analysis of variance (ANOVA) or multiple analyses of variance (MANOVA) if the null hypothesis is rejected.
Post-hoc theorizing – Post hoc theorizing is likely to occur when the analyst attempts to explain analysis results after-the-fact. In this second-rate approach to scientific discovery, the analyst develops hypotheses to explain the data, instead of the converse (collecting data to nullify the hypotheses). The number of post-hoc theories which can be developed to ‘fit’ the data is limited only by the imagination of a group of people. With an abundance of competing hypothesis, and little forethought as to which hypothesis can be afforded more credence, there is little in the way of statistical justification to prefer one hypothesis to another. More importantly, there is little evidence to eliminate the prospect of illusory correlation.
Post-industrial waste – It consists of by-products of the manufacturing process, such as trimmings in the production of steel. These waste products are frequently put back into the manufacturing process and called ‘recycling’. Several dispute whether this truly constitutes recycling or simply good business practices.
Post-nucleation – It is the step where, if necessary, the catalyst is converted to its final form when plating on plastic substrates. This is the final step prior to electroless plating.
Post purge – It is a method of scavenging the furnace and boiler passes to remove all combustible gases after flame failure controls have sensed pilot and main burner shut-down and safety shut-off valves are closed.
Post treatment – It is subjecting the steel to specific processes after it has been galvanized.
Post weld artificial aging – It highly improves the joint strength with the ultimate tensile strength reaching 87.3 % of the base metal.
Post-weld heat treatment – It is a heat treatment which follows the welding operation.
Pot – It is a vessel for holding molten metal. It is the electrolytic reduction cell used to make such metals as aluminum from a fused electrolyte.
Pot annealing – It is annealing a metal or alloy in a sealed container under conditions which minimize oxidation. In pot annealing a ferrous alloy, the charge is normally heated slowly to a temperature below the transformation range, but sometimes above or within it, and is then cooled slowly. This process is also called close annealing or pot annealing.
Potable water – It is also called drinking water. It is the water which is provided by a water treatment plant and is used for drinking, cooking, dishwashing, or other domestic purposes needing water which is suitable for human consumption.
Potash – It consists of potassium compounds which are mined for fertilizer and for use in the chemical industry.
Potential – It consists of different functions from which intensity or velocity at any point in a field can be calculated. It is the driving influence of an electro-chemical reaction.
Potential difference – It is a voltage difference, the quantity of work needed to bring a test charge from one point to another divided by charge magnitude.
Potential energy – It is the stored energy in a body or in a system because of its position in a force field or because of its configuration.
Potential deposit – It is a deposit which has not yet been demonstrated to exist by direct evidence (e.g., drilling and / or sampling), but is assessed as potentially existing based primarily on indirect evidence (e.g. surface or airborne geophysical measurements).
Potentially economic – The reference point at which Reserves are defined, normally the point where the ore is delivered to the processing plant, is to be stated. It is important that, in all situations where the reference point is different, such as for a saleable product, a clarifying statement is included to ensure that the reader is fully informed as to what is being reported. Quantities, reported in tons / volume with grade / quality, demonstrated by means of a Pre-feasibility study, Feasibility study or Mining report, in order of increasing accuracy, not justifying extraction under the technological economic, environmental, and other relevant conditions, realistically assumed at the time of the determination, but possibly so in the future. The term potentially economic comprises both marginal and sub-marginal. These two sub-categories are for optional use on a national level.
Potential-pH diagram – It is a graph of the redox potential of a corroding system against the pH of the system, compiled using thermodynamic data and the Nernst equation. The diagram shows regions within which the metal itself or some of its compounds are stable.
Potentially Viable projects – Potentially Viable projects are potential future recovery by mining operations, where development is pending or on-hold.
Potential source – It is a source which has not yet been demonstrated to exist by direct evidence, but is assessed as potentially existing based primarily on indirect evidence.
Potential transformers – Potential transformers are used with volt-meters, watt-meters, watt-hour meters, power-factor meters, frequency meters, synchroscopes and synchronizing apparatus, protective and regulating relays, and undervoltage and overvoltage trip coils of circuit breakers. One potential transformer can be used for a number of instruments, if the total current needed by the instruments connected to the secondary winding does not exceed the transformer rating. Potential transformers are usually rated 50 volt-amperes to 200 volt-amperes at 120 secondary volts. The secondary terminals are never to be short circuited since a heavy-current results, which can damage the windings.
Potentiometer – It is a three-terminal variable resistor, which can be configured as an adjustable voltage divider. It is an instrument which measures electromotive force by balancing against it an equal and opposite electromotive force across a calibrated resistance carrying a definite current.
Potentiodynamic (potentiokinetic) – It is the technique for varying the potential of an electrode in a continuous manner at preset rate.
Potentiometric membrane electrodes – These are electro-chemical devices which can be used to quantify numerous ionic and non-ionic species. This class of electro-chemical sensors can be divided into ion-selective and gas-sensing membrane electrodes. In both the cases, a selective membrane potential is related to the concentration or activity of the species of interest. Potentiometric membrane electrode measurements require an indicating electrode and a reference electrode. The potential of the indicating electrode depends on the activity of the ion of interest, and this potential is measured with respect to the constant potential of the reference electrode using a high-impedance potentiometer. The reference electrode is an important but frequently overlooked component of potentiometric membrane electrode measurement.
Potentiometry – It is defined as the measurement of electrical potential (also designated electromotive force) between two electrodes when the cell current is zero.
Potentiostat – It is an instrument which automatically maintains an electrode in an electrolyte at a constant potential or controlled potentials relative to a suitable reference electrode.
Potentiostatic – It is the technique for maintaining a constant electrode potential.
Potentiostatic etching – It consists of anodic development of microstructure at a constant potential. Adjusting the potential makes possible a defined etching of singular phases.
Pot life – It is the length of time which a catalyzed thermosetting resin system retains a viscosity low enough to be used in processing. It is also called working life.
Poultice corrosion – It is a term used in the automotive industry to describe the corrosion of vehicle body parts because of the collection of road salts and debris on ledges and in pockets which are kept moist by weather and washing. It is also called deposit corrosion or attack.
Pourbaix (potential-pH) diagram – It is a graph of the redox potential of a corroding system against the pH of the system, compiled using thermodynamic data and the Nernst equation. The diagram shows regions within which the metal itself or some of its compounds are stable.
Pouring – It is the transfer of molten metal from furnace to ladle, ladle to ladle, or ladle into moulds.
Pouring basin – In metal casting, it is a basin on top of a mould which receives the molten metal before it enters the sprue or down-gate.
Pouring pit refractory – It is a refractory which is associated with the transfer or flow control of molten steel between furnace and the mould.
Pouring refractories – These are refractories which are used for the transfer of steel from furnace to ingot. Refractories include ladle brick, nozzles, sleeves, stopper heads, mold plugs, hot tops, and mortars used for the brickwork involved.
Pour point – It is the lowest temperature at which a lubricant can be observed to flow under specified conditions. Pour point of oil is an important quality. It is a temperature at which oil still remains fluid. It reflects on the capability of the oil to work at low temperatures.
Pour-point depressant – It is an additive which lowers the pour point of a lubricant.
Powder – It is an aggregate of discrete particles which are normally in the size range of 1 micrometer to 1,000 micrometers.
Powder adhesion – In dry process enameling, it is the ability of an electrostatic powder to remain attached by static attraction to a grounded substrate.
Powder coating – It is the application of an even layer of colour to aluminum extrusions by spraying powdered paint using an electrostatic process then baking on (stove enameling).
Powder cutting – The preferred terms are chemical flux cutting and metal powder cutting. It is a technique which supplements an oxy-fuel torch with a stream of iron or blended iron-aluminum
powder to facilitate flame cutting of difficult-to-cut materials. The powdered material propagates and accelerates the oxidation reaction, as well as the melting and spalling action of the materials to be cut.
Powder designation – It consists of a code number identifying a specific powder.
Powder fill – It is the filling of a die cavity with powder.
Powder lubricant – It is an agent or component incorporated into a mixture to facilitate compacting and ejecting of the compact from its mould.
Powder flame spraying – It is a thermal spraying process variation in which the material to be sprayed is in powder form.
Powder forging – It is also called powder metallurgy forging. It is the plastic deformation of a powder metallurgy compact or preform into a fully dense finished shape by using compressive force. It is normally done hot and within closed dies.
Powder lubricant – In powder metallurgy, it is an agent or component incorporated into a mixture to facilitate compacting and ejecting of the compact from its mould.
Powder metallurgy (P/M) – It is the technology and art of producing metal powders and utilizing metal powders for production of massive materials and shaped objects.
Powder metallurgy part – It is a shaped object which has been formed from metal powders and sintered by heating below the melting point of the major constituent. A structural or mechanical component made by the powder metallurgy process.
Powder metallurgy tool steels – Powder metallurgy has become a major process for the manufacture of high-performance tool steels and tool steel products. The items now available include as-compacted or hot-worked billets and bars, semifinished parts, near-net shapes, and indexable cutting tool inserts. The powder metallurgy process has been used primarily for the production of advanced high-speed tool steels. However, it is now also being applied to the manufacture of improved cold-work and hot-work tool steels. For majority of applications, the powder metallurgy tool steels offer distinct advantages over conventional tool steels.
Powder metals – These are alloys processed into a fine, grain-like powder through one of several processes. These are mainly made from stainless steel, brass, copper, iron, or bronze, these metals can be blended with other alloys to achieve the desired material properties and characteristics for a particular application. These offer higher flexibility in material usage and mechanical properties, powder metal parts can be highly customized and easily reproduced while yielding high-strength, cost-effective components.
Powder method – It is a method of X-ray diffraction involving a poly-crystalline and preferably randomly oriented powder sample and a narrow beam of the mono-chromatic radiation.
Powder production – It is the process by which a powder is produced, such as machining, milling, atomization, condensation, reduction, oxide decomposition, carbonyl decomposition, electrolytic deposition, or precipitation from a solution.
Powder rolling – It is also called roll compacting, or rolled compaction. It consists of the progressive compacting of metal powders by the use of a rolling mill.
Powder technology – It is a broad term encompassing the production and utilization of both metal and non-metal powders.
Powder rolling mill – In the powder rolling mill, metal powder is introduced between the rolls and compacted into a ‘green strip’, which is subsequently sintered and subjected to further hot-working and / or cold working and annealing cycles.
Power – It is the quantity of energy transferred or converted per unit time. In the International System of Units, the unit of power is the watt, equal to one joule per second. Power is a scalar quantity. Specifying power in particular systems can need attention to other quantities, e.g., he power involved in moving a ground vehicle is the product of the aerodynamic drag plus traction force on the wheels, the velocity of the vehicle. The output power of a motor is the product of the torque that the motor generates and the angular velocity of its output shaft. Similarly, the power dissipated in an electrical element of a circuit is the product of the current flowing through the element and of the voltage across the element. In electrical engineering, it is the rate of transfer of electrical energy within a circuit. Its SI (International System of Units) unit is the watt, the general unit of power, defined as one joule per second. Electric power is normally produced by electric generators, but can also be supplied by sources such as electric batteries. It is normally supplied by the electric power industry through an electrical grid. Electric power can be delivered over long distances by transmission lines and used for applications such as motion, light, or heat with high efficiency. In case of statistics, in general, the power of a statistical test of some hypothesis is the probability which it rejects the alternative hypothesis when the alternative is false. The power is greatest when the probability of a Type II error is least. Power is 1-beta, whereas level of confidence is 1-alpha.
Power and free conveyor – These conveyors are basically a special design of the ‘load-propelling or pusher trolley’ conveyors. In a normal pusher trolley conveyor the non-powered trolleys, supported from a monorail, carry the load and are pushed by dogs / pushers attached to the chain trolleys mounted on a separate track. A power and free conveyor is one in which the power trolleys run directly above the free trolleys, which run in double channel track, and arrangements are made such that at desired points the non-powered load carrying trolleys can be engaged to or disengaged from the power trolleys. The power trolley dogs / pushers are rigid attachments on the trolleys or chain. They engage or disengage with the free trolleys by switching them in from a branch line to the mainline, and by horizontal turns and vertical curves in the power line. The switching operations can be made mechanically or through actuation of pneumatic cylinder synchronous with movement of power trolleys.
Power belt curve – It is a curve conveyor which is guided by tapered pulleys that use a belt.
Power BJT – It is a bipolar junction transistor (BJT) which can be used in circuits handling a watt or more of power.
Power cables – Power cables are used for distribution and transmission of electrical energy. These cables are assembly of one or more individually insulated flexible electrical conductors, normally held together with an overall sheath which is used to transmit electric power. Power cable can be considered to be just a conductor, overlying insulation, and frequently an exterior shield or jacket. It is used to convey electric power. It is the purpose of the cable to convey the electric current to the intended device or location. In order to accomplish this, a conductor is provided which is adequate to convey the electric current imposed. Equally important is the need to keep the current from flowing in unintended paths rather than the conductor provided. Electrical insulation (dielectric) is provided to largely isolate the conductor from other paths or surfaces through which the current can flow. Hence, it can be said that any conductor conveying electric signals or power is an insulated conductor.
Power conditioner – It is a system which is intended to alter some property of the bulk power supply to improve it for some application. Examples are filters, surge suppressors, voltage regulators, uninterruptible power supplies, and several others.
Power consumption – It is the rate at which the electrical energy is consumed.
Power converter – It is a device which is intended to convert electric power to another form of electric power, such as conversion between alternating current and direct current or changing frequency or phase number.
Power conveyor – It is a conveyor system which needs power to operate and move packages.
Power distribution – It is the portion of an electrical grid which is between the sub-station or bulk supply and the end consumer.
Power-driven hammer – It is a forging hammer with a steam or air cylinder for raising the ram and augmenting its downward blow.
Powered feeder – It is the mechanized section of a conveyor system responsible for transferring products from a horizontal orientation to an inclined position through powered movement.
Powered roller conveyor – It is a conveyor which at uses powered rollers to move materials. It is a conveyor system with rollers powered by a central drive unit, demanding regular inspections for roller health, motor functionality, and overall system performance. It is also called live roller conveyor. In this type of roller conveyor, all or a selected number of rollers are driven by one or a number of motors depending on the selected drive arrangement. The driven rollers transmit motion to the loads by friction. The powered roller conveyors can be installed at a slightly inclined position, up to 10-degree up or up to 17-degree down. The load can be moved in either direction by changing the direction of rotation of the rollers, where these are called reversing conveyors. Powered roller conveyors are intensively used in heavy process plants like rolling mills to feed heavy and at times hot metal to or to take the material in the mill to various other process equipment. The roller conveyors can be reversing type or non-reversing type.
Power electronics – It is the class of electronic devices which are handling power higher than a watt.
Power engineering – It is that part of electrical engineering which deals with the generation, distribution and consumption of electrical power.
Power factor – It is the ratio of apparent power flowing to a load divided by the real power. Power factor of an alternating current power system is defined as the ratio of the real power absorbed by the load to the apparent power flowing in the circuit. Real power is the average of the instantaneous product of voltage and current and represents the capacity of the electricity for performing work. Apparent power is the product of root mean square (RMS) current and voltage. Because of the energy stored in the load and returned to the source, or because of a non-linear load that distorts the wave shape of the current drawn from the source, the apparent power may be greater than the real power, so more current flows in the circuit than would be required to transfer real power alone. A power factor magnitude of less than one indicates the voltage and current are not in phase, reducing the average product of the two. A negative power factor occurs when the device (normally the load) generates real power, which then flows back towards the source.
Power-factor correction – It is a device which is intended to bring the power factor of some load closer to 1. Power factor correction is the process of compensating for the lagging current by creating a leading current by connecting capacitors to the supply. A sufficient capacitance is connected so that the power factor is adjusted to be as close to unity as possible.
Power-flow study – It is a numerical analysis of the flow of electric power in an inter-connected system. A power-flow study normally uses simplified notations such as a single-line diagram and per-unit system, and focuses on different aspects of alternating current power parameters, such as voltage, voltage angles, real power and reactive power. It analyzes the power systems in normal steady-state operation. Power-flow or load-flow studies are important for planning future expansion of power systems as well as in determining the best operation of existing systems. The principal information got from the power-flow study is the magnitude and phase angle of the voltage at each bus, and the real and reactive power flowing in each line.
Power generation – It is the practice of converting other energy sources to electric power.
Power grid – It is an inter-connected network of generators, transmission lines, and apparatus for reliable and economic transmission and utilization of electric power.
Power inverter – It is a device which converts direct current power to alternating current power.
Power-line communication – It is the impression of carrier waves on a power line circuit for signalling purposes.
Power MOSFET – It is a metal oxide semi-conductor field effect transistor which is suitable for use in circuits handling more than a watt of power.
Power of the test – It is the probability which one rejects a false null hypothesis with a particular statistical test.
Power plant – It is a facility which converts other energy forms into electric power.
Power quality – It means conformance of an electrical power supply with its specifications.
Power rating – It is the nominal power which an equipment, a device, apparatus, or machine can handle, with specified or customary temperature rise and life expectancy.
Power spectral density (PSD) – It is the measure of signal’s power content versus frequency. A power spectral density is typically used to characterize broadband random signals. The amplitude of the power spectral density is normalized by the spectral resolution employed to digitize the signal. For vibration data, a power spectral density has amplitude units of g2/hertz (‘g’ is acceleration).
Power storage – It is a facility which changes electric power into some form which can be stored and usefully reconverted back to electric power, e.g., pumped storage or battery systems.
Power stroke – In the context of an internal combustion engine, the term power stroke is (i) a phase of the engine’s cycle (e.g. compression stroke, exhaust stroke), during which the piston travels from top to bottom or vice versa, (ii) the type of power cycle used by a piston engine, and (iii) stroke length which nis the distance travelled by the piston during each cycle. The stroke length, along with bore diameter, determines the engine’s displacement.
Power supply – It is a sub-system of a computer or other electronic device which turns electric power from a wall plug or batteries into a form suitable for use by the system.
Power-system automation – It is the implementation of power-operated switching and control which allows automatic operation of power system elements, instead of manual operation.
Power-system protection – It is the technology of limiting the spread of failures of a power system to a minimum, and of preventing permanent damage to device, equipment, apparatus, or conductors by such faults.
Power transformer – It is an electrical device which is designed to transfer electrical power from one circuit to another without altering the frequency. It functions on the principle of electro-magnetic induction and is essential for transmitting power between generators and primary distribution circuits.
