Glossary of technical terms for the use of metallurgical engineers Terms starting with alphabet ‘R’
Glossary of technical terms for the use of metallurgical engineers
Terms starting with alphabet ‘R’
R2P2 – It means ‘reducing risks protecting people’. It is a document which describes the decision-making process of the health, safety and environment. It aims to make the procedures and protocols which the health, safety and environment follows transparent so as to ensure that the decision-making process of health, safety and environment, including risk assessment and risk management, is perceived as valid.
Rabbit ear – It is the recess in the corner of a metal-forming die to allow for wrinkling or folding of the blank.
Raceway – It is also called race. It is the groove or path in which the rolling elements in a rolling-contact bearing operate. In blast furnace, raceway consists of combustion zone in front of the tuyeres in a blast furnace. In this zone burning of the fuel takes place.
Rack – It is also called plating rack. It is a fixture used to hold work and conduct current to it during electroplating.
Rack and pinion – It is a type of linear actuator which comprises a circular gear (the pinion) engaging a linear gear (the rack). Together, they convert between rotational motion and linear motion. Rotating the pinion causes the rack to be driven in a line. Conversely, moving the rack linearly causes the pinion to rotate.
Rack and pinion gears – A straight bar with teeth cut straight across it, is called a rack. Basically, this rack is considered to be a spur gear unrolled and laid out fiat. Thus, the rack-and pinion is a special case of spur gearing. The rack-and-pinion is useful in converting rotary motion to linear and vice versa. Rotation of the pinion produces linear travel of the rack. Conversely, movement of the rack causes the pinion to rotate. The rack-and-pinion is used extensively in machine tools, lift trucks, power shovels, and other heavy machinery where rotary motion of the pinion drives the straight-line action of a reciprocating part. Normally, the rack is operated without a sealed enclosure in these applications, but some type of cover is normally provided to keep dirt and other contaminants from accumulating on the working surfaces.
Racking – It is a term which is used to describe the placing of metal parts to be heat treated on a rack or tray. This is done to keep parts in a proper position to avoid heat-related distortions and to keep the parts separated. It is also the process of arranging articles on a rack in order to transport them more efficiently through the galvanizing process.
Radar – It means ‘radio detection and ranging. It consists of the techniques for observing the speed and position of objects by reflected radio waves.
Radar cross section – It is the effective reflecting area of a radar target, which varies with frequency, geometry, and surface composition.
Radial-axial horizontal rolling machine – It is a type of metal forming technology which is used to produce seamless rings, employing both radial and axial rollers to control the ring’s dimensions during the rolling process, particularly for large-diameter and high-precision rings.
Radial centrifugal pump – It is a type of pump where the fluid exits the impeller in a radial direction, meaning perpendicular to the pump’s shaft, creating higher discharge pressures but typically smaller volume flow rates. In this pump, the fluid handled is conveyed radially, i.e., It enters through the suction pipe, is collected by the impeller, and then escapes vertically to the pump shaft from the pump’s impeller and through a spiral casing. This material handling method which uses centrifugal force enables higher pressures than can be achieved with axial pumps, where the fluids are conveyed axially, that is, parallel to the pump shaft.
Radial crushing strength – It is a material property which describes a material’s resistance to compressive forces applied radially, meaning from the side, and is typically measured by a destructive test where a hollow cylinder is subjected to increasing radial load until fracture. It is the relative capacity, of a plain sleeve sample made by powder metallurgy, to resist fracture induced by a force applied between flat parallel plates in a direction perpendicular to the axis of the sample. It refers to the ability of a powder compact to resist fracture when a force is applied perpendicular to its axis, between flat parallel plates.
Radial distribution function analysis – It is diffraction method which gives the distribution of inter-atomic distances present in a sample along with information concerning the frequency with which the particular distances occur.
Radial draw forming – It consists of the forming of sheet metals by the simultaneous application of tangential stretch and radial compression forces. The operation is done gradually by tangential contact with the die member. This type of forming is characterized by very close dimensional control.
Radial forging – It is a process using two or more moving anvils or dies for producing shafts with constant or varying diameters along their length or tubes with internal or external variations. It is frequently incorrectly referred to as rotary forging.
Radial friction welding (RFW) – It is a solid-state joining process where a rotating, solid, bevelled ring is radially compressed into a V-preparation created by the pipe ends, generating friction heat and forging the materials together without melting. The process adopts the principle of rotating and compressing a solid ring around two stationary pipe ends. The pipes to be welded are bevelled to provide a ‘V’ groove when they are butted together. They are then securely clamped to prevent axial and rotational movement. A solid, internally bevelled ring of compatible material with a bevelled angle that is less than that of the pipes is positioned around the pipe end.
Radial grain flow – It refers to the directional orientation of metal grains, typically elongated and aligned, which flows outwards from a central point or axis, similar to spokes on a wheel.
Radial lip seal – It is a radial type of seal which features a flexible sealing member, referred to as a lip. The lip is normally of an elastomeric material. It exerts radial sealing pressure on a mating shaft in order to retain fluids and / or exclude foreign matter.
Radial-load bearing – It is a bearing in which the load acts in a radial direction with respect to the axis of rotation.
Radial marks – These are macroscale ridges or thin ledges appearing as lines on a fracture surface. Radial marks are created under conditions of rapid crack growth. The lines frequently radiate from the fracture origin and are visible to the unaided eye or at low magnification. Radial marks can result from the intersection and connection of brittle cleavage fractures propagating at different levels. Alternatively, relatively tall, sharp-edged ridges can be created by small-scale ductile shear on intersecting planes. The appearance of radial lines varies considerably with the ductility of the material prior to and during fracture. In some microstructures (e.g., pearlitic steels), the lines can be poorly defined as diffuse ridges parallel to the direction of crack growth and may not be visible near the initiation site, but only after some growth of the crack front.
Radial roll – It is also called main roll or king roll. It is the main driven roll of the rolling mill for rings in the radial pass. The roll is supported at both ends.
Radial roll forming process – It is a metal forming process where a small metal ring is continuously stretched and formed between rollers to produce a ring of larger dimensions, focusing on changing the ring’s thickness radially.
Radial rolling force – It is the action produced by the horizontal pressing force of the rolling mandrel acting against the ring and the main roll.
Radial stress – It refers to the stress acting toward or away from the central axis of a cylindrical object, such as a pipe or pressure vessel, and is a normal stress which acts along the radius.
Radial wafer technique – It refers to methods and processes used to analyze and control variations in properties (like resistivity or thickness) across the radius of a wafer.
Radiant energy – It is the energy transmitted as electro-magnetic radiation.
Radiant intensity – It is the radiant power or flux emitted per unit solid angle expressed, e.g., in watts per steradian.
Radiant power (flux) – It is the energy emitted by a source or transported in a beam per unit time, expressed, e.g., in ergs per second or watts.
Radiant tubes – They consist of a method of heating a furnace without contaminating the furnace atmosphere with the products of combustion. The radiant tubes aim to transfer heat as uniformly as possible within the interior of the tube and transfer the heat within the furnace. The transfer of heat to the inner surface of the tube is dependent on the tube’s effective surface area. A tube with a nominal inside diameter of 100 millimeters can have a much higher effective internal surface area because of the surface roughness, which resembles small bumps and troughs. The internal surface area of the tube can also be increased using internal fins.
Radiant tube burner – It is also called radiant burners. It is an indirect-fired burner where combustion occurs within a heat-resistant tube, and the heat is transferred to the target material or process by radiation, preventing contamination of the atmosphere by combustion products. Radiant tube burner operates by combusting a fossil fuel, which heats a solid surface that radiates infrared (IR) energy to a load. This burner is normally used in a number of lower temperature heating applications, drying applications, and in industrial heat treatment applications, particularly when a controlled atmosphere is needed, such as in furnaces for annealing, hardening, or sintering. Both gas-fired and electric radiant heaters are normally used.
Radiant tube furnace – It uses long, heat-resistant tubes to transfer heat from combustion products to the materials being heated, preventing contamination of the furnace atmosphere with combustion gases.
Radiation – It is the process of emitting energy as waves or particles. The energy thus radiated is frequently used for ionizing radiation except when it is necessary to avoid confusion with non-ionizing radiation.
Radiation-absorbed dose (rad) – It is the quantity of energy (from any type of ionizing radiation) deposited in any medium (e.g., water, tissue, air). An absorbed dose of 1 rad means that 1 gram of material absorbed 100 ergs of energy (a small but measurable quantity) as a result of exposure to radiation. The related international system unit is the gray (Gy), where 1 Gy is equivalent to 100 rad.
Radiation control area – It is a defined area where specific protection measures and safety provisions are needed to control exposures or to prevent contamination during normal working conditions and to prevent or limit potential exposures.
Radiation damage – It is a general term for the alteration of properties of a material arising from exposure to ionizing radiation (penetrating radiation), such as x-rays, gamma rays, neutrons, heavy-particle radiation, or fission fragments in nuclear fuel material.
Radiation dose constraints – It is a numerical dose figure based on knowledge and assessment which is used as a planning aid for minimizing individual radiation dose.
Radiation heat transfer – It is the process where thermal energy is transferred through electromagnetic waves, without requiring a medium, and can occur even in a vacuum. In the radiation heat transfer process, the thermal energy is exchanged between two surfaces obeying the laws of electromagnetics.
Radiation loss – It is a comprehensive term used in a boiler-unit heat balance to account for the conduction, radiation, and convection heat losses from the boiler to the ambient air.
Radiation protection – It is the protection of people from the harmful effects of ionizing radiation.
Radiation shielding – It is reducing the level of radiation between a radioactive source and a person by interposing a shield of absorbing material.
Radiation source – It is a material or device that emits radiation, which can be in the form of waves or particles, and can be either natural or man-made.
Radiation thermometer – It is also known as a pyrometer or infrared thermometer. It is a non-contact device which measures an object’s temperature by detecting the infrared radiation it emits, without needing physical contact.
Radiator – It is a heat exchanger which is used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in automobiles, buildings, and electronics. A radiator is always a source of heat to its environment, although this can be for either the purpose of heating an environment, or for cooling the fluid or coolant supplied to it, as for automotive engine cooling and heating, ventilation, and air conditioning (HVAC) dry cooling towers. Despite the name, majority of the radiators transfer the bulk of their heat through convection instead of thermal radiation.
Radical – It is an atom, molecule, or ion which has at least one unpaired valence electron. With some exceptions, these unpaired electrons make radicals highly chemically reactive. Several radicals spontaneously dimerize. Majority of the organic radicals have short lifetimes. A notable example of a radical is the hydroxyl radical (OH-), a molecule which has one unpaired electron on the oxygen atom. Two other examples are triplet oxygen and triplet carbene (–CH2) which have two unpaired electrons. Radicals can be generated in a number of ways, but typical methods to produce radicals involve redox reactions. Ionizing radiation, heat, electrical discharges, and electrolysis. Radicals are intermediates in several chemical reactions, more so than is apparent from the balanced equations.
Radio – It is the technology of radio frequency devices.
Radioactive contamination – It is the deposition of, or presence of radioactive substances on surfaces or within solids, liquids, or gases (including the human body), where their presence is unintended or undesirable. Such contamination presents a hazard since the radioactive decay of the contaminants produces ionizing radiation (namely alpha, beta, gamma rays and free neutrons). The degree of hazard is determined by the concentration of the contaminants, the energy of the radiation being emitted, the type of radiation, and the proximity of the contamination to organs of the body. It is important to be clear that the contamination gives rise to the radiation hazard, and the terms ‘radiation’ and ‘contamination’ are not interchangeable. The sources of radioactive contamination can be classified into two groups namely natural and man-made.
Radioactive decay – It is the process by which an unstable atomic nucleus loses excess nuclear energy by emitting radiation in any of several forms, including as gamma radiation, as alpha or beta particles, or by ejecting electrons from its atomic orbitals.
Radioactive element – It is an element which has at least one isotope that undergoes spontaneous nuclear disintegration to emit positive particles, negative particles, or rays.
Radioactive materials – These materials refer to substances with unstable atomic nuclei which emit spontaneously ionizing radiation as they decay, releasing energy in the process. These are frequently mixed with hazardous waste from nuclear reactors, laboratories, or research institutions.
Radioactive pollutants – These pollutants refer to the release of radioactive substances into the environment, causing contamination and posing risks to human health and the environment. These pollutants Radioactive materials originate from the (i) mining and processing of ores, (ii) use of isotopes in research and industrial activities, and (iii) radioactive discharge from nuclear power plants and nuclear reactors. These isotopes are toxic to the life forms since they accumulate in the bones, teeth and can cause serious disorders.
Radioactive pollution – It is defined as a form of physical, nuclear pollution to living organisms and the environment (hydrosphere, lithosphere, and atmosphere) arising from exposure to the release of ionizing radiation from radioactive elements such as uranium. Such releases occur as a result of radioactive decay of radioactive elements during (i) nuclear explosions and testing, (ii) disposal of nuclear waste, (iii) mining radioactive ores, and (iv) accidents at nuclear power plants.
Radioactive source – It contains radioactive material of a particular radio-nuclide (an unstable form of an element emitting radiation), which can vary based on the application for which the source has been manufactured. Radioactive sources emit ionizing radiation, typically in the form of alpha and beta particles, gamma rays or neutron radiation. Earlier, only radionuclides of natural origin, such as Radium-226 – an isotope of radium has been available for use. Today, radionuclides artificially produced in nuclear facilities and accelerators, including Caesium-137, Colbalt-60, and Iridium-192, are extensively used. These radioactive sources are used for medical, industrial, agricultural, research and educational purposes. Some examples of the application of radioactive sources include mapping underground sources of water, integrity testing of mechanical structures and measuring soil density for construction projects etc.
Radioactive waste – It is a waste material which emits energy as rays, waves, streams or energetic particles. It contains radionuclides and is no longer considered useful. It can be solid, liquid, or gas.
Radioactivity – It is the property of the nuclei of some isotopes to spontaneously decay (lose energy). Normal mechanisms are emission of or other particles and splitting (fissioning). It is the spontaneous emission of radiation, normally alpha or beta particles, frequently accompanied by gamma rays, from the nucleus of an unstable isotope. It is also, the rate at which radioactive material emits radiation. It is measured in units of becquerels or disintegrations per second. Other measurements are used (e.g., Sieverts) which relate to physiological effects.
Radio-analysis – It is an analytical technique, such as neutron activation analysis, which makes use of the radioactivity of an element or isotope.
Radio-chemistry – It is the branch of chemistry involving the study of radioactive substances and radioactivity, including the use of radioactive isotopes to study non-radioactive isotopes and ordinary chemical reactions
Radio direction finding (RDF) – It is the use of radio waves to determine the direction to a radio source. It differs from radar in that only the direction is determined by any one receiver; a radar system normally also gives a distance to the object of interest, as well as direction. By triangulation, the location of a radio source can be determined by measuring its direction from two or more locations.
Radio frequency – It consists of electromagnetic waves with frequencies less than that of infrared radiation. It is commercially important radio frequencies range from tens of kilohertz up to around a terahertz.
Radio frequency interference (RFI) – It refers to unwanted signals which disrupt microwave instruments by interfering with the frequencies they measure, both internally and externally. It can be caused by different sources such as power circuits, signal voltages, and communication frequencies, impacting the accuracy of measurements in passive microwave applications.
Radio-frequency spectrometer – It is an instrument which measures the intensity of radiation emitted or absorbed by atoms or molecules as a function of frequency at frequencies from 10 kHz (kilohertz) to 100 GHz (gigahertz).
Radio-frequency spectroscopy – It is the branch of spectroscopy concerned with the measurement of the intervals between atomic or molecular energy levels that are separated by frequencies from around 10 to the power 5 hertz to 10 to the power 9 hertz as compared to the frequencies which separate optical energy levels of around 6 × 10 to the power 14 hertz.
Radiograph – It is a photographic shadow image resulting from uneven absorption of penetrating radiation in a test object.
Radiographic (X-ray) testing – It is also called radiography inspection. It is normally used to determine whether a weld is sound. It involves subjecting a weld or weld area to an X-ray source with an X-ray sensitive film plate on the under-side of the weld. The results are shown on the developed film (a photo-micrograph) and interpreted according to specification.
Radiography – It is a method of non-destructive inspection in which a test object is exposed to a beam of X-rays or rays and the resulting shadow image of the object is recorded on photographic film placed behind the object, or displayed on a viewing screen or television monitor (real-time radiography). Internal discontinuities are detected by observing and interpreting variations in the image caused by differences in thickness, density, or absorption within the test object.
Radio-isotope leak test system – It is a leak test system which uses a radioactive tracer gas and a detector for measuring the emission from the tracer.
Radioisotopes – Radioisotopes are radioactive isotopes of an element. They can also be defined as atoms which contain an unstable combination of neutrons and protons.
Radiology – It is the general term given to material inspection methods which are based on the differential absorption of penetrating radiation, either electromagnetic radiation of very short wavelength or particulate radiation, by the part or test-piece (object) being inspected. Because of differences in density and variations in thickness of the part or differences in absorption characteristics caused by variations in composition, different portions of a test-piece absorb different quantities of penetrating radiation. These variations in the absorption of the penetrating radiation can be monitored by detecting the unabsorbed radiation that passes through the test-piece.
Radio-nuclide – It is an unstable nuclide which hat emits ionizing radiation.
Radio transmitter – It is an apparatus designed to generate radio frequency electric current, which, connected to an antenna, can radiate energy through space.
Radium (Ra) – It a chemical element with atomic number 88. It is an alkaline earth metal. It is an element which is a radioactive decay product of uranium frequently found in uranium ore. Pure radium is silvery-white, but it readily reacts with nitrogen (rather than oxygen) upon exposure to air, forming a black surface layer of radium nitride (Ra3N2). It has several radioactive isotopes. All isotopes of radium are radioactive, the most stable isotope being radium-226 with a half-life of 1,600 years. When radium decays, it emits ionizing radiation as a by-product, which can excite fluorescent chemicals and cause radio-luminescence. For this property, it was widely used in self-luminous paints. Of the radioactive elements which occur in quantity, radium is considered particularly toxic, and it is carcinogenic because of the radioactivity of both it and its immediate decay product is radon.
Radius – Radius of a circle or sphere is any of the line segments from its centre to its perimeter. It is the distance from the centre of the circle to any point on its circumference. Radius also means to remove the sharp edge or corner of forging stock by means of a radius or form tool.
Radius of bend – It is the radius of the cylindrical surface of the pin or mandrel which comes in contact with the inside surface of the bend during bending. In the case of free or semi-guided bends to 180-degree in which a shim or block is used, the radius of bend is one-half the thickness of the shim or block.
Radius of curvature – It is the reciprocal of the curvature. For a curve, it equals the radius of the circular arc which best approximates the curve at that point. For surfaces, the radius of curvature is the radius of a circle which best fits a normal section or combinations thereof. In the case of a space curve, the radius of curvature is the length of the curvature vector.
Radon – It is a heavy radioactive gas given off by rocks containing radium (or thorium). These rocks have existed since the formation of earth’s crust and radon is frequently the single largest contributor to an individual’s background radiation dose, and is the most variable from location to location. Radon is a noble gas (a group VIII element). Other members of the series are helium, neon, argon, krypton, and xenon.
Radon survey – It is a geochemical survey technique which detects traces of radon gas, a product of radioactivity.
RAFT – RAFT is the ‘raceway adiabatic flame temperature’. The flame temperature is an important parameter since it affects the slag and metal chemistry, evaporation and recirculation of the alkali elements present, and the flow of metal in the hearth. It is difficult to measure the flame temperature and so it is normally calculated from an energy balance of the raceway zone. The calculated value is known as RAFT.
Rafter – It is one of a series of sloped structural members which extend from the ridge or hip to the wall plate, downslope perimeter or eave, and which are designed to support the roof deck and its associated loads. A pair of rafters is called a couple.
Rail – It is a steel bar extending horizontally between supports which is used as a track for rail road cars or other railway vehicles. The rail, as the most important component of the track superstructure, means the running surface, carrier and guiding element for the rolling wagons. It is the defining feature and most important component of the rail track. The main function of the rail is to provide a smooth and continuous level surface for movement and to provide guidance in lateral direction for movement of the wheels. Rails have asymmetric shape. Rail steel is used to make rails for the rail track as well as the tracks for moving equipments like cranes, transfer cars, charging and pusher cars in coke oven battery, and material handling equipment (stacker, reclaimers, and bender reclaimers) etc.
Railcar – It is a self-propelled railway vehicle is which designed to transport passengers. The term ‘railcar’ is normally used in reference to a train consisting of a single coach (or carriage, car, unit), with a driver’s cab at one or both ends.
Rail gauge – In rail transport, it ids the gauge of rail track. It is the distance between the two rails of a railway track. All vehicles on a rail network are required to have wheelsets which are compatible with the track gauge.
Rail mills – As the name suggest, rails mills are used for rolling of rail sections from the blooms.
Rail network – It refers to a system of inter-connected railway lines which are used for mass transportation of materials including movement of liquid metal. It has a significant carrying capacity. It connects different plant facilities and provides approaches to different production units. It greatly affects in-plant movement and traffic. Rail network is highly dependent on the plant general layout and can become very complex.
Rail profile – It is the cross-sectional shape of a rail, perpendicular to its length. The weight of a rail per unit length is an important factor in determining rail strength and hence axle loads and speeds. Weights are measured in kilograms per metre.
Rail road ballast – It is a layer of coarse granular material (like crushed stone or gravel) placed under and around railroad tracks to provide stability, drainage, and support for the rails and sleepers, ensuring a smooth and safe ride.
Railroad car – It is a is a vehicle used for the carrying of passengers on a rail transport network. Such cars, when coupled together and hauled by one or more locomotives, form a train.
Railroad switch – It is also called turnout. It is a mechanical installation enabling railway trains to be guided from one track to another. The most common type of switch consists of a pair of linked tapering rails, known as points (switch rails or point blades), lying between the diverging outer rails (the stock rails). These points can be moved laterally into one of two positions to direct a train coming from the point blades toward the straight path or the diverging path. A train moving from the narrow end toward the point blades (i.e. it is directed to one of the two paths, depending on the position of the points) is said to be executing a facing-point movement.
Rail sleepers – They are also called railroad ties, railway ties or crossties. They are an important railway component. They are rectangular supports which are placed across the track ballast, serving as a foundation for the rails, and helps to distribute the weight and vibrations of passing trains. Normally, the rail sleepers are always laying between two rail tracks to keep the correct space of gauge.
Rail steel – It is a specialized type of steel used in railway track construction. The properties of rail steel are achieved through control of carbon and manganese contents. Carbon content of rail steel can go up to a maximum of 0.82 % and manganese content up to a maximum of 1.7 %. The normal rails are made of steel containing 0.7 % carbon and 1 % manganese, which are called as carbon-manganese rail steel. Real steel has high strength, durability, and ability to withstand heavy loads and constant wear and tear. It is having a pearlitic structure based on its carbon-manganese composition. Its wear-resistant pearlite consists of alternating lamellae of soft iron and very hard iron carbide (also known as cementite). The smaller the spacing between cementite layers, the harder and more wear-resistant the rail steel is. Rails not only wear, they also break. Their inherent toughness is poor as a result of the presence of the brittle carbide phase. Fracture can occur from relatively minor stress-concentrating features inside the rail, or on the surface, as a result of manufacture or subsequent handling damage. Pearlitic rails have been developed almost to their limit. Now rails are also being made of a carbide free bainitic steel which is a tough rail steel with excellent wear resistance. Rail steel forms the main structural component of railway tracks, ensuring safe and efficient transportation of trains.
Rail stressing – It is a rail engineering process. It is used to prevent heat and cold tension after installation of continuous welded rail (CWR). Environmental heat causes continuous welded rail to expand and hence can cause the fixed track to buckle. Environmental cold can lead to the contraction of the fixed railway track causing brittleness and cracks. Before it is installed, the rail is altered by stretching with hydraulic tensors or heated to its stress-free temperature to make these dangerous problems less likely.
Rail track – It is a structure which allows trains to move by providing a smooth, low-friction surface for their wheels to roll on. It is also known as a railroad track, permanent way. It is made up of two parallel steel rails which are a fixed distance apart. The rails are connected by railroad ties, which are normally bolted to the rails. The ties are set into loose gravel or ballast, which helps transfer the load to the underlying foundation.
Rail traction – It refers to the system or method which is used to move trains or vehicles on rails, encompassing the power source, transmission, and mechanisms which generate the driving force.
Railway tank car – It is also called tank wagon. I is a specialized type of railroad car designed to transport liquids and gases in bulk, frequently pressurized or non-pressurized, and insulated or non-insulated, depending on the specific commodity
Railway wagons – These are unpowered railway vehicles which are used for the transportation of cargo. A variety of wagon types are in use to handle different types of goods, but all goods wagons in a railway network typically have standardized couplers and other fittings, such as hoses for air brakes, allowing different wagon types to be assembled into trains.
Rail wheel – It is a type of wheel specially designed for use on railway tracks. The wheel acts as a rolling component, typically press fitted onto an axle and mounted directly on a railway carriage or locomotive, or indirectly on a bogie. The powered wheels under the locomotive are called driving wheels. Wheels are initially cast or forged and then heat-treated to have a specific hardness. New wheels are machined using a lathe to a standardized shape, called a profile, before being installed onto an axle. All wheel profiles are regularly checked to ensure proper interaction between the wheel and the rail. Incorrectly profiled wheels and worn wheels can increase rolling resistance, reduce energy efficiency, and can even cause a derailment. The International Union of Railways has defined a standard wheel diameter of 920 millimeters, although smaller sizes are used in some rapid transit railway systems and on ro-ro carriages.
Rain erosion – It is a form of liquid impingement erosion in which the impinging liquid particles are raindrops. This form of erosion is of particular concern to designers and material selectors for external surfaces of rotary-wing and fixed-wing aircraft.
Rain forest – It is a dense, moist forest characterized by a high annual rainfall and frequently featuring tall, broad-leaved evergreen trees forming a continuous canopy. Rainforests are defined by their abundant rainfall, typically receiving 2,000 millimeters to 10,000 millimeters of rain annually.
Rain shadow – It is a region of relatively low rainfall on the leeward (downwind) side of a mountain range, where the mountains block the passage of rain-producing weather systems, casting a ‘shadow’ of dryness behind them.
Rainwater – It is simply the water which falls from the sky as rain.
Rainwater harvesting – It is the process of collecting and storing rainwater which otherwise runs off into drains. It is a water conservation method which can be used for several purposes.
Rain gutter – It is also called surface water collection channel. It is a component of a water discharge system for a building.
Raise – It consists of a vertical or inclined underground working which has been excavated from the bottom upward.
Raised face – The raised face is the most common used flange face. It is called raised face since the gasket is raised 1.5 millimeters to 6 millimeters above the bolt circle face. The flange facings are machine finished to meet the requirements of the standards and has unconfined gasket. They are suitable for average service conditions. For severe service involving high pressure, high temperature, thermal shock, or cyclic operations, this type of flange facing is normally not satisfactory.
Raised floor – It provides an elevated structural floor above a solid substrate (frequently a concrete slab) to create a hidden void for the passage of mechanical and electrical services. Raised floors are widely used in modern office buildings, and in specialized areas, where there is a requirement to route mechanical services and cables, wiring, and electrical supply. Such flooring can be installed at varying heights from 50 millimeters to heights above 1 meter to suit services which can be accommodated beneath. Additional structural support and lighting are frequently provided when a floor is raised enough for a person to crawl or even walk beneath.
Rake – It is the angular relationship between the tooth face, or a tangent to the tooth face at a given point, and a given reference plane or line. In geology, rake is the trend of an orebody along the direction of its strike. In railway terminology, a rake refers to a formation of coupled passenger coaches or freight wagons, essentially the train itself excluding the locomotive or engine. In geology, rake is the angle between a feature on a bedding plane and the strike line. Rake is also a long-handled tool with tines.
Rake classifier – It is a mechanical classifier consists of a rectangular tank with a sloping / inclined bottom. The tank is provided with movable rakes. The feed in the form of a suspension is introduced continuously near the middle of the tank. The lower end of the tank has a weir overflow from which the fines that are not settled leave with the overflow liquid. The heavy materials sink to the bottom of the tank. The rakes scrap the settled solids upwards along the bottom of the tank to the top of the tank. The reciprocating rakes keep the slurry in continuous agitation. The time of raking stroke is so adjusted that fines do not have time to settle and so remain near the surface of the slurry while the heavy particles have time to settle. Rake classifiers are also used for close circuit grinding.
Rake mechanism – Rake-mechanism of rolling mill cooling bed consists of (i) fixed straightening rakes, (ii) movable rake mechanism, and (iii) fixed rake-mechanism. Fixed straightening rakes are cast Iron toothed blocks, which receive the hot bars from the bar receiving mechanism. These fixed rakes help to straighten the bars, which are at a temperature of above 700 deg C. Movable rake mechanism consists of fabricated steel tooth rakes which are mounted on eccentric rollers to enable them to move in the x and y axis. The rakes have profile cut to suit the smallest and maximum size of bars. This mechanism collects the bars from the fixed straightening rakes and transfers them towards the delivery side of the cooling bed. Fixed rake-mechanism also consists of fabricated steel toothed rakes, which receive the bars from movable rake mechanism as the bars are transferred toward the delivery side of the cooling bed.
Raking, ladle – It means the practice of manually drawing off solid, or semi-solid slag, from the top of a ladle at the skimming station.
Ram – It is the moving or falling part of a drop hammer or press to which one of the dies is attached; sometimes applied to the upper flat die of a steam hammer. It is also referred to as the slide. It is also the moving parts of the pile hammer, consisting of a piston and a driving head, or driving head only.
Raman line (band) – It is a line (band) which is part of a Raman spectrum and corresponds to a characteristic vibrational frequency of the molecule being probed.
Raman radiation – It is also called Raman effect. It is the inelastic scattering of light by matter, resulting in a change in the light’s frequency and energy because of interactions with the vibrational and rotational modes of the molecules.
Raman scattering – It is also called Raman effect. It is the inelastic scattering of photons by matter, meaning that there is both an exchange of energy and a change in the light’s direction. Typically, this effect involves vibrational energy being gained by a molecule as incident photons from a visible laser are shifted to lower energy.
Raman shift – It is the displacement in wave number of a Raman line (band) from the wave number of the incident monochromatic beam. Raman shifts are normally expressed in units of per centimeter. They correspond to differences between molecular vibrational, rotational, or electronic energy levels.
Raman spectroscopy – It is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Raman spectroscopy is normally used in chemistry to provide a structural fingerprint by which molecules can be identified. Raman spectroscopy relies upon inelastic scattering of photons, known as Raman scattering. A source of mono-chromatic light, normally from a laser in the visible, near infrared, or near ultra-violet range is used, although X-rays can also be used. The laser light interacts with molecular vibrations, phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The shift in energy gives information about the vibrational modes in the system.
Raman spectrum – It is the spectrum of the modified frequencies resulting from inelastic scattering when matter is irradiated by a mono-chromatic beam of radiant energy. Raman spectra normally consist of lines (bands) at frequencies higher and lower than that of the incident mono-chromatic beam.
Rammed graphite moulds – These are casting moulds created by packing a mixture of graphite powder and binders around a pattern, offering a method to cast reactive materials like titanium without mould material reaction.
Ramming – It consists of packing foundry sand, refractory, or other material into a compact mass. It is the compacting of moulding (foundry) sand for forming a mould. In refractories ramming is a process of installing or shaping an unshaped refractory involving repeated impact.
Ram mix, ramming mix – It consists of unshaped refractory which is non-coherent before use, made up of aggregate, bond and if necessary, liquid, and placed by ramming (mechanical or manual) or vibration. As per the type of product, the main bond can be ceramic, chemical, or organic. Ram mixes are used as-delivered or after the addition of liquid(s).
Ramming refractory materials – These materials are in loose dry form with graded particle size. They are mixed with water for use. Wet ramming materials are used immediately on opening. Ramming materials are used mostly in cold condition so that desired shapes can be obtained with accuracy.
Random error – This type of error is normally because of the accumulation of a large number of small effects and can be of real concern only in measurements needing a high degree of accuracy. The cause of such error is unknown or not determined in the ordinary process of making measurement. Random error is an indeterminate error. This error takes place because of the causes which cannot be directly established because of random variations in the parameter or the system of measurement. Hence, there is no control over them. Their random nature causes both high and low values to average out. Multiple trials help to minimize their effects. Random errors can be analyzed statistically.
Random failures – These failures are normally attributed to hardware. They are failures occurring at a random time, which result in one or more of degradation of the component capability to perform its scope. Based upon historical data, random failures can be characterized by a parameter called failure rate. In other words, a random failure involves only the equipment. Random failures can occur suddenly without warning or be the outcome of slow deterioration over time. These failures can be characterized by a single reliability parameter, the device failure rate, which can be controlled and managed using an asset integrity program.
Random intermittent welds – These are intermittent welds on one or both sides of a joint in which the weld increments are made without regard to spacing.
Random orientation – It is a condition of a poly-crystalline aggregate in which the orientations of the constituent crystals are completely random relative to each other.
Random pattern – It is a winding with no fixed pattern. If a large number of circuits is needed for the pattern to repeat, a random pattern is approached. It is a winding in which the filaments do not lie in an even pattern.
Random sequence – It is a longitudinal welding sequence wherein the weld-bead increments are deposited at random to minimize distortion.
Random variable – It is a parameter or variable which deviates from some measure of average performance or central tendency in a predictable way.
Random vibration – It is motion which is non-deterministic, meaning that the exact behaviour at a future point in time cannot be predicted, but general trends and statistical properties can be known. The randomness is a characteristic of the excitation or input, not the mode shapes or natural frequencies. Some common examples include an automobile riding on a rough road, wave height on the water, or the load induced on an airplane wing during flight. Structural response to random vibration is normally treated using statistical or probabilistic approaches. Mathematically, random vibration is characterized as an ergodic and stationary process.
Raney cobalt – It is a cobalt-based catalyst similar to Raney nickel. It is prepared by treating a cobalt-aluminum alloy with alkali. It is used for certain chemo-selective reductions, mainly in hydrogenation reactions.
Raney nickel – It is a heterogeneous hydrogenation catalyst, a fine-grained solid composed mainly of nickel derived from a nickel-aluminum alloy. It is used in organic chemistry for different reduction reactions, particularly hydrogenation.
Range – Range is the difference between the maximum and minimum values for which the instrument can be used for the measurement. The instrument range is stated by the manufacturer of the instrument.
Rangeability – It is the ratio of the largest flow coefficient to the smallest flow coefficient within which the deviation from the specified flow characteristic does not exceed the stated limits. A control valve which still does a good job of controlling when flow increases to 100 times the minimum controllable flow has a rangeability of 100 to 1. Rangeability can also be expressed as the ratio of the maximum to minimum controllable flow rates.
Range of stress (Sr) – It is the algebraic difference between the maximum and minimum stress in one cycle, i.e., Sr = Smax – Smin.
Rank, coal – It is measured through a process called petrography whereby the amount of light which is reflected off the coal is quantified as its ‘reflectance’ (R). The higher is the reflectance, the higher is the coal rank.
Rankine cycle – It is an idealized thermodynamic cycle describing the process by which certain heat engines, such as steam turbines or reciprocating steam engines, allow mechanical work to be extracted from a fluid as it moves between a heat source and heat sink. Heat energy is supplied to the system through a boiler where the working fluid (typically water) is converted to a high-pressure gaseous state (steam) in order to turn a turbine. After passing over the turbine the fluid is allowed to condense back into a liquid state as waste heat energy is rejected before being returned to boiler, completing the cycle. Friction losses throughout the system are frequently neglected for the purpose of simplifying calculations as such losses are usually much less significant than thermodynamic losses, especially in larger systems.
Raoult’s law – It is a law of thermodynamics which states that the partial pressure of each gaseous component of an ideal mixture of liquids is equal to the vapour pressure of the pure component multiplied by its molar fraction in the mixture.
Rapid gravity filter – It is also known as a rapid sand filter. It is a water purification method which uses gravity to draw water through a bed of granular media (like sand or anthracite) at a high flow rate, effectively removing suspended particles and impurities.