Power turn conveyor – It is a conveyor system with a curved section which allows materials to change direction, necessitating periodic checks for alignment, belt condition, and overall functionality.
ppm – It is the abbreviation for parts per million. It is used in chemical determinations as one part per million parts by weight.
Practice – It is a human activity which involves the introduction of a new source of exposure of people to a hazard or increases an existing exposure. A new practice needs a justification decision.
Prandtl number (Pr) – It is a dimensionless number which is defined as the ratio of momentum diffusivity to thermal diffusivity.
Praseodymium – It is a chemical element having symbol Pr and the atomic number 59. It is the third member of the lanthanide series and is considered one of the rare-earth metals. It is a soft, silvery, malleable and ductile metal, valued for its magnetic, electrical, chemical, and optical properties. It is too reactive to be found in native form, and pure praseodymium metal slowly develops a green oxide coating when exposed to air.
Pre-ageing – It is a thermal treatment after quenching and before the end of the precipitation incubation period.
Pre-alloyed powder – It is a metallic powder composed of two or more elements which are alloyed in the powder manufacturing process and in which the particles are of the same nominal composition throughout.
Pre-arc (or Pre-spark) period – In emission spectroscopy, it is the time interval after the initiation of an arc (or spark) discharge during which the emitted radiation is not recorded for analytical purposes.
Precambrian shield – It is the oldest, most stable regions of the earth’s crust.
Pre-cast concrete piles – These piles are produced either in a manufacturing plant or in a casting yard. Reinforcement is provided to resist handling and driving stresses. Pre-cast piles can also be pre-stressed using high strength steel pre-tensioned cables. Square and octagonal piles are cast in horizontal forms, while round piles are cast in vertical forms. After the piles are cast, they are to be cured under damp sand, straw, or mats for the period needed by the specifications, frequently 21 days, if cured under ambient temperatures. With the exception of short lengths, pre-cast concrete piles are to be reinforced with sufficient steel to prevent damage or breakage while they are being handled from the manufacturing plant / casting beds to the driving positions. The piles are required to contain longitudinal reinforcing steel in a quantity not less than 2 % of the volume of the pile. Lateral steel is to be at least 6 millimetres diameter round bars, spaced not more than 300 millimetres apart, except at the top and bottom of a pile, where the spacing is not to exceed 75 millimetres. The concrete cover over the reinforcing steel is to be at least 50 millimetres.
Preceramic polymers – These are also known as polymer precursors. These polymers can be converted into ceramics by pyrolysis. They normally contain carbon or silicon.
Precious metals – These are relatively scarce, highly corrosion resistant, valuable metals found in periods 5 and 6 (groups VIII and Ib) of the periodic table. They include ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold.
Precipitant – It is a chemical compound or reagent which causes a chemical reaction resulting in the formation of a solid precipitate when added to a solution.
Precipitate – It is a solid substance which separates from a liquid solution or diffuses out of a solid alloy during the process of precipitation. It also means to separate from another substance by forming a distinct, condensed solid phase.
Precipitate-free zone (PFZ) – It is a region adjacent to the grain boundary in which there is no (or little) precipitate, while there is a precipitate present in the grain interior (normally fine) and precipitates in the grain boundary. It is frequently associated with poor corrosion resistance and / or poor fracture toughness. The presence of a precipitate free zone frequently results in fracture in the region.
Precipitation – It is the separation of a new phase from solid or liquid solution, normally with changing conditions of temperature, pressure, or both. It is the process of producing a separable solid phase within a liquid medium, e.g., by transforming the dissolved solute of a supersaturated solution into an insoluble solid, or the diffusion of a distinct solid phase out of a solid alloy. A reagent that causes such a reaction is called the precipitant, and the separable solid itself is the precipitate. More generally, the term can refer to the formation of any new condensed phase by changing the physical properties of a system (e.g., water vapour condensing into liquid water droplets). In metals, it is the separation of a new phase from solid or liquid solution, normally with changing conditions of temperature, pressure, or both.
Precipitation annealing – It is the heating of a quenched and precipitation hardened work-piece for some time at a temperature between the artificial ageing temperature and the solution treatment temperature. It produces considerable softening by coalescing the hardening precipitates.
Precipitation (deposit) etching – It consists of development of microstructure in a metallographic sample through formation of reaction products at the surface of the microsection.
Precipitation hardening – It is the hardening in metals which is caused by the precipitation of a constituent from a super-saturated solid solution.
Precipitation hardening stainless steels – These steels are chromium-nickel stainless steels containing precipitation-hardening elements such as copper, aluminium, or titanium. Precipitation-hardening stainless steels can be either austenitic or martensitic in the annealed condition. Those which are austenitic in the annealed condition are frequently transformable to martensite through conditioning heat treatments, sometimes with a sub-zero treatment. In most cases, these stainless steels attain high strength by precipitation hardening of the martensitic structure.
Precipitation heat treatment – It is artificial aging of metals in which a constituent precipitates from a super-saturated solid solution.
Precision – It means how close the results of multiple experimental trials or observations are to each other. In case of instruments, precision is the degree of exactness for which an instrument is designed or intended to perform. It is a measure of consistency or repeatability of measurements, i.e., successive readings do not differ or there is the consistency of the instrument output for a given value of input. A very precise reading is not a perfect accurate reading. Precision is a term which describes an instrument’s degree of freedom from random errors. If a large number of readings are taken of the same quantity by a high precision instrument, then the spread of readings is very small. Precision is frequently, though incorrectly, confused with accuracy. High precision does not imply anything about measurement accuracy. A high precision instrument can have a low accuracy. Low accuracy measurements from a high precision instrument are normally caused by a bias in the measurements, which is removable by recalibration of the instrument. The ISO (International Organization for Standardization) has banned the term precision for describing scientific measuring instruments because of its several confusing everyday connotations.
Precision alignment – It is the accurate adjustment of conveyor components for ensuring proper alignment and efficient material movement, needing regular checks and adjustments.
Precision bearings – These are high-quality bearings which are used in equipment components for improved durability and reduced friction, necessitating regular checks for wear, alignment, and overall bearing condition.
Precision casting – It is a metal casting of reproducible, accurate dimensions, regardless of how it is made. It is frequently used interchangeably with investment casting.
Precision forging – It is a forging produced to closer tolerances than normally considered standard by the industry. With precision forging, a net shape, or at least a near-net shape, can be produced in the as-forged condition.
Precision grinding – It is machine grinding to specified dimensions and low tolerances.
Precision part– It is also called precision sintered part. It is a powder metallurgy part which is compacted and sintered that is closely conforming to specified dimensions without a need for substantial finishing.
Precision plate sawing – It involves sawing plate (mainly aluminum plate products) into square or rectangular shapes to tolerances as close as 0.08 of a millimeter.
Precious metals – These are rare, naturally occurring metallic chemical elements of high economic value. Precious metals, particularly the noble metals, are more corrosion resistant and less chemically reactive than majority of the elements. They are normally ductile and have a high lustre. Precious metals are now regarded mainly as industrial raw materials.
Precoat – In investment casting, it a special refractory slurry applied to a wax or plastic expendable
pattern to form a thin coating that serves as a desirable base for application of the main slurry. It is also to make the thin coating, as well as the thin coating itself.
Precoated metal products – These are mill products which have a metallic, organic, or conversion coating applied to their surfaces before they are fabricated into parts.
Precoated steel sheet – It is sheet which is frequently coated in coil form before fabrication either by the steel mills or by specialists known as coil coaters. This prefinished or precoated sheet is ready for fabrication and use without further surface coating.
Precoating – It consists of coating the base metal in the joint by dipping, electroplating, or other applicable means prior to soldering or brazing.
Pre-combustion capture technologies – These capture technologies involve removing pollutants and carbon di-oxide in the upstream treatment of fossil fuels prior to their combustion for the recovery of heat (through steam), or the production of electric power or hydrogen. A drawback of post-combustion carbon capture is the low carbon di-oxide concentration in the flue gases which leads to a relatively high energy penalty and high cost of carbon capture. Pre-combustion strives to reduce these penalties by decarbonizing the process stream rich in carbon di-oxide before combustion of the remaining hydrogen rich fuel. To achieve decarbonization of hydrocarbon fuels, they are first converted into a syngas through the gasification of a fuel with oxygen (or air). The syngas is a mixture of carbon mono-oxide, hydrogen, carbon di-oxide, and water, depending on the conversion process and the fuel and other components.
Pre-cracked sample – It is a mechanical test sample which is notched and subjected to alternating stresses until a crack has developed at the root of the notch.
Precure – It is the full or partial setting of a synthetic resin or adhesive in a joint before the clamping operation is complete or before pressure is applied.
Precursor – For carbon or graphite fibre, the rayon, poly-acrylo-nitrile, or pitch fibres from which carbon and graphite fibres are derived.
Predictability – It is the extent to which future states of a system can be predicted based on knowledge of current and past states of the system.
Prediction interval – A prediction interval is a calculated range of values known to contain some future observation over the average of repeated trials with specific certainty (probability). The correct interpretation of a prediction interval is that if the analyst is to repeatedly draw samples at the same levels of the independent variables and compute the test statistic (mean, regression slope, etc.), then a future observation lies in the (1-alpha) % prediction interval a times out of 100. The prediction interval differs from the confidence interval in that the confidence interval provides certainty bounds around a mean, whereas the prediction interval provides certainty bounds around an observation.
Predictive analysis – Predictive analysis utilizes historical and present facts to reach future predictions. It can also use data from a subject to predict the values of another subject. There are different predictive models. However, a simple model with more data can work better in general. Hence, the prediction data set and also the determination of the measuring variables are important aspects to consider.
Predictive maintenance – It is defined as measurements which detect the onset of a degradation mechanism, thereby allowing casual stressors to be eliminated or controlled prior to any significant deterioration in the component / equipment physical state. Predictive maintenance is a set of activities which detect changes in the physical condition of equipment (signs of failure) in order to carry out the appropriate maintenance work for maximizing the service life of equipment without increasing the risk of failure. It is classified into two kinds according to the methods of detecting the signs of failure namely (i) condition-based predictive maintenance, and (ii) statistical-based predictive maintenance. Main predictive maintenance technologies are thermography, oil or lubricant analysis, ultrasonic or ultrasound analysis, vibration analysis, motor analysis, and performance trending etc.
Predictive nomogram – It is a mathematical formula, based on statistical modelling, which facilitates forecasting patient outcomes. In survival analysis, the predicted outcome is typically the probability of surviving a given length of time before experiencing the study end point.Prefabricated building – It is a building which is manufactured and constructed using prefabrication. It consists of factory-made components or units which are transported and assembled on-site to form the complete building. Different materials are combined to create a part of the installation process. It is also known as pre-engineering building.
Pre-feasibility mineral resource – Pre-feasibility mineral resource is that part of an indicated and in some circumstances measured mineral resource which has been shown by pre-feasibility study as not economically mineable or can become economically viable subject to changes in technological, economic, environmental and / or other relevant conditions.
Preferred orientation – It is a condition of a polycrystalline aggregate in which the crystal axes are not randomly distributed with respect to the component geometry, but rather show a tendency for alignment of a specific direction(s) of the crystal parallel to a coordinate axis of the bulk material. Some textures are axisymmetric (fibre textures), in which a single direction in a grain is aligned with the principal working direction. In other cases, two directions of the grain are aligned with directions of the bulk body after working (rolling or deformation textures) and textures in rolled sheet after annealing (annealing textures).
Pre-finishing block – Pre-finishing block is configured to produce the needed process feed sections to the no-twist block to support the maximum product finishing speed. All process sections are rolled in the pre-finishing block utilizing an oval-round pass design sequence to minimize the investment in rolls, reduce operating cost and enable high productivity, and high quality of the process sections. The pre-finishing block stands are used to produce the sections needed for the no-twist block. The pre-finishing block utilizes 230 millimeters cantilever roll housings to provide the needed separating force capacity and roll strength needed for the process. Carbide rolls are used for increased pass life, thereby reducing downtime and increasing mill efficiency. The carbide rolls also provide superior surface quality over the life of the groove, further improving the quality of the finished product.
Pre-flux – It is the process of fluxing steel before it enters the galvanizing pot as opposed to using a top flux layer, which is located on top of the molten zinc in the pot.
Prefit – It is a process for checking the fit of mating detail parts in an assembly prior to adhesive bonding, for ensuring proper bond lines. Mechanically fastened structures are sometimes prefitted to establish shimming requirements.
Preform – It consists of brazing or soldering filler metal fabricated in a shape or form for a specific application. It is a pre-shaped fibrous reinforcement formed by distribution of chopped fibres or cloth by air, water flotation, or vacuum over the surface of a perforated screen to the approximate contour and thickness desired in the finished part. It is a pre-shaped fibrous reinforcement of mat or cloth formed to the desired shape on a mandrel or mock-up before being placed in a mould press.
Preform binder – It is a resin applied to the chopped strands of a preform, normally during its formation, and cured so that the preform retains its shape and can be handled.
Preformed ceramic core – It is a preformed refractory aggregate inserted in a wax or plastic pattern to shape the interior of that part of a casting which cannot be shaped by the pattern. The wax is sometimes injected around the preformed core.
Preformed shape – It is the shape made from an unshaped refractory, cast or moulded and pre-treated by the manufacturer, so that it can be directly placed in service.
Pregel – It is an unintentional, extra layer of cured resin on part of the surface of a reinforced plastic. It is not related to gel coat.
Pre-formed shape (rigid) – It is the rigid shape made of ceramic fibre with the addition of inorganic and / or organic binder, fired or unfired.
Preforming – It is the initial pressing of a metal powder to form a compact which is to be subjected to a subsequent pressing operation other than coining or sizing. It is also preliminary forming operations, especially for impression-die forging.
Preheat – It is a non-standard term for preheat temperature.
Preheat current (resistance welding) – It is an impulse or series of impulses which occur prior to and are separated from the welding current.
Preheated air – It is the air at a temperature exceeding that of the ambient air.
Preheating – It is the heating before some further thermal or mechanical treatment. It is the heating of a compound before moulding or casting, to facilitate the operation or reduce the moulding cycle. For tool steel, it is heating to an intermediate temperature immediately before final austenitizing. For some non-ferrous alloys, it is the heating to a high temperature for a long time, in order to homogenize the structure before working. In welding and related processes, it is the heating to an intermediate temperature for a short time immediately before welding, brazing, soldering, cutting, or thermal spraying. In powder metallurgy, it is an early stage in the sintering procedure when, in a continuous furnace, lubricant or binder burn off occurs without atmosphere protection prior to actual sintering in the protective atmosphere of the high heat chamber.
Preheat temperature – It is a specified temperature which the base metal is required to attain in the welding, brazing, soldering, thermal spraying, or cutting area immediately before these operations are performed.
Preimpregnation – In case of reinforced plastics, it is the practice of mixing resin and reinforcement and effecting partial cure before use or shipment to the user.
Preliminary Feasibility study – A Preliminary Feasibility study (Pre-Feasibility study) is a comprehensive study of a range of options for the technical and economic viability of a mineral project which has advanced to a stage where a preferred mining method, in the case of underground mining, or the pit configuration, in the case of an open pit, is established and an effective method of mineral processing is determined. It includes a financial analysis based on reasonable assumptions on the Modifying factors and the evaluation of any other relevant factors which are sufficient for a Competent person, acting reasonably, to determine if all or part of the Mineral resources can be converted to an Ore reserve at the time of reporting. A Pre- Feasibility study is at a lower confidence level than a Feasibility study.
Preliminary investigation – It is the initial fact-finding stage of the investigative process in the case of an accident or an equipment failure. It involves attending to injured persons, physical detailed observation of the area, collection of samples and taking relevant photographs of failure part, finding out potential reasons, questioning witnesses, preserving the scene of accident or failure, forwarding information to relevant authorities, and preparing a preliminary report for follow-up investigators.
Premix – It is a uniform mixture of components prepared by a powder producer for direct use in compacting. It is also a term which is sometimes applied to the preparation of a premix.
Premix burner – It is a burner which is used in flame emission and atomic absorption spectroscopy in which the fuel gas is mixed with the oxidizing gas before reaching the combustion zone.
Premixed combustion – n this method, fuel and air are mixed before the burner head. A chemical reaction occurs between fuel and air at the flame formation place. This technology is used in premixed burners.
Pre-moulding – It is the lay-up and partial cure at an intermediate cure temperature of a laminated or chopped-fibre detail part to stabilize its configuration for handling and assembly with other parts for final cure.
Pre-painted steel sheets – These sheets are produced by forming polymer films 10 micrometers to 30 micrometers thick on the surfaces of galvanized steel sheets in order to provide specific colours and designs. They are mainly used in applications such as roofing, siding, and shutters on various buildings. On the other hand, organic composite coated steel sheets are produced by forming thin organic composite films 1 micrometer to 2 micrometers thick on the surfaces of galvanized steel sheets. They are used in applications which do not need such aesthetic designs as pre-painted steel sheets, e.g., roofing, siding, and structural materials of non-residential, industrial and commercial buildings. Basic properties required of organic composite coated steel sheets are formability (the property which suppresses the peeling and scoring of metal coatings during roll forming) and corrosion resistance. In addition to these properties, pre-painted steel sheets have to have an excellent surface appearance, free from cracks and other damage. This has to be maintained even after forming.
Preply – It is a composite material lamina in the raw-material stage, ready to be fabricated into a finished laminate. The lamina is normally combined with other raw laminae before fabrication. A preply includes a fibre system which is placed in position relative to all or part of the needed matrix material to constitute the finished lamina. An organic matrix preply is called a prepreg. Metal-matrix preplies include green tape, flame-sprayed tape, and consolidated mono-layers.
Prepolymer – It is a chemical intermediate whose molecular weight is between that of the monomer or monomers and the final polymer or resin.
Prepreg – · In composites fabrication, either ready-to-mould material in sheet form or ready-to-wind material in roving form, which can be cloth, mat, unidirectional fibre, or paper, impregnated with resin and stored for use. The resin is partially cured to a B-stage and supplied to the fabricator, who lays up the finished shape and completes the cure with heat and pressure. The two distinct types of prepreg available are commercial prepregs, in which the roving is coated with a hot melt or solvent system to produce a specific product to meet specific customer requirements; and wet prepreg, in which the basic resin is installed without solvents or preservatives but has limited room-temperature shelf life.
Pre-reactor – It is used in hydro-refining of crude benzol. The vapours from the top of the evaporator at the temperature of 180 deg C are heated in a heat exchanger to the temperature range of 190 deg C to 225 deg C by passing main reactor effluent through shell side. The reactor is provided with a bed of catalyst. The most commonly used catalyst is the nickel-molybdenum catalyst. In this pre-reactor such as di-olefins, styrene and carbon di-sulphide are removed by hydrogenation. Feed enters from the bottom of the reactors through the catalyst bed. The temperature at the feed at the inlet of the reactor is ranging from 190 deg C to 225 deg C. The life cycle of the catalyst is sensitive to the temperature. Because of the exothermic reaction, the outlet temperatures are in the temperature range of 200 deg C to 235 deg C. Due to continuous operation of the catalyst bed, coke like polymerization products deposit on the catalyst bed resulting in the lower efficiency. This can be overcome by increasing the inlet temperature of the reactor. Catalyst activity can be determined by the temperature difference between inlet and outlet, which is required to be more than 10 deg C. The catalyst can be regenerated by heating the bed with steam and air.
Prescriptive standard – It is a standard which states the requirements in terms of specific details and leaves no discretion to the designer. It is sometimes referred to as a design standard.
Pre-shadowed replica – It is a replica for fractographic or metallographic inspection which is formed by the application of shadowing material to the surface to be replicated. It is formed before the thin replica film is cast or otherwise deposited on the surface.
Pre-sintered blank – It is a compact sintered at a low temperature but at a long enough time to make it sufficiently strong for metal working.
Pre-sintered density – It is the relative density of a pre-sintered compact.
Pre-sintering – It is the heating a powder metallurgy compact to a temperature below the final sintering temperature, normally to increase the ease of handling or shaping of a compact or to remove a lubricant or binder (burn off) prior to sintering.
Press – It is a machine tool having a stationary bed and a slide or ram which has reciprocating motion at right angles to the bed surface, the slide being guided in the frame of the machine. It is the machine used for compacting, sizing, or coining. Presses can be (i) mechanical e.g., eccentric, crank, cam, toggle, knuckle joint, and rotary table, (ii) hydraulic e.g., single action, double action, and multiple action, or (iii) combination mechanical-hydraulic. The term also denotes the process of producing a compact, which is also sometimes called pressing.
Press brake – It is an open-frame single-action press used to bend, blank, corrugate, curl, notch, perforate, pierce, or punch sheet metal or plate. Press brake is mainly designed for the precise bending and forming of thin plate sheets. With the development of technology, from the mechanical press brake to the emergence of the electric press brake, and then to the introduction of computer numerical control technology, the function and efficiency of the press brake have significantly improved. It can bend the sheet into different angles and improve processing accuracy and production efficiency through computer numerical control. Press brakes are ordinarily used for small lots, non-critical work, and long parts.
Press-brake forming – It is a metal forming process in which the work-piece is placed over an open die and pressed down into the die by a punch which is actuated by the ram portion of a press brake. The process is most widely used for the forming of relatively long, narrow parts which are not adaptable to press forming and for applications in which production quantities are very small to warrant the tooling cost for contour roll forming.
Press capacity – It is the rated force a press is designed to exert at a predetermined distance above the bottom of the stroke of the slide.
Press clave – It is a simulated autoclave made by using the platens of a press to seal the ends of an open chamber, providing both the force needed to prevent loss of the pressurizing medium and the heat needed to cure the laminate inside.
Pressed density – It is the weight per unit volume of an unsintered compact.
Press forging – In press forging, the metal is shaped not by means of a series of blows as in hammer forging, but by means of a single continuous squeezing action.
Press forming – It is a sheet metal forming operation which is performed with tooling by means of a mechanical or hydraulic press. It is a metal-working process in which the work-piece takes the shape imposed by the punch and die. The applied forces can be tensile, compressive, bending, shearing, or different combinations of these. In some applications, the metal needs appreciable stretching in order to retain the shape of the formed part.
Pressing – The preferred term is compacting. It is the process of producing a compact
Pressing area – It is the clear distance (left to right) between housings, stops, gibs, gib-ways, or shoulders of strain rods, multiplied by the total distance from front to back on the bed of a metal forming press.
Pressing crack – It is a rupture in a green powder metallurgy compact which develops during ejection of the compact from the die. It is sometimes referred to as a slip crack.
Pressing skin – It is the surface of a compact which is superficially more deformed than the interior because of a preferential alignment of the particles caused by contact with the die wall and punch faces.
Pressing tool – It is also called press tool. It is the complete tool assembly consisting of the die, a die adaptor, the punches, and when needed a core rod.
Press load – It is the quantity of force which is exerted in a given forging or forming operation.
Press quenching -It is a quench in which hot dies are pressed and aligned with a part before the quenching process begins. Then the part is placed in contact with a quenching medium in a controlled manner. This process avoids part distortion.
Press slide – It is the main reciprocating member of a press, guided in the press frame, to which the punch or upper die is fastened. It is sometimes called the ram. The inner slide of a double-action press is called the plunger or punch-holder slide. The outer slide is called the blank holder slide. The third slide of a triple-action press is called the lower slide, and the slide of a hydraulic press is frequently called the platen.
Pressure – It is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure is the pressure relative to the ambient pressure. Different units are used to express pressure. Some of these derive from a unit of force divided by a unit of area. The SI (International System of Units) unit of pressure, the pascal (Pa), e.g., is one newton per square metre.
Pressure bag moulding – It is a process for moulding reinforced plastics in which a tailored, flexible bag is placed over the contact layup on the mould, sealed, and clamped in place. Fluid pressure, normally provided by compressed air or water, is placed against the bag, and the part is cured.
Pressure bonding – It means joining at high temperature of powder metallurgy parts or sections to one another or to wrought metal, sheet, or castings, without using liquid auxiliary metal, such as solder, brazing alloy, or weld metal.
Pressure casting – It consists of making castings with pressure on the molten or plastic metal, as in die casting, centrifugal casting, cold chamber pressure casting, and squeeze casting. It is also a casting made with pressure applied to the molten or plastic metal.
Pressure-controlled welding – It is a resistance welding process variation in which a number of spot or projection welds are made with several electrodes functioning progressively under the control of a pressure-sequencing device.
Pressure controller – It is a device to regulate and control the pressure of fluids or gases within a system. Its primary function is to maintain pressure levels within specified limits, ensuring optimal operation of the system.
Pressure control valve – It is a mechanical device designed to manage and maintain desired pressure levels within a system. The pressure control valve enables the regulation of system pressure to adjust the force on a hydraulic piston rod or the torque on a hydraulic motor shaft. Pressure-control valves are found in practically every pneumatic and hydraulic system. They help in a variety of functions, from keeping system pressures below a desired limit to maintaining a set pressure level in part of a circuit. Different types of pressure control valves include relief, reducing, sequence, counterbalance, safety, and unloading. All of them are typically closed valves, except for reducing valves, which are normally open.
Pressure difference – It is the difference between the pressure on the inlet side of the leak and the pressure on the exit side of the leak.
Pressure distillation – It is consists of distillation under reduced pressure. It is used to purify a liquid which has a tendency to decompose when heated to a high temperature. Under the conditions of reduced pressure, the liquid boils at a temperature lower than its boiling point, and as a result, the liquids do not degrade as they do otherwise.
Pressure-drop – It is the difference in pressure between two points in a system, caused by resistance to flow.
Pressure dye test – It is a form of leak test in which the systems are filled with liquid, fluorescent oil which is then pressurized for the purpose of driving liquid through possible leakage paths and so make its presence visible when the excess liquid has been removed from the exterior. It is also a leak test in which the systems are immersed in a liquid dye or fluorescent oil and then pressurized for the purpose of driving liquid through possible leakage paths and so make its presence visible when the excess liquid has been removed from the exterior.
Pressure evacuation test – It is a leak test in which one or more devices are placed under gas pressure for a period of time, the objective being to accumulate enough gas in those devices which can leak to permit an indication on a leak detector sensitive to the gas when the devices are placed in an evacuated system jointed to the leak detector. It is also known as ‘inside out method’, back pressuring testing, or bomb test.
Pressure gas welding (PGW) – It is an oxy-fuel gas welding process which produces coalescence simultaneously over the entire area of abutting surfaces by heating them with gas flames got from combustion of a fuel gas with oxygen and by application of pressure, without the use of filler metal.
Pressure-impregnation-carbonization (PIC) – It is a densification process for carbon-carbon composites involving pitch impregnation and carbonization under high temperature and isostatic pressure conditions. This process is carried out in hot isostatic press (HIP) equipment.
Pressure intensifier – It is a layer of flexible material (normally a high-temperature rubber) which is used to ensure the application of sufficient pressure to a location, such as a radius, in a lay-up being cured.
Pressure-less sintering – It means sintering of loose powder.
Pressure lubrication – It is a system of lubrication in which the lubricant is supplied to the bearing under pressure.
Pressure measurement – It is a relative measurement which defined as either gauge or absolute. A pressure measurement can further be described by the type of measurement being performed. The three methods for measuring pressure are absolute, gauge, and differential. Absolute pressure is referenced to the pressure in a vacuum, whereas gauge and differential pressures are referenced to another pressure such as the ambient atmospheric pressure or pressure in an adjacent vessel. A pressure measurement can be described as either static or dynamic. The pressure in cases with no motion is static pressure. Frequently, the motion of a fluid changes the force applied to its surroundings. A thorough pressure measurement is to note the circumstances under which it is made. Many factors including flow, compressibility of the fluid, and external forces can affect pressure. Static pressure is uniform in all directions, so pressure measurements are independent of direction in a stationary (static) fluid. Flow, however, applies additional pressure on surfaces perpendicular to the flow direction, while having little impact on surfaces parallel to the flow direction. This directional component of pressure in a moving (dynamic) fluid is called dynamic pressure. An instrument facing the flow direction measures the sum of the static and dynamic pressures and this measurement is called the total pressure. Since dynamic pressure is referenced to static pressure, it is neither gauge nor absolute and it is known as the differential pressure. While static gauge pressure is of primary importance in determining the net loads on pipe or vessel walls, dynamic pressure is used to measure flow rates and air / gas speed. Dynamic pressure can be measured by taking the differential pressure between instruments parallel and perpendicular to the flow. The presence of the measuring instrument inevitably acts to divert flow and create turbulence, so its shape is critical to the accuracy and the calibration curves are frequently non-linear.
Pressure measurement devices – There are three distinct groups of pressure measurement devices. One is based upon the measurement of the height of a liquid column, another is based on the measurement of the distortion of an elastic pressure chamber, and a third encompasses electrical sensing devices. In liquid column pressure measuring devices the pressure is balanced against the pressure exerted by a column of a liquid with known density. The height of the liquid column directly correlates to the pressure to be measured. Majorities of the forms of liquid column measurement devices are called manometers. Elastic element pressure measuring devices are those in which the measured pressure deforms an elastic material. The magnitude of the deformation is around equivalent to the applied pressure. Different types of elastic element measuring devices include Bourdon tubes, bellows, and diaphragms. Electrical sensing devices are based on the fact that when electrical conductors are stretched elastically, their length increases while the diameter decreases. Both of these dimensional changes result in an increase in electrical resistance of the conductor. Strain gauges and piezoelectric transducers are examples of electrical pressure sensing devices. To avoid maintenance issues, the location of pressure measuring devices are to be carefully considered to protect against vibration, freezing, corrosion, temperature, and over-pressure etc. For example, in the case of a hard to handle fluid, an inert gas is sometimes used to isolate the sensing device from direct contact with the fluid. Optical fibre can be used for pressure measurement in high temperature environments.
Pressure measuring instruments – The normal pressure measuring instrument types are pressure transmitters, level probes, pressure switches, and process transmitters. Basically, these electronic pressure measuring instruments consist of a pressure connection, a pressure sensor, electronics, an electrical connection and the case. In addition, there are also simpler instrument types known as pressure sensor modules which are often consisting of no more than a pressure sensor and simple mechanical and electrical interfaces. These types are particularly suitable for complete integration into users’ systems.
Pressure mottling – It is non-uniform surface appearance resulting from uneven pressure distribution between adjacent layers of the product.
Pressure pipe – Pressure pipe, as distinguished from pressure tubes, is a commercial term for pipe that is used to convey fluids at higher pressure or higher temperature, or both, but which is not subjected to the external application of heat. This product is not differentiated from other types of pipes by standards, and the applicable specifications are listed with the other types of pipes. Pressure pipe ranges in size from 3 millimeters nominal to 650 millimeters actual outer diameter in different wall thicknesses. Pressure pipe is supplied in random lengths, with threaded or plain ends, as needed.
Pressure plate – It is a plate located beneath the bolster which acts against the resistance of a group of cylinders mounted to the pressure plate to provide uniform pressure throughout the press stroke when the press is symmetrically loaded.
Pressure reducing valve – It is an automatic control valve which is designed to reduce a higher unregulated inlet pressure to a constant, reduced downstream (outlet) pressure regardless of variations in demand and / or upstream (inlet) fluid pressure.
Pressure regulator – It is a valve which controls the pressure of a fluid to a desired value, using negative feedback from the controlled pressure. Regulators are used for gases and liquids, and can be an integral device with a pressure setting, a restrictor, and a sensor all in the one body, or consist of a separate pressure sensor, controller, and flow valve.
Pressure relief valves – Pressure relief valves release excess pressure to prevent system damage. They are used as a safety device to protect equipment from over-pressure occurrences in a technological process. Loss of heating and cooling, mechanical failure of valves, and poor draining and venting are some of the common causes of over-pressure. The relieving system depends on the process at hand. Pressure relief valves either bypass the fluid to an auxiliary passage or open a port to relieve the pressure to the atmosphere. Technological processes operating at high pressure normally have several pressure relief valves to follow the safety codes and procedures specified for these processes. Each of the pressure relief valves has different levels of pressure ratings to release different amounts of material to the atmosphere in order to minimize environmental impact.
Pressure roller – It is a specialized roller which is used to maintain contact between the driving belt and the load-carrying rollers within a belt-driven live roller conveyor system.
Pressure rolling process – It is a mechanical strengthening process which has some similarities to the shot peening process. It is normally applied to work-pieces with cylindrical symmetry. A roll is pressed against the work-piece to get high-compressive residual stresses. Very deep affected zones can be obtained.
Pressure-sensitive adhesive – It is a viscoelastic material which, in solvent-free form, remains permanently tacky. Such material adheres instantaneously to majority of the solid surfaces with the application of very light pressure.
Pressure sintering – It is a hot-pressing technique which normally uses low loads, high sintering temperatures, continuous or discontinuous sintering, and simple moulds to contain the powder. Although the terms pressure sintering and hot pressing are used interchangeably, there exist distinct differences between the two processes. In pressure sintering, the emphasis is on thermal processing, while in hot pressing, applied pressure is the main process variable.
Pressure-state-response (PSR) framework – This framework links pressures on the environment as a result of human activities, with changes in the state (condition) of the environment (land, air, water, etc.). Society then responds to these changes by instituting environmental and economic programmes and policies, which feed-back to reduce or mitigate the pressures or repair the natural resource.
Pressure swing adsorption (PSA) – It is a technique which is used to separate some gas species from a mixture of gases (typically air) under pressure as per the species’ molecular characteristics and affinity for an adsorbent material. It operates at near-ambient temperature and significantly differs from the cryogenic distillation which is normally used to separate gases. Selective adsorbent materials such as zeolites (also known as molecular sieves), and activated carbon etc. are used as trapping material, preferentially adsorbing the target gas species at high pressure. The process then swings to low pressure to desorb the adsorbed gas. The pressure swing adsorption process is based on the phenomenon that under high pressure, gases tend to be trapped onto solid surfaces, i.e., to be ‘adsorbed’. The higher the pressure, the more gas is adsorbed. When the pressure is dropped, the gas is released, or desorbed.
Pressure swing distillation (PSD) – It is a method that makes use of the pressure sensitivity of azeotropic mixtures for separation. Hence, by designing more than one column operating at significantly different pressures, the distillation boundaries are shifted so that the separation can be achieved.
Pressure switch – In several applications electronic pressure switches replace the mechanical pressure switches which were earlier very commonly used. This is because they offer, as a result of their design principle, additional functions such as digital display, adjustable switch points and considerably higher reliability. An electronic pressure switch is based on an electronic pressure transmitter and hence offers the entire functionality of a transmitter. With the integrated electronic switch, which can close or open an electrical circuit, it is able to perform simple control tasks. The switch point and the reset point can be set individually. By default, a pressure-switch only outputs binary signals such as switch point or reset point ‘reached’ or ‘not reached’ but it does not output how far the measured pressure is from the switch or reset point. Hence, several pressure switches have a display and additionally an analog output signal. The set parameters and measured pressure can be read off the display. In addition, the measured pressure can be transmitted by the analog output signal to a downstream control unit. Hence, the widely adopted type of electronic pressure switch includes a switch, a pressure transmitter and a digital indicator, all in one instrument.
Pressure test – It is a hydraulic or pneumatic test for pipes and tubes to prove that they material can withstand a specified pressure for a specified time without leakage or rupture.
Pressure testing method – It is a method of leak testing in which the component being tested is filled completely with a gas or liquid which is then pressurized. The outside of the component is examined for the detection of any leaks.
Pressure transducer – Pressure transducers are normally available in a multitude of sensor modules which can be directly matched to the requirements of the process. They have, for example, a user-specific pressure connection and / or a user-specific electric interface. Only very few suppliers of electronic pressure measurement technology even offer the so-called ‘bare’ pressure sensor as a module. For these, the users are to develop their own design solutions in order to get the pressure to the sensor and evaluate the sensor signal. For pressure transducers, it is normally the case that their correct function is to be ensured by the user’s design-related measures. Hence, this option is generally only suitable for mass-produced equipment.
Pressure transmitter – A pressure transmitter has standardized interfaces, both on the process side and on the electrical output signal side, and converts the physical pressure value to a standard industrial signal. The pressure connection is used to lead the pressure directly onto the sensor. It has a ‘standardized’ thread and an integrated sealing system to enable easy connection of the pressure transmitter simply by screwing it in at the relevant measuring point. A suitable case protects the sensor and the electronics against environmental influences. The electronics transform a weak sensor signal into a standardized and temperature compensated signal (e.g., the common industrial signal of 4-20 mA). The output signal is transmitted through a ‘standardized’ plug or cable for subsequent signal evaluation.