Rapid hardening cement – As the name indicates, it develops the strength rapidly than ordinary portland cement. This cement develops at the age of three days, the same strength as that expected from the ordinary portland cement in seven days. With this cement the initial strength is higher, but they equalize at 2-3 months. Setting time for this type is similar for that of ordinary portland cement. The rapid rate of development of the strength is due to higher C3S (tri calcium silicate) and lower C2S (di calcium silicate) and due to finer grinding of the cement clinker (the minimum fineness is 3250 sq cm per gram. Rate of heat evolution is higher than ordinary portland cement due to the increase in C3S and C3A (tri-calcium aluminate), and due to its higher fineness. Chemical composition and soundness requirements are similar to those of ordinary portland cement. The uses of this cement is indicated where a rapid strength development is desired (to develop high early strength, i.e. its 3 days strength equal that of 7 days ordinary portland cement, for example (i) when formwork is to be removed for re-use, (ii) where sufficient strength for further construction is wanted as quickly as practicable, such as concrete blocks production, sidewalks and the places which cannot be closed for a long time, and repair works needed to construct quickly, (iii) for construction at low temperatures, to prevent the frost damage of the capillary water, (iv) this type of cement does not use at mass concrete constructions.
Rapid omnidirectional compaction (ROC) – It is a powder consolidation technique that uses a non-gaseous pressure transmission medium, typically a fluid, to apply pressure from all directions, resulting in rapid and uniform densification of the powder.
Rapid prototyping – It is a relatively new field in manufacturing which involves techniques / devices that produce prototype parts directly from computer-aided design (CAD) models in a fraction of the time needed using traditional techniques. The prototypes are used as form models (i) to check the touch and feel of the part, (ii) as fit models, to verify geometry and alignment of the part in its intended application, and (iii) in some cases as function models assembled onto a working mechanism to test the ability of the part under design to perform its intended duty. The prototyped object can also be a mould or a pattern for secondary techniques which produce preproduction or production tooling. Rapid prototyping techniques normally produce prototypes by decomposing a three-dimensional CAD model into parallel cross sections. Typically, each cross section is constructed atop the previous cross section, building the part layer by layer from layers that are 0.1 millimeter to 0.2 millimeter thick. The layers are bonded together either before or after cutting or as a natural consequence of layer formation. The construction materials available for these techniques include photo-polymerizable or thermo-plastic resin, paper, wax, and metal or ceramic powder. Secondary operations expand the list of available materials to include castable metals and certain forms of composites.
Rapid rewetting – It refers to the swift reintroduction of water to a previously dry soil or ecosystem, frequently after a period of drought or drainage, which can trigger a surge in microbial activity and nutrient mineralization.
Rapid solidification – It is the cooling or quenching of liquid (molten) metals at rates that range 10 to the power 4 deg C per second to 10 to the power 8 deg C per second.
Rapid solidification techniques – These techniques have gained significant attention in the field of materials science because of their potential to produce materials with unique microstructures and properties. The primary objective of rapid solidification is to achieve a high cooling rate during the solidification process, which results in the formation of a fine-grained microstructure. This is achieved by applying external cooling or by quenching the liquid metal to achieve rapid cooling rates in the range of 10 to the power 4 deg C per second to 10 to the power 8 deg C per second. The process of rapid solidification can be achieved using different techniques, including melt spinning, spray forming, gas atomization, and laser processing.
Rapid thermal processing (RTP) – It is a semiconductor manufacturing process which heats silicon wafers to temperatures exceeding 1,000 deg C for not more than a few seconds. During cooling wafer-temperatures are to be brought down slowly to prevent dislocations and wafer breakage because of the thermal shock. Such rapid heating rates are frequently attained by high intensity lamps or lasers. These processes are used for a wide variety of applications in semiconductor manufacturing including dopant activation, thermal oxidation, metal reflow and chemical vapour deposition.
Rare-earth elements (REE) – They also called the rare-earth metals or rare earths, and sometimes the lanthanides or lanthanoids, although scandium and yttrium, which do not belong to this series, are normally included as rare earths. Rare earth elements are a set of 17 nearly indistinguishable lustrous silvery-white soft heavy metals. Compounds containing rare earths have diverse applications in electrical and electronic components, lasers, glass, magnetic materials, and industrial processes. Scandium and yttrium are considered rare-earth elements since they tend to occur in the same ore deposits as the lanthanides and show similar chemical properties, but have different electrical and magnetic properties.
Rare earth garnets – These are also known as rare-earth iron garnets (RIGs). These are ferrimagnetic insulators with the chemical formula R3Fe5O12, where ‘R’ represents trivalent rare-earth ions, and are known for their unique magnetic properties and potential in spintronics and magneto-optical applications.
Rare earth metals – They are also known as rare earth elements. These are relatively scarce minerals. They consist of a group of 17 chemically similar metals that includes the elements scandium and yttrium (atomic numbers 21 and 39, respectively) and the lanthanide elements (atomic numbers 57 through 71).
Rare earths – They are a group of 15 elements in the periodic table known as the Lanthanide series. Rare earths are categorized into Light Rare Earths (lanthanum to samarium) and Heavy Rare Earths (europium to lutetium). They are key enablers for technologies looking to lower emissions, reduce energy consumption, as well as improve efficiency, performance, speed, durability, and thermal stability. They are also a key component in technologies that seek to make products lighter and smaller. Rare earths react with other metallic and non-metallic elements to form compounds each of which has specific chemical behaviours. This makes them indispensable and non-replaceable in many electrical, optical, magnetic, and catalytic applications.
Ratchet drive – It is a shaft or valve which is operated by means of a ratchet mechanism. The ratchet delivers an intermittent stepped rotation through a gear in one direction only.
Ratcheting – It consists of progressive cyclic inelastic deformation (growth, for example) which occurs when a component or structure is subjected to a cyclic secondary stress super-imposed on a sustained primary stress. The process is called thermal ratcheting when cyclic strain is induced by cyclic changes in temperature, and isothermal ratcheting when cyclic strain is mechanical in origin (even though accompanied by cyclic changes in temperature).
Ratchet marks – It consists of lines or markings on a fatigue fracture surface that results from the intersection and connection of fatigue fractures propagating from multiple origins. Ratchet marks are parallel to the overall direction of crack propagation and are visible to the unaided eye or at low magnification.
Rated capacity – It is the manufacturers stated capacity rating for mechanical equipment. For example, the maximum continuous capacity in kilograms of steam per hour for which a boiler is designed.
Rate determining step – The overall rate of a reaction is frequently approximately determined by the slowest step which is known as the rate-determining step. For a given reaction mechanism, the prediction of the corresponding rate equation (for comparison with the experimental rate law) is frequently simplified by using this approximation of the rate-determining step.
Rated flow coefficient – It is the flow coefficient of the valve at rated travel.
Rated speed – It is the number of blows per minute of the hammer when operating at a particular maximum efficiency.
Rated travel – it is the distance of movement of the closure member from the closed position to the rated full-open position. The rated full-open position is the maximum opening recommended by the manufacturers.
Rate equation – It is also known as the rate law or empirical differential rate equation. It is an empirical differential mathematical expression for the reaction rate of a given reaction in terms of concentrations of chemical species and constant parameters (normally rate coefficients and partial orders of reaction) only.
Rate law – It is a mathematical equation which describes how the rate of a chemical reaction depends on the concentrations of its reactants. It is also known as the rate equation.
Rate-limiting step – It is the slowest step in a chemical reaction which involves more than one step. The rate of this step determines the overall reaction rate.
Rate of blow-down – It is a rate normally expressed as a percentage of the water fed.
Rate of creep – It is the slope of the creep-time curve at a given time determined from a Cartesian plot.
Rate-of-oil-flow – It is the rate at which a specified oil will pass through a sintered porous compact under specified test conditions.
Rate of reaction – It is the speed at which a chemical reaction takes place. It is defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per unit time. Rates of reaction can vary dramatically.
Rate of rise – It is the time rate of pressure increase at a given time in a vacuum system which is suddenly isolated from the pump by a valve. The volume and temperature of the system are held constant during the rate of rise measurement.
Rate of strain hardening – It is the rate of change of true stress with respect to true strain in the plastic range.
Rating, equipment – Rating of an equipment refers to the specified limits or characteristics assigned by the manufacturer, defining the equipment’s safe and optimal performance under specific conditions, often displayed on a rating plate.
Rating life – It is currently the fatigue life in millions of revolutions or hours at a given operating speed which 90 % of a group of substantially identical rolling-element bearings survive under a given load.
Rationalization – It is a process used to merge similar packaging lines, allowing the benefits of a smaller inventory and improved economies of scale.
Ratio pyrometer – It is also known as a two colour pyrometer. It is a non-contact temperature measurement device which measures the ratio of infrared radiation emitted by a target at two different, closely spaced wave-lengths, allowing for temperature determination independent of emissivity variations.
Rattail – It is a surface imperfection on a casting, occurring as one or more irregular lines, caused by expansion of sand in the mould.
Raw material – It is also known as a feed-stock, or unprocessed material. It is a basic material which is used to produce goods, finished goods, energy, or intermediate materials that are feed-stock for future finished products.
Raw material cost – Normally it is the major component of the production cost. Raw material cost is dependent on quality of raw material, yield of product, handling loss, moisture content of the raw material, and wastages associated with the use of the raw material etc. Raw material cost is also influenced by the level of waste recycling.
Raw refractory dolomite – It refers to the natural, unheated form of the mineral dolomite [CaMg(CO3)2] used as a refractory material, meaning it is resistant to high temperatures and maintains its structural integrity under extreme heat conditions.
Raw water – It is the water in its natural state, prior to any treatment for drinking. It is the water supplied to the plant before any treatment.
Rayleigh scattering – It is the scattering of electro-magnetic radiation by independent particles which are smaller than the wavelength of radiation.
Rayleigh step bearing – It is a stepped-pad bearing having one step only in each pad.
Rayleigh waves – These are a type of surface acoustic wave which travel along the surface of solids. These waves can be produced in materials in several ways, such as by a localized impact or by piezo-electric transduction, and are frequently used in non-destructive testing for detecting defects. Rayleigh waves are part of the seismic waves that are produced on the earth by earthquakes. When guided in layers they are referred to as Lamb waves, Rayleigh–Lamb waves, or generalized Rayleigh waves
Rayon – It has regenerated cellulose composition. It is slightly stronger than cotton, but tensile strength is lowered by water. Its chemical resistance is similar to cotton. It also has high moisture absorption and hence, poor dimensional stability. It is susceptible to mildew attack. It is practically non-existent in conveyor belt today.
Razor streak – It is an impurity, metallic or non-metallic, which is trapped in the cast product and elongated subsequently in the direction of working. It can be revealed during working or finishing as a narrow streak parallel to the direction of working.
R-chart – It is also called range chart. It is a type of control chart which is used in statistical process control (SPC) to monitor the variability (range) of a process over time by plotting the range of variation within samples taken from the process. R-charts help identify whether a process is in a state of statistical control by monitoring the range of variation within sub-groups. The chart includes control limits, which are lines that define the expected variation of the process.
R-curve – In linear-elastic fracture mechanics, it is a plot of crack-extension resistance as a function of stable crack extension, which is either the difference between the physical crack size, or the effective crack size, and the original crack size. R-curves normally depend on sample thickness and, for some materials, on temperature and strain rate.
Reach truck – It is a narrow-aisle, right-angle stacking truck which is designed for unit load handling with rack interface. These lift trucks are meant to operate in narrow aisles and are best for storing and retrieving pallets in racks. They are engineered with two outer legs which help distribute the load weight, and a single set of wheels in the back.
Reactance – In electrical circuits, reactance is the opposition presented to alternating current by inductance and capacitance. Along with resistance, it is one of two elements of impedance. However, while both elements involve transfer of electrical energy, no dissipation of electrical energy as heat occurs in reactance; instead, the reactance stores energy until a quarter-cycle later when the energy is returned to the circuit. Greater reactance gives smaller current for the same applied voltage. Reactance is used to compute amplitude and phase changes of sinusoidal alternating current going through a circuit element. Like resistance, reactance is measured in ohms, with positive values indicating inductive reactance and negative indicating capacitive reactance. It is denoted by the symbol X’X’. An ideal resistor has zero reactance, whereas ideal reactors have no shunt conductance and no series resistance. As frequency increases, inductive reactance increases and capacitive reactance decreases.
Reactant – It is a substance which is consumed in the course of a chemical reaction. It is sometimes used interchangeably with reagent.
Reaction – It is a process which leads to the chemical transformation of one set of chemical substances to another. It is a chemical transformation or change brought about by the interaction of two substances.
Reaction barrier – It is the energy deficit which is to be overcome in order for a particular chemical reaction to proceed. In transition state theory, the reaction barrier is interpreted as the difference between the zero-point energy of the activated complex formed in the reaction and that of the initial reactants.
Reaction blading – This concept is used in the design of steam turbine. Here the pressure drop per stage is equally divided between fixed and moving blades. In the fixed blades steam is accelerated to a velocity only slightly higher than that of the moving blades. Continued expansion of the steam in the moving blades provides thrust and gives the steam a relative velocity equal and opposite to its former absolute velocity. In reaction blading the energy transferred to the rotor in a single stage is only around half which is transferred by impulse blading. Efficiencies, however, are comparable. It turns out that the velocity value is around twice as high for impulse blading as it is for reaction blading. This means, in turn, that an impulse turbine needs fewer stages for the same power output than a reaction turbine. However, the efficiency is about the same for both the types.
Reaction bonding – It is frequently used in materials science. It is a process where a chemical reaction, like the reaction between silicon and carbon, forms a bond between materials, typically creating a solid material or joining two materials together. Reaction bonding also refers to a process where monomeric units coalesce to form clusters through bonding reactions, leading to elongation of linear chain segments and branching. This process results in the formation of equilibrium distributions of cluster sizes with different numbers of branch points.
Reaction flux – It is a flux composition in which one or more of the ingredients reacts with a base metal upon heating to deposit one or more metals.
Reaction injection moulding (RIM) – It is a process for moulding polyurethane, epoxy, and other liquid chemical systems. Mixing of two to four components in the proper chemical ratio is accomplished by a high-pressure impingement-type mixing head, from which the mixed material is delivered into the mould at low pressure, where it reacts (cures). It is also known as structural reaction injection moulding.
Reaction kinetics – It is concerned with understanding the rates of chemical reactions. It is different from chemical thermodynamics, which deals with the direction in which a reaction occurs but in itself tells nothing about its rate. Reaction kinetics includes investigations of how experimental conditions influence the speed of a chemical reaction and yield information about the reaction’s mechanism and transition states, as well as the construction of mathematical models which also can describe the characteristics of a chemical reaction.
Reaction mechanism – It consists of the step-by-step sequence of elementary reactions by which a larger chemical reaction or overall change occurs. A complete mechanism is to describe and explain which bonds are broken and which are formed (and in what order), as well as all reactants, products, and catalysts involved; the quantities of each; all intermediates, activated complexes, and transition states; and the stereochemistry of each chemical species. Since the detailed processes of a complex reaction are not observable in majority of the cases, a reaction mechanism is frequently a theoretical conjecture based on thermodynamic feasibility and what little support can be gained from experiment.
Reaction rate – It is the speed at which reactants are converted into products in a chemical reaction.
Reaction rate constant – It is also called reaction rate coefficient. It is a proportionality constant which quantifies the rate and direction of a chemical reaction by relating it with the concentration of reactants.
Reaction sintering – It can be defined as a fabrication process in which two or more components of the required compound react together during the sintering operation. It is the sintering of a metal powder mixture consisting of at least two components which chemically react during the treatment. It is a process at a certain temperature when the powder compact is synthesized through the chemical reaction among solid phase, liquid phase, and gas phase, and sintering densification is completed.
Reaction stress – It is a stress which cannot exist in a member if the member is isolated as a free body without connection to other parts of the structure.
Reaction turbine – In the reaction turbine, the rotor blades themselves are arranged to form convergent nozzles. This type of turbine makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the stator as a jet which fills the entire circumference of the rotor. The steam then changes direction and increases its speed relative to the speed of the blades. A pressure drop occurs across both the stator and the rotor, with steam accelerating through the stator and decelerating through the rotor, with no net change in steam velocity across the stage but with a decrease in both pressure and temperature, reflecting the work performed in the driving of the rotor. In the reaction turbine, the fixed blades and the moving blades which constitute one stage are practically identical in design and function, each accounting for about half of the pressure-drop which is converted to kinetic energy in the entire stage. In the fixed blades, the pressure is harnessed to increase the velocity of the steam so that it slightly exceeds the velocity of the moving blades in the direction of rotation. In the moving blades, the pressure drop is again used to accelerate the steam but at the same time to turn it around (with respect to the blades), so that its absolute tangential velocity is almost zero as it enters the next bank of stationary blades. Hence, thrust is imparted to the moving blades as the absolute tangential velocity of the steam is reduced from slightly above blade speed to around zero. An imaginary observer moving with the steam cannot tell whether he is passing through the fixed blades or the moving ones. As he approaches either type of blade, it appears to be nearly motionless, but as he travels in the channel between blades, his velocity increases steadily until he reaches their trailing edges, which then seems to be receding rapidly.
Reactive bond – It is a chemical bond between atoms which, in a particular context, is relatively unstable and hence easily broken or invaded by other chemical species or radicals, e.g., the double bond in ethylene (CH2=CH2) is highly reactive in the presence of other ethylene molecules, leading to a polymerization reaction which forms polyethylene.
Reactive bonding – It is a wafer bonding procedure which uses highly reactive nano-scale multi-layer systems as an intermediate layer between the bonding substrates. The multi-layer system consists of two alternating different thin metallic films. The self-propagating exothermic reaction within the multi-layer system contributes the local heat to bond the solder films. Based on the limited temperature the substrate material is exposed, temperature-sensitive components and materials with different coefficient of thermal expansions, i.e. metals, polymers and ceramics, can be used without thermal damage.
Reactive evaporation – It is a vacuum deposition process in which trace quantities of an active gas are added to the vacuum chamber. The gas reacts with an evaporating material in the chamber, promoting deposition of the material on a substrate.
Reactive intermediate – It is a short-lived, unstable, highly reactive chemical species which is generated briefly in a chemical reaction but rapidly undergoes further reactions which transform it into a more stable species. It is hence a transient intermediary between the stable reactants and products of the overall reaction. The existence of intermediates, when detectable, is critical to an accurate understanding of a reaction mechanism.
Reactive ion-beam assisted deposition (RIBAD) – It is a thin-film deposition technique which combines physical vapour deposition (PVD) with ion bombardment, where a reactive gas is used to feed the ion source. It is a combination of two surface treatment processes, namely, vacuum deposition and ion implantation in which a reactive gas is used to feed the ion source. The deposition process is normally accountable for the material build-up, while the ion flux imparts the kinetic energy required to achieve adhesion and the needed coating properties. This process improves film properties like adhesion and density.
Reactive ion plating – It is a type of physical vapour deposition (PVD) where a reactive gas or vapour is introduced into the plasma, allowing for the deposition of compound materials by bombarding the substrate with energetic particles and reacting them with the depositing material.
Reactive maintenance – It is also known as breakdown maintenance or run-to failure maintenance. It basically consists of running the equipment till a breakdown takes place. No actions are taken or efforts are made to maintain the equipment till the failure of the equipment. In this type of maintenance strategy, the maintenance action is taken up when the equipment breaks down completely and needs repair to resume operation. Sometimes breakdown maintenance is the default maintenance strategy, relying on reactive maintenance. The reactive maintenance strategy is preferable where repair of the equipment is simple and easier, and where preventive maintenance carried out in stopping or disrupting normal production runs is very costly. Under the reactive maintenance strategy approach, there is no expenditure on maintenance manpower nor on cost of spares and consumables till there is a breakdown of the equipment. However, a large expenditure is needed when there is a breakdown in the equipment both in terms of manpower costs and capital costs. This approach can result into secondary equipment or process damage from equipment failure. Also, longer shutdown is needed for repair which affects the production. Unplanned shutdown of the equipment because of the failure disturbs the production planning. All these affect the supply of the products to the customers. With this type of maintenance approach, the life of the equipment gets shortened resulting in more frequent replacement. Further since the equipment is run to failure, a large material inventory of repair parts is needed to be maintained.
Reactive materials – These are substances which readily undergo chemical changes, frequently violently, when exposed to certain conditions like heat, pressure, shock, friction, air, or water, potentially leading to hazardous reactions like explosions or fires.
Reactive metal – It is a metal which readily combines with oxygen at elevated temperatures to form very stable oxides, for example, titanium, zirconium, and beryllium. Reactive metals can also become embrittled by the interstitial absorption of oxygen, hydrogen, and nitrogen.
Reactive power – It is that component of apparent power which flow because of the return to the source of energy stored in a load’s electric or magnetic fields, which does no useful work at the load.
Reactive sputtering – It is the sputtering of elemental targets in the presence of chemically reactive gases which react with both the vapour flux ejected from the target and the target surface. It is a physical vapour deposition (PVD) technique where a reactive gas (like oxygen or nitrogen) is introduced during the sputtering process, causing the sputtered atoms to react and form a compound film on the substrate.
Reactive steel – The term is used for some grades of steel which react more quickly with molten zinc. This is normally caused by steel chemistry, particularly silicon and phosphorous content.
Reactivity – It is the tendency of a particular chemical substance to undergo a chemical reaction, either by itself or with other substances, normally referring to either or both of two distinct observations namely (i) whether or not a substance reacts under a specific set of circumstances, and how quickly it reacts (i.e., the reaction rate). Thermodynamically, a chemical reaction occurs since the products (taken as a group) exist at a lower free energy than the reactants, and hence are more energetically ‘stable’, but the concept of reactivity can also embody kinetic factors, depending on the usage. Chemical stability and stability and chemical compatibility are related but distinct concepts.
Reactivity series It is also called activity series. It is an empirical, calculated, and structurally analytical progression of a series of metals, arranged by their general reactivity from highest to lowest and used to summarize information about their reactions with acids and water and the methods used to extract them from ores.
Reactor, chemical – The reactor is an apparatus / vessel in which chemical operations are carried out for pilot or industry purposes. The reactors change in scale from a small unit to the massive structures. Reactors are designed based on several factors, but the most important factors are the kinetics and thermodynamics. Reactors are one of the main parts of any industrial process since the conversion of crude substrates into invaluable chemicals is performed in the reactors. Reactor design has received much attention in the past because of the significant energy involved.
Reactor coolant system – It is the system which is used to remove energy from the reactor core and transfer that energy either directly or indirectly to the steam turbine.
Reactor, electrical – It refers to an inductor, or a coil, used to introduce reactance into an alternating current circuit, primarily to control current flow and improve power system stability. It is also known as a line reactor. It is a coil wired in series between two points in a power system to minimize inrush current, voltage notching effects, and voltage spikes. Reactors can be tapped so that the voltage across them can be changed to compensate for a change in the load that the motor is starting. Reactors are rated by the ohms of impedance that they provide at a given frequency and current. Reactors can also be rated by the I2R (square of current multiplied by resistance) loss across the device at a certain frequency at a rated current. Two common types of reactors are the dry-type and the oil-immersed. The dry-type is open and relies on the air to circulate and dissipate the heat. Dry-type reactors are common in low-voltage applications. Oil-immersed reactors are common in high-voltage applications. Oil-immersed reactors are placed in tanks and require a magnetic shield to prevent eddy currents from circulating in the tank. The shield is made from laminated steel sheets like the transformer core and motor stators. Reactors may be used as line or load reactors. Line reactors are used when low line impedance allows high inrush current, when power factor correction capacitors are used, or when a motor drive causes notching.
Reactor pressure vessel – It is the part of the nuclear power plant which houses the reactor core and the cooling system.
Reactor protection system – It is a system which is designed to automatically shut-down the reactor and maintain it shut-down when needed. Facilities to instigate a manual back-up are provided in whole or part.
Reactor vendor – It is an organization which deals with reactor and reactor design.
Readiness review – It is a final review of an engineered system from the viewpoint of readiness for safe operation. All critical personnel are brought together and all safety hazards are reexamined to see whether the hazards have been adequately addressed. Operating procedures are assessed to ensure that personnel are properly trained, not only for normal operation, but also for emergency situations.
Reagent – It is another name for a reactant. It is a substance or compound which added to a system to cause a chemical reaction. It is a test substance which is added to a system in order to bring about a chemical reaction, or to see whether a reaction occurs.
Reagent chemicals – These are high-purity chemicals which are used for analytical reactions, for testing of new reactions where the effects of impurities are unknown, and for chemical work where impurities are either to be absent or at a known concentration.
Real area of contact – It is also known as actual contact area. In tribology, it is the total area of contact formed by summing the localized asperity contact areas within the apparent area of contact.
Real leak – It is a crack, crevice, fissure, hole or passage way in the wall of an enclosure, capable of passing air, or other gases, from one side of the wall to the other under an action of a pressure or concentration differential existing across the wall.
Real-time computing (RTC) – It is the computer science term which is used for hardware and software systems subject to a ‘real-time constraint’, e.g., from event to system response. Real-time programs must guarantee response within specified time constraints, often referred to as ‘deadlines’. The term ‘real-time’ is also used in simulation to mean that the simulation’s clock runs at the same speed as a real clock. Real-time responses are frequently understood to be in the order of milli-seconds, and sometimes micro-seconds. A system not specified as operating in real time cannot normally guarantee a response within any time-frame, although typical or expected response times can be given. Real-time processing fails if not completed within a specified deadline relative to an event. Deadlines are always to be met, regardless of system load.
Real-time data (RTD) – It is information which is delivered immediately after collection. There is no delay in the timeliness of the information provided. Such data is normally processed using real-time computing although it can also be stored for later or off-line data analysis. Real-time data is not the same as dynamic data. It can be dynamic (e.g., a variable indicating current location) or static (e.g., a fresh log entry indicating location at a specific time).
Real-time data visualization – It is the process of visually representing data as it is generated and processed, allowing users to monitor and analyze data instantly, enabling quick decision-making and trend identification.
Real-time operating system (RTOS) – It is an operating system (OS) for real-time computing applications which processes data and events which have critically defined time constraints. A real-time operating system is distinct from a time-sharing operating system, such as Unix, which manages the sharing of system resources with a scheduler, data buffers, or fixed task prioritization in multi-tasking or multi-programming environments. All operations are to verifiably complete within given time and resource constraints or else fail safe. Real-time operating systems are event-driven and preemptive, meaning the operating system can monitor the relevant priority of competing tasks, and make changes to the task priority. Event-driven systems switch between tasks based on their priorities, while time-sharing systems switch the task based on clock interrupts.
Real-time radiography – A method of nondestructive inspection in which a two-dimensional radiographic image can be immediately displayed on a viewing screen or television monitor. This technique does not involve the creation of a latent image; instead, the unabsorbed radiation is converted into an optical or electronic signal, which can be viewed immediately or can be processed in near real time with electronic and video equipment.
Real-time system – It has been described as one which ‘controls an environment by receiving data, processing them, and returning the results sufficiently quickly to affect the environment at that time’. The term ‘real-time’ is used in process control and enterprise systems to mean ‘without significant delay’.
Reamer – It is a rotary cutting tool with one or more cutting elements (teeth), used for enlarging a hole to desired size and contour. It is supported principally by the metal around the hole it cuts.
Reaming – It is an operation in which a previously formed hole is sized and contoured accurately by using a rotary cutting tool (reamer) with one or more cutting elements (teeth). The principal support for the reamer during the cutting action is obtained from the work-piece.
Reaming shell – It is a component of a string of rods which is used in diamond drilling. It is set with diamonds and placed between the bit and the core barrel to maintain the gauge (or diameter) of the hole.
Rear-end condition – It is a condition which is occurring in the last metal to be extruded. It is a result of the oxidized surface of the billet feeding into the extrusion.
Rear view – It is directly opposite to the front view and is at the back of the object.
Rear-wheel drive (RWD) – It is a form of engine and transmission layout used in motor vehicles, in which the engine drives the rear wheels only. Majority of the rear-wheel drive vehicles feature a longitudinally-mounted engine at the front of the vehicle.
Reasonable expectations – It is based on high level of confidence. This term is used within the E1 classification and concerns the likelihood that all necessary conditions will be met. It is also used in the F1.3 Sub-category and concerns the likelihood that all necessary approvals / contracts for the project to proceed to development will be forthcoming.
Reasonable prospects – It is based on moderate level of confidence. This term is used within the E2 and E3 classification and concerns the likelihood that all necessary conditions will be met.
Reasonable Time frame – It is the Time frame within which all approvals, permits and contracts necessary to implement the project are to be obtained. This is to be the time normally accepted as the typical period required to complete the task or activity under normal or typical circumstances.
Reasonably available control technology (RACT) – It is the control technology which that is reasonably available, and both technologically and economically feasible. It is normally applied to existing sources in non-attainment areas. In majority of the case, It is less stringent than new source performance standards.
Re-association – it is the recombination of the products of dissociation.
Re-blending – It means to mix or combine something again, or to blend something which has already been blended.
Reboiling – In porcelain enamel, it is the gas evolution occurring and recurring during repeated firing of the ground coat. It is sometimes considered a defect.
Rebonded fused grain refractory – It is a fired refractory brick or shape made predominantly or entirely from fused grain.
Rebound – It is the gunned material which is not adhering to the gunned or shotcreted surface during the gunning process.
Recalescence – It is the increase in temperature which occurs after undercooling, since the rate of liberation of heat during transformation of a material exceeds the rate of dissipation of heat. It is also a phenomenon, associated with the transformation of iron to iron on cooling (super-cooling) of iron or steel, which is revealed by the brightening (re-glowing) of the metal surface owing to the sudden increase in temperature caused by the fast liberation of the latent heat of transformation.
Recarburize – It is carried out to increase the carbon content of molten cast iron or steel by adding carbonaceous material, high-carbon pig iron, or a high-carbon alloy. It also means to carburize a metal part to return surface carbon lost in processing It is also known as carbon restoration.
Recarburizing – It means increasing the carbon content of molten cast iron or steel by adding carbonaceous material, high-carbon pig iron, or a high-carbon alloy. It is also carburizing a metal part to return surface carbon lost in processing.
Receiver – It is the apparatus which takes radio-frequency currents induced in an antenna and turns them into useful signals. In pneumatics, a ‘receiver’ is a pressure vessel which stores compressed air, acting as a buffer between the compressor and the fluctuating demand of pneumatic equipment, ensuring a steady air supply.
Recess – It is a groove or depression in a surface.
Recharge – It is the process by which water is added to a zone of saturation, normally by percolation from the soil surface, like the recharge to an aquifer.
Rechargeable battery – It is a battery which can have a useful portion of its capacity restored by connection to a supply of electric current.
Reciprocal lattice – It is a lattice of points, each representing a set of planes in the crystal lattice, so that a vector from the origin of the reciprocal lattice to any point is normal to the crystal planes represented by that point and has a length that is the reciprocal of the plane spacing.
Reciprocal linear dispersion – It is the derivative dL/dx, where ’L’ the wavelength and ‘x’ is the distance along the spectrum. The reciprocal linear dispersion normally is expressed in Angstrom per millimeter.
Reciprocating compressor – It is a positive-displacement machine which uses a piston to compress a gas and deliver it at high pressure.
Reciprocating feeder – The feeder has reciprocating tray. The reciprocating motion is imparted by crank or eccentric and connecting rod. The feeder discharge is volumetric in nature, and is less susceptible to flowability of material, as compared to vibrating feeder. However, material movement on tray is of simple dragging nature, instead of jumping type as in case of vibrating feeder. This results into more wear of tray. The magnitude of vibrating forces is comparatively high but at a very low frequency (e.g. about 60 cycle per minute). The commonly used reciprocating feeders have capacity range up to 250 cubic meter per hour, for material of average abrasiveness. The higher capacities are possible. The feeder can handle larger lumps compared to the vibrating feeders.
Reciprocating pin-on-flat test – It is also known as tribometer. It, is a method which is used to study friction and wear, where a pin (or ball) moves back and forth (reciprocates) against a stationary flat surface, allowing people to assess the wear and friction characteristics of materials.
Reciprocating pump – It is a type of positive displacement pump that uses a piston, plunger, or diaphragm moving in a back-and-forth (reciprocating) motion to displace fluid, creating a constant volume flow suitable for low-flow, high-pressure applications.
Reciprocating rake bar screens – These are essentially automated bar screens which utilize a single rake to clean a stationary bar rack. The rake, attached to a reciprocating mechanism, moves back and forth across the bar rack, efficiently removing accumulated debris.
Reciprocating screen – It is a type of screening equipment which uses a back-and-forth, or reciprocating, motion to separate materials based on size. It is frequently used in industries like waste-water treatment and mining.
Reciprocating wear tests – These tests simulate real-world mechanical interactions by subjecting materials to repetitive back-and-forth motion. These tests provide crucial insights into friction, material degradation, and durability under cyclic loading conditions, helping engineers understand and improve component performance. Different test configurations, including pin-on-flat, ball-on-flat, and cylinder-on-flat, allow people to study different contact geometries and wear mechanisms. By controlling parameters like load, stroke length, and frequency, these tests reveal how materials behave under specific operating conditions.
Reciprocity – In electrical networks, it is a theorem which states that the current injected into one point in a network produces a voltage at a second point which is identical to the voltage produced at the first point by injection of the same current at the first point. In electro-magnetism, reciprocity is an observation which electric currents and electric fields can be analyzed from either point of view as regards the source of the energy in the system, e.g., in radio, a good transmitting antenna is normally also a good receiving antenna.
Recirculating systems – When working with thicker material and cold rolled and hot rolled steel (especially with scale), the recirculating system of applying lubricant is normally the best approach. Here, sufficient amounts of lubricant not only have to protect the metal working tools, but the scale and metal fines which are generated by the process are to be flushed off the tooling and into the reservoir. The use of baffles, settling tanks and filters help collect large quantities of contaminants and metal fines, helping keep the coolant relatively clean. Magnets can be extremely helpful in keeping the amount of metal being recirculated down to a minimum.
Recirculation – It is the reintroduction of part of the flowing fluid to repeat the cycle of circulation.
Reclaimed water – It is also called recycled water. It is treated waste-water which is cleaned and reused for non-potable purposes like industrial processes, and ground-water replenishment.
Reclaimer – It is a large machine used in bulk material handling applications. A reclaimer’s function is to recover bulk material such as ores from a stockpile. Reclaimers are volumetric machines and are rated in cubic meters per hour for capacity, which is often converted to tons per hour based on the average bulk density of the material being reclaimed. Reclaimers normally travel on a rail between stockpiles in the stockyard. There are several types of reclaimers which are available for suiting the specific needs such as buffer storage or storage for blending the material properties (material can be free flowing or sticky material), and reliability. The two types of reclaimers which are in common use are (i) scraper reclaimers, and (ii) bucket reclaimers. Each type has varied designs to suit an application. Reclaimers are normally electrically powered by means of a trailing cable.
Reclain – It is the porcelain enamel overspray which is removed from the spray booth and reconditioned for use.
Reclamation – It is the restoration of a site after mining or exploration activity is completed.
Recognition – It is the public appreciation for a person’s or group’s achievements. It is the act of showing appreciation and acknowledgement for employees for their contributions to the organization which links to the purpose, mission and values of the organization. Employee recognition can take on different forms, such as peer-to-peer recognition, manager-led recognition and leadership-led recognition. But what is critical to employee recognition success is making sure that employee reward and recognition tactics are delivered in a way which makes recognition meaningful, unified, shine through a spotlight and timely.
Recoil – It is rebound or spring back through force of impact or elasticity. This term is widely used with particular reference to automatic weapons. In this specific setting, the recoil spring is used to compensate and absorb the bullet force momentum and to convert energy into the activation of a weapon’s reloading system.
Recoiling – In case of a rolled coil, it involves rewinding a large, processed steel coil into smaller, more manageable coils, frequently for easier handling, storage, and transportation. The recoiling operation of a rolled coil is carried out in a recoiling line.
Recoil line – It is a blemish on a drawn sheet metal part caused by a slight change in metal thickness. The mark of radial line results from transfer of the blank from the die to the punch during forming, or from a reaction to the blank being pulled sharply through the draw ring.
Reconnaissance – It is a preliminary survey of ground. A Reconnaissance study identifies areas of enhanced mineral potential on a regional scale based primarily on results of regional geological studies, regional geological mapping, airborne and indirect methods, preliminary field inspection, as well as geological inference and extrapolation. The objective is to identify mineralized areas worthy of further investigation towards deposit identification. Estimates of quantities are only to be made if sufficient data are available and when an analogy with known deposits of similar geological character is possible, and then only within an order of magnitude.
Reconnaissance Mineral resource – It is the estimates based on regional geological studies and mapping, airborne and indirect methods, preliminary field inspections as well as geological inference and extrapolation.
Record – As per the ‘records management standards’ ISO 15489.1, a record is defined as ‘information created, received, and maintained as evidence and information by an organization or person, in pursuance of legal obligations or in the transaction of business’.
Record drawing – It is the as-built drawing which provide a comparison between what has been built and the original plan. It is the ‘final construction issue’ drawing by the consultant team to create record of the completed project.