Pressure tubes – Pressure tubes are given a separate classification by both the standards and the manufacturers. The chemical composition limits for carbon steel and for alloy steel as well as the strength requirements are covered in the standards for these tubes. Pressure tubes are distinguished from pressure pipes in that they are suitable for the application of external heat while conveying pressurized fluids. Pressure tubes are used in different components of the boilers. These tubes are produced to actual outside diameter and minimum or average wall thickness (as specified by the user) and can be hot finished or cold finished, as needed.
Pressure vessel – It is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure. In nuclear power plant a pressure vessel is a closed, strong-walled container housing the core of most power reactors and designed to hold gases or liquids at high pressures. It also normally contains the moderator, neutron reflector, thermal shield, and control rods.
Pressure-viscosity coefficient – It is the slope of a graph showing variation in the logarithm of viscosity with pressure. The use of the term pressure-viscosity coefficient assumes a linear relationship.
Pressure welding – It is a group of welding processes which join metals at temperatures essentially below the melting points of the base materials, without the addition of a filler metal. Pressure may or may not be applied to the joint. The pressure welding processes are cold welding, diffusion welding, forge welding, hot pressure welding, pressure-controlled welding, pressure gas welding, and solid-state welding.
Pressurized gas lubrication – It is a system of lubrication in which a gaseous lubricant is supplied under sufficient external pressure to separate the opposing surfaces by a gas film.
Pressurized heavy water reactor – It is a reactor type which uses natural uranium as its fuel and heavy water as the coolant.
Pressurized water reactor – It is a reactor whose primary coolant is maintained under such a pressure that no bulk boiling occurs. The reactor uses light water as a moderator and as a coolant.
Pre-stressed concrete – It is a form of concrete which is used in construction. It is substantially ‘prestressed’ (compressed) during production, in a manner which strengthens it against tensile forces which exist when in service. This compression is produced by the tensioning of high-strength ‘tendons’ located within or adjacent to the concrete and is done to improve the performance of the concrete in service. Tendons can consist of single wires, multi-wire strands or threaded bars which are normally made from high-tensile steels, carbon fibre or aramid fibre. The essence of prestressed concrete is that once the initial compression has been applied, the resulting material has the characteristics of high-strength concrete when subject to any subsequent compression forces and of ductile high-strength steel when subject to tension forces. This can result in improved structural capacity and / or serviceability compared with conventionally reinforced concrete in several situations.
Pre-stressed structure – It is a load-bearing structure whose overall integrity, stability, and security depend, primarily, on prestressing which is the intentional creation of permanent stresses in the structure for the purpose of improving its performance under different service conditions. The basic types of prestressing are (i) pre-compression with mostly the structure’s own weight, (ii) pre-tensioning with high-strength embedded tendons, and (iii) post-tensioning with high-strength bonded or unbonded tendons.
Pre-tinning – It is a non-standard term for precoating.
Pre-treatment – It is subjecting steel to specific processes before galvanizing.
Pre-vapourizer – It is used during hydro-refining of crude benzol. It consists of a vertically mounted shell and tube heat exchanger. The feed is mixed with a part of recycles gas (containing H2 gas around 15 % of the total gas) before it is fed to the vaporizer. This feed is heated to around 160 deg C to 165 deg C by means of the main reactor effluent passing through shell side. The heated feed which is at a temperature of 160 deg C to 165 deg C is fed to the third mixing nozzle of stage evaporator. Pre-vaporizer is provided with turbulence promoters in the tube side to achieve high turbulence so that more heat exchange can occur and no scale formation is attained. This arrangement is provided as the feedstock in partial vapour stage (gas-liquid stage) to prevent rapid fouling of the tubes. This arrangement also provides easy cleaning of the tubes by simply pulling the turbulence promoters.
Prevention of significant deterioration (PSD) program – It applies to the construction of new major stationary sources and to major modifications of existing stationary sources. It also applies to modifications of existing minor stationary sources if the modification itself constitutes a major source. The basic goals of this program are to (i) ensure that economic growth occurs in harmony with the preservation of existing clean air resources, (ii) protect the public health and welfare from any adverse effects which can occur, and (iii) preserve, protect, and improve the air quality in areas of special natural, recreational, scenic or historic value.
Preventive action – It is a proactive way to prevent potential problems before they occur. It is a key part of quality management systems and is frequently used in conjunction with the corrective action.
Preventive maintenance – It is defined as ‘actions performed on a time or machine run based schedule which detect, preclude, or mitigate degradation of a component or equipment with the aim of sustaining or extending its useful life through controlling degradation to an acceptable level’. Preventive maintenance is carried out at pre-determined intervals or corresponding to prescribed criteria and intended to reduce the probability of failure or the performance degradation of an item. The maintenance cycles are planned as per the need and the incidence of operating faults is reduced.
Preventive order – It is a legislation-based command to prevent environmental, natural resource, or safety issues.
Price optimization process – It is the mathematical program which calculates how demand varies at different price levels then combines that data with information on costs and inventory levels to recommend prices that will improve profits. The process allows organizations to use pricing as a powerful profit lever, which often is underdeveloped. Price optimization process is used to tailor pricing for customer segments by simulating how targeted customers respond to price changes with data driven scenarios. Given the complexity of pricing thousands of items in highly dynamic market conditions, the results and insights obtained through the price optimization process help to forecast demand, develop pricing and promotion strategies, control inventory levels and improve customer satisfaction. Price optimization process is to factor in three critical pricing elements namely (i) pricing strategy, (ii) the value of the product to both buyer and seller, and (iii) tactics that manage all elements affecting profitability.
Price-to-earnings ratio – The current market price of a stock divided by the organization’s net earnings per share for the year.
Primary – It is the simplest, most commonly known, or canonical form of a chemical compound with multiple similar or isomeric forms. For example, in a primary alcohol, the carbon is bonded to a single substituent group (R1CH2OH), whereas a secondary alcohol is doubly substituted (R1R2CHOH) and a tertiary alcohol is triply substituted (R1R2R3COH). In case of X-ray, primary is the beam incident on the sample.
Primary air – It is the air introduced with the fuel at the burner.
Primary alloy – It is any alloy whose major constituent has been refined directly from ore, and not recycled scrap metal.
Primary alpha – It is the alpha phase in a crystallographic structure which is retained from the last high-temperature alpha-beta working or heat treatment. The morphology of alpha is influenced by the prior thermo-mechanical history.
Primary boiling – It is the evolution of gas during the initial firing of porcelain enamel. It is sometimes considered a defect.
Primary coil – It is the coil in a transformer which is connected to the input voltage source. It is responsible for generating a magnetic field when an alternating current flows through it, which induces a voltage in the secondary coil. This process is crucial for transforming electrical energy from one voltage level to another, highlighting the primary coil’s role in efficient power transmission.
Primary cooling zone – In a continuous casting machine, it consists of water-cooled copper mould through which the liquid steel is fed from the tundish for generating a solidified outer steel shell sufficiently strong enough to maintain the strand shape as it passes into the secondary cooling zone.
Primary creep – It is the first, or initial, stage of creep, or time-dependent deformation.
Primary crystals – It is the first type of crystals which separate from a melt during solidification.
Primary crusher – It breaks up large pieces of rock or concrete from the blasting or excavation process and turns them into smaller, more manageable chunks. This is the first step in the crushing process. The smaller pieces can then either be pre-screened or fed directly into a secondary impact or cone crusher.
Primary crushing – In an ore mine, it is the first crushing of mined ore.in the process. Run of Mine (ROM) materials are brought directly from the blasting areas and crushed in a primary crusher for the first round of crushing. At this point, the material receives its first reduction in size from its raw state. Two types of crushers which are used in primary crushing are jaw crusher and gyratory crusher.
Primary current distribution – It is the current distribution in an electrolytic cell which is free of polarization. It refers to the theoretical distribution of electric current within the electrolyte, solely based on the resistance of the solution, neglecting any effects of electrode kinetics (overpotential) or concentration gradients, essentially showing how current would flow if the only factor affecting its distribution was the electrolyte’s resistivity and cell geometry; it is considered a simplified model to analyze the basic current flow patterns within the cell.
Primary deposits – These are valuable minerals deposited during the original period or periods of mineralization, as opposed to those deposited as a result of alteration or weathering.
Primary energy consumption – It measures the total energy demand of a country. It covers consumption of the energy sector itself, losses during transformation (for example, from oil or gas into electricity) and distribution of energy, and the final consumption by end users. It excludes energy carriers used for non-energy purposes (such as petroleum not used not for combustion but for producing plastics).
Primary etching – It is the development of cast structures including coring.
Primary extinction – It is a decrease in intensity of a diffracted X-ray beam which is caused by perfection of crystal structure extending over such a distance (around 1 micrometer or higher) that interference between multiply reflected beams inside the crystal decreases the intensity of the externally diffracted beam.
Primary instruments – These are also called absolute instruments. These instruments are those instruments which give the value of electrical quantity to be measured in terms of the constants of the instruments and their deflection only e.g. tangent galvanometer. These instruments are rarely used except in standard laboratories, especially for calibration of secondary instruments. Working with absolute instruments for routine work is time consuming since every time a measurement is made, it takes a lot of time to compute the magnitude of the quantity under measurement. The use of the absolute instruments is simply confined within laboratories as standardizing instruments.
Primary leakage – In seals, it is the leakage of a mechanical seal, with the fluid escaping from the region between the end faces of the primary sealing elements.
Primary metal – It is the metal which is extracted from minerals and free of reclaimed metal scrap.
Primary mill – It is a mill for rolling ingots or the rolled products of ingots to blooms, billets, or slabs. This type of mill is frequently called a blooming mill or slabbing mill and sometimes called a cogging mill.
Primary passive potential (passivation potential) – It is the potential corresponding to the maximum active current density (critical anodic current density) of an electrode which shows active-passive corrosion behaviour.
Primary pollutants – These are those substances which are directly produced by a process, such as ash from a volcanic eruption or carbon mono-oxide gas from the exhaust of an automobile. Primary pollutants can be transformed in the lower atmosphere by solar radiation and heat or by chemical action in the atmosphere into secondary pollutants, such as ozone and other photochemical pollutants or acid rain. Primary air pollutants are emitted directly into the air from sources. They can have effects both directly and as precursors of secondary air pollutants.
Primary processing discontinuities – Primary processing discontinuities refers to the discontinuities which originate during hot or cold forming processes such as rolling, forging, extrusion, drawing, and welding etc. Also, some of the inherent discontinuities in the material can propagate and become significant.
Primary scale – It is composed of three well defined layers of iron oxides. Adjacent to the steel is the thickest layer consisting of wustite having an approximate composition of FeO. The intermediate layer consists of magnetite (Fe3O4) while the outermost layer is hematite (Fe2O3). The thicknesses of these layers depend on several factors linked to the rolling of the steel and the availability of oxygen at the steel surface. The layer at the surface of the steel is richest in oxygen and constitutes 0.5 % to 2 % of scale thickness. The layer at the metal surface is richest in iron and constitutes about 85 % of the scale thickness. The intermediate layer of scale constitutes around 13 % to 14.5 % of scale thickness.
Primary sensing element (PSE) – It is a device directly sensing the process variable and translating the sensed quantity into an analog representation (electrical voltage, current, resistance, mechanical force, or motion etc. Examples are thermocouple, thermistor, bourdon tube, microphone, potentiometer, electro-chemical cell, and accelerometer etc.
Primary shaping processes – In these processes, the material initially has no shape but gets a well-defined geometry through the process. Examples are casting, melt extrusion, die casting, and pressing of metal powder.
Primary standard – It is a standard which is designated or widely acknowledged as having the highest metrological qualities and whose value is accepted without reference to other standards of the same quantity. The concept of primary standard is equally valid for base quantities and derived quantities.
Primary waste-water treatment – It is the removal of particulate materials from waste-water, normally done by allowing the solid materials to settle as a result of gravity. Typically, it is the first major stage of treatment encountered by the waste-water as it enters a treatment facility. Primary treatment plants normally remove 25 % to 35 % of the biological oxygen demand (BOD) and 45 % to 65 % of the total suspended matter. It is also a process which used for the decomposition, stabilization, or disposal of sludges produced by settling.
Primary winding – Primary winding of transformers is the coil which draws power from the source. Transformers have separate coils, and contain several turns of wire and a magnetic core, which forms a path for and concentrates the magnetic flux. The winding receiving electrical energy from the source is called the primary winding. The winding which receives energy from the primary winding, through the magnetic field, is called the secondary winding. Either the high-voltage or low-voltage winding can be the primary or the secondary. With generator set-up at power plants, the primary winding is the low-voltage side (generator voltage), and the high voltage side is the secondary winding (transmission voltage). Where power is used, the primary winding is the high-voltage side, and the secondary winding is the low-voltage side.
Primary X-ray – It is the emergent beam from the X-ray source.
Prime mover – A prime mover is defined to be a machine which transforms energy from thermal, electrical, or pressure form to mechanical form, typically an engine or turbine. It is the heart of an energy system. Normally, the output of a prime mover is the rotary motion, so it is always being used to couple with an electric generator.
Primer – It is also known as undercoat. It is a preparatory coating put on materials before painting. Primer ensures better adhesion of paint to the surface, increases paint durability, and provides additional protection for the material being painted.
Primes – It consists of metal products, principally sheet and plate, of the highest quality and free from blemishes or other visible imperfections.
Priming – It is the discharge of steam containing excessive quantities of water in suspension from a boiler, because of violent effusion. It is the representation of wetness fraction in percentage.
Principal stress (normal) – It is the maximum or minimum value of the normal stress at a point in a plane considered with respect to all possible orientations of the considered plane. On such principal planes the shear stress is zero. There are three principal stresses on three mutually perpendicular planes. The state of stress at a point can be (i) uniaxial, which is a state of stress in which two of the three principal stresses are zero, (ii) biaxial, which is a state of stress in which only one of the three principal stresses is zero, and (iii) triaxial, which is a state of stress in which none of the principal stresses is zero. Multiaxial stress refers to either biaxial or triaxial stress.
Principle of measurement – It is the scientific base of a measurement. Examples are (i) the thermoelectric effect applied to the measurement of temperature, (ii) the Josephson effect applied to the measurement of electric potential difference, (iii) the Doppler effect applied to the measurement of velocity, and (iv) the Raman effect applied to the measurement of the wave number of molecular vibrations.
Printed board drawing sets – It consist of those drawings which define the configuration of printed wiring or printed circuit boards and assemblies. They establish requirements for assembly and test. A typical drawing set includes an assembly drawing, schematic diagram, master drawing, and may include an artwork master. It specifies the engineering requirements for assembly and includes (i) identification of parts, materials, and processes required for the assembly, (ii) electrical insulating requirements, (iii) reference designations, terminal identification, polarity symbols, and index marks, (iv) control dimensions, (v) jumper wires, (vi) requirements for identification and traceability marking, spot bonding, conformal coating, and masking, part mounting, support, and assembly, cleanliness, part orientation and polarity, electrostatic discharge protection, special solder plug, lead forming, and electric testing , (vii) solder mask, and (ix) reference document identification.
Principal structural element – It is an element of structure which contributes considerably to the carrying of flight, ground, or pressurization loads and whose integrity is essential in maintaining the overall structural integrity of the airplane.
Printed circuit – It is an electronic circuit consisting of thin strips of a conducting material such as copper, which have been etched from a layer fixed to a flat insulating sheet called a printed circuit board, and to which integrated circuits and other components are attached.
Printed circuit board (PCB) – It is a laminated sandwich structure of conductive and insulating layers, each with a pattern of traces, planes and other features (similar to wires on a flat surface) etched from one or more sheet layers of copper laminated onto or between sheet layers of a non-conductive substrate. Printed circuit boards are used to connect or ‘wire’ components to one another an electronic circuit. Electrical components can be fixed to conductive pads on the outer layers, normally by soldering, which both electrically connects and mechanically fastens the components to the board. Another manufacturing process adds vias, metal-lined drilled holes which enable electrical inter-connections between conductive layers, to boards with more than a single side. Printed circuit boards are used in nearly all electronic products today.
Printed wiring boards – They are like the printed circuit boards are very important for all electronic devices. One important feature of a printed wiring board is its high component density. Hence, a good number of packaging techniques are used which include chip on board, chip scale packaging, and ball grid array. Also, the components of the surface mount have a miniature size. This offers maximum density of the component, coupled with providing some maintenance for the thermal, electrical, and the signal integrity of the device. One important factor in printed wiring board’s interconnection design is the speed of operation of electronic devices. Also, the speed of signal proportion has an inverse proportion to the dielectric constant) of the printed wiring board’s substrate material. Increasing the gates number, as well as clock rates will lead to an increase in the consumption of power. Printed wiring boards are poor heat conductors. Hence, proper care is needed when using the methods for the dissipation of the heat that which has been generated by the printed wiring board’s power consumption. Metal slugs, as well as conductive planes, thermal vias, heat sinks in printed wiring boards, are good techniques.
Printer – It is a device which makes permanent human readable images and text from computer data.
Printing – It is a method in which a carrier material is saturated with an etchant and pressed against the surface of the sample. The etchant reacts with one of the phases, and substances form that react with the carrier material, leaving behind a life-size image. It is used for exposing particular elements, e.g., sulphur (sulphur prints).
Prior appropriation – It is a law doctrine under which users who can demonstrate earlier use of a particular resource are given right which take precedence over all future users of the resource.
Prior-beta grain size – It the size of beta grains established during the most recent beta-field excursion. Grains can be distorted by subsequent sub-transus deformation. Beta grain boundaries can be obscured by a superimposed alpha-beta microstructure and detectable only by special techniques.
Prior particle boundary (PPB) – It is one of the common defects in a powder metallurgy superalloy, and it is a layer of tiny and continuous second phase omentum (apron like structure) on the original powder surface during heating process in milling and hot isostatic pressing or hot extrusion. This layer of precipitates may hinder the diffusion and connection between powder particles, resulting in a weak interface, damaging the alloy structure, and endangering the tensile, impact, and other mechanical properties of a powder metallurgy superalloy.
Priority – It is the concept that the person first using a resource has a better right to it than those commencing their use later. An appropriator is normally assigned a ‘priority date’. However, the date is not significant in and of itself, but only in relation to the dates assigned other resource users from the same source of the resource. Priority is only important when the quantity of available resource is not sufficient to meet the needs of all those having a right to use the resource.
Pristine-M process technology -This technology is for the drying of the low rank coals. It is a technology for converting raw low rank coal into a cleaner burning more efficient fuel. It addresses the need for a low moisture coal which is economical to transport, stable in transportation and does not reabsorb moisture. It is a low-cost coal de-watering technology which has succeeded in drying coal and stabilizing it cheaply using volatile matter (VM) released by the feed raw coal. It reduces the moisture content of low-rank coals, while also stabilizing and sealing the treated coals to prevent moisture re-absorptions and spontaneous combustion. The process also increases the calorific value (CV) of the low-rank coals to values which are comparable with the bituminous coals.
Prism – It is a transparent optical element whose entrance and exit apertures are polished plane faces. Using refraction and / or internal reflection, prisms are used to change the direction of propagation of
monochromatic light and to disperse polychromatic light into its component wavelengths.
PRMS – PRMS is Petroleum Resources Management System (PRMS), which was approved by the Society of Petroleum Engineers (SPE) Board and endorsed by the World Petroleum Council (WPC), the American Association of Petroleum Geologists (AAPG), the Society of Petroleum Evaluation Engineers (SPEE), and the Society of Exploration Geophysicists (SEG).
Probabilistic safety assessment – It is a mathematical tool for calculating the risk of certain problems or accidents occurring at a plant. It is the methodology to probabilistically estimate risks. Fault tree analysis and event tree analysis are integral techniques for probabilistic safety assessment.
Probability – It is a term used in statistic. It is concerning events and numerical descriptions of how likely they are to occur. The probability of an event is a number between 0 and 1, the larger the probability, the more likely an event is to occur. This number is frequently expressed as a percentage (%), ranging from 0 % to 100 %. A simple example is the tossing of a fair (unbiased) coin. Since the coin is fair, the two outcomes (‘head’ and ‘tails’) are both equally probable, the probability of ‘heads’ equals the probability of ‘tails’, and since no other outcomes are possible, the probability of either ‘heads’ or ‘tails’ is 1/2 (which can also be written as 0.5 or 50 %).
Probability density functions – It is synonymous with probability distributions, knowing the probability that a random variable takes on certain values, judgements can be made as to how likely or unlikely were the observed values. In general, observing an unlikely outcome tends to support the notion that chance is not acting alone. By posing alternative hypotheses to explain the generation of data, an analyst can conduct hypothesis tests to determine which of two competing hypotheses best supports the observed data.
Probability distribution – It is a statistical function which describes the probability of different possible values of a variable. It is a statistical function that describes all the possible values and probabilities for a random variable within a given range. Probability distributions are often depicted using graphs or probability tables.
Probability sample – It is a type of sample for which one can specify the probability that any member of the population is selected into it. This type of sample enables generalization of the study results to a known population.
Probability of detection – It is defined as the fraction of nominal discontinuity sizes expected to be found given their existence. The concept of probability of detection is used in different industry sectors to establish the capability of an inspection to detect flaws. This is normally expressed as a probability of detection curve, which relates the likelihood of detection to a characteristic parameter of the flaw, normally its size.
Probability of false alarm – In period (frequency) search, it is defined as the probability which a value resulting from a time-series analysis based on some form of periodogram is caused by noise. For example, the probability of false alarm is the probability of having an alarm, for a given material, in a given location if there is no mine in that location.
Probable Mineral reserves – Probable Mineral reserves are economically mineable part of indicated or in some cases, a Measured Mineral resource.
Probable Ore reserve – A Probable Ore reserve is the economically mineable part of an Indicated, and in some circumstances, a Measured Mineral resource. The confidence in the Modifying factors applying to a Probable Ore reserve is lower than that applying to a Proved Ore reserve.
Probable reserves – It consists of valuable mineralization which is not sampled enough to accurately estimate the terms of tonnage and grade. It is also called ‘indicated reserve’.
Probe – It is a physical device / instrument which is used to detect defects in the finished product restricting its utilization or making it unfit for use. Probe is used for sorting out the defective products from prime products.
Probe gas – It is a tracer gas which issues from a fine orifice so as to impinge on a restricted test arca.
Probe ion – It is an ionic species intentionally produced by an ion source and directed onto the sample surface at a known incident angle and a known energy.
Probe test – It is a leak test in which the tracer gas is applied by means of a probe so that the arca covered by the tracer gas is localized. This enables the individual leaks to be located.
Problem – It consists of the difference between an actual situation and a desired situation. The problem is defined as any event or situation, unforeseen, unwanted in an organization, a project, or a job which needs to be addressed and resolved before it becomes too complex.
Procedure – It is a step-by-step description of how to do a task, job, or activity properly.
Procedure qualification – It is the demonstration which welds made by a specific procedure can meet prescribed standards.
Procedure qualification record (PQR) – It is a document providing the actual welding variables used to produce an acceptable test weld and the results of tests conducted on the weld to qualify a welding procedure specification.
Process – It is the physical system which is to be controlled or measured. A process consists of a set of interrelated or interacting activities, which transforms inputs into outputs. These activities need allocation of resources such as people and materials. All the organizational processes are required to be aligned with the objectives, scope, and complexity of the organization, and are to be designed to add value to the organization. The assessment of the process effectiveness and efficiency can be carried out through internal or external reviews. In a process, inputs and intended outputs can be tangible (such as equipment, materials or components) or intangible (such as energy, or information). Outputs can also be unintended, such as wastes or pollution generation. Every process has customers and other interested parties (who can be either internal or external to the organization), with needs and expectations about the process, who define the required output of the process. It is also a grouping of basic operational elements used in welding, cutting, adhesive bonding, or thermal spraying.
Process annealing – It is a heat treatment used to soften metal for further cold working. In ferrous sheet and wire industries, it is heating to a temperature close to but below the lower limit of the transformation range and subsequently cooling for working. In the non-ferrous industries, it is heating above the recrystallization temperatures at a time and temperature sufficient to permit the desired subsequent cold working.
Process approach – The application of a system of processes within the organization, together with the identification and interactions of these processes, and their management to produce the desired outcome, can be referred to as process approach. The purpose of the process approach is to improve the organizational effectiveness and efficiency in achieving its defined objectives. Hence, a process approach means that the organization manages its operations as a system of processes and not as departments, or people, or products. This system is used to gather data to provide information about process performance, which is then to be analyzed to determine if there is any need for corrective action or improvement. The process approach includes establishing the organizational processes to operate as an integrated and complete system. This include (i) the management system integrates processes and measures to meet objectives, (ii) processes define interrelated activities and checks, to deliver intended outputs, and (iii) detailed planning and controls can be defined and documented as needed, depending on the organizational context.
Process audit – This audit is the testing of a process or a series of processes in production and administration. It is used in particular where specific key processes take place. It is first and foremost required to establish whether the production is under control and whether the actions / control are appropriately matched to the requirements of the quality criteria and quality evidence. These process competence investigations are frequently part of customer requirements. The process audit is to be used as early as possible, similar to the sample or first-sample verification.
Process average – It is a level at which a process is performing on an average.
Process behaviour over time – A succession of parts emanating from a process under statistical control show variability in their measurements because of a constant set of common causes. These variable measurements tend to collect into a predictable pattern of variation which can be easily described by a few simple statistical measures namely, a mean, a standard deviation, and a frequency distribution. These measures stand as a model which predicts how the process is going to behave if subject only to a constant set of common causes.
Process capability – It is a statistical measure of the inherent process variability of a given characteristic. A person can use a process-capability study to assess the ability of a process to meet specifications. During a quality improvement initiative, such as Six Sigma, a capability estimate is typically got at the start and end of the study to reflect the level of improvement which has occurred. Several capability estimates are in widespread use. The first is potential capability (Cp) and actual capability during production (Cpk) are process capability estimates. Cp and Cpk show how capable a process is of meeting its specification limits, used with continuous data. They are valuable tools for evaluating initial and ongoing capability of parts and processes. The second is sigma which is a capability estimate typically used with attribute data (i.e., with defect rates).
Process computer system (PCS) – It performs functions such as process control to optimize plant operation, and information services to operators. Process models to apply higher level control strategies are integrated in process computer system with special plant measurement systems.
Process control – It is a system used in modern manufacturing which uses the principles of control theory and physical industrial control systems to monitor, control and optimize continuous industrial production processes using control algorithms. This ensures that the industrial machines run smoothly and safely in factories and efficiently use energy to transform raw materials into high-quality finished products ith reliable consistency while reducing energy waste and economic costs, something which cannot be achieved purely by human manual control.
Process control panel – It is a flat, frequently vertical, area where control or monitoring instruments are displayed or it is an enclosed unit which is the part of a system that users can access. These panels are designed to monitor and control process parameter levels such as temperature, flow, current, and pressure from the field instruments which are connected to it. These panels are used in a wide variety of industries.
Process control software – The most widely adopted user friendly approach is the fill-in-the-forms or table-driven process control languages (PCL). Popular process control languages include function block diagrams, ladder logic, and programmable logic. The core of these languages is a number of basic function blocks or software modules, such as analog in, digital in, analog out, digital out, proportional–integral–derivative, summer, splitter, etc. Using a module is analogous to calling a sub-routine in conventional ‘Fortran’ or ‘C’ programmes. In general, each module contains one or more inputs and an output. The programming involves commuting outputs of blocks to inputs of other blocks through the graphical-user interface. Users are needed to fill in templates to indicate the sources of input values, the destinations of output values, and the parameters for forms / tables prepared for the modules. The source and destination blanks can specify process I/O (input / output) channels and tag names when appropriate. To connect modules, some systems need filling in the tag names of modules originating or receiving data. User specified fields include special functions, selectors (minimum or maximum), comparators (less than or equal to), and timers (activation delays).
Process control systems – These systems refer to the monitoring, controlling, and regulating of industrial processes using a variety of technologies and approaches. The objective of process control systems is to ensure that the process runs within the specified parameters, yields a consistent and high-quality result, and performs as efficiently as feasible.
Process design – It is the choice and sequencing of units for desired physical and / or chemical transformation of materials. Process design is central to the process engineering, and it can be considered to be the summit of that field, bringing together all of the field’s components. Process design can be the design of new facilities or it can be the modification or expansion of existing facilities. The design starts at a conceptual level and ultimately ends in the form of fabrication and construction plans. Process design is distinct from equipment design, which is closer in spirit to the design of unit operations. Processes often include many unit operations. In case of operation management, process design is the process of creating and improving systems which convert inputs into outputs. Process design involves understanding how work is done within an organization and then designing and implementing ways to improve it. There are several types of process designs, but all share some standard features. Process designs is required to take into account the resources needed to complete the process, the desired output of the process, and any constraints on the process. In addition, process designs is to be flexible enough to accommodate changes in inputs or outputs.
Process diagrams – These are the most effective way of communicating information about a process. A process diagram consists of activities, events, and gateways, which a sequence flow puts in a flow sequence. Activities, events, and gateways are summarized under the term flow object. A process diagram is the key to the development and management of an industrial production process. It is a diagram of the steps in a process and their sequence. It constitutes a simplified sketch which uses symbols to identify instruments and vessels and to describe the primary flow path through a unit.
Process-driven design – It is a design approach in which the manufacturing process plan or method of assembly is developed prior to developing the product design.
Process flow diagram – It is a type of flow-chart which demonstrates the relationships between major components of a plant unit. It is very frequently used in process engineering, though its concepts are sometimes applied to other processes as well. It is used to document a process, improve a process, or model a new process. Depending on its use and content, it can also be called a process flow chart, flow-sheet, schematic flow diagram, macro flow-chart, top-down flow-chart, system flow diagram, or system diagram. Process flow diagram primarily defines (i) a schematic representation of the sequence of all relevant operations occurring during a process and includes information considered desirable for analysis, (ii) the process presenting events which occur to the material(s) to convert the feed-stock(s) to the specified products, and (iii) an operation occurring when an object (or material) is intentionally changed in any of its physical or chemical characteristics, is assembled or dis-assembled from another object or is arranged or prepared for another operation, transportation, inspection or storage. Process flow diagram normally includes (i) plant design basis indicating feed-stock, product and main streams flow rates and operating conditions, (ii) identify the scope of the process, (iii) shows graphically the arrangement of major equipment, process lines, and main control loops, and (iv) shows needed utilities which are used continuously in the process.
Process improvement – It refers to the practice of finding ways to make existing processes faster, more accurate, more efficient, and more reliable. This practice is to be considered an ongoing exercise rather than a one-time action.
Processing window – It is the range of processing conditions, such as stock (melt) temperature, pressure, shear rate, and so on, within which a particular grade of plastic can be fabricated with optimal or acceptable properties by a particular fabricating process, such as extrusion, injection moulding, sheet moulding, and so on. The processing window for a particular plastic can vary significantly with design of the part and the mould, with the fabricating machinery used, and with the severity of the end-use stresses.
Process management – It is a concept which is based on the observation that each product that an organization provides to the market is the outcome of a number of activities performed. Processes are the key instrument for the organization of these activities and for improving the understanding of their interrelationships. The organization can reach its goals and objectives in an efficient and effective manner only if people and other organizational resources play together well. Processes are an important concept for facilitating this effective collaboration.
Process management systems – These are the systems which integrate all the functions required to manage a technological process system. Process management systems provide a common database for all functions and allow the integration of analog loop control, discrete logic control, data acquisition, data management, statistical calculations, and reporting. Communications and inter-connection are also by means of soft wiring, that is, by configuration and programming instead of physical hard wiring.
Process measurements – The most commonly measured process variables are temperatures, flows, pressures, levels, and composition, when appropriate, other physical properties are also measured. The selection of the proper instrumentation for a particular application is dependent on factors such as the type and nature of the fluid or solid involved, relevant process conditions, rangeability, accuracy, and repeatability needed, response time, installed cost, and maintainability and reliability.
Process metallurgy – It is the science and technology of winning metals from their ores and purifying metals. It is sometimes referred to as chemical metallurgy. Its two chief branches are extractive metallurgy and refining.
Process model – It is an ‘algorithm to predict the behaviour of an open or closed system’. It allows predictive control and operator assistance, off-line process optimization, improved understanding of the underlying physical phenomena, and the on-line estimation of parameters which cannot be determined directly through measurements. The term process model refers to the deterministic models based on physical and thermodynamic relationships, and hence excludes purely statistical approaches.
Process models – Process models are processes of the same nature which are classified together into a model. Hence, a process model is a description of a process at the type level. Since the process model is at the type level, a process is a representation of it. The same process model is used repeatedly for the development of several applications and hence, has several representations. One possible use of a process model is to prescribe how things are to be / can be done in contrast to the process itself which is really what happens. A process model is roughly an anticipation of what the process is going to look like. What the process is going to be is determined during actual system development. The goals of a process model are to be is (i) descriptive which includes tracking of what actually happens during a process and taking the point of view of an external observer who looks at the way a process has been performed and determining the improvements which are to be made to make it perform more effectively or efficiently, (ii) prescriptive which includes defining the desired processes and how they are to be / can be performed and establishing rules, guidelines, and behaviour patterns which, if followed, lead to the desired process performance (they can range from strict enforcement to flexible guidance), and (iii) explanatory which includes (i) providing explanations about the rationale of processes, (ii) exploring and evaluating the several possible courses of action based on rational arguments, (iii) establishing of an explicit link between processes and the requirements which the model needs to fulfill, and (iv) pre-defining of the points at which data can be extracted for reporting purposes.
Process optimization – It is the discipline of adjusting a process so as to make the best or most effective use of some specified set of parameters without violating some constraint. Common goals are minimizing cost and maximizing throughput and / or efficiency. Process optimization is one of the major quantitative tools in industrial decision making. When optimizing a process, the goal is to maximize one or more of the process specifications, while keeping all others within their constraints. This can be done by using a process mining tool, discovering the critical activities and bottlenecks, and acting only on them.
Process safety – It is a disciplined framework for managing the integrity of operating systems and processes which operates under hazardous conditions and handle hazardous materials. It relies on good design principles, engineering, and operating and maintenance practices. It deals with the prevention and control of undesirable events which have the potential to release hazardous materials and energy to the surrounding environment. It is normally accepted that ‘process safety’ is about preventing incidents which, while having a low likelihood of their occurrence, are associated with severe potential consequences. Process safety is needed for the protection of people and property from episodic and catastrophic incidents which can result from unplanned or unexpected deviations in process conditions.
Process simulation – It is used for the design, development, analysis, and optimization of technical process of simulation of technological processes, environmental systems, power stations, complex manufacturing operations, biological processes, and similar technical functions. Process simulation is a model-based representation of chemical, physical, biological, and other technical processes and unit operations in software. Basic prerequisites for the model are chemical and physical properties of pure components and mixtures, of reactions, and of mathematical models which, in combination, allow the calculation of process properties by the software.
Process steam – Process steam is a popular mode of conveying energy and can come into contact with the final process or product. It is the steam used for industrial purposes other than for producing power. It is the general term used for steam which is used in process applications such as a source of energy for process heating, process cooling, pressure control and mechanical drives among others. It is the steam used in various industrial processes mainly to utilize its heat and moisture. The most common operational end uses employed for process steam include stripping, fractionation, process heating and cooling, quenching, dilution, vacuum draw, pressure regulation, injection and source of process water etc.
Process transmitter – The process transmitter is a pressure transmitter with a pressure range which can be set within a predefined pressure range (turndown). It is mainly used in technological processes, since in this application area it is necessary to adjust every single measuring point to a multitude of specific requirements which are to be individually set by the operator on site. The process transmitters have very high measurement accuracy within the entire pressure range. In addition, the pressure range, the zero point and further parameters can normally be set individually. For this purpose, several process transmitters have both digital display and additional operating elements and extensive operating software directly within the instrument.
Process variable (PV) – It is the parameter whose quantity is to be measured in a process. Examples of parameters are pressure, level, temperature, flow, electrical conductivity, pH, position, and speed etc.
Process wastes – These are solid wastes which are generated during the production processes. These also includes wastes from the laboratories attached to the production processes. Examples of process wastes are slag, dust, sludge, scrap, refractories, scale, muck, and debris etc.
Process water – It is the water which comes into contact with raw material, product, by-product, or waste. All process water from the manufacturing plant is required to receive extensive treatment and be in compliance with all local regulatory requirements. Process water is used to keep the refinery product streams and equipment cool. By cooling the water in large cooling towers and re-circulating it, the quantity of fresh water needed is minimized.
Product – It is the collection of organizational capabilities valuable to a defined customer segment. A product can be just software and data. A product encompasses not only tangible physical goods but also services, experiences, and even ideas which can be marketed and sold. Products principally serve external customers. In case of mining terminology, product is defined as the products of the project which can be bought, sold, or used, including electricity, heat, hydrocarbons, hydrogen, minerals, and water. It is noted that with some projects, such as for renewables, the products (electricity, heat etc.) are different from the sources (wind, solar irradiation etc.). In other projects, the products and sources can be similar e.g., in petroleum projects both the sources and products are oil and / or gas, although the fluid state and properties can change from reservoir to surface conditions.