Recording instrument – It is a device which continuously records the variation of a measured quantity (like voltage, current, or temperature) with respect to time, frequently on a chart or dial, providing a permanent record of the measurements.
Record management – As per the ‘records management standards’ ISO 15489.1, records management is the ‘field of management responsible for the efficient and systematic control of the creation, receipt, maintenance, use and disposition of records, including processes for capturing and maintaining evidence of and information about business activities and transactions in the form of records’.
Record reliability – A reliable record is defined as one whose contents can be trusted as a full and accurate representation of the transactions, activities or facts to which they attest and can be depended upon in the course of subsequent transactions or activities. Records are required to be created at the time of the transaction or incident to which they relate, or soon afterwards, by individuals who have direct knowledge of the facts or by instruments routinely used within the organization to conduct the activity or transaction. The background of the record’s creation is important in determining its reliability. Automated, real-time capture of objective transaction information normally has the highest reliability, whereas timely first-hand accounts by individuals have slightly less reliability, as the content is necessarily filtered through personal subjective interpretation. Also, the record’s provenance or lineage can be used as evidence in support of a record’s reliability, with records created at the time of the event considered to be the most reliable.
Record integrity – The integrity of a record refers to its being complete and unaltered. It is necessary that a record is to be protected against unauthorized alteration. Records management policies and procedures are to specify what additions or annotations can be made to a record after it is created, under what circumstances additions or comments can be authorized, and who is authorized to make them. Any authorized comment, addition or deletion to a record is to be explicitly indicated and traceable. For the integrity of records, there is the need for systematic management policies and procedures to guard against alteration and fraud. This again explains the need to capture a complete and auditable record of a record’s provenance as an important indicator of the record’s integrity. The risk of fraud in the provenance record (in addition to fraud in the record itself), has led to the development of secure provenance, especially in the electronic records. Also, the systems themselves need to have integrity. The perceived need for system integrity is also helping to build the case for the transparency. Another aspect of integrity is the contextual and structural integrity of the content of records. This includes the physical and logical format and the relationships between content elements. Failure to maintain the structural integrity of the records can damage a record’s reliability and authenticity. It also has an impact on the record’s usability.
Record usability – A usable record is one which can be found and understood in its original context. A usable record can be located, retrieved, presented, and interpreted. It is to be capable of later presentation as directly connected to the organizational activity or transaction which produced it. The contextual linkages of records are to carry the information needed for an understanding of the transactions which created and used them. It is to be possible to identify a record within the context of broader organizational activities and functions. The links between records which document a sequence of activities are to be maintained. There are hence two aspects of a record’s usability namely (i) the usability of the record itself, and (ii) the functionality of the system which is managing the record. To keep an individual record usable, it is to be preserved over time. In general, the main objective of preservation is to allow future users to retrieve, access, decipher, view, interpret, understand, and experience documents, data, and records in meaningful and valid (that is, authentic) ways. One of the challenges for preservation is that records are to be altered to preserve them, and this impact on the record’s integrity and authenticity. Hence, a balance is to be maintained between authenticity and usability. The second aspect of usability relates to the functionality of the system in which the record is being managed. The system is to have capability so that a usable record can be located, retrieved, presented and interpreted. In order to do that, sufficient information is to be captured about the record and the context of its creation and use. This information is to be sufficient to locate the record, while the contextual linkages are to provide an understanding of the transactions which created and used them
Recovery – It is the time-dependent portion of the decrease in strain following unloading of a sample at the same constant temperature as the initial test. Recovery is equal to the total decrease in strain minus the instantaneous recovery. It is also the reduction or removal of work-hardening effects in metals without motion of large-angle grain boundaries. Recovery is the proportion of the desired component obtained by processing an ore, normally expressed as a percentage. Recovery is also the percentage of valuable metal in the ore which is recovered by metallurgical treatment.
Recovery Hopkinson bar techniques – These techniques are also known as momentum trapping techniques. They are used to study the dynamic mechanical behaviour of materials under high strain rates by trapping residual stress waves using momentum trap bars, allowing for samples recovery after testing.
Recovery mechanisms – These are processes or strategies designed to restore systems, data, or functionality to a usable state after a failure, disruption, or damage. These mechanisms aim to minimize downtime, data loss, and operational disruption.
Recrystallization – It is the formation of a new, strain-free grain structure from that existing in cold-worked metal, normally accomplished by heating. It is also the change from one crystal structure to another, as occurs on heating or cooling through a critical temperature. Recrystallization is a process, normally physical, by which one crystal species is grown at the expense of another or at the expense of others of the same substance but smaller in size.
Recrystallization annealing – It consists of annealing cold-worked metal to produce a new grain structure without phase change.
Recrystallization controlled rolling (RCR) – Although conventional controlled rolling can lead to very fine ferrite grain sizes, the low finishing temperature (750 deg C to 900 deg C) of this method leads to increased rolling loads for heavy plate and thick-walled seamless tube. For thicker sections, recrystallization-controlled rolling is used to refine austenite grain size. This process can result in ferrite grain sizes on the order of 8 micrometers to 10 micrometers. Recrystallization controlled rolling involves the recrystallization of austenite at successively lower temperatures below roughing temperatures but still above 900 deg C. Recrystallization is not to be sluggish for this method to succeed, and hence vanadium can be beneficial because vanadium carbide is readily dissolved at rolling temperature and hence unavailable for suppressing recrystallization. However, vanadium steels need stable carbonitrides, such as titanium nitride, to retard grain growth after recrystallization. Niobium steels, on the other hand, can undergo recrystallization controlled rolling at higher temperatures with Nb(C,N) precipitates eventually forming. This precipitation of Nb(C,N) restricts austenite grain growth and can preclude the need for a titanium addition.
Recrystallization temperature – It is the approximate minimum temperature at which complete recrystallization of a cold-worked metal occurs within a specified time.
Recrystallization texture – It refers to the preferred orientation (or texture) of crystals which form during the recrystallization process, which is the replacement of deformed grains with new, strain-free grains.
Recrystallized grain size – It is the grain size which is developed by heating cold-worked metal. The time and temperature are selected so that, although recrystallization is complete, essentially no grain growth occurs. In aluminum and magnesium alloys, it is the grain size after recrystallization, without regard to grain growth or the recrystallized conditions.
Rectangular lifting magnet – It is built with either of two basic magnetic circuits, the two-pole or three-pole circuit, and it also can be permanent or electro-magnet. Pole plate and core material are normally hot rolled steel or low carbon steel. For the plates of rectangular lift magnets hot rolled steel plate is welded and joined into the required box shape. Using these stock materials, there is no limitation to lift magnet geometry.
Rectification – It consists of work done to correct dimensional errors. In chemical engineering, rectification is a thermal separation process, which is also known as counter-current distillation, that concentrates a volatile mixture by repeatedly vaporizing and condensing the mixture, resulting in a higher purity of the more volatile component. Rectification aims to improve the purity of a substance through repeated distillation cycles, unlike simple distillation which separates components based on boiling points. It involves a multi-stage distillation process carried out in a column, where vapor and liquid streams interact in a counter-current manner. Rectification is also the mechanism by which out-of-band radio frequency and microwave signals are converted to in-band signals. This process is very much an envelope detector. In electrical engineering, rectification is the process of converting alternating current to direct current, typically achieved using devices like diodes which allow current to flow in only one direction.
Rectifier – It is a device which converts alternating current (which periodically reverses) to direct current which flows in only one direction. Rectifier can be a solid-state, vacuum tube, or electro-mechanical device.
Rectifier transformers – These are specialized transformers which are used to convert alternating current to direct current in various applications, such as industrial power supplies, traction systems, and electrochemical processes. These transformers frequently include diodes or thyristors within the same tank. The process of rectification involves changing the direction of current flow in the circuit, and transformers are used to step down or step up the voltage level of the alternating current power supply. One of the challenges of rectifier transformers is the generation of harmonics in the output voltage waveform. Harmonics are the multiples of the fundamental frequency and can cause unwanted effects such as increased losses, electromagnetic interference, and distortion of the wave-form. To reduce the harmonic content in the output voltage, a technique called pulse rectification can be used.
Rectiformer – It is a combination of a transformer and a rectifier, which is used in electro-chemical processes or supply of electro-static precipitators.
Recuperative burner – Recuperative burners preheat incoming combustion air by capturing waste heat from exhaust gases. This preheated air enhances fuel efficiency and reduces energy consumption. They use a heat exchanger positioned within the exhaust flue. Exhaust gases leaving the furnace transfer their thermal energy to the heat exchanger, warming the incoming air stream. This preheated air then mixes with fuel, resulting in a more efficient combustion process. In case of a recuperative burner, the structure of the burner is the similar to the radiation heat exchanger tube which heats the inlet air up to the higher temperature (about 750 deg C) by recovering the heat from the exhaust gas to the inlet air. Hence, the exchanged heat in the burner can improve the combustion efficiency and save the fuel cost approximately 25 % to 30 %. Recuperative burners are frequently used in industries where moderate heat recovery is sufficient and initial cost savings are crucial, such as in small to medium-sized industrial furnaces.
Recuperative heating – It involves preheating combustion air by capturing waste heat from exhaust gases using a heat exchanger, improving combustion efficiency and fuel economy.
Recuperator – It consists of the equipment for transferring heat from gaseous products of combustion to incoming air or fuel. The incoming material passes through pipes surrounded by a chamber through which the outgoing gases pass. Recuperator normally recovers heat from the exhaust gases of a furnace of medium temperature or high temperature and transfer it to incoming combustion air. Recuperators can be categorized by the relative directions of gas flow such as (i) ‘in parallel-flow heat exchangers’ where both the gases flow in the same general direction, (ii) ‘in counter flow exchangers’ where both the gases flow in opposite directions, or (iii) ‘in cross-flow’ where the gases flow at right angles to each other. Counter flow heat exchangers have the greatest effectiveness while the parallel flow arrangement has the lowest effectiveness. Recuperators can be based on the principle of heat transfer by radiation, convection, or combinations. Recuperators are constructed out of either metallic or ceramic materials. Metallic recuperators are used in applications with temperatures below 1,050 deg C, while heat recovery at higher temperatures is better suited to ceramic tube recuperators which can operate with hot side temperatures as high as 1,500 deg C and cold side temperatures of around 950 deg C.
R-curve – It is a plot of crack-extension resistance as a function of stable crack extension, which is the difference between either the physical crack size or the effective crack size and the original crack size. R-curves normally depend on sample thickness and, for some materials, on temperature and strain rate. It is also known as J-R curve.
Recursive least squares (RLS) filter – It is an adaptive filter algorithm which recursively finds the coefficients that minimize a weighted linear least squares cost function relating to the input signals. This approach is in contrast to other algorithms such as the least mean squares (LMS) which aim to reduce the mean square error.
Recycling – It is the process by which salvaged materials become usable products. It is the process of converting waste products into reusable materials. Recycling differs from reuse, which simply means using a product again.
Red brass – It is a type of brass alloy, characterized by a reddish tint because of a high copper content (typically 77 % to 86 %). It finds applications in plumbing, industrial components, electrical hardware, and decorative items because of its durability, corrosion resistance, and machinability. Red brass fittings and components are widely used for pump housings, impellers, and valves because of their ability to resist saltwater corrosion. These components ensure reliable performance for vessels and offshore equipment.
Redesign – It is the process of redoing an existing design to improve some deficiency in the existing design.
Red mud – It is a residue, containing a high percentage of iron oxide, obtained in purifying bauxite in the production of alumina in the Bayer process. In fretting wear, a mud is powdery form of debris, normally consisting of iron oxides, which is expelled from a ferrous metal joint near the location where fretting wear is occurring.
Redox – It is also called reduction–oxidation or oxidation–reduction. It is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a decrease in the oxidation state. The oxidation and reduction processes occur simultaneously in the chemical reaction. There are two classes of redox reactions. The first is electron-transfer in which only one (normally) electron flows from the atom, ion, or molecule being oxidized to the atom, ion, or molecule which is reduced. This type of redox reaction is frequently discussed in terms of redox couples and electrode potentials. The second is atom transfer in which an atom transfers from one substrate to another, e.g., in the rusting of iron, the oxidation state of iron atoms increases as the iron converts to an oxide, and simultaneously, the oxidation state of oxygen decreases as it accepts electrons released by the iron. Although oxidation reactions are normally associated with forming oxides, other chemical species can serve the same function. In hydrogenation, bonds like C=C are reduced by transfer of hydrogen atoms.
Redox equilibrium – It refers to a state where the rates of oxidation and reduction reactions are equal, meaning that there is no net change in the concentrations of reactants and products in a redox system. Redox equilibrium play an important role in the electron transport chain.
Redox potential – it is the potential of a reversible oxidation-reduction electrode measured with respect to a reference electrode, corrected to the hydrogen electrode, in a given electrode.
Redrawing – It is the second and successive deep-drawing operations in which cup-like shells are deepened and reduced in cross-sectional dimensions.
Redraw rod – The preferred term is drawing stock.
Red shift – It is a systematic displacement toward the longer wavelengths of the spectrum.
Redsmelt process – It is an ironmaking process which is based two reduction steps. These are (i) pre-reduction of iron bearing materials in a rotary hearth furnace (RHF), and (ii) smelting of the hot pre-reduced iron (DRI, direct reduced iron). Originally a submerged arc furnace (SAF) has been used for the second step. Submerged arc furnace has now been replaced by a coal and oxygen blown converter (oxy-coal reactor) known as ‘New Smelting Technology’ (NST). The rotary hearth furnace reduces green pellets made out of iron ore, reductant fines and binders to produce hot, metallized direct reduced iron which is charged to the NST converter for its smelting to hot metal.
Reduce or reduction – It refers to a chemical process where a substance gains electrons, or experiences a decrease in its oxidation state.
Reduce, reuse, and recycle – These are frequently referred to as the three ‘Rs’ These are fundamental principles in sustainable waste management and environmental conservation. These principles are essential in minimizing waste generation, maximizing resource efficiency, and reducing the negative impact on the environment. Reduce emphasizes the importance of reducing the quantity of waste being produced. This principle involves being mindful of the consumption habits and making conscious choices to minimize waste generation. Reuse encourages to find ways to extend the lifespan of items instead of discarding them after a single use. Reusing items is a powerful way to minimize waste and conserve resources. By embracing the concept of reuse, it is possible to reduce the demand for new products and decrease the quantity of waste generated. Recycle is the process of converting waste materials into new products to prevent the waste of potentially useful materials. This practice helps conserve natural resources, reduce energy consumption, and decrease greenhouse gas emissions. By separating recyclable materials from general waste and supporting recycling programs, it is possible to contribute to a more sustainable and circular economy.
Reduced metal powder – It refers to metal powder produced by chemically reducing metal oxides or compounds with a reducing agent, like carbon or hydrogen, without melting the metal.
Reduced-ply belt – Reduced-ply belts consist of carcasses with either fewer plies than comparable multiple-ply belts or special weaves. The features of reduced-ply belt include (i) straight warp ply carcass structure which allows designs to provide higher tension than ordinary multi-ply belts, (ii) provides high bendability and impact resistance, and (iii) belts can be easily joined.
Reducer – It is a pipe fitting which is used to join two different pipe sizes together. Reducers can be either concentric or eccentric which refers to the relative position of the center lines of the outlet and inlet. Special attention is to be given when using reducers in a horizontal orientation as the slope prevents free draining of a system if not installed correctly.
Reducer rolling – It is also known as roll forging. It is a longitudinal rolling process which reduces the cross-sectional area of heated bars or billets by passing them between two rotating roll segments with forming grooves, creating workpieces with varying cross-sections along the rolling direction.
Reducers – The reducers change the number of revolutions of the electric motor to the required revolutions of the rolls. They increase the torque. They can be one-stage, two-stage and three-stage type. The gear ratio of each stage can range from 4 to 6.
Reducibility – Reducibility refers to the ease with which a substance can be reduced, meaning the tendency to gain electrons or have its oxidation state decreased during a chemical reaction. It also means being capable of being reduced or made simpler, smaller, or less in size, amount, degree, or importance. In a more technical context, it refers to the ability to solve a problem by transforming it into a simpler, known problem.
Reducing agent – It is also known as a reductant, reducer, or electron donor. It is a compound which causes reduction, thereby itself becoming oxidized. It is also a chemical which, at high temperatures, lowers the state of oxidation of other batch chemicals. Reducing agent is a chemical species which donates an electron to an electron recipient (called the oxidizing agent, oxidant, oxidizer, or electron acceptor). Examples of substances that are common reducing agents include hydrogen, carbon mono-oxide, the alkali metals, formic acid, oxalic acid, and sulphite compounds. Reducing agents in the blast furnace are carbon of coke, and the carbon mono-oxide gas generated in the furnace by the combustion of coke and injected pulverized coal.
Reducing atmosphere – It is a furnace atmosphere which tends to remove oxygen from substances or materials placed in the furnace. It is an atmosphere which tends to (i) promote the removal of oxygen from a chemical compound, and (ii) promote the reduction of immersed materials. It is also a chemically active protective atmosphere which at high temperature reduces metal oxides to their metallic state. Reducing atmosphere is a relative term and such an atmosphere can be reducing to one oxide but not to another oxide.
Reducing flame – It is a gas flame which is produced with excess fuel in the inner flame. It is also a gas flame resulting from combustion of a mixture containing too much fuel or too little air.
Reducing and sizing mill (RSM) – It is a type of rolling mill which is used to reduce the diameter (and potentially the wall thickness) of pipes or bars, improving their accuracy and surface quality. This mill is frequently located between the finishing block mill and the high-speed laying head. It is normally designed with a split structure and independent twin-module block transmissions, it ensures flexibility and ease of production and maintenance. It uses a series of rollers or stands to progressively reduce the diameter of the product, frequently while also adjusting the wall thickness to achieve the desired dimensions.
Reducing valve – It is a regulating device which serves to reduce the fluid pressure supply to the needed delivery pressure. Reducing valve automatically reduces supply pressure to a pre-selected pressure as long as the supply pressure is at least as high as the selected pressure. The main parts of the reducing valve are the main valve, an upward-seating valve which has a piston on top of its valve stem, an upward-seating auxiliary (or controlling) valve, a controlling diaphragm, and an adjusting spring and screw.
Reduction – In cupping and deep drawing, it is a measure of the percentage decrease from blank diameter to cup diameter, or of diameter reduction in redrawing. In forging, rolling, and drawing, it is either the ratio of the original to final cross-sectional area or the percentage decrease in cross-sectional area. Reduction is also a reaction in which there is a decrease in valence resulting from a gain in electrons. It is the removal of oxygen from a chemical compound. In sampling, reduction is the process of preparing one or more sub-samples from a sample. Reduction can also refer to decreasing the valence of an ion or atom by the addition of electrons.
Reduction cell – It is a pot or tank in which either a water solution of a salt or a fused salt is reduced electrolytically to form free metals or other substances.
Reduction gear boxes / reducers – The reduction gear boxes / reducers are used in the rolling mills where speed of motor is higher than required for rolls. Depending on the required reduction in speed, reducers can be used having 1, 2 or 3 stages.
Reduction in area (RA) – It is the difference between the original cross-sectional area of a tensile sample and the smallest area at or after fracture as specified for the material undergoing testing. It is also known as reduction of area.
Reduction of oxide – It refers to the process of removing oxygen from metal oxide particles (like iron oxide) in the powder, typically during the sintering stage, to produce a pure metal powder or a metal with desired properties. It is the process of converting a metal oxide to metal by applying sufficient heat in the presence of a solid or gaseous material, such as hydrogen, having a higher attraction for oxygen than does the metal.
Reduction- oxidation (Redox) processes– These processes are used for the chemical oxidation or chemical reduction. These involve use of oxidants or reductants to bring about a change in the chemical composition of a compound or group of compounds to less harmful or hazardous compounds.
Reduction potential – It a measure of the tendency of a chemical species to acquire electrons from or lose electrons to an electrode and hence be reduced or oxidized respectively. Redox potential is expressed in volts (V). Each species has its own intrinsic redox potential, e.g., the more positive the reduction potential (reduction potential is more frequently used because of the general formalism in electro-chemistry), the higher the species’ affinity for electrons and tendency to be reduced.
Reduction ratio – It refers to the ratio of the volume of the loose powder to the volume of the final compact or part produced after compaction. It is also the quotient of the reduced oxygen content into the total initial content of a powder. In mechanical working, it is the quotient of the reduced cross-section into the original cross-section in metal working such as extrusion, it is an indication of the degree of plastic deformation.
Reduction reaction – In electro-chemistry, it is a chemical reaction which is taking place at cathodic sites by the consumption of electrons.
Reduction roasting – Reduction roasting is the removal of oxygen from a component of an ore normally by using a reductant such as carbon mono-oxide. The rotary kiln is used as a reduction furnace. It can employ a wide range of carbon carriers not suitable as reductants for shaft furnaces from anthracite and coke breeze to charcoal fines, lignite, and brown coal. The charge (ore and reductant) normally moves through the rotary kiln counter-current to the hot gases. Coupled reactions mainly ore reduction by carbon mono-oxide gas and reaction of carbon with carbon di-oxide with regeneration of carbon mono-oxide, occur in the charge. The reactivity of carbon is critical for the process as a whole. Some of the carbon mono-oxide gas formed escapes from the charge so that oxidizing gases from the free kiln volume cannot permeate into it. Reducing conditions depend on (i) the temperature, reactivity, and quantity of the reductant, (ii) the residence time, and (iii) the charge holdup at the discharge end of the kiln. The rate of reduction can be controlled to meet a variety of objectives, from the formation of magnetite (Fe3O4) to the production of direct reduced iron (DRI).
Redundancy – It is the intentional duplication of critical components or functions of a system with the goal of increasing reliability of the system, normally in the form of a backup or fail-safe, or to improve actual system performance.
Redundant – It applies to things which are unnecessary or can be left out.
Redwood viscosity – It is a commercial measure of viscosity expressed as the time in seconds needed for 50 cubic centimeters of a fluid to flow through a tube of 10 millimeters length and 1.5 millimeters diameter at a given temperature.
Reed switch – It is an electrical switch which is made of two thin strips of ferro-magnetic metal. It touches when subject to a magnetic field.
Reel – It is a spool or hub for coiling or feeding wire or strip. It also means to straighten and planish a round bar by passing it between contoured rolls.
Reel breaks – These are transverse breaks or ridges on successive inner laps of a coil which results from crimping of the lead end of the coil into a gripping segmented mandrel. These are also called reel kinks.
Reentrant angle – It is an interior angle of a polygon higher than 180-degree.
Reference accident – It is one of a range of accidents at a nuclear reactor or other nuclear installation that can reasonably be foreseen in safety analysis as giving rise to the most significant release of radionuclides from the site. It refers to a hypothetical or specific accident scenario which is used as a benchmark or standard for safety analysis, emergency planning, or design criteria.
Reference electrode – It is a non-polarizable electrode with a known and highly reproducible potential used for potentiometric and voltametric analyses.
Reference line – In data visualization and other contexts, it is a line which is used to provide a visual reference point for comparison or context within a chart, graph, or other visual representation. It can be a horizontal or vertical line indicating a threshold, a target value, or a specific data point. Reference lines help users interpret data by providing a visual anchor against which to compare the data points displayed in a chart or graph.
Reference material – In materials characterization, it is a material of definite composition which closely resembles in chemical and physical nature of the material with which an analyst expects to deal. It is a material or substance, one or more of whose property values are sufficiently homogeneous and well established to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning values to materials. It is a reference material which can be in the form of a pure or mixed gas, liquid or solid. Examples are water for the calibration of viscometers, sapphire as a heat-capacity calibrant in calorimetry, and solutions used for calibration in chemical analysis. Reference material is used for calibration or standardization.
Reference sample – It is a carefully selected sample or material which is used as a benchmark for comparison with other samples, hence, ensuring quality consistency and serving as a standard for analysis and evaluation.
Reference temperature – It is the temperature of collapse of pyrometric cone. It is the temperature at which the tip of a pyrometric reference cone reaches the level on which the base of the cone is mounted when the cone is heated at a specified rate under specified conditions.
Refined aluminum – It is the aluminum of very high purity (99.95 % or higher) achieved by special metallurgical treatments.
Refined copper – It is the metal containing at least 99.85 % of copper, or metal containing at least 97.5 % of copper, provided that the content of any other element does not exceed the limit specified as silver -0.25 %, arsenic 0.5 %, cadmium 1.3 %, chromium 1.4 %, magnesium 0.8 %, lead 1.5 %, sulphur 0.7 %, tin 0.8 %, tellurium 0.8 %, zinc 1 %, zirconium 0.3 % and other elements, each 0.3 %. Other elements are, e.g., aluminum, beryllium, cobalt, iron, manganese, nickel, and silicon. Refined copper is produced by electrolytic refining, electrolytic extraction, chemical refining or fire refining. Other refined copper (containing at least 97.5 % by weight of copper) is normally produced by alloying refined copper with one or more other elements up to the maximum content limits as given above. In practical application, it applies to refinery shapes which are directly consumed without further refining.
Refined steel – It refers to steel which has undergone a process to remove impurities and unwanted elements, resulting in a purer and more desirable composition for specific applications.
Refinery – It is known as oil refinery or petroleum refinery. It is an industrial process plant where petroleum (crude oil) is transformed and refined into products such as gasoline (petrol), diesel fuel, fuel oils, asphalt base, heating oil, kerosene, liquefied petroleum gas and petroleum naphtha.
Refining – It is the branch of process metallurgy dealing with the purification of crude or impure metals. It consists of purifying an impure metal. It is to be distinguished from other processes such as smelting and calcining in that those two involve a chemical change to the raw material, whereas in refining the final material is chemically identical to the raw material. Refining hence increases the purity of the raw material through processing. There are several processes including pyro-metallurgical and hydro-metallurgical techniques.
Refining combined burner (RCB) – In the electric arc furnace, it is a system which allows for both oxygen and fuel (like coal or natural gas) to be injected into the furnace to refine the molten steel, optimizing the process and reducing maintenance costs. It is a single, automated unit which can inject both oxygen and fuel into an electric arc furnace, facilitating the refining process. It is installed on the side of the furnace, near the molten metal, and can be used to blow oxygen and fuel into the arc furnace.
Refining, copper – It consists of further purification of blister copper by removal of its oxygen content and recovery of any rare or precious metals which has been present in the ore by either (i) fire refining in a furnace, (ii) electrolytic refining, in which the blister copper is cast into anodes, suspended in an acid solution and deposited on to plates at the cathode by electrolysis.
Refining furnaces – These are industrial equipment used to heat and refine metals or other materials, mainly to increase purity or achieve a desired composition, and they are crucial in industries like steelmaking, copper refining, and metal casting.
Reflectance – Reflectance of the surface of a material is its effectiveness in reflecting radiant energy. It is the fraction of incident electromagnetic power which is reflected at the boundary. Reflectance is a component of the response of the electronic structure of the material to the electromagnetic field of light, and is in general a function of the frequency, or wavelength, of the light, its polarization, and the angle of incidence. The dependence of reflectance on the wavelength is called a reflectance spectrum or spectral reflectance curve.
Reflection – It is the change in direction of a wave-front at an interface between two different media so that the wave-front returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection (for example at a mirror) the angle at which the wave is incident on the surface equals the angle at which it is reflected. In acoustics, reflection causes echoes and is used in sonar. In geology, it is important in the study of seismic waves. Reflection is observed with surface waves in bodies of water. Reflection is observed with several types of electro-magnetic wave, besides visible light. Reflection of very high frequency (VHF) and higher frequencies is important for radio transmission and for radar. Even hard X-rays and gamma rays can be reflected at shallow angles with special ‘grazing’ mirrors.
Reflection grating – It is a grating which uses reflection off a series of fine, equidistant ridges, rather than transmission through a pattern of slots, to diffract light into its component wavelengths. The gratings used in optical instrumentation are almost exclusively reflection gratings.
Reflection high-energy electron diffraction (RHEED) – Itis a surface-sensitive technique which is used to characterize the surface structure and morphology of crystalline materials, particularly during thin film growth, by analyzing the diffraction patterns of high-energy electrons grazing the sample surface. Reflection high-energy electron diffraction systems gather information only from the surface layer of the sample, which distinguishes reflection high-energy electron diffraction from other materials characterization methods that also rely on diffraction of high-energy electrons. Transmission electron microscopy, another common electron diffraction method samples mainly the bulk of the sample due to the geometry of the system, although in special cases it can provide surface information.
Reflection method – It is the technique of producing a diffraction pattern by X-rays or electrons which have been reflected from a sample surface.
Reflection polariscope – It is an optical instrument which uses polarized light to visualize internal stresses or strains in transparent materials like glass or plastics by reflecting light off the sample’s surface.
Reflection, X-rays –It is the coherent scattering of X-rays by the atoms of a crystal which necessarily results in beams in characteristic directions.
Reflector sheet – It is a clad product consisting of a facing layer of high-purity aluminum capable of taking a high polish, for reflecting heat or light, and a base of commercially pure aluminum or an aluminum-manganese alloy, for strength and formability.
Reflowing – It is the melting of an electrodeposit followed by solidification. The surface has the appearance and physical characteristics of a hot dipped surface (especially tin or tin alloy plates). It is also called flow brightening.
Reflow soldering – It is a non-standard term for a soldering process variation in which preplaced solder is melted to produce a soldered joint or coated surface.
Reflux – It is the heating of a substance at the boiling temperature and returning the condensed vapours to the vessel to be reheated.
Refractive index – It is a standard of measurement used particularly to establish the qualities of optical glass. The index is the ratio of the sine of the angle of incidence of a ray of light to the sine of the angle of refraction (the change in direction when a ray of light passes from one medium to another) by the glass. The second medium normally used to establish the index is a vacuum.
Refractive index (electrons) – It is the ratio of electron wavelength in free space to its wavelength in a material medium.
Refractory – It is a material of very high melting point with properties which make it suitable for such uses as furnace linings and kiln construction. It is also the quality of resisting heat.
Refractories – These are inorganic, non-metallic, porous, and heterogeneous materials which are composed of thermally stable mineral aggregates, a binder phase, and additives. The principal raw materials used in the production of refractories are the oxides of silicon, aluminum, magnesium, calcium, and zirconium. There are some non-oxide refractories like carbides, nitrides, borides, silicates and graphite. Refractories are heat resistant materials used in almost all processes involving high temperatures and / or corrosive environment. Refractories insulate and protect industrial furnaces and vessels due to their excellent resistance to heat, chemical attack, and mechanical damage. Refractories are defined as non-metallic materials having those chemical and physical properties that make them applicable for structures or as components of systems that are exposed to environments above 540 deg C.
Refractories, acid – These are refractories which contain a substantial quantity of silica which can react chemically with basic refractories, basic slags, or basic fluxes at high temperatures.
Refractories, basic – These are refractories whose major constituent is lime, magnesia, or both, and which can react chemically with acid refractories, acid slags, or acid fluxes at high temperatures. Commercial use of this term also includes refractories made of chrome ore or combinations of chrome ore and dead-burned magnesite.
Refractories, neutral – These are refractories which are resistant to chemical attack by both acid and basic slags, refractories, or fluxes at high temperatures.
Refractoriness – It is the characteristic property of a refractory which allows it to withstand a high temperature in its environment and conditions of use. It is the capability of maintaining a desired degree of chemical and physical identity at high temperatures and in the environment and conditions of use.
Refractoriness-under-load (RUL) – It is a particular measure of the behaviour of a refractory subjected to the combined effects of load, rising temperature and time. It evaluates the softening behaviour of fired refractory bricks at rising temperature and constant load conditions. It gives an indication of the temperature at which the brick is going to collapse in service condition with similar load. However, under actual service conditions the bricks are heated only on one face and most of the load is carried by the relatively cooler rigid portion of the refractory bricks. Hence, the refractoriness under load test gives only an index of refractory quality, rather than a figure which can be used in a refractory design. Under service conditions, where the refractory used is heating from all sides such as checkers, partition walls etc. the refractoriness under load test data is quite significant. For refractoriness under load, samples in cylindrical shape of 50 millimeters height and 50 millimeters diameter are heated at a constant rate under a load of 0.2 mega pascal (MPa) and the change in height includes the thermal expansion and also the expansion of test equipment. The test results are taken from the recording. The initial temperature is taken at 0.6 % compression while the final temperature is taken at 20 % compression or when the sample has collapsed.
Refractoriness under load (differential) – In order to eliminate errors as a result of the inherent expansion of the test equipment when the refractoriness under load is being tested, and to enable tests to be carried out in an oxidizing atmosphere, a different method has been developed to determine the resistance at rising temperature and constant load which is the refractoriness under load (differential) test. In this method same type of samples are used as for the refractoriness under load test bur they have an internal bore to permit rods to be fitted to the upper and the lower sides. With this method, temperature values are obtained by differential measurements in an oxidizing atmosphere and these values are considerably lower than the refractoriness under load values.
Refractory – It is a material (normally an inorganic, non-metallic, ceramic material) of very high melting point with properties which make it suitable for such uses as furnace linings and kiln construction. It is the quality of resisting heat. It consists of non-metallic materials which are having those chemical and physical properties that make them applicable for structures, or as components of systems, which are exposed to environments above 540 deg C. Refractory also means resistant to high temperature.
Refractory alloy – It is a heat-resistant alloy. It is an alloy having an extremely high melting point. It is an alloy which is difficult to work at high elevated temperatures.
Refractory block – It is a normally rectangular refractory shape of a size larger than normally can be laid with one hand. All sides may not be plane and parallel.
Refractory brick – It is also known as a fire brick. It is a ceramic material designed to withstand high temperatures and extreme conditions. It is a normally rectangular refractory shape with one dimension higher than the other two and of a size that usually can be laid with one hand. All sides may not be plane and parallel such as wedges, arches, keys, and circle brick. They are normally used in lining furnaces, kilns, fire-boxes, and other applications requiring high-temperature resistance.
Refractory castable – It is a castable. It consists of non-coherent mixture of aggregate and bond. It is mainly supplied dry and placed by casting after the addition and mixing of water or another liquid.
Refractory cermets – These are composite materials which combine a ceramic phase (high melting point, refractory) with a metallic phase (for ductility and conductivity). These materials are designed to have high-temperature resistance, hardness, and wear resistance.
Refractory fibres – These are non-metallic, inorganic, continuous, or non-continuous filaments having those chemical and physical properties which make them applicable for structures, or as components of systems, which are exposed to environments above 540 deg C.
Refractory lining – It refers to a protective layer behind the working lining in contact with furnace contents, encased in a metal shell. It needs knowledge of mechanical properties like thermal expansion, thermal conductivity, and Young’s modulus for proper design and installation. It is the brickwork or castable used in boilers and furnaces to protect metal surfaces and for boiler baffles.
Refractory metal – It is a metal which is having an extremely high melting point and low vapour pressure, e.g., niobium, tantalum, molybdenum, tungsten, and rhenium.
Refractory ore – It is the ore which resists the action of chemical reagents in the normal treatment processes and which can need pressure leaching or other means to affect the full recovery of the valuable minerals.
Refractory relining – It refers to the process of replacing or renewing the protective layer (the lining) made of refractory materials inside a high-temperature furnace or other processing unit which has been damaged or worn down, hence ensuring structural integrity and operational effectiveness.
Refractory shape – It consists of a refractory piece which is forming a stable mass with specific dimensions.
Refractory waste – It refers to the leftover, non-recyclable material derived from the manufacturing of refractory products like bricks, castables, and ceramics. These are typically high-temperature resistant materials used in industries such as steel, glass, and cement production.
Refrigerants – These are the working fluids of refrigeration cycles which absorb heat from a reservoir at low temperatures and reject heat at higher temperatures.
Refrigeration – It consists of cooling a space, substance, or system to lower and / or maintain its temperature below the ambient one (while the removed heat is ejected to a place of higher temperature). Refrigeration is an artificial, or human-made, cooling method. It refers to the process by which energy, in the form of heat, is removed from a low-temperature medium and transferred to a high-temperature medium. This work of energy transfer is traditionally driven by mechanical means, but it can also be driven by heat, magnetism, electricity, laser, or other means.
Regeneration, catalyst – It is the process of restoring the activity or performance of a catalyst which has been deactivated due to factors such as poisoning, sintering, or ageing. It is the process of restoring the activity and performance of a deactivated catalyst by removing accumulated deposits or other deactivating agents, frequently through methods like thermal treatment or chemical washing, to extend its lifespan and maintain efficiency.
Regenerative braking – It is a braking scheme that returns energy to the source.