Product audit – It is the product audit can be considered as a shortened version of the process audit. In the product audit, the quality of products or components is tested at a specific part of the product production. At the same time, the documentation used up to this point and, if applicable, the fabrication and testing equipment used are also tested. A product audit is carried out to (i) establish the quality level of the products to be supplied, (ii) verify that the products to be supplied meet the specified quality standard, (iii) establish the quality level of the products delivered to testing stations, (iv) determine the capability of testing stations to identify quality defects and to make quality decisions, (v) assess the quality-control procedures, (vi) assess whether controlled production is taking place, and (vii) determine the reproducibility of the test results. The concept of the product audit is also to determine whether the necessary means and procedures are available to produce and assess a quality product.
Product design – It describes the process of imagining, creating, and iterating products which solve users’ problems or address specific needs in a given market. It is the process of creating new products for organizations to sell to their customers. It involves the generation and development of ideas through a systematic process that leads to the creation of innovative products. Hence, it is a major aspect of new product development.
Product design process – It consists of a sequence of steps which are followed by a product team to develop a design solution. It consists of a series of design tasks which follow a product from start to finish i.e., from idea to the final product ready to be commercially available to the target user.
Product design specification (PDS) – It is a detailed description of the intended and unintended uses which a product is going to be put to, a list of any special features required or desired, and a detailed list of the functional requirements with qualitative or quantitative goals and limits for each. It is also known engineering design specification.
Product diversification strategy – It is a form of organizational development. Organizations which implement the strategy can diversify their product range by modifying existing products or adding new products to the range. The strategy provides opportunities for the organization to grow the business by increasing sales to existing customers or entering new markets.
Product documentation – It consists of all of the documentation, whether on paper or in digital form, which defines the steps in designing the product and specifies the steps needed for its manufacture. These include product design specification, quality function deployment (QFD) matrices, concept selection results, geometric dimensioning and tolerancing schemes, detail drawings, bill of materials, and manufacturing process plans.
Product footprint – It is the part of the product which touches any part of the conveyor, including wheels, belts, or rollers.
Product integrity – In the manufacturing sense, it is the absence of voids, pores, cracks, and harmful inclusions.
Production drawing – It also referred to as working drawing. A component or part drawing is termed as a production drawing, if it facilitates its manufacture. It is an authorized document to produce the component on the shop floor. It furnishes all the dimensions, limits, and special finishing processes such as heat treatment, honing, griding, lapping, and surface finish etc., to guide the technician on the shop floor in producing the component. The title also mentions the material used for the product, and number of parts needed for the assembled unit etc. Since a technician normally makes one component at a time, it is advisable to prepare the production drawing of each component on a separate sheet. However, in some cases the drawings of related components can be given on the same sheet.
Production planning and control (PPC) – It is part of the production system of the organization and responsible for the smooth coordinated production in the organization. It is a tool available to the plant management to achieve the stated objectives of meeting the production targets in an efficient manner. It balances the available capacities with the product requirements to meet the market demands. With production planning and control plans, the production of the plant becomes systematic and becomes focal point for all the departments for the achievement of the departmental targets and objectives. Production planning and control carries out planning of production to establish the route of production and to make schedules which ensures optimum utilization of materials, production facilities and workforce. By close monitoring, it also ensures that the plant operation is carried out as per the plans and the results are obtained in terms of quantity, quality, delivery schedule and cost of production. The main objectives of production planning and control are (i) to prepare and monitor the production schedules, (ii) to carry out planning for the procurement of raw materials, fuels, utilities, and other materials, (iii) to plan product dispatch along with the marketing or sales department, (iv) to facilitate in the attainment of maximum utilization of resources, (v) to plan production of products of the needed quality, (vi) to plan with minimum manufacturing cycle time, (vii) to plan maintenance of optimum inventory levels at various production stages, (viii) to integrate maintenance schedules of the shop with production plan, (ix) to plan production with maximum flexibility in operations, (x) to achieve coordination between process, work-force and other connected departments, (xi) to collect various data and analyze it for monitoring and decision making, (xii) to act as a custodian for the data of production system, (xiii) to identify bottlenecks in fulfillment of production plans, and (xiv) to facilitate cost and budget controls and to achieve the goals at minimum cost.
Production plant – It is an industrial facility, frequently a complex consisting of several buildings filled with machinery, where workers manufacture items or operate machines which process input raw materials into products and by-products.
Production process – It is a process which uses resources, such as raw materials, labour, capital, utilities, power, and equipment, and turns them into finished goods or services for the customers. The goal of the production process is not only to produce but to do so efficiently. The goods or services are to be delivered to customers as quickly as possible. The production process is to be effective since it impacts the organizational performance.
Production scheduling – It is the process which determines the production schedule, identifies long-term raw material requirements, determines the pack-out schedule for end products and determines product available for sale. The information generated or modified by the production scheduling function includes (i) the production schedule, (ii) the actual production against the planned production, (iii) the production capacity and resource availability, and (iv) current order status.
Production systems – Production systems are systems which are used to produce goods or services. These systems frequently involve multiple steps or processes which are to be completed in order to produce the final product.
Productivity – It means the efficiency of production of goods or services expressed by some measure. Measurements of productivity are frequently expressed as a ratio of an aggregate output to single input or an aggregate input used in a production process, i.e. unit output per unit of resource input, typically over a specific period of time. The most common example is the (aggregate) labour productivity measure, one example of which is the output per worker. There are several different definitions of productivity (including those which are not defined as ratios of output to input) and the choice among them depends on the purpose of the productivity measurement and data availability. The key source of difference between different productivity measures is also normally related (directly or indirectly) to how the outputs and the inputs are aggregated to get such a ratio-type measure of productivity. Productivity is a crucial factor in the production performance of processes and organizations. Increasing productivity can help organizations to be more profitable.
Products liability – It is a legal term which describes the action whereby an injured party (plaintiff) seeks to recover damages for personal injuries or property loss from a producer and / or seller (defendant) when the plaintiff alleges that a defective product or design caused the injury or loss.
Product lifecycle management (PLM) – It is the process of managing the entire lifecycle of a product from its inception through the engineering, design, and manufacture, as well as the service and disposal of manufactured products. Product lifecycle management integrates people, data, processes, and business systems and provides a product information backbone for organizations and their extended enterprises.
Product mix – It refers to all the products an organization offers to its customers. It includes different categories of products, each with multiple options. Some products can be closely related, while others serve different needs. A well-balanced product mix helps an organization attract a wider audience, meet diverse customer preferences, and increase sales.
Product / process performance factors – These play varying roles and are important system factors / variables which play in influencing product / process performance. These factors are classified into four categories namely (i) signal factors which can be adjusted by the user to attain the target performance, (ii) control factors which are the product / process design parameters whose values are to be determined during the design process, (iii) noise factors which are either inherently uncontrollable or impractical to control because of technological / economic reasons, and (iv) scaling / leveling factors which are special cases of control factors that can be easily adjusted to achieve a desired functional relationship between a signal factor and the output response.
Product profile – It talks about competitor’s product, research and development activities, brand equity and loyalty, and patents.
Product quality – It refers to the characteristics, features, and attributes of a product which determine its ability to meet customer expectations and perform its intended function. Quality encompasses different aspects, such as reliability, durability, performance, safety, and conformance to specifications. Achieving and maintaining high product quality involves rigorous quality control measures, adherence to standards and regulations, continuous improvement initiatives, and feedback from customers and stakeholders. Product quality refers to the intrinsic attributes and characteristics of a product which determine its overall excellence and ability to meet customer needs and expectations. High-quality products are those which excel in different dimensions of quality, such as functionality, durability, usability, accessibility, and conformance. High-quality products conform to established quality standards and validation specifications. They consistently meet predetermined quality criteria.
Product quality management – The goal of the product quality management is to minimize the mistakes of the operators and the break-down of equipments and machines so as to have stable processes, hence, ensuring that the customers remain happy with the product performance and reorder the products. For this the organization is to put a relentless focus on product quality. Product quality management includes the following four major components. They are (i) quality planning, (ii) quality control, (iii) quality assurance, and (iv) quality improvement.
Products of combustion – These are the gases, vapours, and solids resulting from the combustion of fuel. These are the end product when fuels, such as hydrocarbons, remain after the process of combustion. Hence, these are released and scattered into the atmosphere. Products of combustion include heat, light, chemical species, pollutants, mechanical work, and plasma.
Product yield – In a manufacturing process, product yield is the usable output quantity divided by the input quantity at every stage of the production process.
Pro-eutectoid carbide – It consists of primary crystals of cementite formed directly in ferrous alloys from the decomposition of austenite exclusive of that cementite resulting from the eutectoid reaction.
Pro-eutectoid ferrite – It consists of primary crystals of ferrite formed directly in ferrous alloys from the decomposition of austenite exclusive of that ferrite resulting from the eutectoid reaction.
Pro-eutectoid phase – It consists of particles of a phase in ferrous alloys which precipitate during cooling after austenitizing but before the eutectoid transformation takes place.
Profile – It is a term normally used to refer to a cross-sectional view of an object or material. In civil engineering, a profile consists of a plotted line which indicates grades and distances (and typically depths of cut and / or elevations of fill) for excavation and grading work. Constructors of roadways, railways (and similar works) normally chart the profile along the centre line. Profile is also the anchor pattern on a surface produced by abrasive blasting or acid treatment. It is also a wrought product which is long in relation to its cross-sectional dimensions, which is of a form other than that of sheet, plate, rod, bar, tube, wire, or foil.
Profile, class 1 hollow extruded – It is a hollow extruded profile, the void of which is round and 25 millimeters or more in diameter and whose weight is equally distributed on opposite sides of two or more equally spaced axes.
Profile, class 2 hollow extruded – It is a hollow extruded profile other than class 1, which does not exceed a 125 millimeters diameter circumscribing circle and has a single void of not less than 10 millimeters diameter or 70 square millimeters area.
Profile, class 3 hollow extrude – It is a hollow extruded profile other than class 1 or class 2.
Profile, cold-finished. A profile brought to final dimensions by cold working to obtain improved surface finish and dimensional tolerances.
Profile, cold-finished extruded – It is a profile produced by cold finishing an extruded profile.
Profile, cold-finished rolled – It is a profile produced by cold finishing a rolled profile.
Profile (contour) rolling – In ring rolling, it is a process used to produce seamless rolled rings with a predesigned shape on the outside or the inside diameter, requiring less volume of material and less machining to produce finished parts.
Profile, drawn – It is a profile brought to final dimensions by drawing through a die.
Profile, extruded – It is a profile produced by hot extruding.
Profile, flute hollow – It is a hollow profile having plain inside surfaces and outside surfaces which comprise regular, longitudinal, concave corrugations with sharp cusps between corrugations.
Profile, helical extruded – It is an extruded profile twisted along its length.
Profile, hollow – It is a profile in which any part of its cross section completely encloses a void.
Profile, lip hollow – It is a hollow profile of normally circular cross-section and nominally uniform wall thickness with one hollow or solid protuberance or lip parallel to the longitudinal axis. It is used mainly for heat-exchange purposes.
Profile, pinion hollow – It is a hollow profile with regularly spaced, longitudinal serrations outside, and round inside, used mainly for making small gears.
Profile, rolled – It is a profile produced by hot rolling.
Profile, semi-hollow – It is a profile in which any part of its cross section is a partially enclosed void the area of which is substantially higher than the square of the width of the gap. The ratio of the area of the void to the square of the gap is dependent on the class of semi-hollow profile, the alloy, and the gap width.
Profile, solid – It is a profile other than hollow or semi-hollow.
Profile, stepped extruded -It is an extruded profile with a cross section which changes abruptly in area at intervals along its length.
Profile, streamline hollow – It is a hollow profile with a cross section of tear-drop shape.
Profile, structural – It is a profile in certain standard alloys, tempers, sizes, and sections, such as angles, channels, H sections, I-beams, tees, and zees, commonly used for structural purposes.
Profile, tapered extruded – It is an extruded profile with a cross section which changes continuously in area along its length or a specified portion thereof.
Profile tolerance – It defines a uniform boundary around a surface within which the elements of the surface must lie. Profile is a complex tolerance which simultaneously controls a feature’s form, size, orientation, and sometimes location. Profile is a three-dimensional tolerance that applies in all directions regardless of the drawing view where the tolerance is specified. It is usually used on parts with complex outer shape and a constant cross-section like extrusions.
Profiling – It is an operation which produces an irregular contour on a work-piece, for which a tracer or template controlled duplicating equipment normally is used.
Profit and loss projection – It presents the plan of revenues and expenses of the organization over the specific accounting period. Profit and loss projection follows the same pattern as the profit and loss statement. However, it reflects the data about the future.
Profit and loss statement – It is the income statement of an organization detailing revenues minus total costs to give total profit.
Programmable automation – This automation system is used for a changeable sequence of operation and configuration of the machines using electronic controls. However, non-trivial programming effort can be needed to reprogram the machine or sequence of operations. Investment on programmable equipment is less, as production process is not changed frequently. The system consists of equipment designed to accommodate a specific class of product changes. This type of automation is typically used in batch processes where job variety is low and product volume is medium to high, and sometimes in mass production also.
Programmable automation controller (PAC) – It is a term which is loosely used to describe any type of automation controller that incorporates higher-level instructions. The systems are used in industrial control systems (ICS) for machinery in a wide range of industries, including those involved in critical infrastructure.
Programmable logic controller – It is an industrial computer which has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity which needs high reliability, ease of programming, and process fault diagnosis. Programmable logic controller can range from small modular devices with tens of inputs and outputs (I/O), in a housing integral with the processor, to large rack-mounted modular devices with thousands of I/O, and which are frequently networked to other programmable logic controller and Supervisory Control and Data Acquisition (SCADA) systems. They can be designed for several arrangements of digital and analog I/O, extended temperature ranges, immunity to electrical noise, and resistance to vibration and impact.
Programmable real-time unit (PRU) – It is a small processor core which is tightly integrated with an input / output subsystem, offering low-latency control of input / output pins.
Programming language – It is a formalism for human-readable instructions to a computer.
Progression – It is the constant dimension between adjacent stations in a progressive die.
Progressive aging – It consists of aging by increasing the temperature in steps or continuously during the aging cycle.
Progressive collapse – It is the process where a primary structural element fails, resulting in the failure of adjoining structural elements, which in turn causes further structural failure. Progressive collapses can be accidental, as the result of design deficiencies, fire, unintentional overload, material failure or natural phenomenon. They can also be induced deliberately as a demolition method, specifically that of building implosion, or caused by acts of terrorism or war.
Progressive die – It is a die with two or more stations arranged in line for performing two or more operations on a part. It is one operation is normally performed at each station.
Progressive dipping – It is the act of dipping steel more than once in cleaning solutions and molten zinc metal in order to produce a coating which covers the entire surface of the steel. It is normally done when the steel article / fabrication is too large to fit entirely into the pot in one dip.
Progressive forming – It is the sequential forming at consecutive stations with a single die or separate dies.
Project – It is a type of assignment, typically involving research or design, which is carefully planned to achieve a specific objective. It is a series of structured tasks, activities, and deliverables which are carefully executed to achieve a desired outcome. It consists of a group of tasks, performed in a definable time period, in order to meet a specific set of objectives. It is a temporary activity. It is a one-time program hence different from operations where tasks are repeated in a routine way. Every project has a life cycle, with a specific start and end. The work scope of a project can be categorized into definable tasks. Project has a budget within which it is required to be completed. During the execution of the project, there is likely requirement of multiple resources. Several of these resources can be scarce and may have to be shared with others. Project has a life cycle which includes (i) initiation, (ii) planning, (iii) execution, (iv) monitoring and control, (v) commissioning and handing over, and (vi) closing of the project activities. In case of mining terminology, project means a defined development or operation which provides the basis for environmental, social, economic and technical evaluation and decision-making. In the early stages of evaluation, including verification, the project can be defined only in conceptual terms, whereas more mature projects are to be defined in significant detail. Where no development or operation can currently be defined for all or part of a source, based on existing technology or technology currently under development, all quantities associated with that source (or part thereof) are classified in category F4. These are quantities which, if produced, can be bought, sold, or used.
Projected area – It is the area of a cavity, or portion of a cavity, in a mould or die casting die measured from the projection on a plane which is normal to the direction of the mould or die opening.
Projected balance sheet – It displays liabilities, equity of the owner and the assets which the organization is planning to have during the projected period of the financial plan.
Projected cash flow – It evaluates the state of the future working capital as well as it determines whether there is a necessity of borrowings or not.
Project evaluation and review technique (PERT) – It is also called programme evaluation and review technique. It is a statistical tool used in project management, which has been designed to analyze and represent the tasks involved in completing a given project. It is normally used in conjunction with the critical path method (CPM). It is a method of analyzing the tasks involved in completing a project, especially the time needed to complete each task, and to identify the minimum time needed to complete the total project. It incorporates uncertainty by making it possible to schedule a project while not knowing precisely the details and durations of all the activities. It is more event-oriented than start- and completion-oriented, and is used more for projects where time is the major constraint rather than cost. It is normally applied to very large-scale, one-time, complex, non-routine infrastructure projects. It is a management tool which relies on arrow and node diagrams of activities and events, where arrows represent the activities or work necessary to reach the events or nodes which indicate each completed phase of the total project.
Project implementation strategy and schedule – It consists of the implementation strategy of the project. The implementation schedule is normally presented in a detailed bar chart or in a PERT (project evaluation review technique) chart. The information is useful for project monitoring during its execution.
Projection – A projection is a potential future evolution of a quantity or set of quantities, frequently computed with the aid of a model. Projections are distinguished from predictions in order to emphasize that projections involve assumptions concerning, for example, future socio-economic and technological developments which may or may not be realized, and are hence, subject to substantial uncertainty.
Projection distance – It is the distance from the eye-piece to the image screen.
Projection lens – It is the final lens in the electron microscope corresponding to an ocular or projector in a compound optical microscope. This lens forms a real image on the viewing screen or photographic film.
Projections – A three-dimensional object can be represented in a single plane, such as on a sheet of paper, using projecting lines and planes. All projection theory is based on two variables namely line of sight (projecting lines) and plane of projection. The projection is produced by connecting the points where the lines of sight pierce the projection plane. As a result, the 3D object is transformed into a 2D view. If the distance from the observer to the object is infinite, then the projection lines are assumed to be parallel, and the projection is called a parallel projection. Parallel projection is orthographic if the plane of projection is placed between the observer and the object, and the plane is perpendicular to the parallel lines of sight.