Regenerative burner – A regenerative burner is with a heat recovery system that recovers the waste heat of the furnace exhaust gas to heat up the combustion air needed for the burning of the fuel at the burner. Use of regenerative burners for reheating furnaces can provide significant energy savings. The regenerative burners are designed to recover the heat to the inlet air by transferring the heat from the exhaust gas to the inlet air which is to be used in the combustion. The regenerative burner has two set of burners each with a regenerator and the reversing valve. The regenerator uses the ceramic (usually alumina) balls to collect the heat. While the first regenerative burner is firing, the other is exhausting the furnace gases. The exhaust gas is passed through the regenerative burner body and transfers the heat to the ceramic balls. Hence, the heat from exhaust gas is transferred to the inlet air since it is passed through the heated ceramic balls. The reversing valve sets the direction of the air flow that enters into the burner head, which makes the inlet air temperature similar to the operating temperature. Because of a high preheat combustion air temperature, the regenerative burner can save the fuel and make the combustion highly efficient.
Regenerative circuit – It is a circuit which uses positive feedback. It can be an amplifier or an oscillator.
Regenerative heating – As in recuperative heating, waste heat from the furnace is used to pre-heat combustion air. Regenerative heating is a cyclic process whereby exhaust gases pass over and hence heat up refractory blocks in one of two pre-heating chambers. Once the first chamber has been heated up, exhaust gases are diverted to heat the second chamber, while cold combustion gas is introduced into the first chamber to be pre-heated by the hot refractory blocks. Continuous reversal of this process provides a permanent flow of pre-heated gas for combustion.
Regenerator – It is same as recuperator except that the gaseous products or combustion heat brick checker work in a chamber connected to the exhaust side of the furnace while the incoming air and fuel are being heated by the brick checker work in a second chamber, connected to the entrance side. At intervals, the gas flow is reversed so that incoming air and fuel contact hot checker work while that in the second chamber is being reheated by exhaust gases. Regenerator is normally used for large capacity furnaces. In regenerator, a minimum of two chambers are used so that while one is absorbing heat from the exhaust gases, the other is transferring heat to the combustion air. The direction of air-flow is altered about a fixed interval of time. Important relations exist between the size of the regenerator, time between reversals, thickness of brick, conductivity of brick and heat storage ratio of the brick. The time between the reversals is an important aspect in a regenerator. Long periods mean higher thermal storage and hence higher cost. Also, long periods of reversal result in lower average temperature of preheat and consequently reduce fuel economy. Regenerators are especially suited for high temperature applications with dirty exhaust gases. The major disadvantages are its large size and the capital costs, which are significantly greater than costs of recuperators. Other disadvantages of regenerator are the accumulation of dust and slagging on the surfaces which reduce efficiency of the heat transfer. Heat losses from the walls of the regenerator and air in leaks during the gas period and out-leaks during air period also reduces the heat transfer efficiency.
Regime – It is a preferred state of the climate system, frequently representing one phase of dominant patterns or modes of climate variability.
Region – It is a territory characterized by specific geographical and climatological features. The environment and climate of a region is affected by regional and local scale forcing such as topography, land use characteristics, lakes, industries etc. as well as remote influences from other regions.
Regional metamorphism – It is the metamorphism caused by both the heat of igneous processes and tectonic pressure.
Region of instability – Normally fan curves arc downward from the zero-flow condition, i.e., as the back-pressure on the fan decreases, the airflow increases. Majority of fans have an operating region in which their fan performance curve slopes in the same direction as the system resistance curve. A fan operating in this region can have unstable operation. Instability results from the fan’s interaction with the system as the fan attempts to generate more air flow, which causes the system pressure to increase, reducing the generated air flow. As the air flow decreases, the system pressure also decreases, and the fan responds by generating more air flow. This cyclic behaviour results in a searching action which creates a sound similar to breathing. This operating instability promotes poor fan efficiency and increases wear on the fan components.
Regular castable – It is a refractory castable with a hydraulic bond containing cement but without a deflocculant and with a calcium oxide content higher than 2.5 % on a calcined basis.
Regular lay – Regular lay in the wire rope denotes that the wires are twisted in one direction, and the strand in opposite direction to form the rope. The wires in regular lay line up with the axis of the rope. The direction of the wire lay in the strand is opposite to the direction of the strand lay. Regular lay wire ropes are distinguished between right-hand ordinary lay (RHOL) and left-hand ordinary lay (LHOL). Due to the difference in direction between the wires and strand, regular lay ropes are less likely to untwist or kink. Regular lay roes are also less subject to failure from crushing and distortion because of shorter length of exposed outer wires. Regular lay ropes are naturally more rotation-resistant, and also spool better in a drum than lang lay ropes. The advantages of regular lay ropes are (i) better structural stability, (ii) higher number of broken wires is allowed, and (iii) identification of broken wires is easier.
Regular port valve – It is a term normally applied to plug valves. The regular port of such a valve is customarily around 40 % of the line pipe area. It corresponds to a venturi or reduced-bore valve of the same nominal pipe size. Venturi ball valves frequently are a logical alternative to plug valves with advantages in price torque and low maintenance.
Regular reflection – It is the condition in which all the incident light is reflected at the same angle as the angle of the incident light relative to the normal at the point of incidence. The reflection surface then appears bright, or mirrorlike, when viewed with the naked eye.
Regular spangle – They are visible multifaceted zinc crystal structure on zinc coated steel. The cooling rate is uncontrolled which produces a variable grain size.
Regulating pressure – It refers to the process of controlling and maintaining a fluid’s pressure at a desired level, frequently by reducing a high input pressure to a lower output pressure, using a device like a pressure regulator.
Regulating transformer – It is also known as a voltage regulator. It is a device which maintains a stable voltage output despite fluctuations in the input voltage or load, ensuring electrical equipment operates optimally. Originally, regulating transformers were installed in power systems to compensate for voltage fluctuations. However, studies have shown that they also have several other important advantages for transmission systems. By carefully choosing the transformation ratios, it is possible to control the active and reactive power flow in the power system to allow for a more economic utilization of the transmission capacity. In addition, the power losses associated with energy distribution can be considerably reduced and circulating currents largely avoided.
Regulating valve – It is also known as a control valve. It is a throttling valve which exercises automatic control over some variable (normally pressure). It is not an on-off valve. It is a device which is used to adjust and control the flow of fluids or gases by varying the size of the flow passage, hence enabling precise regulation of flow rate, pressure, temperature, or liquid level.
Regulation – It refers to statutory rules or laws which are formally written down and enacted by a legislative body, and have the force of law.
Regulator – It is a device for controlling the delivery of welding or cutting gas at some substantially constant pressure.
Regulatory bodies – These are government agencies which regulates and enforces rules and regulations in a specific area.
Regulatory compliance – It is the process of adhering to laws, regulations, standards, and other rules set forth by governments and other regulatory bodies. It is an important aspect of organizational working, since organizations are required to follow certain laws and regulations to maintain their operations. Regulatory compliance helps ensure that organizations do not engage in unethical or illegal practices. The compliance standards are specific to industries and locations and can result in large penalties if not followed correctly.
Regulatory instruments – These are rules-based tools which focus on enforcing compliance with minimum standards. Their goal is compliance with the law and their driving mechanism is deterrence. Regulatory tools include laws and regulations.
Regulatory norms – These are the norms which are legally binding rules and guidelines established by statutory authorities or regulatory bodies to control an industry, process, or sector, ensuring compliance and responsible conduct.
Regelation – It is the phenomenon in which ice converts to liquid because of the applied pressure and then re-converts to ice once the pressure is removed. It is the phenomenon of ice melting under pressure and refreezing when the pressure is reduced. This can be demonstrated by looping a fine wire around a block of ice, with a heavy weight attached to it. The pressure exerted on the ice slowly melts it locally, permitting the wire to pass through the entire block. The wire’s track refills as soon as pressure is relieved, so the ice block will remain intact even after wire passes completely through. This experiment is possible for ice at −10 deg C or cooler, and while essentially valid, the details of the process by which the wire passes through the ice are complex. The phenomenon works best with high thermal conductivity materials such as copper, since latent heat of fusion from the top side needs to be transferred to the lower side to supply latent heat of melting.
Rehabilitation – It is a treatment or treatments designed to facilitate the process of recovery from injury, illness or disease to as normal a condition as possible.
Rehbinder effect – It is the modification of the mechanical properties at or near the surface of a solid, which is attributable to interaction with a surfactant.
Reheat behaviour – It consists of the changes in length or volume which are taking place in a fired refractory when subjected to a reheat test.
Reheat change (after shrinkage and after expansion) – After heating to high temperature and subsequent cooling, a permanent change in the dimension (permanent linear change) frequently occurs which is described as after expansion or after shrinkage. If a refractory brick has very strong after-shrinkage then the joints get enlarged and the brickwork is loosened and no longer tight. In opposite case, after expansion is also dangerous since this can cause the destruction of the brickwork through pressure. The permanent linear change (PLC) of the refractories can be influenced. For getting a brick with a constant volume, the burning of the raw materials and the firing of the bricks is to be controlled in such a manner so that equilibrium is achieved at the desired temperature.
Reheating furnace – It is one of the key equipments in a hot rolling mill. It consumes the majority of energy needed for the rolling of steel. It is normally used to heat the steel stock (billets, blooms, or slabs etc.) to the rolling temperatures which are suitable for plastic deformation of steel and hence for rolling in the hot rolling mill. Reheating furnace is an important equipment for the hot rolling of steel. It is the heart of any hot rolling mill. The heating process in a reheating furnace is a continuous process. Fuel used in these furnaces can be pulverized coal, liquid fuel, or gaseous fuel. Types of the reheating furnaces used in the rolling mills are (i) pusher furnace, (ii) walking beam furnace, (iii) walking hearth furnace, (iv) roller hearth furnace, and (v) rotary hearth furnace. The rotary hearth furnace is normally used in pipe rolling mills. The steel stock to be rolled is charged at the entrance of the reheating furnace. During its travel in the reheating furnace, the steel stock is pre-heated, heated, and soaked as it passes through pre-heating, heating and soaking zone of the reheating furnace. At the end of the soaking zone of the furnace, the steel stock is discharged from the furnace by ejector for rolling in the rolling mill. The temperature of the heated steel material at the time of discharged depends on several factors and it can vary in the range of 1,100 deg C to 1,250 deg C.
Reheat test – It is the prescribed heat treatment of a fired refractory free of externally applied stresses to determine its linear or volume stability by measurements before and after the heating.
Reheat turbines – These turbines are used almost exclusively in electrical power plants. In a reheat turbine, steam flow exits from a high-pressure section of the turbine and is returned to the boiler where additional superheat is added. The steam then goes back into an intermediate pressure section of the turbine and continues its expansion.
Reichert cones – These are essentially an improved version of the trays. They are cone-shaped with a central single feed point. Normally, they contain multiple stages mounted vertically above each other. The more common configurations are (i) 4DS (four double/single stages), and (ii) 2DSS.DS (two double/single /single stages plus a double/single stage), the first one is used as the roughers while the second as the cleaners. The process variables are (i) feed rate (increased rate reduces performance above an optimum), (ii) feed density (needs to be kept between 60 % to 63 % solids otherwise either recovery or grade suffers), and (iii) insert settings (range 1 to 9 with increasing opening the recovery is more but the grade gets lower). The advantages are (i) high capacity for floor area, and (ii) high feed density (63 % solids) so low volume-pumping needed. The disadvantages are (i) low upgradation ratio (typically 3:1), (ii) controlled specific gravity of the feed is needed, (iii) low recovery of fines, (iv) feed needs screening, (v) low tolerance for slimes, (vi) bottom separating surfaces of cones not visible or easily accessible, and (vii) needs wash water for density control during cleaner stages.
Reinforced concrete – It is a composite material in which concrete’s relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is normally, though not necessarily, steel reinforcement bars (known as rebar) and is normally embedded passively in the concrete before the concrete sets. However, post-tensioning is also employed as a technique to reinforce the concrete. In corrosion engineering terms, when designed correctly, the alkalinity of the concrete protects the steel rebar from corrosion.
Reinforced concrete structures drawing – The two main groups of drawings for showing reinforced concrete structures are general arrangement drawings, and reinforcement drawings. General arrangement drawings are floor plans, roof plans, sections and elevations, drawn to a small scale and provide overall view of the work. They supply the setting out dimensions, the positions and sometimes the sizes of all the members. A reference grid is provided similar to that for a structural steel building. Reinforcement drawings of structural elements are drawn to a larger scale and give detailed information about the reinforcement. There is no justification for ambiguity, and it is necessary that all drawings are easy to read, and cannot be misunderstood.
Reinforced plastics – These are moulded, formed, filament- wound, tape-wrapped, or shaped plastic parts consisting of resins to which reinforcing fibres, mats, fabrics, and so on, have been added before the forming operation to provide some strength properties greatly superior to those of the base resin.
Reinforced polymer – It is also known as fibre-reinforced polymer or fibre-reinforced plastic. It is a composite material which is made of a polymer matrix reinforced with fibres. The fibres are normally glass, carbon, or aramid, although other fibres such as paper or wood or asbestos have been sometimes used. The polymer is normally an epoxy, vinylester or polyester thermosetting plastic. Phenol formaldehyde resins are still in use.
Reinforced reaction injection moulding (RRIM) – It is a reaction injection moulding with a reinforcement added.
Reinforcement – It is a strong material bonded into a matrix to improve its mechanical properties. Reinforcements are normally long fibres, chopped fibres, whiskers, particulates, and so on. The is not to be used synonymously with filler.
Reinforcement bar – It is also called reinforcing bar, rebar, reinforcing steel or steel reinforcement. It is a tension device which is added to concrete to form reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Concrete is strong under compression, but has low tensile strength. Rebar normally consists of steel bars which significantly increase the tensile strength of the structure. Reinforcement bar surfaces feature a continuous series of ribs, lugs, or indentations to promote a better bond with the concrete and reduce the risk of slippage. The most common type of reinforcement bar is carbon steel, typically consisting of hot-rolled round bars with deformation patterns embossed into its surface. Steel and concrete have similar coefficients of thermal expansion, so a concrete structural member reinforced with steel experiences minimal differential stress as the temperature changes.
Reinforcing material lay-up quality control – It refers to the processes and procedures which are used to ensure the quality and integrity of a composite material’s structure during the layering (lay-up) of reinforcing materials (like fibres) and resin, critical for achieving desired mechanical properties.
Reinstatement – It refers to the act of restoring someone or something to a former position, status, or condition.
Relative biological effectiveness (RBE) – It is the ratio of the dose of a reference radiation (like X-rays) to the dose of another radiation needed to produce the same biological effect. It essentially quantifies how much more effective one type of radiation is compared to another in causing a specific biological outcome.
Relative density – It is also called specific gravity. It is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Relative density for solids and liquids is nearly always measured with respect to water at its densest (at 4 deg C) and for gases, the reference is air at room temperature (20 deg C). The term ‘relative density’ is preferred in International System of Units, whereas the term ‘specific gravity’ is gradually being abandoned.
Relative erosion factor – It refers to a factor which quantifies the influence of specific factors (like rainfall, soil type, topography, or land management) on the rate of soil erosion, compared to a baseline or standard condition.
Relative flow coefficient – It is the ratio of the flow coefficient at a stated travel to the flow coefficient at rated travel.
Relative humidity – It is the ratio of partial density of water vapour in the air to the saturation density of water vapour at the same temperature. It is the ratio of the mass of water vapour present in a unit volume of gas to the maximum possible mass of water vapour in unit volume of the same gas at the same temperature and pressure.
Relative operating characteristic (ROC) curve – It is a graphical representation of a classifier’s performance, plotting the true positive rate (sensitivity) against the false positive rate (1-specificity) across different threshold settings, allowing for the visualization of trade-offs between sensitivity and specificity.
Relative potency factor (RPF) – This factor quantifies potencies of substances with respect to a defined effect, relative to the potency of a chosen index substance. Relative potency factors can be used to express combined exposures of multiple substances in terms of the exposure value of the chosen index substance (i.e., in index substance equivalents). Hazard characterizations, and hence also relative potency factors are based on mass units (e.g., micrometers), and not on mol units. Relative potency factors can be different for different levels of the human organism (external, internal, specific compartment). These factors can be given as data or computed from hazard characterizations. These factors can be specified with uncertainty. Computation from uncertain hazard characterizations allows to include correlations between uncertain relative potency factors which originate from using the same index substance.
Relative sea level (RSL) – It is defined as the sea level which is observed with respect to a land-based reference frame. It is frequently contrasted with eustatic sea level, which is a measure of the total mass or volume of the oceans. Relative sea level can change by the processes changing eustatic sea level (e.g., ice melt and thermal expansion), but also by changes on land such as subsidence and isostatic rebound. In sequence stratigraphy, relative sea level is similarly defined as the distance from the ocean surface to the bottom of the sediment on the ocean floor. Hence, relative sea level is independent of the thickness of the sediment layer at the bottom of the ocean, which makes it a different concept than water depth.
Relative sintering temperature – It is the ratio of the sintering temperature to the melt ing temperature of the substance as expressed on the Kelvin scale. It refers to the sintering temperature expressed as a percentage of the material’s melting point, typically between 60% and 80% of the melting temperature, to achieve optimal densification and bonding.
Relative speed – It is the vector norm of the relative velocity. It is the speed of one object in relation to another. It is used to compare the speeds of two or more objects moving at different rates.
Relative standard deviation (RSD) – It is the standard deviation expressed as a percentage of the mean value given by RSD = 100 (S/X) [Dsquare/(n-1)], where ‘S’ is the standard deviation, ‘D’ is the difference between individual results and the average, ‘n’ is the number of individual results, and ‘X’ is the average of individual results. It is also known as coefficient of variation.
Relative steam velocity – It refers to the velocity of steam as seen by a moving blade, rather than a stationary observer. It is a crucial concept in understanding turbine performance and design.
Relative thermal index (RTI) – It is a measure of a material’s ability to retain its properties when exposed to high temperatures over an extended period, indicating its thermal endurance. It is a characteristic parameter which reflects a material’s resistance to thermal degradation, specifically its ability to maintain its physical and / or electrical properties under high-temperature conditions. Relative thermal index is determined by subjecting a material to a series of progressively higher temperatures and measuring its properties at each temperature. A higher value of relative thermal index indicates a material’s better ability to withstand high temperatures without significant degradation of its critical properties.
Relative transmittance – It is the ratio of the transmittance of the object in question to that of a reference object. For a spectral line on a photographic emulsion, it is the ratio of the transmittance of the photographic image of the spectral line to the transmittance of a clear portion of the photographic emulsion. Relative transmittance can be total, specular, or diffuse.
Relative units, temperature – Relative units are compared with a physical and chemical process which always produces the same temperature. Degrees Celsius (international system), also called degrees centigrade and represented by the symbol ‘degree C’. This measurement unit is defined by assigning the value 0 degree to the freezing point of water and the value 100 degree to the boiling point of water when both measurements are taken at a pressure of one atmosphere. The scale is then divided into 100 equal parts in which each corresponds to 1 degree. Degrees Fahrenheit (international system) measurement unit is based on divisions between the freezing and evaporation points of ammonium chloride solutions. In this scale, the zero and hundred corresponds to the freezing and evaporation temperatures of ammonium chloride in water. As per this scale 32 degrees Fahrenheit corresponds to the melting point of ice and 212 degrees Fahrenheit corresponds to boiling point of water. The difference between the two points is 180 degrees which is divided into 180 equal portions, determines the degree Fahrenheit.
Relative velocity – It is the velocity of an object ‘B’ relative to another object ‘A’ is the velocity which the object ‘B’ appears to have to an observer moving with ‘A’. The relative velocity of an object ‘B’ relative to an observer ‘A’, is the velocity vector of ‘B’ measured in the rest frame of ‘A’.
Relativistic heavy ion collider (RHIC) – It is a particle accelerator which collides beams of heavy ions (like gold) at nearly the speed of light to study the fundamental forces and properties of matter, including the creation and properties of a state of matter called quark-gluon plasma.
Relaxation curve – It is a plot of either the remaining, or relaxed, stress as a function of time.
Relaxation oscillator – It is an oscillator which relies on an active device periodically changing state. Such oscillators normally produce a square-wave or sawtooth waveform, different from the approximately sinusoidal waveshape of a harmonic oscillator.
Relaxation rate – It is the absolute value of the slope of a stress-relaxation curve at a given time.
Relaxation time – It is the time needed for a stress under a sustained constant strain to diminish by a stated fraction of its initial value.
Relaxed stress – It is the initial stress minus the remaining stress at a given time during a stress-relaxation test.
Relay – It is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch can have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof. Relays are used where it is necessary to control a circuit by an independent low-power signal, or where several circuits are to be controlled by one signal.
Release – A release occurs when a hazardous substance goes from a controlled condition (for example, inside a truck, barrel, storage tank, or landfill) to an uncontrolled condition in the air, water, or land.
Release agent – It is a material which is applied in a thin film to the surface of a mould to keep the resin from bonding to the mould. It is also called parting agent.
Release film – It is an impermeable layer of film which does not bond to the resin being cured.
Release paper – It is a sheet, serving as a protectant or carrier, or both, for an adhesive film or mass, which is easily removed from the film or mass prior to use.
Reliable data – It means that data which can be trusted to be accurate, complete, consistent, and free from errors, ensuring that it is trustworthy and can be used confidently for decision-making.
Reliability – It is the probability which an item survives a given operating period, under specified operating conditions, without failure. It is a quantitative measure of the ability of a product or service to fulfill its intended function for a specified period of time. It is defined as the probability which a product, system, or service performs its intended function adequately for a specified period of time, or operates in a defined environment without failure. Reliability is closely related to availability, which is typically described as the ability of a component or system to function at a specified moment or interval of time. Reliability frequently plays a key role in the cost-effectiveness of systems.
Reliability centered maintenance (RCM) – It is a process used to determine what must be done to ensure that any physical asset continues to function in order to fulfill its intended functions in its present operating context. It is a method to identify and select failure management policies to efficiently and effectively achieve the required safety, availability and economy of operation. It is a process to establish the safe minimum levels of maintenance while ensuring an equipment continues to perform to its design function within the current operating context. It achieves this by providing a means for determining optimal maintenance and operational strategies based on the probability and consequence of the analyzed failure modes. It is a systematic approach to determine the maintenance requirements of plant and equipment in its operation. It uses preventive maintenance, predictive maintenance, real-time monitoring, and run to failure and proactive maintenance. These techniques are used in an integrated manner to increase the probability which a machine or component is going to function in the required manner over its design life cycle with a minimum of maintenance. The aim of reliability centered maintenance is to create such maintenance strategy which helps minimize the total operating costs while increasing reliability of the system. Reliability centered maintenance basically combines several well-known techniques and tools, in a systematic approach managing risks, as a basis for maintenance decisions.
Reliability engineering – It is a sub-discipline of systems engineering which emphasizes the ability of equipment to function without failure. Availability, testability, maintainability, and maintenance are frequently defined as a part of ‘reliability engineering’ in reliability programmes.
Reliability function – It is theoretically defined as the probability of success. In practice, it is calculated using different techniques, and its value ranges between 0 and 1, where 0 indicates no probability of success while 1 indicates definite success. This probability is estimated from detailed (physics of failure) analysis, previous data sets, or through reliability testing and reliability modeling.
Relief radius – It refers to the radius of the rounded corners or edges of the roll grooves, designed to facilitate metal flow and prevent jamming or sticking during the rolling process.
Relief response – It is also known as emergency management. It is the generic name of an inter-disciplinary field dealing with the strategic organizational management processes used to protect critical assets of the organization from hazard risks which can cause disasters or catastrophes and to ensure their continuance within their planned lifetime.
Relief valve – It is also known as pressure relief valve (PRV). It is a type of safety valve which is used to control or limit the pressure in a system since excessive pressure can otherwise build up and create a process upset, instrument or equipment failure, explosion, or fire.
Relief valve, safety relief valve – It is a quick-acting, spring-loaded valve which opens (relieves) when the pressure exceeds the spring setting. It is frequently installed on the body cavity of ball and gate valves to relieve thermal overpressure in liquid services. It is an automatic pressure relieving device actuated by the pressure upstream of the valve and characterized by opening pop action with further increase in lift with an increase in pressure over popping pressure.
Relieving – It is the buffing or other abrasive treatment of the high points of an embossed metal surface to produce highlights which contrast with the finish in the recesses. It is also the removal of material from selected portions of a coloured metal surface by mechanical means to achieve a multi-coloured effect.
Reluctance motor – It is a type of electric motor which induces non-permanent magnetic poles on the ferro-magnetic rotor, relying on varying magnetic reluctance. The rotor carries no windings.
Remainder – It is the quantity ‘left over’ after performing some computation. In arithmetic, the remainder is the integer ‘left over’ after dividing one integer by another to produce an integer quotient (integer division). In algebra of polynomials, the remainder is the polynomial ‘left over’ after dividing one polynomial by another.
Remaining stress – It is the stress remaining at a given time during a stress-relaxation test.
Remanence (Br) – It is the magnetic induction remaining in a magnetic circuit after removal of the applied magnetizing force. It is sometimes called remanent induction. It is the force the electromagnet uses to hold the ferromagnetic piece after cancelling the magnetic field. Its approximate value is 5 % of holding force (Fm) depending on the piece (size, roughness, and material etc.).
Remanufacture – It is a form of green design in which parts and components are rebuilt or refurbished after a portion of their life so that they can be reissued and used as essentially new parts.
Remedial action – It is the action which is taken to investigate, monitor, assess and evaluate the release or threat of release of hazardous substances or contaminants to the environment. It can also refer to the actual ‘clean-up’ of the environment by the different removal, treatment, monitored remediation, or corrective actions. The term clean-up is sometimes is used interchangeably with the terms remedial action, removal action, response action, remedy, remediation, or corrective action.
Remedial investigation (RI) – It establishes (i) the nature and extent of the contamination and the sources, (ii) identifies current and potential impacts to public health, welfare, and the environment, (iii) identifies current and reasonably foreseeable uses of land and waters of the state, and (iv) gets and evaluates any information necessary for identification and comparison of alternative remedial actions.
Remedial maintenance – It is a set of activities which are performed to eliminate the source of failure without interrupting the continuity of the production process.
Remedial objective (RO) – It establishes remedial goals for the current and reasonably foreseeable uses of lands and waters of the region which have been or are threatened to be affected by a release of hazardous substance.
Remediation – It is a general term for providing a remedy. Environmental remediation deals with the clean-up, or other methods to contain pollution, toxic spills, hazardous materials, or contaminants from soil, groundwater, sediment, or surface water etc. for the general protection of human health and the environment.
Remediation (or Reclamation), mineral deposits – Remediation (or Reclamation) is the restoration of a Project site conditions which are required by regulatory or other provisions.
Remote control – It is the operation of a valve or other flow-control device from a point at a distance from the device being controlled. It can be accomplished by electrical, pneumatic, or hydraulic means.
Remote-field eddy current (RFEC) inspection – It is a non-destructive examination technique which is suitable for the examination of conducting tubular goods using a probe from the inner surface. Because of the remote-field eddy current, the technique provides what is, in effect, a through-wall examination using only the interior probe. Although the technique is applicable to any conducting tubular material, it has been primarily applied to ferro-magnetics since conventional eddy current testing techniques are not suitable for detecting opposite-wall defects in such material unless the material can be magnetically saturated. In this case, corrosion / erosion wall thinning and pitting as well as cracking are the flaws of interest. One advantage of remote-field eddy current inspection for either ferro-magnetic or non-ferromagnetic material inspection is that the probe can be made more flexible than saturation eddy current or magnetic probes, hence facilitating the examination of tubes with bends or diameter changes. Another advantage of remote-field eddy current inspection is that it is approximately equal (within a factor of 2) in sensitivity to axially and circumferentially oriented flaws in ferro-magnetic material. The major disadvantage of remote-field eddy current inspection is that, when applied to non-ferromagnetic material, it is not normally as sensitive or accurate as traditional eddy current testing techniques.
Remote racking system – It is a system for inserting circuit breakers into switchgear which allows the operator to stay at a safe distance from any possible arc hazard.
Remote sensing – It is the small scale or large scale acquisition of information of an object or phenomenon by the use of either recording or real-time sensing device(s) which are wireless, or not in physical or intimate contact with the object (such as by way of aircraft, spacecraft, satellite, buoy, or ship). In practice, remote sensing is the stand-off collection through the use of a variety of devices for gathering information on a given object or area.
Removable fasteners – It is a type of fastener which permits the parts to be readily disconnected without damaging the fastener, e.g. nut and bolt.
Removal action – It is an immediate, short-term clean-up action to address a release or threatened release of hazardous substances. This action is initiated to reduce or eliminate an immediate threat to public health and / or the environment.
Removal of minerals – This step is done to the clean water (from previous step) to remove minerals which can build-up on steam turbines or other process equipment. Depending on the water source, this step can be done by one or more of these processes (i) softening, (ii) demineralization (ion exchange), and (iii) reverse osmosis (membrane).
Removal of oxygen – Dissolved oxygen and other gases primarily consisting of carbon di-oxide (CO2) in boiler feedwater is major cause of boiler system corrosion. While oxygen results in localized corrosion (pitting), CO2 forms carbonic acid and damages condensate piping. Removal of oxygen can be done by (i) deaeration, or (ii) oxygen scavenging.
Renewable electricity – It is the electric power which is derived from primary energy sources that replenish on a rapid scale or that are not appreciably diminished by human exploitation.
Renewable energy – It is also called green energy. It is the energy made from renewable natural resources which are replenished on a human timescale. The most widely used renewable energy types are solar energy, wind power, and hydropower. Bioenergy and geothermal power are also significant in some countries. Some also consider nuclear power a renewable power source, although this is controversial, as nuclear energy requires mining uranium, a non-renewable resource. Renewable energy installations can be large or small and are suited for both urban and rural areas.
Reoil – It means oil put on the sheet after cleaning and before coiling for shipment to prevent water stain.
Reoxidation products – These are the inclusions because of reoxidation of steel. Example of such inclusion is the alumina inclusion generated when (i) the aluminum remaining in the liquid steel is oxidized by iron oxide in the slag, or (ii) by the exposure of the liquid steel to the atmosphere.
Repair – It means responding to the breakdown of equipment and undertaking work to correct the problem in order to return the equipment to a working condition. It is also performing finishing work on the piece after galvanizing in order to meet standards or specifications, or coating areas of steel which have been exposed due to post galvanizing fabrication, installation, or extremely rough handling.
Repair engineering – It needs a thorough understanding of composite structural mechanics and structural joining of composites and metal structures. These two aspects, in combination with other considerations, such as damage removal, surface preparation, and repair fabrication, need a clearly defined engineering process. The level of repair is to be determined by such factors as damage criticality, operational requirements, and repair station capabilities. All of these add up to a unique repair for most composite structural damage restoration.
Repeatability – It is a term which is used to refer to the test-result variability associated with a limited set of specifically defined sources of variability within a single laboratory.
Repeatability (of results of measurements) – It is the closeness of the agreement between the independent results of successive measurements of the same measurand carried out under the same conditions of measurement which is obtained with the same method on identical test material, under the same conditions (same operator, same apparatus, same laboratory and after short intervals of time). These conditions are called repeatability conditions. Repeatability conditions include (i) the same measurement process, (ii) the same observer, (iii) the same measuring instrument, used under the same conditions, (iv) the same location, and (v) repetition over a short period of time. Repeatability can be expressed quantitatively in terms of the dispersion of characteristics of the results. The measure of repeatability is the standard deviation qualified as repeatability standard deviation.
Repeated bending test – It is also known as a cyclic bending test or fatigue bending test. It evaluates a material’s ability to withstand repeated bending forces without failure, simulating real-world conditions where materials are subjected to cyclic loading.
Repeated impact – It is the preferred term when all impacts are superimposed on the same point or zone.
Repeated loading – It is also known as cyclic or repetitive loading, It refers to the continuous and repeated application of a load (stress, strain, and force etc.) to a material or structural component, potentially leading to fatigue and eventual failure.
Repeated stress – It refers to a type of stress which varies from zero to a maximum value of the same nature (tension or compression), or a stress which changes over time in a repeated fashion. In case of human resource, repeated stress refers to ongoing or chronic exposure to environmental or psychological factors which cause physical or emotional strain. It can result from long-term job demands, relationship difficulties, financial pressures, or other life challenges.
Repeated tension test – It is also known as a cyclic tensile test. It is a mechanical test where a material sample is subjected to repeated cycles of tensile (pulling) stress until failure, allowing engineers to assess its fatigue strength and durability.
Repeaters and looping channels – Repeaters are devices used to receive the work piece as it emerges out from one stand and loop it through 180-degree into an adjacent stand automatically. This consists of grooved channels or troughs which guide the leading end of the rolling stock through 180 degree or in some cases through an S-shaped path in forward running repeaters. The front end of the stock is driven round the repeater by the succeeding stock until it is gripped by the next stand. The speed matching between the adjacent stands is normally such that the succeeding stand runs slightly slower than the balancing speed which causes the loop to grow in size. The repeating channels are designed to allow the stock to kick out on to a flat table under these conditions. Sometimes the repeaters function as twist guides as well.
Repeating coil – It is an old name for a transformer, which is especially used in telephone circuits.
Replacement ore – It is the ore formed by a process during which certain minerals have passed into solution and have been carried away, while valuable minerals from the solution have been deposited in the place of those removed.
Replica – It is a reproduction of a surface in a material. It is normally accomplished by depositing a thin film of suitable material, such as a plastic, onto the sample surface. This film is subsequently extractedand examined by optical microscopy, scanning electron microscopy, or transmission electron microscopy, the latter being the most common. Replication techniques can be classified as either surface replication or extraction replication. Surface replicas provide an image of the surface topography of a sample, while extraction replicas lift particles from the sample.
Replicability – It means getting consistent results across studies aimed at answering the same scientific question, each of which has obtained its own data. Two studies can be considered to have replicated if they get consistent results given the level of uncertainty inherent in the system under study.
Replicast process – It is a casting process which utilizes dimensionally precise replicas, typically made from expanded polystyrene, to create molds for casting, resulting in high-quality, complex castings with minimal finishing needs.
Replicate – In electron microscopy, it means to reproduce using a replica.
Repository – It consists of long-term radioactive waste storage facility.
Repowering – It means refurbishing the equipment of a power plant, with a view to improved efficiency or life span.
Representative volume element (RVE) – It is the smallest volume of a heterogeneous material which, when averaged, provides a statistically representative description of the material’s overall properties and behaviour.
Repressing – It is the application of pressure to a previously pressed and sintered powder metallurgy compact, normally for the purpose of improving some physical or mechanical property or for dimensional accuracy.
Reprocessing – It refers normally to the processes used to separate spent nuclear reactor fuel into nuclear materials which can be recycled for use in new fuel and material which is to be discarded as waste.
Reproducibility – It is a term which is used to describe test-result variability with specifically defined components of variance obtained both from within a single laboratory and between laboratories.
Reproducibility (of results of measurements) – It is the closeness of the agreement between the independent results of measurements of the same measurand carried out on identical test material but under different conditions (different operators, different apparatus, different laboratories, and / or after different intervals of time). However, it is to be noted that a valid statement of reproducibility requires specification of the conditions changed. The changed conditions include (i) principle of measurement, (ii) method of measurement, (iii) observer, (iv) measuring instrument, (v) reference standard, (vi) location, (vii) condition of use, and (viii) time. Reproducibility can be expressed quantitatively in terms of the dispersion characteristics of the results. The measure of reproducibility is the standard deviation qualified as reproducibility standard deviation. Reproducibility is closely related to replicability and repeatability. It is a major principle underpinning the scientific method. For the findings of a study to be reproducible means that results obtained by an experiment or an observational study or in a statistical analysis of a data set are to be achieved again with a high degree of reliability when the study is replicated. There are different kinds of replication but typically replication studies involve different researchers using the same methodology. Only after one or several such successful replications should a result be recognized as scientific knowledge.
Repulsion motor – It is a wound rotor induction motor using a pair of short-circuited brushes on a commutator.
Request for quotation (RFQ) – It is a process wherein an organization asks a set of potential suppliers or service providers to submit their quotations and stand a chance to supply or provide goods or services. Once the organization receives the quotations, it can choose the vendor which best matches its criteria for the goods or services.
Requirements list – In engineering design, it is a detailed list of the functional requirements with qualitative or quantitative goals and limits for each.
Rerolling quality – It means the quality of the rolled billets from which the surface defects have not been removed or completely removed.
Reroll stock – It is a semi-finished rolled product of rectangular cross-section in coiled form suitable for further rolling. Examples are foil stock and sheet stock.
Research – It is defined as the creation of new knowledge and/or the use of existing knowledge in a new and creative way so as to generate new concepts, methodologies and understandings. This could include synthesis and analysis of previous research to the extent that it leads to new and creative outcomes.