Projection welding – It is a resistance welding process which produces coalescence of metals with the heat got from resistance to electric current through the work parts held together under pressure by electrodes. The resulting welds are localized at pre-determined points by projections, embossments, or intersections.
Project management – It consists of the process of supervising the work of a team to achieve all project goals within the given constraints. This information is normally described in project documentation, created at the beginning of the development process. The primary constraints are scope, time, and budget. The secondary challenge is to optimize the allocation of necessary inputs and apply them to meet predefined objectives. The objective of project management is to produce a complete project which complies with the project’s objectives.
Project monitoring – It is an integral part of the project management. It provides understanding of the progress of the project so that appropriate corrective actions can be taken when the performance deviates significantly from the planned path. It consists of regular systematic collection and analysis of information to track the progress of the project implementation against pre-set targets and objectives. It is an important management tool. It is used properly, provides continuous feedback on the project implementation progress as well assists in the identification of potential successes and constraints to facilitate timely decisions. Effective monitoring of the project is a critical element of good project management. It supports informed and timely decision making by the management and provides accountability for achieving results. It is a key part of project cycle management. Project monitoring clarifies project objectives, links activities and their resources to objectives, translates objectives into performance indicators and sets targets, routinely collects data on these indicators, compares actual results with targets, and reports progress to the management and alerts the management about the problems which frequently gets cropped up during the implementation of the project.
Project plan – It is a formal, approved document of the project which guides the project execution and is required for the management and control of the project. It forms the basis for all the actions which are required to be taken by the project team for the implementation of the project. The planning document is not of permanent nature since it is necessary to continuously update it as the work of the project progresses.
Project planning – It describes the suggested methodology of implementation of the project. It describes the recommended methodology for the procurement of the plant, equipment, and materials as well as for the works to be carried out at the plant site. It also recommends the types of the contracts to be entered so that the project can be completed in scheduled time.
Promoter – It is a chemical, itself a feeble catalyst, which greatly increases the activity of a given catalyst.
Proof – It means to test a component or system at its peak operating load or pressure. It is a reproduction of a die impression in any material. It is frequently a lead or plaster cast.
Proof load – It is a pre-determined load, normally some multiple of the service load, to which a sample or structure is submitted before acceptance for use.
Proof pressure – It is the test pressure which pressurized components sustain without detrimental deformation or damage. The proof pressure test is used to give evidence of satisfactory workmanship and material quality.
Proof stress (Rp) – It is a specified stress to be applied to a member or structure to indicate its ability to withstand service loads. It is the stress or applied load which produces a permanent elongation equal to a specific percentage of the original gauge length. In alloys which do not show a yield point it is used as an equivalent to the elastic limit. If a proof stress is specified, the non-proportional elongation is to be stated. The most common values used in specifications is 0.2 % or 1 % and the Rp symbol used for the stress will be supplemented by an index giving this prescribed percentage of the original gauge length, e.g. Rp0.2 = 0.2 % proof stress.
Propane – It is a three-carbon alkane with the molecular formula C3H8. It is a gas at standard temperature and pressure, but compressible to a transportable liquid. It is a by-product of natural gas processing and petroleum refining. It is frequently a constituent of liquefied petroleum gas (LPG), which is normally used as a fuel in domestic and industrial applications and in low-emissions public transportation.
Propeller fans – These fans generate high air flow rates at low pressures. These fans are not combined with extensive ductwork since they generate little pressure and are inexpensive because of their simple construction. They achieve maximum efficiency, near-free delivery, and are frequently used in roof top ventilation applications. They can generate flow in reverse direction, which is helpful in ventilation applications. These fans have relative low energy efficiency and are comparatively noisy.
Propensity scores – it is the predicted probabilities of receiving the treatment for different subjects. Subjects which have the same propensity scores can be treated in statistical analyses as though they are randomly assigned to treatment groups.
Propensity-score analysis – it is a statistical analysis which controls for propensity scores and thereby balances the distributions on control variables across groups of subjects.
Property – In science, a property is anything which describes a material or substance. It is a characteristic of that material. For example, how hard the material is, its colour, or its shape. Elasticity is a property of rubber. In other words, rubber is elastic.
Property of unique interest – It is a material property which is of such importance or uniqueness to the application that this single property predominates all other considerations in materials selection.
Property-prediction system (PPS) – It is used for simulating the metallurgical process occurring during heat treatment and predicting the microstructure and mechanical properties of quenched and tempered or case-hardened steel. The system consists of several modules, which form a logical chain for property prediction. Before starting to design a property prediction system, one has to ascertain first those internal parameters (for example, Ac3 temperature, transformation kinetic data, hardness values of the microstructural elements, and so on) which have the most determinative effects on the properties. Then the algorithm, the logical chain of these internal parameters, has to be stated and finally, the connections between the input data, the internal parameters, have to be investigated. If all of these connections are clear, mathematically formulated, and joined into a chain, one can handle this set of connections as a system. The programmes of the property prediction system are based on a phenomenological model of kinetics of transformation taking place in non-isothermal conditions. The programme permits the prediction of the progress of transformations, of the microstructure, and of the mechanical properties as a function of time and of position in the cross section of the heat-treated work-piece.
Proportion – For a variable with ‘n’ observations, of which the frequency of a particular characteristic is ‘r’, the proportion is r/n. For example, if the frequency of an activity is 11 times in 55 years, then the proportion is 11/55 = 0.2 of the years, or one fifth of the years.
Proportional control – It is the ‘P’ part of a PID (proportional–integral–derivative) controller. With proportional action, the controller output is proportional to the quantity of the error signal.
Proportional–integral–derivative (PID) controller – It is a feedback-based control loop mechanism which is normally used to manage machines and processes which need continuous control and automatic adjustment. It is typically used in industrial control systems and different other applications where constant control through modulation is necessary without human intervention. The proportional–integral–derivative controller automatically compares the desired target value (set-point) with the actual value of the system (process variable). The difference between these two values is called the error value. It then applies corrective actions automatically to bring the process variable to the same value as the set-point using three methods. The proportional (P) component responds to the current error value by producing an out-put which is directly proportional to the magnitude of the error. This provides immediate correction based on how far the system is from the desired setpoint. The integral (I) component, in turn, considers the cumulative sum of past errors to address any residual steady-state errors which persist over time, eliminating lingering discrepancies, and the third, the derivative (D) component predicts future error by assessing the rate of change of the error, which helps to mitigate overshoot and improve system stability, particularly when the system undergoes rapid changes. The proportional–integral–derivative controller reduces the likelihood of human error and improves automation.
Proportional limit – It is the maximum stress at which strain remains directly proportional to stress; the upper end of the straight-line portion of the stress-strain or load-elongation curve. Materials, in general, show some nonlinear elastic behaviour, so the elastic limit is (slightly) higher than the proportional limit.
Proportioning probe – It is a probe which can vary, sample pure air ratios, between 100 % sample and 100 % pure air without substantially changing the total flow rate from the probe.
Propyl – It consists of the alkyl functional group derived from either of the two isomers of propane, with the generic chemical formula –C3H7. It can occur as a substituent in organic compounds or exist independently as an ion or radical. In IUPAC (International Union of Pure and Applied Chemistry) nomenclature, the presence of a propyl substituent is indicated with the prefix propyl in the name of the compound.
Propylene – It also known as propene, is an unsaturated organic compound with the chemical formula CH3CH=CH2. It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colourless gas with a faint petroleum-like odour.
Pro rata – It means in equal portions or in proportion. The term is used in many legal and economic contexts. More specifically, pro rata means (i) in proportionality to some factor which can be exactly calculated, (ii) to count based on an amount of time which has passed out of the total time, and (ii) proportional ratio.
Prospect – It is a mining area, the value of which has not been determined by exploration.
Prospecting – Prospecting is the systematic process of searching for a mineral deposit by narrowing down areas of promising enhanced mineral potential. The methods utilized are outcrop identification, geological mapping, and indirect methods such as geophysical and geochemical studies. Limited trenching, drilling, and sampling can be carried out. The objective is to identify a deposit which is to be the target for further exploration. Estimates of quantities are inferred, based on interpretation of geological, geophysical, and geochemical results.
Prospective projects – Prospective projects are potential future recovery by successful exploration activities. An Exploration project is associated with one or more major occurrences, i.e., a deposit that has not yet been demonstrated to exist by direct evidence (e.g., drilling and / or sampling), but has been assessed primarily on indirect evidence (e.g., surface, or airborne geophysical measurements).
Prospector – Prospector is a person who identifies the discovery, measure both width and length, and estimate the mineralized area.
Protective atmosphere – It is a gas or vacuum envelope surrounding the part to be brazed, welded, or thermal sprayed, with the gas composition controlled with respect to chemical composition, dew point, pressure, flow rate, and so forth. Examples are inert gases, combusted fuel gases, hydrogen, and vacuum. It is also the atmosphere in a heat treating or sintering furnace designed to protect the parts or compacts from oxidation, nitridation, or other contamination from the environment.
Protective coatings – These are materials which can be applied as a thin film on suitable surfaces to inhibit or prevent degradation associated with the substrate. Surface coatings are important in maintaining the form, function, and properties of an object as they provide a shield against the environmental conditions.
Protective potential – It is the threshold value of the corrosion potential which has to be reached to enter a protective potential range.
Protective potential range – It is a range of corrosion potential values in which an acceptable corrosion resistance is achieved for a particular purpose.
Protective relay – It is an electro-mechanical or electronic device which detects faults on a power system and can signal circuit breakers to operate.
Protocol standards – These standards are also called ‘Standards of Practice’. Protocol standards are standards which define everything from the dimensions and electrical characteristics of a flashlight battery to the shape of the threads on a machine screw and from the size and shape of an IBM (International Business machines) punched card to the ‘quality assurance requirements’ for measuring equipment. Such standards can be defined as documents describing the operations and processes which are to be performed in order for a particular end to be achieved. They are called a ‘protocol’ by Europeans to avoid confusion with a physical standard.
Proton – It is an elementary particle with unit atomic mass approximately and unit positive electric charge. It is one of the two elementary particles found in atomic nuclei.
Proton precession magnetometer – It is a geo-physical instrument which measures magnetic field intensity in terms of vertical gradient and total field.
Prototype – It is a full-scale working model of the design which is technically and visually complete.
Protuberances – These are the small-scale irregularities on a surface. These are minute imperfections on a seal face or surface of a mating ring which are the result of normal surface finishing processes. Protuberances, their shapes, sizes, and mechanical properties are the basis for developing several theoretical models for friction, lubrication, and wear behaviour.
Protrusion – It is imperfection which can occur during the moulding or firing process of a brick or a block.
Proximate analysis – It is defined as a technique to measure the chemical properties of a compound based on four particular elements namely moisture content, fixed carbon, volatile matter and ash content. The various parameters of proximate coal analysis in case of thermal coal have considerable significance. Fixed carbon acts as a main heat generator during burning and it gives a rough estimate of heating value of coal. The volatile matter also contributes to the heating value of coal. Increase in percentage of volatile matter in coal proportionately increases flame length and helps in easier ignition of the coal. It has also had implications regarding minimum limit of furnace height and volume and influences secondary oil support. Ash is an impurity which does not burn. It is important parameter in design of furnace grate, combustion volume, pollution control devices and ash handling plant. Ash increases transportation, handling, storage cost of the coal and affects the combustion efficiency and the furnace efficiency. It also causes clinkering and slagging problems in the furnace. Moisture increases transportation, handling, storage cost and decreases the heat content per kilogram of coal. It increases heat loss because of the evaporation and superheating of vapour. Moisture helps in binding of the fines and in radiation heat transfer.
Proximity effect – It is the increase in circuit resistance when the magnetic fields of multiple alternating currents interact.
Proximity sensor – It is a sensor in a conveyor system which detects the presence or absence of materials without physical contact, necessitating regular inspections for accurate sensing and responsiveness.
Proved Mineral reserves – Proved Mineral reserves is the Economically mineable part of Measured Mineral resource.
Proved Ore reserve – A Proved Ore reserve is the economically mineable part of a Measured Mineral resource. A Proved ore reserve implies a high degree of confidence in the Modifying factors.
Proven reserves – These are reserves which have been sampled extensively by closely spaced diamond drill holes and developed by underground workings in sufficient detail to render an accurate estimation of grade and tonnage. It is also called ‘measured reserves’.
Prow formation – In sliding metals, it is the formation of a wedge or wedges of plastically sheared metal in local regions of interaction between sliding surfaces. This type of prow is also known as a wedge. It is similar to a built-up edge. In hydrodynamic lubrication, it is the establishment of a pressure gradient in a fluid flowing into a converging channel. This is also known as the wedge effect.
Pseudo-binary system – It is a three-component or ternary alloy system in which an intermediate phase acts as a component. It is a vertical section through a ternary diagram.
Pseudo-carburizing – It consists of simulating the carburizing operation without introducing carbon. This is usually accomplished by using an inert material in place of the carburizing agent, or by applying a suitable protective coating to the ferrous alloy.
Pseudo-nitriding – It consists of simulating the nitriding operation without introducing nitrogen. This is normally accomplished by using an inert material in place of the nitriding agent or by applying a suitable protective coating to the ferrous alloy.
Pseudo-plastic behavior – It is a decrease in viscosity with increasing shear stress.
Pseudo-R2 measure – It consists of any of several analogs of the linear regression R2 used for non-linear models such as logistic regression, Poisson regression, and Cox regression, etc.
Psycho-social work environment – It is the content of work and work demands, the social relationships at work, the organization of work and the work culture, which each can affect the mental and physical well-being of workers including management. All these work aspects are sometimes referred to as workplace stressors, which may have cognitive, emotional or motivational effects on workers.
P-T diagram – It is a two-dimensional graph of phase relationships in a system of any order by means of the pressure and temperature variables.
PTFE-coated conveyor belt – It is a conveyor belt coated with poly-tetra-fluoro-ethylene (PTFE) for enhanced non-stick properties and resistance to heat. Periodic inspections are necessary to assess wear and overall belt condition.
P-T-X diagram – It is a three-dimensional graph of the phase relationships in a binary system by means of the pressure, temperature and concentration variables.
Public relations – It is a strategic communication process which builds mutually beneficial relationships between organization and its publics. It is the deliberate, planned and sustained effort to establish and maintain mutual understanding between on organization and its publics. It is the management of communication between the organization and its publics. It is the attempt by information persuasion and adjustment to engineer public support for an activity, cause, movement or organization. It helps the organization and its publics adapt mutually to each other. Public relations is a distinctive management function which helps establish and maintain mutual lines of communication, understanding, acceptance, and cooperation between an organization and its publics.
Public reports – These are reports prepared for the purpose of informing investors or potential investors and their advisers on Exploration results, Mineral resources or Ore reserves. They include, but are not limited to, annual and quarterly company reports, press releases, information memoranda, technical papers, website postings, and public presentations.
Public utilities – Public utilities are meant to supply goods and services which are considered necessary such as water, gas, electricity, telephone, waste disposal, and other communication systems. The transmission lines used in the transportation of electricity, or natural gas pipelines, have natural monopoly characteristics. A public utility organization is an organization that maintains the infra-structure for a public service (frequently also providing a service using that infrastructure).
Puckering – It is wrinkling or buckling in a drawn shell in an area originally inside the draw ring.
Puckers – These are areas on prepreg materials where material has locally blistered from the separator film or release paper.
Puddle – It is a non-standard term for weld pool.
Puffed compact – It is a compact which is expanded by internal gas pressure.
Pugh concept selection method – It is a group process of selecting a design concept or material in which the selection criteria and concepts are arranged in matrix form, and for each criterion the concepts are compared one at a time to a datum (reference) concept.
Pull cracks – In a casting, these are cracks which are caused by residual stresses produced during cooling and that result from the shape of the object.
Pull cord switch – It is a safety device in a conveyor system which stops the conveyor when the pull cord is activated, demanding regular inspections for proper tension and responsiveness.
Pulley – It is a wheel on an axle or shaft which is enabling a taut cable or belt passing over the wheel to move and change direction, or transfer power between itself and a shaft. A sheave or pulley wheel is a pulley using an axle supported by a frame or shell (block) to guide a cable or exert force. A pulley can have a groove or grooves between flanges around its circumference to locate the cable or belt. The drive element of a pulley system can be a rope, cable, belt, or chain.
Pulley lagging – It is the application of a layer of material to pulley surfaces to enhance grip and reduce slipping with the conveyor belt, necessitating regular inspections for maintenance and effectiveness.
Pull gun technique – It is a non-standard term for backhand welding.
Pulp – It is pulverized or ground ore in solution.
Pulp moulding – It is the process by which a resin- impregnated pulp material is pre-formed by application of a vacuum and subsequently is oven cured or moulded.
Pull through – It is a reddish spot in a porcelain enamel coating caused by iron pickup during enameling, iron oxide left on poorly cleaned base metal, or burrs on iron or steel base metal which protrude through the coating and are oxidized during firing. It is also called copperhead.
Pulsation – It is the rapid fluctuations in pressure.
Pulse (resistance welding) – It is a current of controlled duration of either polarity through the welding circuit.
Pulse repetition rate – It refers to the number of pulses emitted per unit time by a system, such as a laser or radar. It is crucial in determining the maximum counting rate for accurate measurements in various scientific applications.
Pulse transformer – It is a transformer designed to create or transmit pulses.
Pulse-width modulation (PWM) – It is the transmission of information by varying the duration of pulses, or, varying the average output voltage of a power converter by varying the duration of pulses. It is useful for controlling the average power or amplitude delivered by an electrical signal. The average value of voltage (and current) fed to the load is controlled by switching the supply between 0 % and 100 % at a rate faster than it takes the load to change significantly. The longer the switch is on, the higher the total power supplied to the load. Along with maximum power point tracking (MPPT), it is one of the primary methods of controlling the output of solar panels to that which can be utilized by a battery. Pulse-width modulation is particularly suited for running inertial loads such as motors, which are not as easily affected by this discrete switching. The goal of pulse-width modulation is to control a load. However, the pulse-width modulation switching frequency is to be selected carefully in order to smoothly do so.
Pulse-amplitude modulation (PAM) – It bis the transmission of information by varying the magnitude of a stream of pulses of fixed frequency.
Pulse-code modulation – It is a system for conveying analog information by altering some property of a stream of pulses.