Research and development (R&D) – It is defined as activities designed to advance and sustain the capabilities of the organization in pursuit of its mission. The R&D plan of the organization supports strategic planning by identifying and communicating the set of R&D needs which are reliant on external support. It is intended to help stakeholders understand the context for specialized needs and how they relate to the bigger picture of strengthening the effectiveness and improving the efficiency of organization. Research is planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge is going to be useful in developing a new product or service or a new process or technique or in bringing about a significant improvement to an existing product or process. Development is the translation of research findings or other knowledge into a plan or design for a new product or process or for a considerable improvement to an existing product or process whether intended for sale or use. It includes the conceptual formulation, design, and testing of product alternatives, construction of prototypes, and operation of pilot plants.
Researcher development skill framework (RDSF) – It is made up of five components consisting of a centre and four quadrants, which together cover both the discipline specific and generic skills needed by researchers. centre represents researcher and research. It places the researchers and their research at the centre. The core skills namely (i) subject knowledge (ii) discipline specific skills, and (iii) intellectual ability are unique to the researchers and their research area. In addition to the centre piece, the researcher development skill framework has four quadrants. Within each quadrant there are three skills categories which are then broken down into skills areas with examples. To help develop these skills, training, workshops, and resources are needed. Quadrant 1 represents personal and professional development. It includes (i) self-management, (ii) career management, and leadership and interpersonal skills. Quadrant 2 represents research management. It includes (i) research planning and income management, (ii) data management, digital literacy, and administration, and (iii) research conduct, integrity and ethics. Quadrant 3 represents communication. It includes (i) academic literacy and writing, (ii) verbal and visual presentation skills, and (iii) publication and dissemination. Quadrant 4 represents engagement and impact. It includes (i) outreach and influence, (ii) knowledge exchange and innovation, and (iii) education.
Research management – It includes (i) research planning and income management, (ii) data management, digital literacy and administration, and (ii) research conduct, integrity and ethics. The skill areas for research planning and income management include (i) research project development, (ii) grant seeking (pre-award), and (iii) grant management (post award).
Research plan – It is a framework which shows how a researcher intends to approach the research topic. The plan can take several forms such as a written outline, a narrative, a visual / concept map or timeline. It is a document which changes and develops as researchers conduct their research. Components of a research plan include (i) research conceptualization which introduces the research question, (ii) research methodology which describes the approach to the research question, (iii) literature review, critical evaluation and synthesis, which consists of systematic approach to locating, reviewing and evaluating the work (text, exhibitions, and critiques etc.) relating to the research topic, and (iv) communication which is geared toward an intended audience, shows evidence of researcher’s inquiry.
Restricted Resources / Reserve – Restricted Resources / Reserve is that part of any resource / reserve category which is restricted from extraction by laws or regulations. For example, restricted reserves meet all the requirements of reserves except that they are restricted from extraction by laws or regulations.
Reserves – Reserves are that part of the reserve base which can be economically extracted or produced at the time of determination. The term reserves need not signify that extraction facilities are in place and operative. Reserves include only recoverable materials. Hence, terms such as ‘extractable reserves’ and ‘recoverable reserves’ are redundant and are not a part of the classification system.
Reserve base – Reserve base is that part of an identified resource which meets specified minimum physical and chemical criteria related to current mining and production practices, including those for grade, quality, thickness, and depth. The reserve base is the in-place demonstrated (measured plus indicated) resource from which reserves are estimated. It can encompass those parts of the resources which have a reasonable potential for becoming economically available within planning horizons beyond those that assume proven technology and current economics. The reserve base includes those resources which are currently economic (reserves), marginally economic (marginal reserves), and some of those that are currently subeconomic (subeconomic resources). The term Geological reserve has been applied by others normally to the reserve-base category, but it also can include the inferred-reserve base category.
Reservoir – It is a man-made lake which collects and stores water for future use. Reservoir for hydraulic fluid is a tank for holding the fluid required to supply the system, including a reserve to cover any losses from minor leakage and evaporation. The reservoir is generally designed to provide space for fluid expansion, permit air entrained in the fluid to escape, and to help cool the fluid. The reservoir tank is either vented to the atmosphere or closed to the atmosphere and pressurized. Hydraulic oil flows from the reservoir tank to the pump, where it is forced through the system and eventually returned to the reservoir tank. The reservoir tank not only supplies the operating needs of the system, but it also replenishes fluid lost through leakage. Furthermore, the reservoir serves as an overflow basin for excess fluid forced out of the system by thermal expansion (the increase of fluid volume caused by temperature changes), the accumulators, and by piston and rod displacement. The reservoir also furnishes a place for the fluid to purge itself of air bubbles which can enter the system. Foreign matter picked up in the system can also be separated from the hydraulic fluid in the reservoir or as it flows through line filters. Reservoir tank is either pressurized or non-pressurized.
Reservoir area – It is the total surface of a reservoir measured in a horizontal plane at an elevation corresponding to the full supply level of the reservoir.
Reservoir capacity – It is the total volume of water a reservoir is capable of holding when filled up to the full supply or normal water level.
Reservoir equipment – It refers to the components and tools used in and around a reservoir, primarily for hydraulic systems, which include air breathers, gauges, filters, and suction strainers, to manage fluid levels, prevent contamination, and ensure proper system function.
Reset – It means the realigning or adjusting of dies or tools during a production run. It is not to be confused with the operation setup which occurs before a production run.
Resettable fuse – It is a circuit protective device which opens on excess current, and then, on cooling off, restores the circuit automatically.
Residual current circuit breaker – It is a circuit breaker which detects unbalance of phase currents because of the ground fault.
Residual dissolved oxygen – It refers to the quantity of oxygen that remains dissolved in a liquid, such as water, after a process designed to remove or reduce it, like purging or deaeration. When a liquid is treated to remove dissolved oxygen (e.g., through deaeration in boilers or water treatment), the remaining oxygen which cannot be removed is considered residual dissolved oxygen.
Residual elements – These are defined as elements which are not added on purpose to steel and which cannot be removed by simple metallurgical processes. These are small quantities of elements unintentionally present in an alloy. Examples of residual elements are copper, nickel, arsenic, lead, tin, antimony, molybdenum, and chromium etc. The presence of residual elements in steel can have strong effects on mechanical properties. There is hence clearly the need to identify and to quantify the effects of residual elements in order to keep these effects within acceptable limits. Residual elements, or at least some of them, have an influence on processing conditions and regimes, from casting to the final annealing, and possibly on all mechanical properties.
Residual fuels – These are the products remaining from crude petroleum by removal of some of the water and an appreciable percentage of the more volatile hydro-carbons.
Residual gas analysis – It is a technique which is used to identify and quantify the different gas species present in a vacuum environment, helping to understand vacuum purity, identify leaks, and monitor contamination.
Residual gas analyzer (RGA) – It is a small and normally rugged mass spectrometer, typically designed for process control and contamination monitoring in vacuum systems. When constructed as a quadrupole mass spectrometer, there exist two implementations, utilizing either an open ion source (OIS) or a closed ion source (CIS). Residual gas analyzers can be found in high vacuum applications such as research chambers, surface science setups, accelerators, and scanning microscopes etc. These analyzers are used in majority of the cases to monitor the quality of the vacuum and easily detect minute traces of impurities in the low-pressure gas environment.
Residual impacts – It consists of the impacts of climate change which occur after adaptation.
Residual ores – These ores are normally products of the surficial weathering of rocks but can include ores formed by hydrothermal oxidation and leaching. Ores of this type were formed extensively in Precambrian iron formations by leaching of silica, which commonly constituted in excess of 50 % of the rock. Oxidation changed iron carbonate, silicate minerals, and magnetite to hematite or limonite.
Residual resistance ratio – It is a metric used to assess the purity and quality of a material, defined as the ratio of its electrical resistance at room temperature (typically 273 K or 293 K) to its resistance at a very low temperature, frequently around 4.2 K (the boiling point of helium).
Residual-resistivity ratio – It is also known as residual-resistance ratio or just is normally defined as the ratio of the resistivity of a material at room temperature and at 0 K. Of course, 0 K can never be reached in practice so some estimation is usually made. Since the residual-resistance ratio can vary quite strongly for a single material depending on the quantity of impurities and other crystallographic defects, it serves as a rough index of the purity and overall quality of a sample. Since resistivity normally increases as defect prevalence increases, a large residual-resistance ratio is associated with a pure sample. residual-resistance ratio is also important for characterizing certain unusual low temperature states such as the Kondo effect and super-conductivity. Since it is a unitless ratio there is no difference between a residual resistivity and residual-resistance ratio.
Residual risk – It is the risk which remains in unmanaged form, even when disaster risk reduction measures are in place and for which emergency response and recovery capacities are to be maintained. The presence of residual risk implies a continuing need to develop and support effective capacities for emergency services, preparedness, response and recovery together with socio-economic policies such as safety nets and risk transfer mechanisms.
Residuals – It refer to ‘tramp elements’ such as copper (Cu) and tin (Sn), which are typically introduced into the steelmaking process in the form of unsorted or contaminated scrap and which can impair the physical and mechanical properties of steel.
Residual strain – It is the strain which is associated with residual stress.
Residual strength – It is the load or force (normally mechanical) which a damaged object or material can still carry without failing. It is the strength which a material can still withstand, even with cracks or other defects present. Material toughness, fracture size and geometry as well as its orientation all contribute to residual strength.
Residual stress – It is the stress existing in a body at rest, in equilibrium, at uniform temperature, and not subjected to external forces. It is frequently caused by the forming or thermal processing curing process. It is an internal stress not depending on external forces resulting from such factors as cold working, phase changes, or temperature gradients. It is stress present in a body which that is free of external forces or thermal gradients. It is the stress remaining in a structure or member as a result of thermal or mechanical treatment or both. Stress arises in fusion welding mainly since the weld metal contracts on cooling from the solidus to room temperature.
Residual stress sensitivity factor – It quantifies how much a material’s fatigue strength is reduced because of the presence of residual stresses and geometric stress concentrations (like notches).
Residue – These are contaminants (oil, grease, dirt, rust and mill scale) which unless removed, prevents complete galvanizing of the steel surface.
Resilience – It is the quantity of energy per unit volume released on unloading. It is the capacity of a material, by virtue of high yield strength and low elastic modulus, to show considerable elastic recovery on release of load. Resilience is also the ability of ceramic fibres to spring back after compression to 50 % of thickness. Resilience is the ratio of the thickness of a product after the application and relaxation of a compressive force which reduces the original thickness to 50 % of its original value, to its original thickness.
Resilient seat – It is a valve seat containing a soft seal, such as an O-ring, to ensure tight shut-off.
Resin – It is a solid or highly viscous liquid that can be converted into a polymer. Resins can be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. It is a bead-like material used in chemical exchange for softeners and de-alkalizers.
Resin bonding – It is the use of resin to produce a bond in a refractory when heated to a relatively low temperature (up to 800 deg C).
Resin content – It is the quantity of resin in a laminate expressed as either a percentage of total weight or total volume.
Resin film infusion (RFI) – It is a variant of the resin transfer moulding process in which a layer of solid resin film is placed along with a dry preform in a matched.
Resin impregnation – It is a process where a resin, frequently a polymer, is introduced into a porous material, typically under vacuum, pressure, or both, to ensure the resin penetrates and fills voids, improving structural integrity and other properties upon curing.
Resin matrix composites – These are materials where a matrix of organic resin (like epoxy or polyester) surrounds and binds together reinforcing fibres or particles, resulting in a composite with improved properties compared to the individual components.
Resinoid – It consists of a class of thermosetting synthetic resins, either in their initial temporarily fusible state or in their final infusible state.
Resinoid wheel – It is a grinding wheel bonded with a synthetic resin.
Resin pocket – It is an apparent accumulation of excess resin in a small, localized section visible on cut edges of moulded surfaces, or internal to the structure and non-visible.
Resin-rich area – It is the localized area filled with resin and lacking reinforcing material.
Resin-starved area – It is the localized area of insufficient resin. It is normally identified by low gloss, dry spots, or fibre showing on the surface.
Resin system – It is a mixture of resin and ingredients such as catalyst, initiator, diluents, and so on, needed for the intended processing and final product.
Resintering – It is the application of pressure to a sintered compact, normally for the purpose of improving a physical or a mechanical property or for dimensional accuracy.
Resin transfer moulding (RTM) – It is a closed-mould process which is used to produce composite parts by injecting resin into a mould containing preformed, dry fibre reinforcements, which then cures, resulting in a strong, durable component.
Resist – It is the coating material which is used to mask or protect selected areas of a substrate from the action of an etchant, solder, or plating. It is a material which is applied to prevent flow of brazing filler metal into unwanted areas.
Resistance – It is the act of opposing or withstanding something, or the power to do so. It is a force which acts to stop the progress of something or make it slower. It is also the impediment to gas flow, such as pressure drop or draft loss through a dust collector. It is normally measured in millimeter water column.
Resistance brazing – It is a brazing process in which the heat needed is obtained from the resistance to electric current flow in a circuit of which the work-piece is a part. It is a resistance joining process. The work-pieces are heated locally, and the filler metal which is preplaced between the work-pieces is melted by the heat generated from resistance to the flow of electric current through the electrodes and the work. In the usual application of resistance brazing, the heating current is passed through the joint itself. Equipment is the same as that used for resistance welding, and the pressure needed for establishing electrical contact across the joint is ordinarily applied through the electrodes. The electrode pressure is also the normal means for providing the tight fit needed for capillary behavior in the joint. The heat for resistance brazing can be generated mainly in the workpieces themselves, in the electrodes, or in both, depending on the electrical resistivity and dimensions.
Resistance butt welding – It is used to join components of similar cross section by making a weld across the entire section in a single operation. Heat is produced in the weld region by resistance to the passage of the welding current through the parts, which are held under a preset end force. As the material heats, the force forges the soft material to consolidate and complete the joint. Resistance butt welding is hence a solid-state process. The force across the interface causes deformation which brings the surfaces into sufficiently close contact to make a weld, and there is some expulsion of material which carries oxide film and contaminants out of the joint. Applications include wire and rod joints up to about 16 millimeters diameter, including chain, and narrow strip joints such as automobile road wheel rims.
Resistance, electrical – It is a measure of its opposition to the flow of electric current. Electrical resistance shares some conceptual parallels with mechanical friction. The unit of electrical resistance is the ohm. The resistance of an object depends in large part on the material it is made of. Objects made of electrical insulators like rubber tend to have very high resistance, while objects made of electrical conductors like metals tend to have very low resistance.
Resistance, flow – It is the reciprocal of conductance.
Resistance furnaces – In these furnaces, heat transfer occurs either directly or indirectly as per Ohm’s and Joule’s laws. They can be operated in an alternating current or direct current mode. Furnaces which implement direct resistance include (i) resistance furnaces for solid-state reactions (production of graphite and carbides), (ii) resistance furnaces for the production of copper, nickel, iron, tin, and zinc or their intermediate products from oxides and sulphides and slags, (iii) electro slag refining (ESR) for the production of clean ferrous or non-ferrous metals and alloys such as titanium, steels, and super alloys, (iv) furnaces which employ a combination of arc and resistance heating are used for the production of calcium carbide , ferroalloys, liquid iron, phosphorus, and silicon compounds by reduction, (v) fused-salt electrolysis cells for the production of aluminum and alkali metals can also be considered to be electrochemical thermal reactors, and (vi) salt-bath furnaces for the heat treatment of metals.
Resistance fusion welding – It is also known as electric resistance welding (ERW).It is a welding process which joins metals by passing a strong electric current through the metal combination, generating heat through electrical resistance, and applying pressure to fuse the materials together.
Resistance heating – It is the heating because of the heat generated due to the resistance of the heat conductor. It normally involves the highest electricity costs, and can need circulating fans to assure the temperature uniformity usually achievable by the flow motion of the products of combustion in a fuel-fired furnace. Silicon control rectifiers have made input modulation more economical with resistance heating. Various materials are used for electric furnace resistors. The common material which is used is nickel-chromium alloy, in the form of rolled strip or wire, or of cast zigzag grids (mostly for convection). Other resistor materials are molten glass, granular carbon, solid carbon, graphite, or silicon carbide. It is occasionally possible to use the load that is being heated as a resistor.
Resistance seam welding – It is a resistance welding process which produces coalescence at the faying surfaces of overlapped parts progressively along a length of a joint. The weld can be made with over-lapping weld nuggets, a continuous weld nugget, or by forging the joint as it is heated to the welding temperature by resistance to the flow of the welding current.
Resistance sintering under pressure – It is a hot-pressing technique where a powder compact is simultaneously heated by passing a low voltage, high amperage current through it while applying pressure, leading to densification and consolidation of the material.
Resistance soldering – It is a soldering process in which the heat needed to melt the solder is developed by the resistance of the material when a large electrical current is supplied. Resistance soldering can be applied to electrically conductive materials which allow the passage of electric current. The process can be used for selective spot soldering of conductive materials which allow the passage of electric current. The process can be used for selective spot soldering of small components, for the soldering of closely placed parts on an assembly, or for heat restriction when necessary. It is similar in several ways to resistance brazing. When the current is applied, rapid local heating occurs, melting the solder. This molten solder wets the surface. As a result, the resistance in the material falls and the current increases, tripping a control. The heat rapidly dissipates into the surrounding area, and the solder quickly solidifies. The resistance soldering process can be used in all soldering operations and with all solderable metals. The only limitations are the thickness and the design of the parts to be soldered. Resistance soldering is used to join steels (e.g., carbon, low alloy, and stainless) and non-ferrous alloys (e.g., aluminum and aluminum alloys, nickel and nickel alloys, and copper and copper alloys) up to 3.2 millimeters in thickness.
Resistance spot welding – It is a resistance welding process which produces coalescence at the faying surfaces of a joint by the heat obtained from resistance to the flow of welding current through the work-pieces from electrodes that serve to concentrate the welding current and pressure at the weld areas.
Resistance temperature detector (RTD) – It is a device which measures temperature through the resistance of a conductor. Resistance of the conductor can vary with time. It is this property of the conductor that is used for industrial temperature measurement. The primary purpose of the resistance temperature detectors is to produce a resistance alteration in response to temperature. Metals normally show high temperature coefficients, indicating resistance increases as temperature rises. On the other hand, carbon and germanium typically demonstrate low temperature coefficients, hence showing a resistance decrease with increasing temperature.
Resistance thermometer – It is an instrument for measuring electrical resistance which is calibrated in units of temperature instead. Resistance thermometers are made of a pure metal, such as platinum, nickel, or copper. The electrical resistance of such a material is almost linearly dependent on temperature. Resistance thermometers are stable, having a small drift.
Resistance to slag, glass melts, gasses, and vapours – The slag resistance characterize the resistance of refractories to chemical attack of any type, including that of glass and vapours. The destructive agents coming into contact with refractories are of different composition and the destruction processes are correspondingly many. The method of determination of slag resistance is described in various standards. Refractory brick destructions are not only caused by liquid slags and glass melts but gasses and vapours also influence the service life of the refractory bricks due to several individual reasons.
Resistance welding – It consists of a group of welding processes which produce coalescence of metals with resistance heating and pressure.
Resistance welding electrode – It is the part(s) of a resistance welding machine through which the welding current and, in majority of the cases, force is applied directly to the work. The electrode can be in the form of a rotating wheel, rotating bar, cylinder, plate, clamp, chuck, or modification thereof.
Resistance welding gun – It is a manipulatable device to transfer current and provide electrode force to the weld area (normally in reference to a portable gun).
Resistive circuit – It is a circuit containing resistive elements only, and no capacitors or inductors.
Resistive force – It is also called friction. It is the force which is the resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Types of resistive force include dry, fluid, lubricated, skin, and internal and several others. The study of the processes involved is called tribology.
Resistive pressure measurement – The principle of resistive pressure measurement is based on the measurement of the change in resistance of electric conductors caused by a pressure-dependent deflection. The equation applied for the resistance of an electric conductor is R = r. (l/a) where ‘R’ is electrical resistance, ‘r’ is resistivity, ‘l’ is length, and ‘a’ is the cross-sectional area. If a tensile force is applied to the conductor, its length increases and its cross-sectional area decrease. The resistivity of a metallic conductor is a (temperature-dependent) constant for a particular material and, hence, independent of the geometry, so the electrical resistance increases as a result of the elongation. In the case of compression, the opposite applies. The principle of resistive pressure measurement is achieved using a main body which shows a controlled deflection under pressure. This main body frequently has a ‘thin’ area referred to as the diaphragm, which is weakened intentionally. The degree of deflection caused by the pressure is measured using metallic strain gauges.
Resistivity – It is the property of a material which impedes current flow. It is the ability of a material to resist passage of electrical current either through its bulk or on a surface.
Resistivity survey – It is a geophysical technique which is used to measure the resistance of a rock formation to an electric current.
Resistor – It is a circuit component which primarily has resistance. It is a passive two-terminal electrical component which implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses. High-power resistors which can dissipate several watts of electrical power as heat can be used as part of motor controls, in power distribution systems, or as test loads for generators. Fixed resistors have resistances which only change slightly with temperature, time, or operating voltage. Variable resistors can be used to adjust circuit elements (such as a volume control or a lamp dimmer), or as sensing devices for heat, light, humidity, force, or chemical activity. Resistors are common elements of electrical networks and electronic circuits. Practical resistors as discrete components can be composed of different compounds and forms. Resistors are also implemented within integrated circuits.
Resite – It is also called C-stage. It is the final stage in the reaction of certain thermosetting resins in which the material is practically insoluble and infusible. The resin is in a fully cured thermoset moulding is in this stage.
Resitol – It is also called B-stage. It is an intermediate stage in the reaction of certain thermosetting resins in which the material softens when heated and is plastic and fusible but does not entirely dissolve or fuse. The resin is in an uncured prepreg or premix is normally in this stage.
Resole – It is also called A-stage. It is an early stage in the preparation of certain thermosetting resins in which the material is still soluble in certain liquids, and can be liquid or capable of becoming liquid upon heating.
Resolution – It is the capacity of an optical or radiation system to separate closely spaced forms or entities, in addition, the degree to which such forms or entities can be discriminated. Resolution is normally specified as the minimum distance by which two lines or points in the object are to be separated before they can be revealed as separate lines or points in the image.
Resolver – It is a transformer-like rotary transducer which measures rotation as an analog value.
Resolving power – It is the ability of a given lens system to reveal fine detail in an object.
Resonance – It is a phenomenon which occurs when an object or system is subjected to an external force or vibration that matches its resonant frequency, defined as the frequency which generates the maximum amplitude response in the system. In chemistry, resonance is a way of describing bonding in certain molecules or polyatomic ions by the combination of several contributing structures (or forms, also variously known as resonance structures or canonical structures) into a resonance hybrid (or hybrid structure) in valence bond theory. It has particular value for analyzing delocalized electrons where the bonding cannot be expressed by one single Lewis’s structure. The resonance hybrid is the accurate structure for a molecule or ion. It is an average of the theoretical (or hypothetical) contributing structures.
Resonant cavity – It is an opening which when excited by an electron stream or other means, oscillates at a particular frequency.
Resonant inductive coupling – It is a form of energy transfer between two physically close tuned circuits.
Resource – Resource is a concentration of naturally occurring solid, liquid, or gaseous material in or on the earth’s crust in such form and amount that economic extraction of a commodity from the concentration is currently or potentially feasible. It is the calculated quantity of material in a mineral deposit, based on limited drill information.
Resource classification – Resources are also classified as productive resources (which are needed for achieving goals) and administrative resources (which govern the use of productive resources). The growth of the organization is limited by the bundle of productive resources controlled by the organization and by the administrative framework used to organize the use of these productive resources.
Resource management – It is the process of planning, allocating, and controlling resources to achieve an organization’s goals. Ir is an important aspect in managing the efficient and effective deployment and allocation of the organizational resources when and where they are needed. Resource management needs to be systematized for keeping a close eye on the resources. This process of systematization maximizes the efficiency of the available resources as well as minimizing of the wastage of the resources. Resource management is a fundamental aspect of an organization’s performance.
Resource plans – These plans enable organizations to maximize resource utilization, balance supply and demand and plan resources over the entire period needed for the completion of the planned tasks. Organizations can also use resource plans to identify resources, which could include human, capital, time, or technological equipment needed to achieve strategic goals. Resource plans are used to express resource requirements in terms of resources needed over a period of time. The resource planning provides the organizations the several abilities, which include (i) to increase resource utilization by aligning the right resources to the highest priority work, (ii) to link mission, strategy, work and resources to quickly address changes in budget, mission or environment, (iii) to identify quickly the actions needed to reduce risk and increase performance, and (iv) to conduct more efficient analysis and make better decisions based on current, accurate, integrated, and actionable information.
Respiratory protective equipment – It is used to prevent dangerous chemicals from entering the respiratory system of the wearer. It is also used to provide breathing air when working in a dangerous environment where there is risk of oxygen deficiency or presence of dangerous chemicals in the air at high concentrations. There are three basic classes of respirators which are normally used. They are (i) air purifying respirators, (ii) air supplied respirators, and (iii) self-contained respirators.
Response – It is the provision of emergency services and public assistance during or immediately after a disaster in order to save lives reduces health impacts, ensure public safety and meet the basic subsistence needs of the people affected.
Response curve for N cycles – In fatigue-data analysis, it is a curve fitted to observed values of percentage survival at N number of cycles for several stress levels, where N is a preassigned number such as 106, 107, etc. It is an estimate of the relationship between applied stress and the percentage of the population which would survive N cycles.
Response factor – In chromatography, a response factor is defined as the ratio between the concentration of a compound being analyzed and the response of the detector to that compound. A chromatogram shows a response from a detector as a peak. While there are several ways to quantify the peak, one of the most common is peak area, hence ‘response factor = peak area / concentration. It is important to remember that variations in a gas chromatography (GC) system and analysis methodology can be the cause of a deviation in the response factor.
Response surface modeling – It is a statistical, mathematical, or graphical model which describes the variation of the response variable in terms of the parameters of the problem.
Response time – It is the time needed for a leak detector or leak testing system to yield a signal output equal to 63 % of the maximum signal attained when tracer gas applied continuously to the system under test. In technology, response time is the time a system or functional unit takes to react to a given input. In computing, the responsiveness of a service, how long a system takes to respond to a request for service, is measured through the response time. That service can be anything from a memory fetch, to a disk input-output, to a complex database query, or loading a full web page. Ignoring transmission time for a moment, the response time is the sum of the service time and wait time.
Restoration – It means returning the health of a facility after a disaster to its original condition.
Restoration costs – These costs are the expenses incurred to return something to its original, functional, or natural state, whether it’s a damaged property, an environmental area, or an asset.
Rest potential (Ecorr) – It is the potential of a corroding surface in an electrolyte, relative to a reference electrode. It is also called corrosion potential, open-circuit potential, or freely corroding potential.
Restraint – It is an external mechanical force which prevents a part from moving to accommodate changes in dimension because of the thermal expansion or contraction. It is frequently applied to weldments made while clamped in a fixture.
Restrictor rings – These are rings, normally faced with white metal , placed outside a bearing to prevent fluid from being discharged.
Restrike – It means compacting of a sintered compact.
Restriking – It is the striking of a trimmed but slightly misaligned or otherwise faulty forging with one or more blows to improve alignment, improve surface condition, maintain close tolerances, increase hardness, or effect other improvements. It is a sizing operation in which coining or stretching is used to correct or alter profiles and to counteract distortion. It is also a salvage operation following a primary forging operation in which the parts involved are rehit in the same forging die in which the pieces have been last forged.
Resuing – It is a method of stoping in narrow-vein deposits whereby the wall-rock on one side of the vein is blasted first and then the ore.
Retained austenite – It is the quantity of the high-temperature face-centered cubic phase of iron (austenite) which does not transform to martensite (is retained) when quenched to room temperature. It is the austenite which remains in steel after it has been heat treated and quenched. It occurs when the steel is not quenched to a low enough temperature to transform all of the austenite into martensite.
Retainer – It is also called cage or separator. In a bearing, it is a device which partly surrounds the rolling elements and travels with them, the main purpose of which is to space the rolling elements in proper relation to each other.
Retaining ring – It is a split ring which is used to retain a separable flange on a valve body.
Retardation plate – It is a plate placed in the path of a beam of polarized light for the purpose of introducing a difference in phase. Normally quarter-wave or half-wave plates are used, but if the light passes through them twice, the phase difference is doubled.
Retarding admixtures – These admixtures are used to slow the setting of the concrete and to retard temperature increases. They consist of various acids or sugars or sugar derivatives. Retarding admixtures are particularly useful for large pours where significant temperature increases can occur. They also prolong the plasticity of the concrete, enabling better blending or bonding of successive pours. Retarding admixtures can also slow the hydration of cement on exposed concrete surfaces or formed surfaces to produce attractive exposed aggregate finishes.
Retention pond – It is the temporary containment for a material in an area where it can be treated for proper disposal.
Retention time (RT) – It is a measure of the time taken for a solute to pass through a chromatography column. It is calculated as the time from injection to detection. The retention time for a compound is not fixed as several factors can influence it even if the same gas chromatograph and column are used. These include (i) the gas flow rate, (ii) temperature differences in the oven and column, (iii) column degradation, and (iv) column length. These factors can make it difficult to compare retention times. Even if a person uses the same gas chromatograph just a few days apart, there can be small differences in the retention time of a compound.
Retracting die – It is the part of a method of stripping the compact from the die used.
Retrofitting – It consists of reinforcement or upgrading of existing structures to become more resistant and resilient to the damaging effects of hazards. Retrofitting needs consideration of the design and function of the structure, the stresses which the structure can be subject to from particular hazards or hazard scenarios and the practicality and costs of different retrofitting options. Examples of retrofitting include adding bracing to stiffen walls, reinforcing pillars, adding steel ties between walls and roofs, installing shutters on windows and improving the protection of important facilities and equipment.
Retort – It is a laboratory apparatus which is used for distillation of volatile materials, as in separation of some metals and in destructive distillation of coal. It traditionally consists of a spherical vessel with a long, downward-pointing neck which conducts the condensed vapours produced by distillation into a separate collection vessel.
Return air – It is the air which is removed from conditioned spaces that is either recirculated or exhausted to the outside.
Return current path – It is the path through which the current in an electric cell returns to the source.
Return fine – mosaic embedding iron ore sintering (RF-MEBIOS) process – This process has been developed in order to increase the permeability of the sintering bed for sinter ore productivity. The return fine – mosaic embedding iron ore sintering’ process is a technique in which return fine by-passes granulation. In this process, return fine as dry particle is added to granulated raw materials and then charged into the sintering machine which results into productivity increase of the sintering machine. The productivity increase is caused by increasing the pseudo-particle size at granulation and by decreasing the bulk density of the sinter packed bed after charging. The former is achieved by higher moisture content in the raw materials at granulation. The latter is achieved by higher friction in the sintering bed composed of a dry and wet particle compound, which has a role of decreasing bulk density. By increasing the by-pass return fine ratio and size, the sintering speed and sinter productivity is increased.
Return flow oil burner – It is a mechanical atomizing oil burner in which part of the oil supplied to the atomizer is withdrawn and returned to storage or to the oil line supplying the atomizer.
Return loss – It is a measure of the power loss because of a signal reflection by a discontinuity in a transmission line or an optical fibre.
Reuse – It means using items again by repairing, donating, or selling them. Reuse is even better than recycling since the item does not have to be reprocessed before it can be used again.
Reverberatory furnace – It is a long, flat furnace which is used to slag gangue minerals and produce a matte. It is a furnace in which the flame used for melting the metal does not impinge on the metal surface itself, but is reflected off the walls of the root of the furnace. The metal is actually melted by the generation of heat from the walls and the roof of the furnace.
Reverse-acting actuator – It is an actuator in which the actuator stem retracts with increasing loading pressure. Reverse actuators have a seal bushing installed in the upper end of the yoke to prevent leakage of the loading pressure along the actuator stem.
Reverse air fabric filters – In these fabric filters, the bags are fastened onto a cell plate at the bottom of the filter and suspended from an adjustable hanger frame at the top. Dirty gas normally enters the filter and passes through the bag from the inside, and the dust collects on the inside of the bags. These filters are compartmentalized to allow continuous operation. Before a cleaning cycle begins, filtration is stopped in the compartment to be cleaned. Bags are cleaned by injecting clean air into the dust collector in a reverse direction, which pressurizes the compartment. The pressure makes the bags collapse partially, causing the dust cake to crack and fall into the hopper below. At the end of the cleaning cycle, reverse airflow is discontinued and the compartment is returned to the main stream. The flow of the dirty gas helps maintain the shape of the bag. However, to prevent total collapse and fabric chafing during the cleaning cycle, rigid rings are sewn into the bags at intervals. Space requirements for a reverse air fabric filter are comparable to those of a mechanical shaker filter. The maintenance needs are somewhat higher.
Reverse bending deformation process – It is based on the principle that steel rod is ductile and the hot rolled scale is brittle. When the rod is deformed, the steel bends, but the hot rolled scale breaks and is released from the surface of the rod and fall away provided the scale is there in sufficient quantity and there is sufficient deformation. The deformation mode is principally bending, but can also include stretching deformation. The equipment for the reverse bending deformation process is to use the principle of reverse bending in a controlled manner to achieve consistent results of scale removal without unduly affecting the properties of the steel rod being descaled. One of the important factors affecting the descaling process is the quantity of total deformation of the steel rod. It is normally considered that the optimum quantity of rod deformation necessary for the complete scale breaking ranges from 8 % to 10 %. Less than 8 % can result in incomplete scale breaking, leaving patches of adherent scale, and more than 10 % normally does not accomplish any additional scale breaking, while at the same time adding an undesirable amount of work hardening to the steel. An additional undesirable effect of heavy deformation (higher than 10 %) is the increased back tension on the rod line which can stretch and neck down the steel rod, affecting rod drafting schedules and requiring more power from the first block to pull the rod through the descaling system. The objective of 8 % to 10 % deformation is controlled by the relationship between the size of the sheaves used to do the reverse bending and the size of the steel rod being processed.
Reverse-current cleaning – It is the electrolytic cleaning in which a current is passed between electrodes through a solution, and the part is set up as the anode. It is also called anodic cleaning.
Reversed-phase chromatography (RPC) – It is the bonded-phase chromatography with a non-polar stationary phase and a polar mobile phase.
Reverse drawing – It is the redrawing of a sheet metal part in a direction opposite to that of the original drawing.
Reverse engineering – it is also known as backwards engineering or back engineering). It is a process or method through which a person attempts to understand through deductive reasoning how a previously made device, process, system, or piece of software accomplishes a task with very little (if any) insight into exactly how it does so. Depending on the system under consideration and the technologies used, the knowledge gained during reverse engineering can help with repurposing obsolete objects, doing security analysis, or learning how something works.
Reverse extrusion – It is also known as indirect extrusion or backward extrusion. It is a metal-working process where the die is stationary, and the billet (the metal being shaped) and container move together, forcing the metal to flow in the opposite direction of the ram’s movement.
Reverse flange – It is a sheet metal flange made by shrinking, as opposed to one formed by stretching.
Reverse flow – It refers to the phenomenon where the direction of the liquid flow in a pipe, changes completely, becoming extremely disordered with tangled and meandering paths, as opposed to the smooth and orderly laminar flow. In case of valve, reverse flow is the flow from the shaft / hub side over the back of the disk, ball, or plug. Some rotary control valves are capable of handling flow equally well in either direction. Other rotary designs can need modification of actuator linkage to handle reverse flow.
Reverse helical winding – In filament winding, as the fibre delivery arm traverses one circuit, a continuous helix is laid down, reversing direction at the polar ends, in contrast to biaxial, compact, or sequential winding. The fibres cross each other at definite equators, the number depending on the helix. The minimum region of crossover is three.
Reverse impact test – It is a test in which one side of a sheet of material is struck by a pendulum or falling object, and the reverse side is inspected for damage.
Reverse osmosis (RO) – It is a treatment process which is used in drinking water systems by adding pressure to force water through a semi-permeable membrane. Reverse osmosis removes salinity and majority of the drinking water contaminants and produces a waste stream of highly saline water. It is also used in wastewater treatment.
Reverse polarity – 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. It is also known as direct current electrode positive (DCEP).
Reverse probe – It normally refers to a probe or test point which is mounted in a way that makes it harder to access, frequently for protection or to avoid accidental contact, as opposed to a ‘forward probe’ which is easily accessible.
Reverse pulse jet fabric filter – In these filters, individual bags are supported by a metal cage, which is fastened onto a cell plate at the top of the filter. Dirty gas enters from the bottom of the filter and flows from outside to inside the bags. The metal cage prevents collapse of the bag. Bags are cleaned by a short burst of compressed air injected through a common manifold over a row of bags. The compressed air is accelerated by a venturi nozzle mounted at the reverse jet filter top of the bag. Since the duration of the compressed-air burst is short (0.1 second), it acts as a rapidly moving air bubble, traveling through the entire length of the bag and causing the bag surfaces to flex. This flexing of the bags breaks the dust cake, and the dislodged dust falls into a storage hopper below. Reverse pulse jet fabric filters can be operated continuously and cleaned without interruption of flow because the burst of compressed air is very small compared with the total volume of dusty air through the collector. Because of this continuous cleaning feature, these filters are normally not compartmentalized. The short cleaning cycle of these filters reduces recirculation and redeposit of the dust. These filters provide more complete cleaning and reconditioning of bags than shaker or reverse air cleaning methods. Also, the continuous-cleaning feature allows them to operate at higher air-to-cloth ratios, so the space requirements are lower. This cleaning system works with the help of digital sequential timer attached to the fabric filter. This timer indicates the solenoid valve to inject the air to the blow pipe.
Reverse redrawing – It is s second drawing operation in a direction opposite to that of the original drawing.
Reverse sigmoid curve – It refers to the inverse of the sigmoid function. It is also known as the logit function or log-odds function, which maps a probability (0 to 1) to a real-valued log-odds.
Reversible conveyor belt – It is a type of conveyor system which can change its direction of travel, offering flexibility in material handling and storage applications. The main characteristic is the ability to switch the direction of material flow, allowing for movement in both directions.
Reversible process – It is a process, involving a system and its surroundings, whose direction can be reversed by infinitesimal changes in some properties of the surroundings, such as pressure or temperature.
Reversible reaction – It is a chemical reaction which can proceed in either direction depending on the reaction conditions, i.e., from reactants to products or from products to reactants, especially implying one in which both conversions occur simultaneously.
Reversible temper embrittlement – It is a phenomenon in certain alloy steels where holding or slowly cooling through a specific temperature range (around 400 deg C to 600 deg C) leads to a loss of ductility and toughness, but this embrittlement can be reversed by reheating above 600 deg C and rapid cooling.
Reversible thermal expansion – Refractories like any material expand when heated, and contracts when cooled. The reversible thermal expansion is a reflection on the phase transformations which occur during heating and cooling. The reversible expansion are followed in the design of refractory lining for provision of expansion joints. As a rule, those with a lower thermal expansion co-efficient are less susceptible to spalling.
Reversing mills – These are those rolling mills in which the rolling direction changes after each pass. In these mills the rolls are stopped, reversed, and then brought back up to rolling speed after each pass. In these mills the material is being rolled moves in to and fro directions. Heavy primary mills for bloom and slab rolling are the most common types of reversing mills, but others, including some cold rolling mills, are also reversing mill.
Reversing roller conveyor – In a reversing processing conveyor, the direction of rotation of the driven rollers is changed frequently. As a result, the additional inertial forces for accelerating or decelerating the rollers and the load have to be taken into consideration. The maximum peripheral acceleration of the roller is kept within limits, such that the load moves on rollers without sliding (also called skidding). There is no sliding when the frictional force between roller and load is more than the inertial force needed to accelerate the load.
Reversing shuttle conveyor – It is used for building an in-line, continuous pile, or for feeding multiple fixed discharge points. Similar in form to a troughed belt conveyor, reversing shuttle conveyors are designed with traveling shuttle functionality. The shuttle functionality allows the conveyor to be moved along a track, as well as convey material in both directions, creating opportunity for extreme flexibility. The conveyor is typically half the length of the track rails, e.g., a 100 meters long shuttle conveyor has the ability to transport material throughout the length of a 200 meters storage facility.
Reward system – It is a set of incentives which is given in exchange for specific behaviours, actions, or achievements. It can be used to motivate employees, encourage customers, or promote healthy competition.
Rework – It is an action taken on non-conforming products or services to allow them to meet the original specifications.
Reyn – It is the former English unit of dynamic viscosity.
Reynold’s equation – It is a basic equation of hydrodynamic lubrication.
Reynolds number (Re) – It is a dimensionless quantity which helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. It is a derived relationship combining the density and viscosity of a liquid with its velocity of flow and the cross-sectional dimensions of the flow and takes the form R = (V x D x d)/v, where ‘V’ is the average fluid velocity, ‘D’ is the diameter of the pipe, ‘d’ is the density of the liquid, and ‘v’ is the absolute viscosity. At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers, flows tend to be turbulent. The turbulence results from differences in the fluid’s speed and direction, which can sometimes intersect or even move counter to the overall direction of the flow (eddy currents). These eddy currents begin to churn the flow, using up energy in the process, which for liquids increases the chances of cavitation. The Reynolds number has wide applications, ranging from liquid flow in a pipe to the passage of air over an aircraft wing. It is used to predict the transition from laminar to turbulent flow and is used in the scaling of similar but different-sized flow situations. The predictions of the onset of turbulence and the ability to calculate scaling effects can be used to help predict fluid behaviour on a larger scale, such as in local or global air or water movement, and thereby the associated meteorological and climatological effects.
R-factor It is also called residual factor or reliability factor or the R-value. It is a measure of the disagreement between the crystallographic model and the experimental X-ray diffraction data. Lower is the R-value lower is the disagreement or better is the agreement. In other words, it is a measure of how well the refined structure predicts the observed data. The value is also sometimes called the discrepancy index, since it mathematically describes the difference between the experimental observations and the ideal calculated values.
RF connector – It is an electrical fitting which is used to connect cables carrying radio frequency (RF) currents.
RF engineering – It is the profession which deals with application of radio frequency (RF) energy to useful ends.
RH degassing process – RH degassing process has been named after Ruhrstahl and Heraeus where this process was initially developed. It is normally used for mass production of steel in order to reduce gases and carbon contents in the liquid steel. The main functions of RH degassing plant is the removal of hydrogen, natural and forced decarburization, chemical heating of the liquid steel, and for the precise adjustment of the chemical analysis and temperature of the liquid steel. These activities are carried out under vacuum conditions. The selection of RH degassing is strictly dictated by steel grades to be produced in the steel plant. In the majority of the cases, the installation of RH degassing is more dominant, especially for big heat size, because of its excellent mixing performance, and short cycle time for decarburization and degassing which results into a large number of heats treated per day. Further, due to the excellent mixing behaviour achieved during the process, this short treatment time is attainable irrespective of the size of the ladle. A lot of process improvements have been done on the RH degassing plant since its introduction. These improvements include the installation of oxygen lance, the enlargement of snorkel and vessel diameters, as well as the application of powder injection for desulphurization. When equipped with an additional top-lance, the RH degassing is called RH-TOP degassing. RH degassing unit typically consists of a refractory lined block-type or split-type vessel, equipped with two refractory lined snorkels at the vessel bottom, which is connected to a vacuum pump. Further components are a hydraulic or mechanical vessel or ladle lifting system, in case of an RH-TOP, a multiple function top blowing lance, and a measuring and sampling system. Material addition under vacuum is executed by means of a vacuum hopper system. Refractory repair and preheating of vessels, snorkels and top part can be executed in separate stands. Characteristics of the design are the single vessel installation (vessel lifting system), fast vessel exchange (ladle lifting system) or duplex vessel installation for increased availability. Comprehensive model for decarburization on RH degassing plant has been introduced by Kuwabara considering the vacuum pressure, lift gas flow rate, vessel as well snorkel diameters. It has been reported that the time needed to achieve carbon content of less than 20 ppm (parts per million) can be completed in less than 15 minutes in a RH degassing plant.
Rhenium (Re) – It is a chemical element having atomic number 75. It is a silvery-gray, heavy, transition metal. With an estimated average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the earth’s crust. It has one of the highest melting and boiling points of any element. It resembles manganese and technetium chemically and is mainly obtained as a by-product of the extraction and refinement of molybdenum and copper ores. It shows in its compounds a wide variety of oxidation states ranging from −1 to +7.
Rheocasting – It is the casting of a continuously stirred semi-solid metal slurry. The process involves vigorous agitation of the melt during the early stages of solidification to break up solid dendrites into small spherulites.
Rheodynamic lubrication – It is a regime of lubrication in which the rheological (non-Newtonian) properties of the lubricant predominate. This term is especially applied to lubrication with grease.
Rheology – It is the study of the flow of matter, mainly in a fluid (liquid or gas) state but also as soft solids or solids under conditions in which they respond with plastic flow rather than deforming elastically in response to an applied force. Rheology deals with the deformation and flow of materials, both solids and liquids.
Rheopectic material – It is a material which shows an increase in viscosity with time under a constant shear stress. After removal of the shear stress, the viscosity slowly returns to its original level.
Rheoscope – It is obsolete name for an ammeter; now an instrument for measuring fluid viscosity.
Rheostat – It is obsolete name for a two terminal variable resistor, normally with a rotating shaft to allow manual or motor driven adjustment.
Rhodium (Rh) – It is a chemical element having symbol Rh and atomic number 45. It is a very rare, silvery-white, hard, corrosion-resistant transition metal. It is a noble metal and a member of the platinum group. It has only one naturally occurring isotope, which is 103Rh.
Rhombohedral – It is having three equal axes, with the included angles equal to each other, but not equal to 90-degree.
Rhombohedral crystal – It is defined as a crystal structure with a rhombohedral shape and a specific arrangement of atoms, such as Bi2Se3, which shows a layered structure with a hexagonal lattice within each layer.
Rhombohedral crystal system – It is also known as the trigonal system. It is a crystal system characterized by three equal and interchangeable axes at equal angles to each other, and is frequently considered a division of the hexagonal system.
Rhyolite – It is a fine-grained, extrusive igneous rock which has the same chemical composition as granite.
Rib – It is a long V-shaped or radiused indentation which is used to strengthen large sheet metal panels. It is also a long, normally thin protuberance which is used to provide flexural strength to a forging (as in a rib-web forging).
Rib mark – It is a curved line on a crack surface, normally convex in the general direction toward which the crack is running. The term is useful in referring to a mark of this shape until its specific nature is learned.
Rib samples – Theses sample consist of ore taken from rib pillars in a mine to determine metal content.
Richter scale – It is the most common standard of measurement for earthquakes. It is used to rate the magnitude of an earthquake, which is the quantity of energy released during an earthquake. he Richter scale does not measure quake damage which is dependent on a variety of factors including population at the epicentre, terrain, depth, etc. The Richter magnitude involves measuring the amplitude (height) of the largest recorded wave at a specific distance from the seismic source. Adjustments are included for the variation in the distance between the various seismographs and the epicentre of the earthquakes. The Richter scale is a base-10 logarithmic scale, meaning that each order of magnitude is 10 times more intensive than the last one. In other words, a two is 10 times more intense than a one and a three is 100 times higher. In the case of the Richter scale, the increase is in wave amplitude. That is, the wave amplitude in a level 6 earthquake is 10 times higher than in a level 5 earthquake, and the amplitude increases 100 times between a level 7 earthquake and a level 9 earthquake. The quantity of energy released increases 31.7 times between whole number values.
Ridging (wear) – It is a deep form of scratching in parallel ridges normally caused by plastic flow of the subsurface layer.
Rigger – Rigger is a skilled tradesperson who specializes in using rigging equipment and techniques to safely secure and move heavy loads using cranes, hoists, and other lifting devices.
Rigging – It consists of the engineering design, layout, and fabrication of pattern equipment for producing castings, including a study of the casting solidification programme, feeding and gating, risering, skimmers, and fitting flasks. In handling of materials, rigging is both a noun, the equipment, and verb, the action of designing and installing the equipment, in the preparation to move objects. A team of riggers design and install the lifting or rolling equipment needed to raise, roll, slide or lift objects such as heavy machinery, structural components, building materials, or large-scale fixtures with a crane, hoist, or a block and tackle. Rigging comes from rig, to set up or prepare. Rigging is the equipment such as wire rope, turn-buckles, clevis, jacks which is used with cranes and other lifting equipment in material handling and structure relocation. Rigging systems normally include shackles, master links and slings, and lifting bags in underwater lifting.
Right hand lang lay – In wire rope construction, a right-hand lang lay (RHLL) means the strands are twisted clockwise around the core, and the wires within those strands are also twisted in the same clockwise direction.
Right hand lay – In wire rope construction, right-hand lay refers to the direction in which the strands are twisted around the core, with the strands appearing to rotate clockwise when viewed from the end.
Right-hand ordinary lay (RHOL) – It is also known as a right-hand regular lay. It is a type of wire rope where the individual wires within the outer strands are twisted in the opposite direction to the strands themselves, resulting in a clockwise (right-hand) twist of the strands around the core. similar to a right-hand screw thread.
Right-hand regular lay – In right hand regular lay rope, the wires within the strands are twisted in the opposite direction to the strands themselves, resulting in the wires running along the axis of the rope, and the strands twisting in a right-hand (clockwise) direction.
Right-hand rule – It is a mnemonic (designed to aid the memory) device for remembering the definitions of the directions of current and magnetic field in generators.
Rigid body – It is a solid body in which deformation is zero or negligible, when a deforming pressure or deforming force is applied on it. The distance between any two given points on a rigid body remains constant in time regardless of external forces or moments exerted on it. A rigid body is normally considered as a continuous distribution of mass.
Rigid container sheet – In the context of packaging, it refers to a firm, non-flexible sheet material used to create containers which retain their shape and provide protection to the contents, unlike flexible packaging.
Rigid couplings – These couplings are used for shafts having no misalignment. Since these couplings cannot absorb any misalignment the shafts to be connected by a rigid coupling must have good lateral and angular alignment. As compared with flexible couplings, rigid couplings have limited application. Rigid couplings do not have the ability to compensate for shaft misalignments and are therefore used where shafts are already positioned in precise lateral and angular alignment. Any misalignment between shafts will create high stresses and support bearing loads. Rigid couplings are typically used in applications involving vertical drivers. The rigid coupling transmits not only the rotational motion from the driver (typically an electric motor) to the rotating element of the equipment, but any axial movement (up or down) which occurs between the two pieces of equipment is also transmitted between them. Because of rigidity of the couple, the equipment must be in precise alignment and cannot accept any misalignment.
Rigid packaging – It is designed to be protective and withstand potential impact without breaking or compromising integrity. For this reason, rigid containers are typically used to store products which need special protection against damage, heat, light, odours, and more.
Rimming steel – It is a low-carbon steel containing sufficient iron oxide to give a continuous evolution of carbon mono-oxide while the ingot is solidifying, resulting in a case or rim of metal virtually free of voids. These are steels possessing a rim of purer material (with maximum freedom from surface defects) and is associated with evolution of carbon mono-oxide gas occurring because of the interaction of dissolved iron oxide and carbon during the solidification of low carbon and low manganese steel made under controlled deoxidation. The composition and extent of the rim can be varied and, if needed, by arresting the rimming action after sometime. This steel can be produced with an outer layer of very pure iron which gives rise to a sheet and strip products with excellent surface quality and good formability. The widespread adoption of the continuous casting process has resulted in rimming steels generally being replaced by killed steels.
Ring and circle shear – It is a cutting or shearing machine with two rotary-disk cutters driven in unison and equipped with a circle attachment for cutting inside circles or rings from sheet metal, where it is impossible to start the cut at the edge of the sheet. One cutter shaft is inclined to the other to provide cutting clearance so that the outside section remains flat and usable.
Ring compression type couplings – The coupling consists of two cones which are placed on the shafts to be coupled and a sleeve that fits over the cones. Three bolts are used to draw the cones towards each other and thus wedge them firmly between the shafts and the outer sleeve.
Ringelmann chart – It is a series of four rectangular grids of black lines of varying widths (shade 2 to shade 5) printed on a white background, and used as a criterion of blackness for determining smoke density in stack gas streams. Shade 1 is slightly grey and is normally categorized by air pollution boards as acceptable.
Ringelmann scale – It is also called Ringelmann smoke chart, or simply Ringelmann chart. It is a scale for measuring the apparent density or opacity of smoke. The scale has 5 levels of density inferred from a grid of black lines on a white surface which, if viewed from a distance, merge into known shades of grey. Shade 1 is slightly grey and is normally categorized by air pollution boards as acceptable. It corresponds to an opacity of 20 %. Shades 2, 3, 4 and 5 correspond to opacities of 40 %, 60 %, 80 % and 100 % (completely black) and are normally considered to be ‘black smoke’ by air pollution boards of majority of the countries.
Ring joint facing flange – It is also known as RTJ flange. It is normally used for a leak-proof connection in high pressure applications. The flange has a hexagonal groove sealing surface and is fitted with a metal ring which is compressed in a groove.
Ring rolling – It is one of the metal-forming operations which decreases the thickness (cross section) and increases the diameter (circumference) of the work-piece by squeezing effect as it passes between two rotating rolls. It is an advanced technique, extensively used to produce seamless rings which are normally being used as flanges, pipe flanges, ring gears, structural rings, gas-turbine rings, nuclear reactor parts, aero-engine casing, and different connecting flanges. Ring rolling is an incremental bulk metal forming process used for the production of seamless rings with a wide variety of sizes and shapes as well as processable materials, which allows application of rolled rings in several industries. The process works by reducing a pre-formed cross-sectional area of a ring in two roll gaps, increasing its diameter. For achieving this, a non-driven mandrel moves in the direction of the rotationally driven main-roll in the radial roll gap, reducing the wall thickness of a ring. Also, two driven conical rolls located vertically on the opposite side of the machine shape the axial roll gap, in which the height of the ring is reduced by downwards movement of the upper roll. Two guide rolls ensure circularity as well as alignment of the ring in the machine by inducing lateral forces aiming inwards on both sides of the axis of the machine.
Ring rolling mills – In the ring rolling mills, the donut shape pre-formed work piece is placed between a free turning inside roll and a driven outside roll. The ring rolling mills make the section thinner while increasing the ring diameter. Several cross-sections can be formed by the ring rolling.
Ring seal – It is a piston ring-type seal which assumes its sealing position under the pressure of the fluid to be sealed.
Ring type joint – Ring type gaskets are to be used on the flanges with this type of facing. This type of facing is used in severe service conditions and for hazardous fluids. It is used in petroleum, petrochemical and high-pressure gas pipe work and equipments. Since close tolerances and high standards of machining are required, as a result this type of flange facing is seldom used for flange diameters larger than 900 millimeters. The main disadvantage of this type of facing is the high cost of manufacturing. It is the most expensive face.
Rinsability – It is the relative ease with which a substance can be removed from a metal surface with a liquid such as water.
Rinsing – It is removing of any active solution from the surface of steel by immersion in water rust, corrosion product consisting of hydrated iron oxides.
Ripple – It is a periodic variation in the amplitude of a direct current signal, such as found in a power supply with partly effective filtering. It is the regular modulations in the direct current output wave of a rectifier unit, or a motor-generator set, originating from the harmonics of the alternating current input system in the case of a rectifier, or from the harmonics of the induced voltage of a motor-generator set.
Ripple current – It refers to the unwanted alternating current component which remains in the output current of a power supply, typically after rectification and filtering, and can lead to increased heat dissipation and potential failure of components like capacitors.
Ripple formation – It is the formation of periodic ridges and valleys transverse to the direction of motion on a solid surface. It is also referred to as rippling.
Ripple mark – It is a rib mark with wavelike contour caused by temporary excursion of the crack front out of plane in response to a tilt in the axis of principal tension induced by an elastic pulse. Such marks frequently appear as a series of curved lines, indicating the direction of propagation of the fracture from the concave to the convex side of a given Wallner line, and are sometimes observed when viewing brittle fracture surfaces at high magnification in an electron microscope. Wallner lines are attributed to interaction between a shock wave and a brittle crack front propagating at high velocity. Sometimes a ripple mark is misinterpreted as a fatigue striation. It is also known as Wallner line.
Ripple voltage – It is the residual periodic variation of the direct current voltage within a power supply which has been derived from an alternating current source. This ripple is because of the incomplete suppression of the alternating wave-form after rectification. Ripple voltage originates as the output of a rectifier or from generation and commutation of direct current power.
Rip protection steel cord conveyor belt – This type of belt provides excellent rip protection and impact resistance, minimizes damage to belt carcass from sharp objects or strong impact, and prevents the belt from being torn lengthwise by sharp objects inserted between the belt and other equipment. .
Riser – It is a reservoir of molten metal connected to a casting to provide additional metal to the casting, needed as the result of shrinkage before and during solidification. Riser is also that section of pipeline extending from the ocean floor up the platform. Also, it is the vertical tube in a steam generator convection bank that circulates water and steam upward.
Riser blocks – These are plates or pieces inserted between the top of a metal forming press bed or bolster and the die to decrease the height of the die space. (It is also the spacers placed between bed and housings to increase shut height on a four-piece tie-rod straight-side press.
Riser design – It is also known as risering. It deals with the development of suitable reservoirs of feed metal in addition to the desired casting shape so that undesirable shrinkage cavities in the casting are eliminated or moved to locations where they are acceptable for the intended application of the casting. When metals solidify and cool to form a casting, they normally undergo three distinct stages of volume contraction, or shrinkage. These stages are (i) liquid shrinkage which means that the liquid metal loses volume as it gives up superheat and cools to its solidification temperature, (ii) solidification shrinkage which takes place when the metal freezes, i.e., changing from a liquid to a higher-density solid (for pure metals, this contraction occurs at a single temperature, but for alloys it takes place over some range of temperature or freezing interval), (iii) solid shrinkage which takes place when the solid casting cools from its solidification temperature to room temperature. The last of these, solid shrinkage (also called patternmaker’s shrinkage), is accommodated by making the pattern (and hence the mould cavity) somewhat larger than the desired dimensions of the final casting. Liquid shrinkage and solidification shrinkage are the concern of risering practice.
Riser gating – It is the gating system in which molten metal from the sprue enters a riser close to the mould cavity and then flows into the mould cavity.
Rise time – In urethane foam moulding, it is the time between the pouring of the urethane mix and the completion of foaming.
Rising stem – It is a valve stem which rises as the valve is opened.
Rising stem ball valve – It is a single-seated ball valve which is designed to seal by using the valve’s stem to mechanically wedge the valve’s ball into a stationary seat, affecting a bubble-tight seal. The valve’s stem operates through a guide sleeve assembly which guides the stem through a quarter turn of rotation as the stem is raised or lowered by a handwheel (or actuator). The mechanical action of the stem moves the ball away from the seat prior to the 90-degree rotation of the ball. The design provides lower operating torques and longer seat life while assuring bubble-tight shutoff.
Rising stem gate valve – It is designed so that the stem is raised out of the flow path when the valve is open. Rising stem gate valves come in two basic designs. One design has a stem which rises through the handwheel while others have a stem which is threaded to the bonnet.
Rising stem with inside screw – In this type of stem, the threaded part of the stem is inside the valve body, and the stem packing along the smooth section which is exposed to the atmosphere outside. In this case, the stem threads are in contact with the flow medium. When rotated, the stem and the hand-wheel rise together to open the valve.
Rising stem with outside screw and yoke – In this type of stem, the exterior of the stem is threaded, while the portion of the stem in the valve is smooth. The stem threads are isolated from the flow medium by the stem packing. Two different styles of these designs are available namely one with the hand-wheel attached to the stem, so they can rise together, and the other with a threaded sleeve which causes the stem to rise through the hand-wheel. This type of valve is a common design for 60 millimeters outside diameter pipe size and larger valves.
Risk – It is the probability of damage or injury i.e., the potential for harm to people, property, or the environment. It is the uncertainty which surrounds future events and outcomes. It is the expression of the likelihood and impact of an event with the potential to influence the achievement of an organization’s objectives. Risk is also the probability of a worker suffering an injury or health problem, or damage occurring to property or the environment as a result of exposure to or contact with a hazard. It can be expressed either as a frequency, such as the number of harmful effects in a certain time period, or as a probability, such as the probability of a harmful effect during or after exposure.
Risk assessment – It is the process of quantifying the frequency or probability of a harmful effect to individuals or populations (e.g., related to exposure or activities at work) and is one of the first steps in risk management. It is a systematic process of identifying, analyzing, and evaluating potential risks associated with a particular activity or project, ultimately aimed at understanding and mitigating those risks. It is a scientific evaluation of the probability of harm resulting from exposure to the potential risks. Under risk assessment included are (i) hazard identification taking recourse to hazard indices, inventory analysis, dam break probability, and natural hazard probability etc., (ii) maximum credible accident (MCA) analysis to identify potential hazardous scenarios, (iii) consequence analysis of failures and accidents resulting in fire, explosion, hazardous releases, and dam breaks etc., (iv) hazard and operability (HAZOP) studies, (v) assessment of risk on the basis of the above evaluations, and (vi) preparation of an onsite and offsite (project affected area) disaster management plan.
Risk/benefit analysis – It is a decision-making technique which uses a common value scale, normally monetary units, to balance the risk against benefit.
Risk management – It consists of all actions taken to achieve, maintain or improve work and working conditions so that harmful effects to individuals or populations related to exposure or activities at work are prevented. It is the process of (i) identifying, analyzing, assessing, and evaluating risks, (ii) assigning ownership, (iii) taking actions to mitigate or anticipate them, and (iv) monitoring and reviewing progress.
Risk mapping – It is the process of identifying high-risk areas is known as risk mapping. This is done by correlating a hazard, such as an earthquake, to the terrain and to the probability that such an event occurs. The results of these analyses are normally presented in the form of risk maps, which show the type and degree of hazard represented by a particular natural phenomenon at a given geographic location. Risk mapping is normally the first step in vulnerability reduction.
Risk transfer – It is the process of formally or informally shifting the financial consequences of particular risks from one party to another whereby an organization gets resources from the other party after a disaster occurs, in exchange for ongoing or compensatory financial benefits provided to that other party is known as risk transfer. Insurance is a well-known form of risk transfer, where coverage of a risk is obtained from an insurer in exchange for ongoing premiums paid to the insurer. Risk transfer can occur informally or formally. During formal risk transfer, governments, insurers, multi-lateral banks and other large risk-bearing entities establish mechanisms to help cope with losses in major events. Such mechanisms include insurance and re-insurance contracts, catastrophe bonds, contingent credit facilities and reserve funds, where the costs are covered by premiums, investor contributions, interest rates and past savings respectively.
River pattern – It is a term used in fractography to describe a characteristic pattern of cleavage steps running parallel to the local direction of crack propagation on the fracture surfaces of grains which have separated by cleavage. It is a microscale characteristic pattern of cleavage crack propagation on closely spaced parallel planes connected by a thin ligament. Cracking on the connecting ligament can be ductile or brittle. Crack coalescence occurs as crack propagation occurs on the multiple planes, so that the microscale direction of crack propagation can be identified (i.e., ‘down river’).
Rivet – It is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end.
Riveting – It is the joining of two or more members of a structure by means of metal rivets, the unheaded end being upset after the rivet is in place.
Riveting brass – It is the brass which is formulated to be most suitable for riveting.
RLC circuit – It is a circuit which has only resistors, inductors, and capacitors in it.
Road network – It is a system of roads and points for a production plant and connect different plant facilities and buildings. A road network provides approaches to different production units and buildings. It greatly affects in-plant traffic and movement of man and materials. Road network is highly dependent on the plant general layout and can become very complex.
Roasting – It is a process of heating a sulphide ore to a high temperature in the presence of air. It is a step in the processing of certain ores. More specifically, roasting is frequently a metallurgical process involving gas–solid reactions at high temperatures with the goal of purifying the metal component(s). Frequently before roasting, the ore has already been partially purified, e.g., by froth flotation. The concentrate is mixed with other materials to facilitate the process. The technology is useful in making certain ores usable but it can also be a serious source of air pollution. The roasting can include oxidation, reduction, chlorination, sulphation, and pyro-hydrolysis. In roasting, the ore or ore concentrate is treated with very hot air. This process is normally applied to sulphide minerals. During roasting, the sulphide is converted to an oxide, and sulphur is released as sulphur di-oxide, a gas. Roasting causes some chemical change which facilitate smelting.
Robber – It is an extra cathode or cathode extension which reduces the current density on what is otherwise a high-current-density area on work being electroplated.
Robotics – It is the interdisciplinary study and practice of the design, construction, operation, and use of robots. Within mechanical engineering, robotics is the design and construction of the physical structures of robots, while in computer science, robotics focuses on robotic automation algorithms. Other disciplines contributing to robotics include electrical, control, software, information, electronic, tele-communication, computer, mechatronic, and materials engineering. The goal of most robotics is to design machines which can help and assist humans. Several robots are built to do jobs which are hazardous to people.
Robust control – It is a static control algorithm which can produce acceptable performance over an anticipated useful range of process disturbances.
Robust design – It is an integrated system of tools and techniques which are aimed at reducing product or process performance variability while simultaneously guiding that performance toward an optimal setting. Robustness optimization is chiefly done for design concepts that are new so that the best values of the critical functional parameters are unknown. Robust design follows the methods first proposed by Genichi Taguchi.
Robustness – It means of performance of a system that is always acceptably close to the ideal function of the system. It refers to how consistently a component or product performs under variable conditions in its environment and as it wears during its lifetime.
Rochelle copper – It is a copper electrodeposit obtained from copper cyanide plating solution to which Rochelle salt (sodium potassium tartrate) has been added for grain refinement, better anode corrosion, and cathode efficiency. It is the solution from which a Rochelle copper electro-deposit is obtained.
Rochelle salt – It is also known as sodium potassium tartrate or Seignette salt. It is a double salt of tartaric acid with the chemical formula KNaC4H4O6·4H2O, characterized by its piezoelectric properties and use in sensitive acoustic and vibrational devices.
Rock – It consists of a natural combination of minerals, It is part of the earth’s crust.
Rock-bolting – It is the act of supporting openings in rock with steel bolts anchored in holes drilled especially for this purpose.
Rock-burst – It is a violent release of energy resulting in the sudden failure of walls or pillars in a mine, caused by the weight or pressure of the surrounding rocks.
Rock candy fracture – It is a macro-scale and micro-scale fracture appearance which shows separated-grain facets. Very frequently it is used to describe the macroscale appearance of an intergranular fracture in a large-grained metal, although the term is also used to describe the microscale appearance of facets observed from an intergranular fracture path with equiaxed grains.
Rocket – It is a vehicle which uses jet propulsion to accelerate without using any surrounding air. A rocket engine produces thrust by reaction to exhaust expelled at high speed. Rocket engines work entirely from propellant carried within the vehicle. Hence a rocket can fly in the vacuum of space. Rockets work more efficiently in a vacuum and incur a loss of thrust due to the opposing pressure of the atmosphere.
Rock factor – It is the number of cubic meters of a particular rock type required to make up one ton of the material. One ton of a highly siliceous ore can occupy 0.4 cubic meters, while a ton of dense sulphide ore may occupy only 0.25 cubic meters.
Rocking curve – It is a method for determining the degree of imperfection in a crystal by using monochromatic, collimated X-rays reflecting off a ‘perfect’ crystal to probe a second test crystal. A rocking curve is obtained by monitoring the x-ray intensity diffracted by the test crystal as it is slowly rocked, or rotated, through the Bragg angle for the reflecting planes.
Rocking-die forging – It is also known as orbital or rotary forging. It is a forging process where one die orbits or rocks relative to the other, gradually deforming the work-piece into its final shape. It is frequently used for symmetrical parts like gears and hubs.
Rocking shear – It is a type of guillotine shear which utilizes a curved blade to shear sheet metal progressively from side to side by a rocker motion.
Rock mechanics – It is the study of the mechanical properties of rocks, which includes stress conditions around mine openings and the ability of rocks and underground structures to withstand these stresses.
Rock weathering – It describes the breaking down or dissolving of rocks and minerals on the surface of earth. Water, ice, acids, salts, plants, animals and changes in temperature are all agents of weathering. Once a rock has been broken down, a process called erosion transport the bits of rock and mineral away. No rock on earth is hard enough to resist the forces of weathering and erosion. Weathering wears away exposed surfaces over time. The length of exposure frequently contributes to how vulnerable a rock is to weathering. As it smooths rough, sharp rock surfaces, weathering is frequently the first step in the production of soils. Tiny bits of weathered minerals mix with plants, animal remains, fungi, bacteria, and other organisms. A single type of weathered rock often produces infertile soil, while weathered materials from a collection of rocks is richer in mineral diversity and contributes to more fertile soil. Soils types associated with a mixture of weathered rock include glacial till, loess and alluvial sediments.
Rockwell hardness number – It is a number which is derived from the net increase in the depth of impression as the load on an indenter is increased from a fixed minor load to a major load and then returned to the minor load. Different scales of Rockwell hardness numbers have been developed based on the hardness of the materials to be evaluated. The scales are designated by alphabetic suffixes to the hardness designation. As an example, 65 HRC represents the Rockwell hardness number of 65 on the Rockwell C scale.
Rockwell hardness scales – There are several Rockwell scales other than the B and C scales, which are known as the common scales. The other scales also use a letter for the scale symbol prefix, and many use a different sized steel ball indenter. A properly used Rockwell designation has the hardness number followed by ‘HR’ (Hardness Rockwell), which is followed by another letter which indicates the specific Rockwell scale. For example, 60 HRB indicates that the sample has a hardness reading of 60 on the B scale. The standardized a set of scales (ranges) for Rockwell hardness testing under use is normally designated by a letter. This set is (i) A scale which is used for cemented carbides, thin steel, and shallow case-hardened steel, (ii) B scale which is used for copper alloys, soft steels, aluminum alloys, and malleable iron, etc., (iii) C scale which is used for steel, hard cast irons, pearlitic malleable iron, titanium, deep case hardened steel and other materials harder than the hardness value of B100, (iv) D scale which is used for thin steel, medium case-hardened steel, and pearlitic malleable cast iron, (v) E scale which is used for cast iron, aluminum and magnesium alloys, and bearing metals, (vi) F scale which is used for annealed copper alloys and thin soft sheet metals, (vii) G scale which is used for phosphor bronze, beryllium copper, and malleable irons, (viii) H scale which is used for aluminum, zinc, and lead, and (ix) K, L, M, P, R, S, and V scales which are used for bearing metals and other very soft or thin materials, including plastics.
Rockwell hardness test – It is an indentation hardness test using a calibrated machine which utilizes the depth of indentation, under constant load, as a measure of hardness. It is a hardness measurement method which is based on the net increase in depth of impression as a load is applied. Hardness numbers have no units and are normally given in some scales such as the A, B, C, R, L, M, E and K scales. The higher the number in the scales means the harder is the material. Rockwell hardness test is the most used and versatile of the hardness tests. In the Rockwell method of hardness testing, the depth of penetration of an indenter under certain arbitrary test conditions is determined. It uses either a spherical diamond tipped cone called ‘Brale’ which is of 120-degree angle and 0.2 millimeters tip radius or a steel ball with 1.6 millimeters or 3.2-millimeters diameter ball as the indenter. The type of indenter and the test load determine the hardness scale (A, B, C, etc.). A minor load of 10 kilograms is first applied, which causes an initial penetration and holds the indenter in place. Then, the dial is set to zero and the major load is applied. Upon removal of the major load, the depth reading is taken while the minor load is still on. The hardness number can then be read directly from the scale.
Rockwell hardness testing machine – It is used to measure the hardness of metal. It measures resistance to penetration like the Brinell test, but in this case, the depth of the impression is measured rather than the diametric area. With the Rockwell testing machine, the hardness is indicated directly on the scale attached to the machine. This dial like scale is really a depth gauge, graduated in special units. The Rockwell testing machine uses two loads with one is applied directly after the other. The first load (known as the minor load) of 10 kilograms is applied to the sample to help seat the indenter and remove the effects, in the test, of any surface irregularities. The purpose of the minor load is to create a uniformly shaped surface for the application of the major load. The difference in the depth of the indentation between the minor and major loads provides the Rockwell hardness number.
Rockwell superficial hardness number – Like the Rockwell hardness number, the superficial Rockwell number is expressed by the symbol HR followed by a scale designation. For example, 81 HR30N represents the Rockwell superficial hardness number of 81 on the Rockwell 30N scale.
Rockwell superficial hardness test – It is the same test as used to determine the Rockwell hardness number except that smaller minor and major loads are used. The working of this machine is similar to the standard Rockwell testing machine, but it is used to test thin strip, or lightly carburized surfaces, small parts or parts that might collapse under the conditions of the regular test. In Rockwell testing, the minor load is 10 kilograms force, and the major load is 60 kilograms force, 100 kilograms force, or 150 kilograms force. In superficial Rockwell testing, the minor load is 3 kilograms force, and major loads are 15 kilograms force, 30 kilograms force, or 45 kilograms force. In both tests, the indenter can be either a diamond cone or a steel ball, depending principally on the characteristics of the material being tested.