Pulsed-laser atom-probe field-ion microscope – It is a time-of-flight atom-probe field-ion microscope has been developed which uses nano-second laser pulses to field evaporate surface species.
Pulsed laser deposition (PLD) – It is a physical vapour deposition (PVD) technique where a high-power pulsed laser beam is focused inside a vacuum chamber to strike a target of the material that is to be deposited. This material is vapourized from the target (in a plasma plume) which deposits it as a thin film on a substrate (such as a silicon wafer facing the target). This process can occur in ultra-high vacuum or in the presence of a background gas, such as oxygen which is commonly used when depositing oxides to fully oxygenate the deposited films.
Pultrusion – It is a cost-effective automated process for manufacturing continuous, constant cross-section composite profiles. It refers to both the final product and the process. Most simply, it refers to a method of manufacture wherein a collection of reinforcements saturated with reactive resin is pulled through a heated die which imparts the final geometry to the composite profile. In virtually every case, the continuous reinforcing fibre choices are integral to the processibility and the finished product properties. The resin matrix used is typically a liquid thermosetting resin, which reacts exothermically when heat is introduced to create a cross-linked polymer with exceptional engineering properties. The resulting thermoset composite profile cannot be reshaped or otherwise altered within its operating temperature range. In contrast, the extrusion of aluminum and thermoplastic materials normally involves unreinforced (homogeneous) materials which are heated and pushed through a die, then allowed to cool into the final solid shape. These materials can be reheated and reshaped several times with little loss of basic properties.
Pulverization – It is the process of reducing metal powder particle sizes by mechanical means. It is also called comminution or mechanical disintegration.
Pulverized coal fired (PCF) boilers – These are the boilers which use pulverized coal for the generation of heat. Pulverized coal fired boilers are the most popular utility boilers today. These boilers have a high efficiency but a costly SOx (oxides of sulphur) and NOx (oxides of nitrogen) control. Almost any kind of coal can be reduced to powder and burned like a gas in a pulverized coal fired boiler.
Pulverized coal injection (PCI) – It is a process which involves injecting large volumes of fine coal particles into the raceway of the blast furnace. Pulverized coal is an important auxiliary fuel used in the blast furnace ironmaking. Pulverized coal injection provides auxiliary fuel for partial coke replacement and has proven both economically and environmentally favourable. It can result in substantial improvement in the blast furnace efficiency and hence contribute to the reductions of energy consumption and environmental emissions. When the pulverized coal is injected into the BF through blowpipes and tuyeres, the coal is a source of heat and a reductant, because of the reactions of devolatilization, gasification, and combustion as well as the formation of unburned char.
Pulverized coal-fired boiler – Itis an industrial or utility boiler that generates thermal energy by burning pulverized coal which is blown into the firebox. The basic idea of a firing system using pulverized coal is to use the whole volume of the furnace for the combustion of solid coal. Coal is ground to the size of a fine grain, mixed with air and burned in the flue gas flow. Coal contains mineral matter which is converted to ash during combustion. The ash is removed as bottom ash and fly ash. The bottom ash is removed at the furnace bottom.
Pulverized fuel – It consists of finely ground coal or other combustible material, which can be burned as it issues from a suitable nozzle, through which it is blown by compressed air. Pulverized fuel increases the surface area for combustion, leading to higher thermal efficiency and faster combustion rates.
Pulverized fuel ash – It is the solid material extracted by electrostatic and mechanical means from the flue gases of furnaces fired by pulverized coal.
Pulverized fuel firing – It involves grinding of the fuel into fine particles and spraying them into the combustion chamber for efficient burning.
Pump – It is a device which moves fluids (liquids or gases), or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic or pneumatic energy. Mechanical pumps serve in a wide range of applications.
Pump and treat – It is a common method for cleaning up groundwater using pumps to bring polluted groundwater to the surface where it can be treated by different methods.
Pump down time – It is the time of evacuation.
Pumped-storage hydroelectricity – It is a grid energy storage system that pumps water uphill for later use by a hydroelectric generator plant.
Pumping efficiency – In a bearing, it is the ratio of actual oil flow to the maximum theoretical flow for a bearing with a 180-degree oil film operating at an eccentricity ratio of unity.
Pump-out tubulation – It is a tube extending from an evacuated device through which gas is pumped and which is normally permanently sealed off after the device has been evacuated. It is sometimes called exhaust tubulation.
Punch – It is the male part of a die, as distinguished from the female part, which is called the die. The punch is normally the upper member of the complete die assembly and is mounted on the slide or in a die set for alignment (except in the inverted die). In double-action draw dies, the punch is the inner portion of the upper die, which is mounted on the plunger (inner slide) and does the drawing. Punch is also the act of piercing or punching a hole. It is also referred to as punching. It is the movable tool which forces material into the die in powder molding and most metal forming operations. It is the movable die in a trimming press or a forging machine. It is the tool which forces the stock through the die in rod and tube extrusion and forms the internal surface in can or cup extrusion.
Punching – It is the die shearing of a closed contour in which the sheared-out sheet metal part is scrap. It is producing a hole by die shearing, in which the shape of the hole is controlled by the shape of the punch and its mating die. Multiple punching of small holes is called perforating.
Punching shear test – It is a method which is used to determine the through-thickness shear strength of sheet material which involves blanking a disk out of flat strip using a simple punch-and-die method. It is also known as blanking shear test.
Punch press – In general, it is a mechanical press. In particular, an end wheel gap-frame press with a fixed bed, used in piercing.
Punch radius – It is the radius on the end of the punch which first contacts the work. It is sometimes called nose radius. Punch presses are used for bending, flanging, and hemming low-carbon steel when production quantities are large, when close tolerances must be met, or when the parts are relatively small.
Purchase procedures – These are the rules and regulations that define the organizational purchasing activities and keep purchasing legal and appropriate. These procedures also describe the ethics that purchasing personnel in the organization must embrace. These procedures are evolved to streamline the purchasing activities in the organization and remove adhocism while adhering to current regulatory policies of the land.
Pure aluminum – It a soft, silvery-white, ductile and non-magnetic metal which belongs to the boron group and has atomic number 13. To be considered pure aluminum, the metal needs to consist of 99 % aluminum. It has high electrical and thermal conductivity, and is resistant to oxidation. It is a relatively low strength, extremely flexible metal with virtually no structural applications.
Pure ductile tearing – It consists of microscale ductile crack propagation by micro-void coalescence on the plane of maximum normal stress.
Pure iron – It is a common metal but it is mostly confused with other materials such as steel and wrought iron. All these materials vary in composition. The carbon content of pure iron makes it unique and different from the other metals and ferrous alloys. The carbon content in pure iron is always less than 0.008 %. Wrought iron has a higher carbon content of up to 0.5 %. This shows how less the impurities are in the pure iron. Pure iron has a body centred cubic (bcc) structure at ordinary temperatures and is ferro-magnetic with a curie temperature of 768 deg C. The magnetic and non-magnetic forms are normally referred to as alpha-iron and beta-iron respectively. Iron changes to the face-centered cubic (fcc) form (gamma-iron) on heating to 910 deg C and then back to the body centred cubic structure form (delta-iron) at 1,394 deg C.
Pure metals – These are elements which consist of a single type of atom. They have a highly ordered atomic structure, which makes them relatively soft and malleable. Examples of pure metals include gold, silver, copper, and aluminum. Pure metals are known for their high electrical and thermal conductivity, as well as their lustrous appearance.
Purge – It is to introduce air into the furnace and the boiler flue passages in such volume and manner as to completely replace the air or gas-air mixture contained therein.
Purity – It refers to the degree to which a substance is free from impurities. It is the measurement of the quantity of impurities found in a sample.
Push and pull type pickling lines – These types of lines are used normally for small and medium production capacities. In these lines preferred thickness of hot strip is more than 1.5 millimeters. In these types of lines, the strip is neither welded nor stitched but is pushed or pulled through the line strip by strip. The advantage of the push and pull pickling line is its high flexibility combined with high productivity at low investment costs. Cost-intensive equipment, like welding machines, loopers, and bridle rolls, is not required. The shallow pickling tank design ensures high turbulence and reduced pickling time.
Push-bar conveyor – It is an endless-chain conveyor in which crossbars propel or lift the load by direct engagement or push the load over rollers or a flat surface.
Push bench – It is an equipment which is used for drawing moderately heavy-gauge tubes by cupping sheet metal and forcing it through a die by pressure exerted against the inside bottom of the cup.
Push-button – It is a simple switch mechanism to control some aspect of a machine or a process. Buttons are typically made out of hard material, normally plastic or metal. The surface is normally flat or shaped to accommodate the human finger or hand, so as to be easily depressed or pushed. Buttons are very frequently biased switches, although several un-biased buttons (because of their physical nature) still need a spring to return to their un-pushed state.
Push-button station – It is an electrical mechanism which triggers and operates a magnetic starter.
Pusher – It is an air-powered device which is used for moving products between conveyor lines and chutes.
Pusher arm – It is a mechanical arm in a conveyor system which is used to push or divert materials, necessitating periodic inspections for proper operation, alignment, and overall functionality.
Pusher device – It is a mechanical device in a conveyor system which is used to push materials off the conveyor, needing periodic checks for proper functioning and alignment.
Pusher furnace – It is also called pusher type furnace. It is a type of continuous furnace in which parts to be heated are periodically charged into the furnace in containers, which are pushed along the hearth against a line of previously charged containers hence advancing the containers toward the discharge end of the furnace, where they are removed.
Pusher machine – It is a machine with operates in coke oven battery. The pusher machine travels along the length of the battery and carries out various functions such as (i) remove and replace coke oven doors, (ii) push out hot coke from the oven, (iii) open and close leveller bar doors, (iv) level the coal charge in the oven, (v) clean doors, frame and flash plates, (vi) degraphitize the oven ceiling, and (vii) remove the coke spillage. The pusher machine is located at the coke oven battery side and is normally designed for the single spot operation. The drives of machine can be hydraulic or electro-mechanical. Operator’s cabin, and the hydraulic and electronic equipment cabins are normally equipped with air-conditioners. The main functional units of the coke pusher machine are (i) travelling mechanism, (ii) pushing mechanism, (iii) door latch unscrewing mechanism, (iv) door snatching mechanism, (v) door turning mechanism, (vi) travelling mechanism for door extractor installation, (vii) door cleaning mechanism, (viii) door frame and flash plate cleaning mechanism, (ix) levelling mechanism, (x) leveller bar door opening mechanism, (xi) coal charge spillage collecting system, (xii) coke spillages collecting device with quenching system, (xiii) degraphitizing mechanism.
Pusher sorter – It is a sorting device in a conveyor system which uses pushers to divert materials onto different paths, necessitating regular inspections for proper operation and alignment.
Pusher type furnace – In the pusher type of furnace, cold steel stock is pushed forward with the help of pushers at the charging side. Earlier, these furnaces were designed for heating billets or smaller sections of blooms. The hearth of earlier furnaces was short in length and sloped downward longitudinally towards the discharge end in order to permit easy passage of steel stock through the furnace. Presently pusher furnaces are longer with hearths of around 25 meters to 30 meters in length. These furnaces are equipped with either top firing or top and bottom firing. These furnaces normally have three zones namely (i) preheating zone, (ii) heating zone, and (iii) soaking zone. Multiple zone furnaces such as five zone slab reheating furnaces have also been designed and operated. In pusher type furnace, cold steel stock can be charged in such furnace either from the end or through a side door. In either case, the steel stock is moved forward by pushing the last piece charged with a pusher at the charging end. With each pushing of the cold steel stock against the continuous line of material, a heated piece is discharged at the discharge end either by gravity through an end door upon a roller table feeding the rolling mill, or pushed through a side door to the mill roller table by suitable manual or mechanical means, or withdrawn through the end door by a mechanical extractor.
Pusher-type seal – It is a mechanical seal in which the secondary seal is pushed along the shaft or sleeve to compensate for face wear.
Push–pull converter – It is a converter with two sets of primary switching elements so that the transformer primary voltage can be reversed on each cycle.
Push-pull effect – It consists of factors which push from the initial state towards better opportunities and factors which pull because of their attractive characteristics towards the future state of organization. Push factors are things which are unfavourable while the pull factors are things that attracts.
Push switch – It is a device which closes or opens an electrical circuit when pushed.
Push welding – It is spot or projection welding in which the force is applied manually to one electrode, and the work or backing plate takes the place of the other electrode.
p-value – p-value is the probability of obtaining sample results as least as unfavourable to the null hypothesis as is observed if the null hypothesis is true. The probability value (p-value) of a hypothesis test is the probability of getting a value of the test statistic as extreme, or more extreme, than the one observed, if the null hypothesis is true. Small p-values suggest the null hypothesis is unlikely to be true. The smaller it is, the more convincing is the evidence to reject the null hypothesis. In the pre-computer era, it is common to select a particular p-value, (frequently 0.05 % or 5 %) and reject H0 if (and only if) the calculated probability is less than this fixed value. Now it is much more common to calculate the exact p-value and interpret the data accordingly.
PVC belt I It is a type of conveyor belt which made from polyvinyl chloride (PVC) material which is known for its versatility and resistance to wear. Periodic inspections are essential to assess wear and overall belt condition.
PVC insulated electric power cables – PVC stands for poly-vinyl chloride. These cables are normally used up to and including 11 kilovolts installations. Insulation material used is PVC and conductors are made from electrical purity aluminum or copper. For giving flexibility to the conductors of cables are stranded. These cables are used where combination of ambient temperature and temperature rise because of load results in conductor temperature not exceeding 70 deg C under normal operation and 160 deg C under short circuit conditions. Different cores in a cable are identified by the colours of PVC insulation. Accepted colour codes for PVC insulated cables are for (i) single core – red, yellow, blue, or black, (ii) tin core – red and black, (iii) three core – red, yellow, and blue, (iv) four core – red, yellow, blue, and black, and (v) five core – red, yellow, blue, black, and light grey. In 3.5 core cables, the three main cores are red, yellow, blue for phases and reduced core is black for neutral. Red, yellow, blue colours represent phase ‘R’, ‘Y’, ‘B’ phases and black colour represents neutral ‘N’ phase. For cables of voltage grade up to and including 6.6 kilovolts, method of core identification is (i) different colouring of the PVC insulation, (ii) coloured strips applied on the cores, or (iii) by numerals (1,2,3), either applying numbered strips or by printing on the cores. For cables of voltage grade of 6.35 kilovolts / 11 kilovolts, method of core identification is (i) coloured strips applied on the cores, or (ii) by numerals (1,2,3), either by applying numbered strips or by printing on the cores.
PV factor – It is the product of bearing pressure and surface velocity traditionally expressed in terms of is pascal x metre per second (Pa.m/s).
P-X diagram – It is a two-dimensional graph of the isothermal phase relationships in a binary system. In this graph, the coordinates of the graph are pressure and concentration.
P-X projection – It is a two-dimensional graph of the phase relationships in a binary system produced by making an orthographic projection of the phase boundaries of a P-T-X diagram upon a pressure concentration plane.
Pylon – It is a steel structure used in stackers and reclaimers. It is a support tower structure for suspension bridges or highways. In case of power transmission, it is a large vertical steel lattice tower-like structure used for supporting high-tension overhead power lines.
Pyramidal hopper – It is a hopper in a conveyor system with a pyramidal shape. It is used for efficient material feeding. Regular inspections are necessary to prevent blockages and ensure proper material flow.
Pyramidal plane – In non-cubic crystals, it is a plane which intersects all three axes.
Pyramiding – It is the use of increased buying power to increase ownership arising from price appreciation.
Pyramid of incidents – Pyramid of incidents is also known as Heinrich’s triangle or Bird’s triangle. It provides a theoretical view of the industrial accident prevention. It shows a relationship between serious accidents, minor accidents, and near misses.
Pyrite – It is a yellow iron sulphide mineral, normally of little value. It is sometimes referred to as ;fool’s gold’.
Pyro-hydrolysis – Pyro-hydrolysis is a process where the spent pickle liquor is thermally decomposed in order to convert the spent pickle liquor back into hydrochloric acid and iron oxide. This process is carried out at a very high temperature along with water vapour and oxygen. The spent pickle liquor is pumped into the pyro-hydrolysers which convert the ferrous chloride (FeCl2) into components of ferric oxide (Fe2O3) and hydrochloric acid. Pyro-hydrolysis plants are very energy intensive, mainly because a large amount of fuel combustion is needed to evaporate the metal chloride solution and to heat the roaster contents.
Pyrolysis – It is the process of thermal decomposition of materials at high temperatures, frequently in an inert atmosphere without access to oxygen. Pyrolysis is normally used in the treatment of organic materials. With respect to fibres, the thermal process by which organic precursor materials, such as rayon, polyacrylonitrile (PAN), and pitch, are chemically changed into carbon fibre by the action of heat in an inert atmosphere. Pyrolysis temperatures can range from 800 deg C to 2,800 deg C, depending on the precursor. Higher processing graphitization temperatures of 1,900 deg C to 3,000 deg C normally lead to higher modulus carbon fibers, normally referred to as graphite fibres. During the pyrolysis process, molecules containing oxygen, hydrogen, and nitrogen are driven from the precursor fibre, leaving continuous chains of carbon.
Pyro-metallurgy – It is the high-temperature winning or refining of metals.
Pyrometer – It is a device for measuring temperatures above the range of liquid thermometers.
Pyrometric cone equivalent (PCE) – It is the reference number of the pyrometric reference cone which has bent over to the same degree as test pieces of a refractory or the number of the two cones which have bent over, one a little more and one a little less than the test pieces when the cones and the test pieces have been mounted together and heated under specified conditions.
Pyrometric cones – These are also known as Seger cones. These cones are used in ceramic industries to test the refractoriness of the refractory bricks. They consist of a mixture of oxides which are known to melt at a specific narrow temperature range.
Pyrometric reference cone – It is the blunt-tipped skew triangle pyramid with sharp edges, of specified shape and dimensions and of such composition that, when mounted and heated under specified conditions, it bends in a known manner with reference to its heat temperature.
Pyrophoric powder – It is a powder whose particles self-ignite and burn when exposed to oxygen or air, e.g., fine zirconium powder.
Pyrophoricity – It is the property of a substance with a large surface area to self-ignite and burn when exposed to oxygen or air.
Pyro-shock – It is the dynamic structural shock which occurs when an explosion or impact occurs on a structure.
Pyrrhotite – It is a bronze-coloured, magnetic iron sulphide mineral.
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