Using the 1.6 millimeters diameter, steel ball indenter, a ‘T’ is added (meaning thin sheet testing) to the superficial hardness designation. For example, a superficial Rockwell hardness is 15T-25, which indicates the superficial hardness as 25, with a load of 15 kg using the steel ball. If the 120-degree diamond cone is used instead, then ‘T’ is replaced with ‘N’.
Rod – It is round, thin semi-finished steel length which is rolled from a billet and coiled for further processing. Rod is normally drawn into wire products or used to make bolts and nails. Rod is the hot rolled finished product having a nominal size normally 5 millimeters or higher and hot wound into irregular coils. The cross-section of the rod can also be besides circular, oval, square, rectangular, hexagonal, octagonal, half-round or other shape. Rod has a smooth surface and is normally intended for subsequent conversion. Rod used for wire-drawing purposes in coil form is normally termed as wire rod.
Rod, alclad – It is the rod having on its surface a metallurgically bonded aluminum or aluminum alloy coating which is anodic to the core alloy to which it is bonded, hence electrolytically protecting the core alloy against corrosion.
Rod, cold-finished – It is the rod which is brought to final dimensions by cold working to get improved surface finish and dimensional tolerances.
Rod, cold-finished extruded – It is the rod which is produced by cold working extruded rod.
Rod, cold-finished rolled – It is the rod produced by cold working rolled rod.
Rod, cold-heading – It is the rod of a quality suitable for use in the manufacture of cold-headed products such as rivets and bolts.
Rod drawing – It is a metalworking process where a rod is pulled through a die to reduce its cross-sectional area and increase its length, resulting in a long, thin product like rods or wires. Rod drawing involves applying both tensile and compressive forces to a rod as it is pulled through a die with a smaller opening than the rod’s initial diameter. The main objective is to produce long, thin, and frequently precise rods or wires with a reduced cross-sectional area.
Rod end bearing – It is the connection frequently used between actuator stem and actuator lever to facilitate conversion of linear actuator thrust to rotary force (torque) with minimum of lost motion. Use of a standard reciprocating actuator on a rotary valve body normally needs linkage with two rod end bearings. However, selection of an actuator specifically designed for rotary valve service needs only one such bearing and hence reduces lost motion.
Rod expansion thermometer – It is also known as a solid-expansion thermometer. It measures temperature by detecting the change in length of a metal rod or the deflection of a bimetallic strip as it expands or contracts with temperature changes.
Rod, extruded – It is the rod produced by hot extruding.
Rod mill – It is a hot rolling mill for rolling rod.
Rod mill, grinding – It is a mill for fine grinding, somewhat similar to a ball mill, but employing long steel rods instead of balls to effect grinding. Rod mills are only suited for those kinds of ores which are of a fairly coarse nature but once they are broken, disintegrate readily into small size. Typically, rod mills mill can deliver a product with a fineness of less than 0.1 millimeters. Testing of material is needed before hand to determine the suitability of the ore for processing in an autogenous mill. Rod mill is a tumbling mill which is having a large percentage of its volume (30 % to 40 %) loaded with steel rods. The rods are placed axially in the mill and are loose and free to move within the mill. The internal lining of the drum has a series of lifters which raise the rods and drop them at a predetermined point. The liners prevent long and heavy rods to slide on the cylinder lining and help them to lift up. Because of the high kinetic energy of a dropping rod, it is important to pay attention to protecting the cylinder when choosing a liner for the mill.
Rod, rivet – It is the rod of a quality suitable for use in the manufacture of rivets.
Rod, rolled – It is the rod produced by hot rolling.
Roentgen – It is a legacy unit of measurement for the exposure of X-rays and gamma rays, and is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air (statcoulomb per kilogram).
Roentgen equivalent man – It is a standard unit of radiation dose. It measures the effects of ionizing radiation on humans. The dose equivalent in Roentgen equivalent man is equal to the absorbed dose in rads multiplied by the quality factor of the type of radiation.
Rogowski coil – It is a current sensing coil which produces a voltage proportional to the rate of change of current. By integration, this can be turned into a measure of current.
Roll balancing system – It aims to ensure the precise alignment of the centre of gravity of the rolls with their axis of rotation, minimizing vibrations and ensuring uniform metal deformation during the rolling process.
Roll bearing – It refers to rolling-element bearings (like cylindrical roller bearings or spherical roller bearings) used to support the rotating rolls and minimize friction, allowing for smooth and efficient metal deformation during the rolling process. Roll bearings are needed to withstand heavy loads and high-speed rotations as well as severe operating environments. These bearings, especially which are used in the process of hot rolling, are frequently used under severe conditions, high temperatures with possibilities of intrusion of foreign materials. These bearings are to endure these severe conditions.
Roll bending – It consists of curving sheets, bars, and sections by means of rolls. Roll bending is a process which allows creation of intricate, curved shapes out of metal sheets, bars, and tubes. Roll bending, also known as plate rolling or angle bending. It is a metalworking process which uses a series of rollers to bend a metal piece into a specific curve or radius. The metal is forced through the rollers, progressively applying pressure to shape the material into the desired curvature. This process is normally used for manufacturing pipes, tanks, and other cylindrical or conical shapes.
Roll bite – It refers to the pinch point or contact area between the upper and lower rolls where the metal stock is drawn into and deformed. It is the region where the rotating rolls grip and deform the metal, reducing its thickness and shaping it. Roll bite condition is the condition which determines the material to be rolled to enter the throat of the roll.
Roll camber – It refers to the intentional curvature (or crown) introduced into the rolls, typically with a larger diameter in the centre than at the edges, to counteract bending and ensure a consistent thickness of the rolled product. Roll camber can be varied by (i) bending the work rolls by applying external force, (ii) shifting of work rolls laterally with respect to centerline of the strip, (iii) using shaped rolls (rolls with profiles), and (iv) rotation of the axis of the work roll with respect to axis of backup-roll in horizontal plane (results in deflection of work roll ends, producing camber).
Roll changing – It means rapidly changing top and bottom working rolls and top and bottom backup rolls in case of a four high rolling mill. Roll changing is normally done with the use of an overhead crane and a unit designed to attach to the neck of the roll to be removed from or inserted into the mill.
Roll changing device – It is a special device which is designed to attach to the neck of the roll for the removal or insertion of the rolls into the rolling mill stands.
Roll chatter – It consists of numerous intermittent lines or grooves which are normally full width and perpendicular to the rolling or extrusion direction.
Roll coating – It is a banded condition caused by non-uniform adherence of roll coating to a work roll. It can be created during hot and / or cold rolling. If generated in the hot rolling process, it also is called hot mill pickup.
Roll chock – It is a component which supports the work-rolls and back-up rolls. while they are being rolled. Roll chocks are critical components of rolling mills and play a significant role in the success of the mill operation. The main function of roll chock in rolling mill is to house and accommodate the roll neck bearings. Roll neck bearings serve for accurate mounting of roll necks, in both horizontal and vertical plane. Roll chocks are designed to fit into the window of the housing in such a way that they are important component in a rolling mill for maintaining accurate positioning of the rolls. During rolling, the load on the rolls gets transferred to the roll neck bearings and their assembly (chocks). The important features of roll chocks are that they have special holes (bores) for slider bearings, antifriction bearings, or oil film bearings. They have side support planes. For increasing the wear resistance and to prolong chocks work life, these planes are equipped with lining plates having different hardness of surfaces. The surface of the roll chock in contact with the bearing needs precision, and accuracy, as well as close and smooth finish.
Roll compacting – It is the progressive compacting of metal powders by use of a rolling mill.
Roll configuration – It refers to the arrangement and number of rolls used to shape metal, including two-high, three-high, four-high, and cluster mills, each suited for different applications and desired outcomes.
Rolled compact – It is a compact which is made by passing metal powder between rollers so as to form a relatively long, sheet-like compact.
Rolled finished products – These are the products which have been manufactured normally by rolling and which are normally not further hot worked in the steel plant. The cross-section is uniform over the whole length. It is normally defined by a standard, which fixes the normal size ranges and the tolerances on shape and dimension. The surface is normally smooth, but reinforcing bars or floor plates, for example, can have a regularly raised or indented pattern.
Rolled glass – It is a translucent glass with 50 % to 80 % light transmission, depending on its thickness and type of surface. It is used where transparency of the glass sheet is not important or not desired. To produce rolled glass, molten glass pours from the melting tank over a refractory barrier (the weir) and onto the machine slab where it flows under a refractory gate (the twee), which regulates the volume of glass, and then between two water-cooled rollers. The distance between the rollers determines the thickness of the glass.
Rolled-in metal – It is an extraneous chip or particle of metal rolled into the surface of the product.
Rolled in scale – Scale is the oxide layer of varying thickness and colouring on the surface of the wire rod which can cling loosely or adhere firmly. Rolled in scale forms an irregular impression in the surface of the wire rod and is caused by incomplete descaling after the heating operation. It can cause a pitted surface on the wire rod. The defect results in wire rod surface irregularly. It can be detected visually. By rubbing with an abrasive tool to remove uniform depth scale, the underneath surface can be revealed. The occurrence of rolled in scale is most dependent on the adherence and not the quantity of primary scale produced. Scale adherence is a function of steel composition, furnace heating practices, and prior surface condition of the incoming billets. Modifications sometimes are made to roll pass designs to promote more complete scale breaking and removal. Slab or box passes are the best roughing passes for scale removal.
Rolled-in scratch – It is the scratch which is subsequently rolled. It then appears as a grayish white ladder (distinct transverse lines within the longitudinal indentation).
Rolled metal, rolled steel – Rolled metal / rolled steel refers to a metal / steel which has been shaped and its thickness reduced by passing it through one or more pairs of rollers, a process known as ‘rolling’. This process can be done hot or cold, and is used to create sheets, plates, rods, or other desired shapes and thicknesses.
Rolled-over edge – It is surface condition remaining after portions of a side of an as-cast rolling ingot deforms enough during hot rolling to become top and / or bottom surface(s) of the rolled product at an edge.
Rolled ring – It is a cylindrical product of relatively short height, circumferentially rolled from a hollow section.
Rolled steel joist (RSJ) – It is a common type of beam used for structural steelwork. It is also known as an ‘I-beam’. A rolled steel joist is abeam with an ‘I’ or ‘H’-shaped cross-section. It comes in a variety of standard sizes. It is a very efficient form for carrying bending and shear loads in the plane of the web (the vertical element). It is normally made from mild steel but can also be formed from aluminum or other materials. It is formed by hot rolling, cold rolling, or by extrusion.
Rolled threads – These threads are produced through rolling or sliding dies. Rolled threads (as opposed to threads cut on a lathe, with a cutting die or tap) produce superior surface finish (hence lower stress risers) and improved material properties from cold working the material, resulting in much higher fatigue resistance. Rolled threads increase thread strength by a minimum of 30 % over well-cut threads.
Roll elastic deformation – It refers to the temporary change in shape of the rolls (work rolls and back-up rolls) due to the pressure exerted by the metal being rolled, with the rolls returning to their original shape when the force is removed.
Roller air analyzer – It is an air-elutriation apparatus suitable for the particle size determination of metal powders, especially in sub-sieve range. It consists, essentially, of a device by which powder particles are blown into a settling chamber through which dried and metered air moves at a uniform measurable velocity. Means are provided for collecting the particles carried out of the settling chamber and for removing and re- circulating lodged particles.
Roller bearings – These bearings are very frequently used when maximum load capacity is needed in a minimum of space. They are cylindrical and needle roller bearings where the rolling function is provided by a cylinder of some kind. Roller bearings are low friction and are designed to carry medium to heavy radial loads. In this type of bearing, the primary roller is a cylinder, which means the load is distributed over a larger area, enabling the bearing to handle larger amounts of weight. This structure, however, means the bearing can handle primarily radial loads, but is not suited to thrust loads. For applications where space is an issue, a needle bearing is normally used. Needle bearings work with small diameter cylinders, so they are easier to fit in smaller applications. These bearings are commonly found in general machine applications including gearboxes and transmissions, machine tool and construction equipment.
Roller chain – It is the type of chain drive normally used for transmission of mechanical power on several kinds of industrial machinery, such as conveyors, wire-drawing and tube-drawing machines. It consists of a series of short cylindrical rollers held together by side links. It is driven by a toothed wheel called a sprocket. It is a simple, reliable, and efficient means of power transmission. The major purpose of rollers is to reduce friction, but the rollers in chains have two separate functions, normally being provided by the same roller. These functions are (i) to engage the sprocket teeth and thus transfer any sliding action to the internal members of the chain, which are designed for that purpose, and (ii) to serve as a guide or to support a chain and material carried on it on tracks or ways, as is characteristic of conveyors and some bucket elevators. Rollers in drive chains are normally smaller in diameter than the height of the link plates of the chain. Hence, the link plates serve as guides when the chain engages the sprockets, and can also do so when the chain is riding on guides, as in a bucket elevator. Rollers on conveyor chains normally have diameters considerably larger than the widths of their adjacent sidebars. This is done for two reasons namely (i) the large rollers, called carrier rollers, carry the sidebars well above the conveyor tracks and thus prevent friction, and (ii) larger rollers have a definite mechanical advantage over smaller rollers relative to rotational friction, and thus help reduce chain pull.
Roller-chain flexible coupling – It utilizes two sprocket-like members, or hubs, that are mounted on the driver and the equipment shafts. They are connected by a section of roller chain. This type of coupling is typically applied in low-speed services.
Roller-coater –This method consists of a small movable tank and pumping unit, which feed a wiping head or roller with lubricant. The thickness and the amount of lubricant can be controlled, and the excess flows back to the reservoir. When lubricating pre-coated or polished materials with a roller-coater, it is advisable to use polyurethane or neoprene rolls to make sure the working surfaces are not scratched or marked. Steel rolls can sometimes cause problems on coated surfaces. In many cases, roller-coaters by themselves do not produce enough lubrication film to flush out particles generated by aluminum, galvanized, and hot roll. Sometimes, a sprayer installed in the critical areas of metal working where there is a possibility of buildup to occur, can flush out unnecessary particles. Another issue which can happen when applying lubricant (especially on wide strip) is a result of material which has a ‘crown’. In such a case, the roller can only lubricate the high spots, leaving the outside edges without lubricant. A similar issue can occur on wavy strip. A soft roller can help in adjusting itself to this crown or wavy condition.
Roller conveyor systems – These are used as mechanical handling equipment which moves materials from one location to another. These systems provide quick and efficient transportation for a wide variety of materials, which make them very popular for the material handling in the industries. A roller conveyor supports unit type of load on a series of rollers, mounted on bearings, resting at fixed spacings on two side frames which are fixed to stands or trestles placed on floor at certain intervals. A roller conveyor essentially coveys unit loads with at least one rigid, near flat surface to touch and maintain stable equilibrium on the rollers, like slabs, billets, plates, rolled stock, pipes, logs, boxes, crates, and moulding boxes etc. The spacing of rollers depend on the size of the unit loads to be carried, such that the load is carried at least by two rollers at any point of time. Roller conveyors are used for conveying almost any unit load with rigid riding surface which can move on two or more rollers. These are particularly used between machines, buildings, in warehousing as storage racks, docks, foundries, rolling mills, manufacturing, assembly and packaging industry. They are also used for storage between work-stations and as segment of composite handling system. However, the limitations of rollers conveyors are that they can be best used for objects with rigid flat surfaces, and for movement to relatively short distances. They need side guards to retain the loads from falling off. Gravity roller conveyors have the risk of accelerating loads. Roller conveyors are classified into two groups according to the principle of conveying action. These are (i) not powered or idle roller conveyor, and (ii) powered or live roller conveyor.
Roller crusher – It is a crusher which breaks material by squeezing it between two revolving metal cylinders, with axes parallel to each other and separated by a space equal to the desired maximum size of the finished product. It consists essentially of two opposite directions driven cylinders that are mounted on horizontal shafts. The other shaft is mounted permanently in the frame and is leaning on robust springs. The gap between cylinders can be adjusted, so the size of crushed product is easily adjustable. Usually both cylinders are covered with manganese steel liners. Crushing ratio is normally lower than in other crushers. Roll crusher is suitable for fine crushing. The roll crusher uses compression to crush materials. Reduction ratio is 2 to 2.5 to 1. Roller crushers are not recommended for abrasive materials.
Roller guides – The design of roller guides is based on rolling frictions and hence these guides have a number of advantages over static guides whose design is based on sliding friction. Roller guides ensure faster and accurate adjustment of the guiding elements when compared with the static guides. Since the contact of the rolling stock with the guide is carried through the rollers working on rolling friction, it becomes possible to considerably increase the wear resistance of the working elements (rollers) and to reduce the possibility of such rolling defects like scratches, laps, and score marks etc. The construction and assembly of the roller guides is carried out with sufficient strength to withstand the frequent hits from the rolling stock being rolled which is usually moving at a very high speed in the modern mills. The presence of safety components in the roller guide design make it possible to protect the costly parts, which are seldom replaced. This is especially necessary in the exit roller guide, where there is possibility of the end of the rolling stock jamming as it comes out of the work rolls. Roller guide design usually make is possible to withdraw jammed rolling stock quickly. In modern roller guides, drop forged roller holders in spring steel quality, are used which enables thicker front and tail ends to pass through the guide without disturbing the original setting of the roller guide.
Roller hearth furnace – It is a modification of the pusher-type continuous furnace which provides for rollers in the hearth or muffle of the furnace whereby friction is greatly reduced and lightweight trays can be used repeatedly without risk of unacceptable distortion and damage to the work.
Roller hearth reheating furnace – Roller hearth furnaces are used to advantage when heating very long billet, bloom or slabs in the situation where it is not practical for heating in a pusher or walking beam furnace. In the roller hearth furnace, the hearth consists of a set of water-cooled driven rollers on which the steel stock moves forward. The advantages of the roller hearth reheating furnaces are (i) it has ability to handle very long pieces, (ii) the zone control in this furnace is simpler when cross-firing is employed, (iii) material suffers little or no mechanical damage, (iv) skid marks are not there, and (iv) roller hearth furnace is self-emptying. The disadvantages of the roller hearth furnace include (i) high initial cost per unit of capacity, (ii) if the rollers are not properly insulated then there is increased heat loss due to the water cooling of the rollers, and (iii) roller hearth furnaces are narrower and longer than pusher type or walking beam furnaces of the same capacity.
Roller leveller – It is normally simply referred to as a leveller It is similar to a four-high flattener in that the design involves four-high small diameter work rolls. Unlike the four-high flattener, however, each work roll in the leveller is supported by a number of narrow backup rolls, instead of straight solid backup rolls. This arrangement allows small work rolls and a close work roll spacing in the leveller for more capability in shape correction. A series of backup rolls at the same transverse position for all work rolls under the same frame are called a flight, and they have a common support housing extending from the entry to the exit of the roller leveller. Each flight of backup rolls can be vertically adjusted, independently from other flights, by either a mechanical or a hydraulic mechanism. A deflection of work rolls in the leveller, hence, can be deliberately adjusted in a controlled manner. Roller levellers have normally seven to nineteen work rolls. Some levellers have the five-high or six- high backup design for high surface finish quality strip. The six-high levellers have two additional rows of straight solid intermediate rolls between work rolls and adjustable backup rolls, each at the top and bottom frames. This arrangement prevents marking on the top and bottom surfaces of the strip but limits the capability to correct poor shape since the adjustable roll flights act on the intermediate rolls. The five-high leveller has only one row of the intermediate rolls between work rolls and backup roll, normally in the lower frame, while its upper frame contains only work rolls and backup rolls as in four-high levellers. Hence, it gives better capability for shape correction than the six-high leveller, while preventing marking on one side of the strip surfaces. A roller leveller has a certain capability range in strip thickness for a given work roll diameter and roll spacing. Normally, the upper strip thickness limit is 3 times to 4 times that of the lower limit. Roller levellers have the ability to control the deflection of work rolls so that one portion of the material across the strip width can be subjected to more bending than another portion. The bending causes a tension in the material of the outer layers in the strip and compression in the material of the inner layers near the work roll. At a certain bending radius, the stress in the material at the outer-most layer exceeds the material yield strength and permanent plastic elongated deformation occurs.
Roller leveller breaks – These are obvious transverse breaks normally around 3 millimeters to 6 millimeters apart caused by the sheet metal fluting during roller levelling. These are not to be removed by stretching.
Roller leveller lines – These are lines on sheet or strip which are running transverse to the direction of roller levelling. These lines can be seen upon stoning or light sanding after levelling (but before drawing) and can normally be removed by moderate stretching. These are also known as leveller lines.
Roller levelling – It is also called tension levelling. It is the levelling by-passing flat sheet metal stock through a machine having a series of small-diameter staggered rolls that are adjusted to produce repeated reverse bending. It consists of flattening of sheet, strip or coil metal by passing it through a roll train staggered rolls. Levelling is achieved by precisely bending metal strip back and forth as it is passed through a series of small-diameter offset rolls. The material is normally also under tension loading.
Roller mills – Roller mills are basically of two distinct types. The first has a series of rollers which rotate around a central axis within a drum. The reduction takes place between the rollers and the drum. The second type is where there are a series of fixed rollers and a rotating table. The milling takes place between the rollers and the table. This type of mill is used for dry grinding only and accepts only relatively soft materials. Small machines can have a throughput of only a few tens of kg per hour whereas larger machines are capable of handling up to 40 to 50 tons per hour and occasionally more. Feed size varies according to the machine. The machines are often fitted with screens for closed circuit grinding. Product size can be controlled by changing screens.
Roller pitch -It refers to the distance between the centres of adjacent rollers. In case of roller chain, pitch refers to the distance between the centres of adjacent rollers on a chain link. Itis a key dimension for identifying and selecting the correct chain size.
Roller press – Roller press is considered the global standard technology to produce pillow-shaped briquettes using diverse types of feed stocks. The roller press works on the principle of pressure and agglomeration. It consists of dual cylindrical rollers of the same diameter, rotating horizontally in opposite directions on parallel axes. The two rollers are arranged in such a way that a small gap exists between them and the distance from each other depends on factors such as the feed stock type, the particle size, the moisture content, and the addition of binders. During operation, the raw material is fed into the press and forced through the gap between the rollers on one side. It is then pressed into a die forming the densified product, which comes out on the opposite side. The smooth production of briquettes using this technology needs high quality rollers with dies on which the briquettes are shaped. The type of roller or die used determines the shape of the briquettes and typical bulk densities range from 450 kilograms per cubic meter to 550 kilograms per cubic meter.
Rollers, powered – The rollers of a powered roller conveyor is fundamentally different from those of the unpowered roller conveyor in that the barrel and the shaft portion are integral so that they can be driven by connecting power to their shaft ends. The integral shafts are mounted on bearings housed in the frames at two sides. These are termed as driven rollers. The driven rollers are normally subjected to considerable impact load (specially the reversing type processing conveyors) and hence they are made stronger. The rollers can be made from solid steel forgings or castings or can be fabricated from heavy section of pipes, tubes, and solid shafts, machined all over for proper static and dynamic balancing.
Roller setting – It refers to the configuration and adjustment of the levelling rollers (and sometimes backup rollers) to achieve the desired flatness and stress distribution in a metal strip or sheet.
Roller stamping die – It is an engraved roller used for impressing designs and markings on sheet metal.
Roller straightening – It is the straightening of extrusions by through a series of small diameter, staggered, rolls.
Rollers, unpowered – The normally used rollers are cylindrical rollers which are made from electric resistance welded (ERW) steel pipes with cast or fabricated end flanges to accommodate the anti-friction bearings (normally ball bearings). The through axles are stationery and roller barrels can rotate freely. These rollers are called idler rollers. For conveying, cylindrical objects (drums, pipes, round steel bars etc.), double tapered rollers, or wheel rollers are used.
Roller table – It forms the conveying system for the movement of the work-piece in the rolling mill. It consists of a series of roller either driven by line shafting and bevel gears from a common drive or by individual motors. In some improved designs, the bevel gears have been replaced with spur gears. The roller tables serve to feed the material being rolled into the rolls and receive it from the rolls. Hence, the roller table operates under severe conditions of mechanical impact, repetitive short-term duty cycles and dynamic transients (acceleration and decelerations). The roller table connects the separated stands of large and medium sized mills. There are required on majority of the mills for conveying the rolled stock towards as well as away from rolling stand.
Roller thrust bearings – These bearings much like ball thrust bearings, handle thrust loads. The difference, however, lies in the quantity of weight the bearing can handle. Roller thrust bearings can support significantly larger quantities of thrust load, and are therefore found in car transmissions, where they are used to support helical gears. Gear support in general is a common application for roller thrust bearings.
Roller transport – It refers to a system of moving goods or materials using a series of rollers, typically within a warehouse or production facility. These systems can be gravity-fed or powered, facilitating efficient and automated movement of loads.
Roll fatigue – Fatigue damage can start at the surface or sub-surface. Rolls are also damaged because of fatigue. The damage due to fatigue can start at the surface or the sub-surface. The problem of fatigue in the rolls can arise because of the high loads in the mills. Corrosion fatigue can also be a problem. With corrosion fatigue, there is no safe operation at all, and there is no fatigue limit.
Roll flattening – It is the flattening of metal sheets which have been rolled in packs by passing them separately through a two-high cold mill with virtually no deformation. It is not to be confused with roller leveling. It also refers to the elastic deformation or bending of the rolls themselves under the pressure of the rolling force, which affects the strip’s crown and flatness. It directly impacts the final shape and flatness of the rolled strip. If the rolls flatten excessively, it can lead to variations in the strip’s thickness and unevenness, known as ‘crown’.
Roll force – It refers to the compressive force applied by the rolls during the rolling process, specifically the force exerted by the rolls on the metal being deformed to reduce its thickness or change its cross-section. There are two normal ways of applying the force to the rolling stock. These are screw system and hydraulic system. Screw system uses the basic principle of the screw to adjust the space between the mill rolls. Since in this system, metal touches metal, these configurations wear down over time and can cause quality problems. In hydraulic system, fluid pressure is used to rapidly adjust the roll spacing several times per second. These minute, instantaneous adjustments allow for superior gauge tracking and higher quality products. Roll force is also known as roll separating force. It is the force which the rolls apply to the material to reduce its thickness and change its shape during the rolling process. It is the force which is exerted by the rolls on the work-piece during the deformation process, causing the material to change shape and thickness. Understanding and controlling of roll force is crucial for achieving desired product dimensions, surface quality, and material properties.
Roll forging – It is a process of shaping stock between two driven rolls which rotate in opposite directions and have one or more matching sets of grooves in the rolls. It is used to produce finished parts or preforms for subsequent forging operations.
Roll forming – It is a metal forming through the use of power-driven rolls whose contour determines the shape of the product. It is sometimes used to denote power spinning. Roll forming is a type of rolling involving the continuous bending of a long strip of sheet metal (typically coiled steel) into a desired cross-section. The strip passes through sets of rolls mounted on consecutive stands, each set performing only an incremental part of the bend, until the desired cross-section (profile) is obtained. Roll forming is ideal for producing constant-profile parts with long lengths and in large quantities.
Roll gap – It refers to the space or distance between the two rotating cylindrical rolls through which a material (like metal) is passed to reduce its thickness and / or shape it.
Roll grind – It is the uniform ground finish on the work rolls which is imparted to the sheet or plate during rolling.
Roll grinding machine – It is a specialized piece of equipment which is used to precisely grind and finish the surfaces of rolls used in rolling mills, ensuring accurate and high-quality metal shaping and forming. These rolls, crucial for shaping metal, can wear or become uneven, leading to defects in the final product, necessitating the use of roll grinders for maintenance and repair. Roll grinding machines are necessary for maintaining the quality and performance of rolling mills by precisely grinding and finishing the surfaces of the rolls.
Roll grooves – These refer to the shaped indentations or channels on the surface of the rolls which shape the metal stock as it passes through the mill. There are different types of grooves which are used for rolling of sections. Common grooves are rectangular box grooves, diagonal grooves such as squares and rhombic grooves (diamonds), round or false round grooves as well as oval grooves. Grooves can be symmetric, asymmetric and slit. Important parameters of grooves are height (depth), groove angle, relief radius, bottom radius, widths at collar, top, and middle bottom and middle bottom deflection. Normally, a combination of grooves is used in the roll pass design.
Roll hardness – It is the hardness of the material of a roll. Roll hardness is to be optimum. Higher hardness improves wear resistance but increases the risk of roll failure. Higher hardness also creates issues during machining and grinding of the rolls. It is not a fact that everything improves in the roll if hardness is higher. In fact, opposite is valid.
Rolling – It is a motion of two relatively moving bodies, of opposite curvature, whose surface velocities in the common contact area are identical with regard to both magnitude and direction. It is a type of motion which combines rotation (normally, of an axially symmetric object) and translation of that object with respect to a surface (either one or the other moves), such that, if ideal conditions exist, the two are in contact with each other without sliding. Rolling is also the reduction of the cross-sectional area of metal stock, or the general shaping of metal products, through the use of rotating rolls. Pure rolling is with no sliding and no spin.
Rolling and forging laps – Laps are elongated surface discontinuities which occur during rolling or forging operations due to the presence of some excessive material (fin) that is folded over. They can result because of oversized passes and blanks or improper handling of the material.
Rolling bearings – These are anti friction bearings or rolling element bearing. These bearings use rolling elements (balls or rollers) to reduce friction. In these bearings, axial, thrust, and moment loads can be supported depending on the bearings and how they are mounted. These bearings can be non-recirculating (limited range of motion, extra low friction) or recirculating (unlimited range of motion). These bearings are essential for reducing friction which enables majority of the machinery to operate efficiently and indeed even to exist. In fact, the first widespread application of rolling element bearings has been to enable the first transportation revolution (the bicycle) to take off. Rolling element bearings also enabled a revolution in manufacturing by making it possible to rapidly design and manufacture low-cost high precision machines, such as lathes, mills, and robots which in turn have helped to rapidly increase productivity. Although rolling bearings are ubiquitous, designing with them needs significant care.
Rolling-contact fatigue – It is the repeated stressing of a solid surface because of the rolling contact between it and another solid surface or surfaces. Continued rolling-contact fatigue of bearing or gear surfaces can result in rolling contact damage in the form of sub-surface fatigue cracks and / or material pitting and spallation.
Rolling-contact wear – It is the wear to a solid surface which results from rolling contact between that surface and another solid surface or surfaces.
Rolling direction – It refers to the direction in which a metal is rolled during processing, which is perpendicular to the axes of the rolls, and is often significant for the final properties and appearance of the metal product.
Rolling-element bearing – It is a bearing in which the relatively moving parts are separated by balls, rollers, or needles.
Rolling equipment – It consists of roll stands, rolls, chocks, bearings, drives, and entry and exit guides.
Rolling friction – It is also called rolling resistance. It is defined as the force which resists one solid rolling on another.
Rolling load – It refers to the force exerted on the rolls and supporting structures during the metal deformation process as the metal stock is passed through the gap between the rolls. It is the load with which the rolls press against the metal.
Rolling mandrel – In ring rolling, it is a vertical roll of sufficient diameter to accept different sizes of ring blanks and to exert rolling force on an axis parallel to the main roll.
Rolling mill – It consists of machines which are used to decrease the cross-sectional area of metal stock and to produce certain desired shapes as the metal passes between rotating rolls mounted in a framework comprising a basic unit called a stand. Cylindrical rolls produce flat shapes, while grooved rolls produce rounds, squares, and structural shapes. Different types of rolling mills are four-high mill, Sendzimir mill, and two-high mill.
Rolling mill cooling bed – It is used for the uniform air cooling of the rolled materials (bars or profiles normally referred as ‘bars’) and transport it in a phased manner from the entry side of the cooling bed to its discharge side. It transfers the bars one by one to the roller table, on which they are transported to the finishing section. It is important equipment in the hot rolling of long products in a rolling mill. A cooling bed carefully moves and cools the hot steel rolled bars after the hot rolling process. Cooling beds are to be specifically designed considering the smallest and the maximum size of the bars being rolled in a particular rolling mill. They are designed for receiving, transferring, and cooling of the rolled material. They are sized so that the product cools within a particular cycle time. The length of the cooling bed is determined by the maximum run-out bar length, optimized by the selling lengths to minimize crop losses. The width of a cooling bed is determined on the basis of mill productivity (tons per hour) and the time required for cooling. Cooling beds normally have natural air cooling. However, for achieving faster cooling of the bars, blowers can be installed for blowing air from the bottom of the hot bars.
Rolling mill equipments – These equipments play a very important role in production of the wire rods. The rolling mill optimization, operational flexibility, and the process reliability play a fundamental role. In order to improve the finished product quality (in terms of size tolerances, mechanical properties and surface finish), a reliable and dedicated automation system is also needed. Different automation systems are implemented in modern rolling mills to control thickness/section, the angular speed of the rolls, and the tension between the stands and the related temperatures. Specific thermo-mechanical processes and automated control systems have been developed to enhance the technological properties, tolerances and surface quality of the rolled product.
Rolling mill guide equipments – In hot rolling mills for long products, guide equipments guide the rolling stock at the entry and the exit of the roll pass so as to have smooth rolling of the rolling stock. The guiding equipments are to be sturdy, accurate and stable. Rolling mill guide equipments play a major role in ensuring the surface quality of the rolled product. The guides are to be designed for the wide variety of stock sizes and shapes which are normally encountered in the long product rolling. The guide equipments are usually classified in three ways namely (i) position with respect to the working stand (e.g. entry guide and exit guide etc.), (ii) method of construction, and (iii) type of friction between the rolling stock and the working element of the guide equipment (e.g. sliding or rolling etc.).
Rolling mill scheduling – It involves the systematic planning and organization of various production tasks within a mill facility. It encompasses the coordination of processes such as heating, rolling, and cooling to ensure a continuous flow of materials and efficient utilization of equipment. The scheduling process is essential for meeting production targets, maintaining product quality, and minimizing downtime. The role of scheduling in managing production processes cannot be overstated. It acts as a bridge between the demand for finished products and the capabilities of the rolling mill. Scheduling involves creating a timeline that optimally sequences tasks, from preparing raw materials to the final product’s dispatch. Key terms and concepts in the scheduling include job sequencing, batch processing, lead times, and setup times.
Rolling mill shears – A number of shears are installed in a rolling mill. Rolling mill shears are used to cut steel bars, plates, or other shapes into smaller sizes, either during the rolling process (hot shears) or after (cold shears). Shears are crucial components in rolling mills. Each shear has different objective. Hot shears are used before the cooling bed. These shears cut the metal while it is still hot. Cold shears are used after the cooling bed These shears cut the finished steel products to their required length. Types of shears include (i) flying shears which are synchronized with the rolling speed to provide an accurate cut during the rolling process, (ii) rotary Shears which are used for cutting bars, plates, and other shapes, (iii) crank shears which are a type of flying shear that can be semi-automatic or fully automatic, (iv) cropping shear which is used for cropping both ends of the rolling stock being rolled,(v) cooling bed shear which cuts the rolled bar in cooling bed length, and (vi) dual shears which are a combination of rotary and lever shear used for cutting to cooling bed lengths.
Rolling mill stands – These are the most essential equipment in the rolling mill process. A rolling mill stand is normally fitted with a number of rolls through which the work-piece bar is passed giving it the required cross-section. There are different designs of mill stands each having different applications to the rolling process.
Rolling pressure – It refers to the force exerted by the rolls on the metal being processed, leading to its deformation and shaping. This pressure is crucial for achieving the desired thickness, shape, and mechanical properties of the rolled product. The pressure applied by the rolls causes the metal to deform plastically, meaning it changes shape permanently. Roll pressure is a useful quantity for characterizing the mechanics of the rolling process. It is the average normal stress, pressure, acting between the work piece and roll. The pressure is not constant since the stress acting to deform the work piece is the stress needed to overcome material strength, frictional forces, and any constraints placed on the deformation by process characteristics.
Rolling schedule – It plays a decisive role in rolling of strip in HSM. Traditionally, the most important factor is the evolution of the profiles of the rolls in the mills caused by their wear and thermal expansion. From this derives the `coffin’ schedule which means start narrow, quickly build up to wider material as the thermal crowns increase on the rolls, and gradually fade back to narrow as the rolls wear. Rolling schedule has an important effect on the capability of mill. The rolling mill schedule includes reduction, speed, and temperature schedules. Reduction schedule determines rolling passes and the reduction per pass. Speed schedule determines the bite speed, through speed and maximum rolling speed without variation in acceleration and deceleration of the motor. Temperature schedule controls the temperature drop of mill house and finish rolling temperature by cooling water flow according start rolling temperature. The issues which are important for the rolling schedule are (i) the shape of the strip is good and the crown meets the specifications requirement, (ii) the yield of rolling mill, and (iii) the good performance of strip. The rolling schedule is to ensure that the strips produced in the hot strip mill meets the requirements of dimensions, comprehensive properties and microstructure of the strip.
Rolling sequence – It refers to the specific order and parameters (like temperature, reduction, and pass time) of successive passes or ‘stand’ (pairs of rolls) used to deform metal stock and achieve a desired final shape or thickness.
Rolling slab – It is a rectangular semi-finished product, produced by hot rolling fabricating ingot and suitable for further rolling.
Rolling speed – It refers to the surface speed of the rolls, which is the velocity at which the metal strip is drawn through the gap between the rolls during the rolling process. In the context of physics, rolling speed refers to the linear speed of the centre of mass of a rolling object, which is related to its rotational speed and radius.
Rolling stock – It refers to any railway vehicle which moves exclusively on rails or a tracked transport system. The term includes all powered (e.g., locomotives) and unpowered vehicles (e.g., passenger carriages or coaches and goods wagons etc.).
Rolling velocity – It is the mean of the surface velocities of two bodies at the area of contact. Occasionally the sum of the velocities is quoted instead of the mean.
Roll lathe – It is a specialized lathe which is designed for turning and processing the cylindrical rolls used in rolling mills.
Roll marks – Roll marks are ‘embossed’ elevations or depressions normally recurring periodically and varying greatly in shape and size. The defect can be normally detected with the naked eye or with a low magnification on the scaled or descaled sample. If the defect occurs as elevations on the surface of the rolled product, it is caused by depressions of various kinds in the rolls themselves or in the pinch rolls. Depressions in the wire rods are caused by elevations on such installations, e.g., chips and remnants of scale.
Roll materials – These are the materials from which the rolls are made. In the rolling of steels, the material of the rolls is to be capable of withstanding loads which plastically deforms the rolling stock without itself being plastically deformed. In the rolling of hot steel this is not a difficult problem and iron or steel rolls are suitable if they are operated at a temperature considerably lower than that of the rolling stock. Whether iron or steel rolls are used in any particular case depends on the specific duty they have to perform and whether toughness, resistance to thermal cracking or shock loading or hard-wearing properties is most important. Rolls can be classified as per the roll materials and the method of manufacture, the first main subdivision being (i) iron rolls, (ii) steel rolls, and (iii) carbide rolls (made from tungsten carbide). This division depends on the carbon content of the material. In the case of rolls the demarcation line is normally taken at around 2.4 % C. Normally rolls are referred as being steel base below this figure, and iron base above this figure. There is a marked structural distinction between these two types as there is no free graphitic carbon in steel base rolls. Steel rolls can be either cast, or forged so giving a further subdivision. One other division which cuts across the above classification is that of double poured duplex rolls which may be cast with a hard metal outer surface and a tougher and stronger metal forming the centre of the roll.
Rollover burr – It is the burr which is formed by a cutter when it exits over a surface and allows the chip to be rolled away from the cutter, rather than sheared.
Roll pass – It refers to the grooves or shapes cut into the rolls of a rolling mill to deform and shape metal stock into a desired profile or cross-section. Rolling is carried out between grooved rolls. Two opposite grooves in the collaborating rolls form a pass, which corresponds to a work piece’s cross section shape expected after the pass. After every pass, the cross section decreases and its shape becomes closer to a shape of the final product.
Roll pass design – Development of subsequent pass shapes and its proper location on the rolls is called the roll pass design. It consists of a set of methods for determining the dimensions, shape, number, and type of arrangement of rolling mill passes. Roll pass design also includes the calculation of pressing forces and their distribution on the roll passes. It is an innovative technique to ensure stability, flexibility, and quality in a rolling mill which is rolling rounds and shapes. It involves the calculation of pressing forces and cutting grooves in the roll body through which steel bar which is being rolled is made to pass sequentially and achieve the required contour, shape and size. With roll pass design, a person can determine the shape, dimensions, number, and type of arrangement of rolling mill passes. It is also be possible to carry out power calculation through simulation (gear ratios, motor sizes, and rolling). Roll pass design is an essential part of long product rolling process, since the long products are rolled between the shaped rolls in the long product rolling mills. Roll pass design generally means the cutting of grooves in the roll body through which steel to be rolled is made to pass sequentially to get the desired contour and size. The primary objective of the roll pass design is to ensure production of a product of correct profile within the tolerance limits, free of defects, with good surface quality and the required mechanical properties.
Roll pickup – It consists 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.
Roll pressure distribution – It refers to the variation of pressure exerted by the rolls on the workpiece along the contact arc. This pressure distribution is crucial for understanding and optimizing rolling operations, influencing factors like energy requirements and the final product’s quality.
Rolls – Rolls are the basic part of a roll stand and are normally the most vital and very costly part of a rolling mill. The rolling stock is plastically deformed between the rolls. Rolls ensure the required shape, dimension and surface quality of the rolled product. They transfer the force and torque load. The deformation of rolling stock is directly accomplished by the rolls. Rolls are needed to carry out the heavy work of reduction of the cross section of the metal being rolled. Rolls have to take all kind of stresses, loads from normal and abnormal rolling and which are changing with the roll wear during a rolling campaign. Roll are required never to break, spall or wear. They are expected to give excellent performance without causing any problems. Under the conditions of rolling, the contact area of the roll which comes in contact with the rolling stock suffers wear, while other parts of the roll body and roll necks does not experience plastic deformation or fatigue but are under high loads.
Roll separating force (RSF) – It is the force needed to separate the rolls and deform the material, typically measured as the force per unit width. It is a critical parameter in rolling process design, influencing factors like roll strength, power consumption, and the final shape and size of the rolled product.
Roll shop – It is the area or department which is responsible for the maintenance, repair, and preparation of the rolls used in the rolling process, ensuring they are in optimal condition for producing high-quality rolled products. The functions of the roll shop include (i) to receive roll assembly from the rolling mill after completion of a rolling campaign, (ii) to wash the roll assembly and dismantle the rolls from the assembly, (iii) inspection of the rolls for fire cracks, measurement of diameter, and inspection of the individual parts of the rolls and roll bearing and rotating them wherever necessary, (iv) planning and carrying out grinding / regrooving of the rolls as per plan, (v) storing of ground / regrooved roll in roll racks where these rolls wait for their assembly as per rolling schedule of the mill, (vi) dismantling of the chocks and sending them to assembly area for assembling the ground / regrooved roll as per the rolling schedule, (vii) carrying out the assembly of the roll and chock in pairs, and (viii) sending the assembled roll pair to rolling mill.
Roll stand – It is the fundamental structural unit which houses and supports the rolls, which are used to shape and reduce the thickness of materials. Roll stands are essential components in rolling mills, playing a crucial role in the rolling process by housing and supporting the rolls which deform the metal stock.
Roll stand housing – Roll stand housing creates a framework of the rolling mill stand and for absorbing the total metal pressure on rolls during the process of rolling. Hence, the housing is to be solid and its structure is to enable easy and fast roll changing. Its construction and dimensions have to take into account the sizes of various other elements. Also, there need to be easy access to all parts of the housing and other details of the roll stand. Each of the roll stands has two housings, in which rolls are placed with chocks (bearings). In the upper part of the housing, there are adjusting screws (screw down mechanism) and the roll counter-balancing device along with their drives. The housings need high rigidity, sufficient strength for taking the loads, simplicity of design and minimum cost of production.
From the structural viewpoint, the housings can be classified into three types. These are (i) enclosed housing where the whole housing is made of one piece and which is more beneficial from the strength point of view, (ii) open housing which has the separated cap, connected to the housing by screws for easier rolls changing, and (iii) housing-less roll stand which has rigid chocks connected by solid and pre-stressed joints. The housing-less roll stand has limited stress relaxation (spring-back) of rolls and has smaller and lighter structure.
Roll straightening – It is the straightening of metal stock of different shapes by passing it through a series of staggered rolls, the rolls normally being in horizontal and vertical planes, or by reeling in two-roll straightening machines.
Roll texturing machine – It is a device which utilizes techniques like electrical discharge texturing (EDT) to create controlled surface textures on work rolls, which in turn transfer these textures to the rolled products.
Roll threading – It is the production of threads by rolling the piece between two grooved die plates, one of which is in motion, or between rotating grooved circular rolls. It is also called thread rolling.
Roll transfer car – It is a piece of equipment which is used to transport rolls (both work and backup rolls) between the mill bay, across the bays and the roll shop for maintenance, storage, or replacement. Roll transfer cars facilitate the efficient and safe movement of heavy rolls, which are crucial components in rolling mills, used for shaping metal into various products. These cars are designed to handle the weight and size of rolls, often using a combination of manual and automatic controls for precise positioning and movement.
Roll turning machine – It is also known as a roll lathe. It is a specialized machine which is used in rolling mills to accurately machine and shape the cylindrical rolls used in metal forming processes, improving productivity and product quality. These machines are mainly used for the regrooving of the rolls used for shape rolling. Roll turning machines, particularly CNC (computer numerical control) lathes, are designed to precisely machine the surfaces of rolls used in rolling mills. These machines are crucial for maintaining the quality and consistency of the rolled metal products, as the shape and surface finish of the rolls directly impact the final product.
Roll welding – It is the solid-state welding in which metals are heated, then welded together by applying pressure, with rolls, sufficient to cause deformation at the faying surfaces. It is a process in which two or more sheets or plates are stacked together and then passed through rolls until sufficient deformation has occurred to produce solid-state welds. Two modes of roll welding are common. In the first, the parts to be welded are merely stacked and passed through the rolls. The second method, normally termed pack rolling, involves sealing the parts to be rolled in a pack or sheath and then roll welding of the pack assembly is done. The first method is more generally used in the cold welding of ductile metals and alloys. Sometimes the stack to be welded is first tack welded at several locations to ensure alignment during rolling. Also, when using this method, the deformation during the first rolling pass is required to exceed the threshold for welding (typically higher than 60 % for cold rolling) to keep the parts together. The required first pass reduction can be reduced by hot rolling, if the metals to be rolled can tolerate preheating without excessive oxidation. Once the first pass has been accomplished, the reduction per pass can be decreased, as is frequently desirable because roll-separating forces increase as the parts to be rolled become thinner. However, the non-uniform stress distribution which builds up during a sequence of very light passes can cause the weld to open up or ‘alligator’. Hence, the reduction for subsequent passes is normally a compromise between applying excessive separating forces and ‘alligatoring’. In pack roll welding, the parts to be welded are completely enclosed in a pack that is sealed (typically by fusion welding) and frequently evacuated to provide a vacuum atmosphere. This can be accomplished by a frame that surrounds the parts to be welded, which is sandwiched by two lids, or can simply consist of two covers formed to encapsulate the parts to be welded. Semi-killed or killed low-carbon steel is a common material for the pack, but is not suitable for all alloy and temperature combinations. Although the preparation costs of pack roll welding are significant, the process has the advantages of (i) providing atmospheric protection, which can be particularly important for reactive alloys such as those of titanium, zirconium, niobium, and tantalum, and (ii) permitting welding of complex assemblies involving several layers of parts. A significant limitation of the process is that packs become difficult to process when their length exceeds a certain length.
Romelt process – It is a process for ironmaking. It is a smelting reduction process for the production of hot metal (liquid iron). It is a single stage liquid-phase iron reduction process. In the process, the iron bearing materials are supplied to the slag bath by gravity and agitated by gas. They dissolve in slag. Iron oxides are reduced from slag with the help of coal carbon, which is also supplied by gravity and blown into the bath. In order to intensify heat and mass transfer slag bath bubbling with oxidizing gas, which is injected under the surface of the slag, is carried out. Gas containing carbon mono-oxide and hydrogen evolves from the melted slag. The evolved gas is combusted at the top. The heat of this post combustion mostly provides thermal energy for the reactions taking place in the slag bath. A key element of effective process to take place is the active heat transfer between the zone of post-combustion and slag bath. The special features of the Romelt process include (i) flexibility to use wide range of iron bearing materials, (ii) no preparation needed for the raw materials, (iii) use of non-coking coal as fuel and as reducing agent, (iv) supporting production units such as coke-ovens and sintering plant are not required, (v) has capacity to generate sufficient power to meet overall plant requirements including oxygen plant, (vi) reduces the cost of hot metal as compared to blast furnace route, and (vii) can be used for waste processing in which case the cost of hot metal is further reduced.
Roof beam and shuttering layout drawing – A roof beam is made to strengthen the overall structure of a building. A roof beam is a triangular structure which is normally made on the top of the building.
Roof, building – It is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of temperature, and wind. A roof is part of the building envelope. The characteristics of a roof are dependent upon the purpose of the building that it covers, the available roofing materials, the local traditions of construction, wider concepts of architectural design and practice, and can also be governed by the statutory regulations.
Roof, furnace – It refers to the top surface or cover of a furnace, acting as a vital part of the furnace’s design for heat retention, safety, and process control.
Roofing sheet – It is coiled or flat sheet in specific tempers, widths, and thicknesses suitable for the manufacture of corrugated or V-crimp roofing.
Roof slab layout drawing – The roof slab layout drawing is more prominently made in the AutoCAD architectural software. The main purpose of the roof slabs is to provide a detailed account of the floors, roof faces, and other such surfaces which need precise edge information.
Room-and-pillar mining – It is a method of mining flat-lying ore deposits in which the mined-out area, or rooms, are separated by pillars of approximately the same size.
Room temperature – It refers to the range of temperatures which are normally considered comfortable for human occupancy, typically between 20 deg C to 25 deg C. In engineering contexts, room temperature serves as a standard reference point for different experiments and measurements, frequently used when specific temperature control is not necessary. Room temperature dry normally refers to a storage environment which is neither excessively hot nor cold, and also has low humidity, typically around 20 % to 30 %, to prevent moisture-related issues. Room temperature wet refers to the wet-bulb temperature, which is the lowest temperature achievable through evaporative cooling of air, typically measured using a thermometer with a wet cloth around its bulb.
Room-temperature curing adhesive – It is an adhesive which sets (to handling strength) within an hour at temperatures from 20 deg C to 30 deg C and later reaches full strength without heating.
Room-temperature vulcanizing (RTV) – It consists of vulcanization or curing at room temperature by chemical reaction. It normally applies to silicones and other rubbers.
Room-temperature-vulcanizing silicone – It is a type of silicone rubber which cures at room temperature. It is available as a one-component product, or mixed from two components (a base and curative). Manufacturers provide it in a range of hardnesses from very soft to medium (normally from 15 Shore A to 40 Shore A. Room-temperature-vulcanizing silicones can be cured with a catalyst consisting of either platinum or a tin compound such as dibutyltin dilaurate.
Root – It is non-standard term for joint root and weld root.
Root bead – It is a weld which extends into or includes part or all of the joint root.
Root cause analysis (RCA) – It is also known as root cause failure analysis (RCFA). It is a method of problem solving used for identifying the root causes of faults or problems. It is the process of investigating how an equipment failure, process problem, quality problem, safety incident, environmental incident, and several other problems in a plant has happened. It is widely used analysis process. Root cause analysis is a form of inductive inference (first create a theory, or root, based on empirical evidence, or causes) and deductive inference (test the theory, i.e., the underlying causal mechanisms, with empirical data). Root cause analysis can be decomposed into four steps namely (i) identify and describe the problem clearly, (ii) establish a timeline from the normal situation until the problem occurrence, (iii) distinguish between the root cause and other causal factors (e.g., through event correlation), and (iv) establish a causal graph between the root cause and the problem. Root cause analysis normally serves as input to a remediation process whereby corrective actions are taken to prevent the problem from recurring.
Root crack – It is a crack in either the weld or heat-affected zone at the root of a weld.
Root edge – It is a root face of zero width.
Root face – It is that portion of the groove face adjacent to the joint root.
Root gap – It is a non-standard term for root opening.
Root locus – It is a graphical method for analyzing the properties of a transfer function as some parameter is varied.
Root mean square (RMS) – It is a term describing the surface roughness of a machined surface, calculated as the square root of the average of the squared distance of the surface from the mean line. The root mean square of a set of numbers is the square root of the set’s mean square. Given a set Xi, its root mean square is denoted as either Xrms or RMSx. The root mean square is also known the quadratic meanM2 a special case of the generalized mean. The root mean square of a continuous function is denoted frms and can be defined in terms of an integral of the square of the function. The root mean square value of a set of values (or a continuous-time waveform) is the square root of the arithmetic mean of the squares of the values, or the square of the function which defines the continuous waveform. Root mean square is also the statistical average value of the amplitude generated by a machine, one of its components, or a group of components. The root mean square value of a waveform is the direct current value which corresponds to equivalent heating value.
Root mean square (RMS) speed – The root mean square speed of gas molecules is the measure of the average speed of gas particles at a specific temperature. It is the square root of the average of the squared speeds of a group of values. It is a way to measure how fast gas particles moves in a particular direction.
Root opening – It is the separation at the joint root between the work-pieces.
Root penetration – It is the depth which a weld extends into the joint root.
Root radius – It is a non-standard term for groove radius.
Root reinforcement – It consists of weld reinforcement opposite the side from which welding has been done.
Root surface – It is the exposed surface of a weld opposite the side from which welding was done.
Roping – It is a ropelike appearance in the rolling direction after the metal has undergone severe deformation. Roping or looper lines, is also a phenomenon of surface roughening, witnessed during deep drawing. The name roping is linked to characteristic ‘roping’ marks on drawn shapes. The roping is also caused by non-uniform deformation, non-uniformity linked to irregularities or heterogeneities in the structure. As an example, macro-segregation from the cast structure can produce striated structure or surface banding or roping marks. Alternatively, the roping can also develop from deformed grains or bands of fine grains of similar orientations. In both the cases roping can originate from earlier coarse grains.
Rosette – It is rounded configuration of microconstituents in metals arranged in spirals or radiating from a centre. It also consists of strain gauges which are arranged to indicate at single position strains in three different directions.
Rosette graphite – It is an arrangement of graphite flakes in which the flakes extend radially from the centre of crystallized areas in gray cast iron.
Rosin – It is a resinous material obtained from pine trees and other plants, mostly conifers. The primary components of rosin are diterpenoids, i.e., C20 carboxylic acids. Rosin consists mainly of resin acids, especially abietic acid. Rosin frequently appears as a semi-transparent, brittle substance which ranges in colour from yellow to black and melts at stove-top temperatures.
Rosin mildly activated (RMA) flux – It is a type of solder flux consisting of rosin, solvent, and a small amount of activator, designed for easily solderable surfaces, with low activity and often non-corrosive and non-conductive residues that may be left on the board.
Rosin super activated flux – It is s a type of solder flux. It consists of rosin with very strong activators. It has very high activity. There is a need for thorough cleaning of residues after soldering.
Rotary airlock valve – It is an airlock with an inlet and outlet. It is frequently used in industrial applications, where materials are to be controlled by, high or low pressures. It is also suitable for fluids with varying temperatures, and can withstand high pressures. There are several types of rotors used in rotary airlock valves, each of which performs well in different applications. The rotors in these valves vary in shape, diameter, and strength, and they are designed to minimize material and pressure losses. The rotor vanes are normally made from abrasion-resistant steel, making them perfect for use in corrosive environments. In addition, the rotary airlocks are also suitable for applications where the material that passes through the valve is too abrasive, or explosive. A proper design of a rotary airlock valve can greatly reduce the amount of leakage. In order to create the best seal possible, the body and end covers of a rotary valve must be heavy-duty and precision-machined. The rotor has a raised face inside the end cover, which ensures a proper seal and alignment with the housing. The shaft needs to be large enough to prevent deflection, and it should also be designed to fit tightly inside the housing.
Rotary control valve – – It is a valve style in which the flow closure member (full ball, partial ball, disk, or plug) is rotated in the flow stream to control the capacity of the valve. This valve regulates fluid flow by using a rotating motion (like a quarter-turn) to open, close, or throttle the flow, unlike linear control valves which use a straight-line motion.
Rotary converter – It is an electric machine which converts electric power between two forms, say, alternating current and direct current or single-phase and three phase, or between two different frequencies of alternating current (the latter two can be performed by the same machine).
Rotary die cutting – It is a special kind of die cutting which uses a cylindrical die to cut shapes out of material. It is a high-speed industrial manufacturing process which uses a cylindrical die rotating on a press to cut out shapes from a web of material, offering high accuracy and efficiency for large-volume production.
Rotary drill – It is a machine which drills holes by rotating a rigid, tubular string of drill rods to which is attached a bit. It is normally used for drilling large-diameter blastholes in open-pit mines.
Rotary drum feeders – It is simple and sturdy feeder which is suitable for free flowing and small lump bulk materials. It extracts the material from the storage unit. The discharge is positive volumetric and accurate. This feeder is not suitable for very abrasive materials in continuous duty application. It is also not suitable for sticky materials. The material rubs continuously with rotating periphery. This feeder can be considered as an extremely short belt feeder. The drum prevents the bulk material from flowing out but discharges it by rotation. This feeder is only suitable for materials with good flowability which are not prone to aeration.
Rotary dryer – It is an industrial dryer which uses a rotating cylinder (or drum) to reduce moisture content in materials by bringing them into contact with heated gas. Rotary dryers are designed to efficiently dry a variety of materials, including powders, granules, and bulk solids, by exposing them to heated air or gas within a rotating cylindrical shell.
Rotary encoder – It is a transducer which converts rotation of a shaft to a measurement.
Rotary forging – It is a process in which the work-piece is pressed between a flat anvil and a swiveling (rocking) die with a conical working face, with the platens move toward each other during forging. It is also called orbital forging.
Rotary furnace – It is a circular furnace constructed so that the hearth and workpieces rotate around the axis of the furnace during heating. It is also called rotary hearth furnace.
Rotary hearth furnace (RHF) – It is a type of furnace which is used for various high-temperature industrial processes, particularly in the steel industry. It is very useful for several purposes. Besides being utilized for the heating of circular loads (for example in the pipe rolling mills), the rotary hearth furnaces are also being used for the reduction processes. It is designed to heat and process materials such as iron ore, carbon-based materials, and other metallic and non-metallic substances. The basic structure of a rotary hearth furnace consists of a circular hearth or platform that rotates on a set of wheels or rollers. The hearth is typically made of refractory materials that can withstand high temperatures. The furnace chamber is enclosed and heated using burners or other heat sources.
Rotary kiln – It is an inclined, rotating cylindrical reactor through which a charge moves continuously.The rotary kiln is used when thermal processing of solids which is more severe than drying is needed. The furnace walls (normally lined) make intermittent contact with the flue gas and the charge. Heat needed for the various physical and chemical processes is delivered to the charge by lifting and overturning the charge as it moves through the interior of the rotary kiln. The rotary kiln consists of a lined hollow cylinder, mounted in an inclined position on rolls and rotated slowly by a drive. The charge material moves from the feed end to the discharge end because of the rotary motion and gravity. The inclination is between 1.5 % and 5 %. Speed is between 0.2 revolutions per minute and 2 revolutions per minute. Variable-speed drives are normally used to control the residence. Kiln diameter is normally constant over the full length. Some rotary kilns have internals such as conveying or lifting flights, built in crossed-hanging link chains, or ring dams. In some processes, air-feed pipes or burner tubes for gas or oil are installed on the furnace shell. Air or other gases can also be introduced through ports in the lining. Rotary kiln carries out several functions simultaneously. It is equipment for conveying, mixing, heat transfer, and reaction. These functions are to be in harmony. The most widespread usage of rotary kiln is in the production of cement clinker, limestone calcining, production of calcined and dead burnt dolomite, calcined magnesite, and iron ore reduction for the production of direct reduced iron (DRI) etc.
Rotary kiln process – Rotary kiln carries out several functions simultaneously. It is a device for conveying, mixing, heat transfer, and reaction. These functions are needed to be in harmony. The charge in the kiln moves both radially and axially. Radial motion is determined by the degree of filling (percentage of cross-sectional area occupied by the charge) and the rotational speed. The angle of repose and the kiln inclination govern axial motion. The interior of the charge tends to have a higher bulk density than the exterior, and grain size increases toward the outside. This tendency can be counteracted by the internals, which also improve heat transfer into the charge. Dust production can be limited by pelletizing the feed. Heat transfer occurs principally from the combustion gas (generated by a burner usually installed at the discharge end of the kiln) to the charge. The driving force is normally the temperature difference. The gas can move co-current or counter-current to the longitudinal motion of the charge. Co-current gas flow is advantageous only when the charge temperature does not have to exceed a certain value. The counter-current arrangement is preferred. The different types of heat transfer in a rotary kiln are (i) heat transfer to material by gas radiation and convection, (ii) heat transfer to material by brick radiation, (iii) conductive heat transfer to material from brick, and (iv) heat transfer to brick by radiation, convection, and (v) heat loss by shell radiation and convection.
Rotary kiln sizing and design – Every material is different in terms of how it behaves in the kiln and at what temperatures different reactions are going to occur. When designing a process around a rotary kiln, as well as in the design of the kiln itself, the material is required to undergo thorough chemical and thermal analyses. Various material characteristics play a part in how the material is going to perform in the kiln, and subsequently, how the kiln is to be designed around the material to accomplish the process goal. The following provides an overview of some of the normal material characteristics which can influence the design of the kiln.
Rotary motion – It is also known as rotational or circular motion. It is the movement of an object around a fixed point or axis.
Rotary motion valve – It is the valve in which the valve-closure member travels along an angular or circular path, such as in butterfly, ball, plug, eccentric- and swing check valve.
Rotary oil burner – It is a burner in which atomization is accomplished by feeding oil to the inside of a rapidly rotating cup.
Rotary plough feeders – These feeders are normally of is travelling type. They extract material from storing unit shelf. The feeder travel and thereby storage unit outlet length can be up to 200 meters or so. This feeder is suitable to operate in tunnel under stockpile. The feeder along with civil work is an expensive proposition, and is used to reclaim material from track hopper or long stockpile on storage-yard. The feeder can deal with practically any bulk material, and in large capacity range. The feeder requirement in a particular layout arrangement is without alternative option of matching performance. Thus, this feeder does not compete with other feeders, but competes with the reclaiming machines. It is more as reclaiming machine-cum-feeder. The feeder extracts the material forcefully and so, it can also deal with bulk materials, which have tendency to pack or interlock. The typical capacity range is up to 1250 cubic meters per hour. More capacity is also possible. In general, this is used for lump size up to 450 millimeters. This depends upon the characteristics of the bulk material.
Rotary pump – It is a type of positive displacement pump that uses rotating parts, like vanes, gears, or lobes, to move a fixed volume of fluid with each revolution, resulting in a continuous, non-pulsating flow. Rotary pumps use mechanical devices such as pistons, gears, or screws to discharge a commodity at a smooth, continuous rate of flow. Seven types of rotary pumps include sliding vane, axial piston, flexible member, lobe, gear, circumferential piston, and screw type rotary pump.
Rotary press – It is a machine for forming powder metallurgy parts which is fitted with a rotating table carrying multiple die assemblies in which powder is compacted.
Rotary regenerator – it is also known as heat wheel. Rotary regenerator is similar to fixed regenerator since the heat transfer is facilitated by storing heat in a porous media, and by alternating the flow of hot and cold gases through the regenerator. Rotary regenerators, sometimes referred to as air preheaters and heat wheels, use a rotating porous disc placed across two parallel ducts, one containing the hot waste gas, the other containing cold gas. The disc, composed of a high heat capacity material, rotates between the two ducts and transfers heat from the hot gas duct to the cold gas duct. Heat wheels are generally restricted to low and medium temperature applications due to the thermal stress created by high temperatures. Large temperature differences between the two ducts sometimes lead to differential expansion and large deformations, compromising the integrity of duct wheel air seals. In some cases, ceramic wheels are used for higher temperature applications. Another issue with heat wheels is preventing cross contamination between the two gas streams, as contaminants can be transported in the wheel’s porous material.
Rotary retort furnace – It is a continuous-type furnace in which the work advances by means of an internal spiral, which gives good control of the retention time within the heated chamber.
Rotary roughening – It is a method of surface roughening prior to thermal spraying wherein a revolving roughening tool is pressed against the surface being prepared, while either the work, or the tool, or both, move.
Rotary seal – It is a mechanical seal which rotates with a shaft and which is used with a stationary mating ring.
Rotary shear -It is a sheet metal cutting machine with two rotating-disk cutters mounted on parallel shafts driven in unison.
Rotary stem – This type of stem is a normally used stem model in ball, plug, and butterfly valves. A quarter-turn motion of the stem open or close the valve.
Rotary swager – It is a swaging machine consisting of a power-driven ring which revolves at high speed, causing rollers to engage cam surfaces and force the dies to deliver hammer-like blows on the work at high frequency. Both straight and tapered sections can be produced.
Rotary swaging – It is a bulk forming process for reducing the cross-sectional area or otherwise changing the shape of bars, tubes, or wires by repeated radial blows with one or more pairs of opposed dies.
Rotary switch – It is a switch which is operated manually or electrically with a rotary motion of the contacts.
Rotary table feeders – These feeders are normally used for the volumetric feeding of fine bulk materials solids which have reasonably good flowability. They are suitable to install under storage unit outlet of larger diameter to prevent clogging by the sluggish material. The feeders are suitable for nonabrasive and marginally abrasive bulk materials. The material continuously rubs / slides on the table. However, table can be fitted with thick liner if needed. Discharge is volumetric in nature. The capacity range is normally less than 20 cubic meters per hour. The rotary table feeder can be considered as an inverse of the plough feeder.
Rotary table furnace – It is also known as rotating hearth furnace. In this furnace, materials are placed on the merry-go-round-like hearth. The materials travel on a circular track and undergo reduction reactions / heating while travelling. The reduced product / heated material is later removed after the materials have completed almost a whole revolution. The furnace has several zones.
Rotary transformer – It is a transformer which is used to couple electric signals or power between rotating parts.
Rotary tube piercing (RTP) – It is also known as the Mannesmann process. It is a hot-working metal-working process used to manufacture seamless tubes by forcing a heated cylindrical billet through a rotating piercer, creating a hollow shell.
Rotary valves – These valves use rotational motion to turn a closure member into and out of a seating surface.
Rotary vane feeders – These feeders can be considered as an extremely short apron feeder. They are particularly used to discharge fine freely flowing bulk materials from the storage units, while maintaining sealing so that air / gases do not flow into storage unit when the storage unit is under negative air pressure. These feeders are regular features for discharge of dust from dust collection hopper / enclosure in a dust extraction plant. These feeders can also be used when such sealing is not needed. The discharge is positive volumetric in nature. The other area of application can be process-plant, where material is to flow in a totally enclosed construction. The feeder is suitable for materials which are free-flowing and non-sticky. This feeder application competes with screw feeder, but is not as popular as screw feeder. However, if feeding is to be accomplished with minimum horizontal displacement, then this feeder is the choice.
Rotary variable differential transformer – It is a transformer-like transducer which measures rotation as an analog value.
Rotating biological process– It is a fixed film aerobic process similar to the trickling filter process except that the media is supported horizontally across the tank of the waste-water. The media upon which the bacteria grow is continuously rotated so that it is alternately in the waste-water and the air.
Rotating electrode powder – It is an atomized powder consisting exclusively of solid spherical or near spherical particles.
Rotating electrode process (REP) – In this process, a bar of the desired composition, 15 millimeters to 75 millimeters in diameter, serves as a consumable electrode. The face of this positive electrode, which is rotated at high speed, is melted by a direct current electric arc between the consumable electrode and a stationary tungsten negative electrode. The process is carried out in helium. Centrifugal force causes spherical molten droplets to fly off the rotating electrode. These droplets freeze and are collected at the bottom of the tank, which is filled with helium or argon. A major advantage of this process is the elimination of ceramic inclusions and the lack of any increase in the gas content of the power relative to the alloy electrode.
Rotating equipment loads – Typical heavy rotating equipments include centrifugal air and gas compressors, horizontal and vertical fluid pumps, generators, rotating steam and gas turbine drivers, centrifuges, electric motor drivers, fans, and blowers. These types of equipments are characterized by the rotating motion of one or more impellers or rotors. The rotating equipment loads are (i) dynamic loads because of unbalanced masses, (ii) design levels of unbalance and basis (this information documents the unbalance level the subsequent transmitted forces are based on), (iii) equipment unbalance provided by the manufacturer, (iv) equipment unbalance meeting industry criteria, (v) equipment unbalance determined from trip vibration level and effective bearing stiffness(vi) dynamic load determined from an empirical formula, and (vii) loads from multiple rotating equipments.
Rotating influent distributor – It is normally used in trickling filters for waste-water treatment. It is a mechanism which evenly distributes waste-water across the filter media bed by rotating arms with orifices or spreaders.
Rotating screen effect – The interlaced toothed rotor design of mineral sizers allows free flowing undersize material to pass through the continuously changing gaps generated by the relatively slow-moving shafts.
Rotating shears – These shears have the leading-edge technology and are used when high speed and accuracy are required. This is achieved by an optimized combination of motion control strategies aiming to get the best performance with the minimum effort from the machine. Fast dynamic motion applied to rotating blades and the diverter are necessary to deliver highly versatile and accurate rotating shears, capable of doing head and tail crops, scrapping and cut-to-measure at a speed of up to 100 meters per second. A peculiarity of rotating shears is the synergy between a high inertia system (the shear blades) and a low inertia system (the diverter). The big challenge for upgrades is to use the same motion control system for both parts, optimizing it for the two different tasks.
Rotating wheel test – It is also known as a rotating wheel dip test (RWDT). It is a method used to assess the tracking and erosion resistance of composite insulator housing materials by subjecting them to artificial harsh environments and electrical stress.
Rotational acceleration – It is the rate of change of rotational velocity. It has dimension of squared reciprocal time and SI (International System of Units) units of squared reciprocal seconds. Hence, it is a normalized version of angular acceleration and it is analogous to chirpyness.
Rotational casting – It is a method which is used to make hollow articles from thermoplastic materials. The material is charged into a hollow mould capable of being rotated in one or two planes. The hot mould fuses the material into a gel after the rotation has caused it to cover all surfaces. The mould is then chilled, and the product is stripped out..
Rotational energy – It is also called angular kinetic energy. It is the kinetic energy because of the rotation of an object and is part of its total kinetic energy. Looking at rotational energy separately around an object’s axis of rotation, the dependence on the object’s moment of inertia which is observed is Erotational = 1/2 I x w square, Erotational=12Iω2where ‘w’ ω is the angular velocity, ‘I’ I is the moment of inertia around the axis of rotation, and ‘E’ E is the kinetic energy. The mechanical work needed for or applied during rotation is the torque times the rotation angle. The instantaneous power of an angularly accelerating body is the torque times the angular velocity. For free-floating (unattached) objects, the axis of rotation is normally around its centre of mass. There exists close relationship between the result for rotational energy and the energy held by linear (or translational) motion Etranslational = 1/2 m x v square. Etranslational=12mv2In the rotating system, the moment of inertia ‘I’ takes the role of the mass ‘m’, and the angular velocity ‘w’ω, takes the role of the linear velocity ‘v’. The rotational energy of a rolling cylinder varies from one half of the translational energy (if it is massive) to the same as the translational energy (if it is hollow).
Rotational frequency – It is also known as rotational speed or rate of rotation. It is the frequency of rotation of an object around an axis. Its SI (International System of Units) unit is the reciprocal seconds (per second). Other common units of measurement include the hertz (Hz), cycles per second (cps), and revolutions per minute (rpm).
Rotational moulding – This process is normally applied to the plastics. It involves a heated mould which is filled with a charge or shot weight of the material. It is then slowly rotated (normally around two perpendicular axes), causing the softened material to disperse and stick to the walls of the mould forming a hollow part. In order to form an even thickness throughout the part, the mould rotates at all times during the heating phase, and then continues to rotate during the cooling phase to avoid sagging or deformation. It is the preferred term for a variation of the rotational casting process which uses dry, finely divided (35 mesh, or 500 micrometers) plastic powders, such as polyethylene, rather than fluid materials. After the powders are heated, they are fused against the mold walls forming a hollow item with uniform wall thickness.
Rotational speed, fan – Rotational speed of a fan is typically measured in revolutions per minute (rpm). Fan rotational speed has a considerable impact on fan performance. Rotational speed is to be considered alongside with other issues, such as variation in the fan load, air stream temperature, ambient noise, and mechanical strength of the fan. Variations and uncertainties in system requirements are critical to fan type and fan rotational speed selection. Fans which generate high air flow at relatively low speeds (for example, forward-curved blade centrifugal fans) need a relatively accurate estimate of the system air flow and pressure demand.
Rotational velocity – It is the vector quantity whose magnitude equals the scalar rotational speed. In the special cases of spin (around an axis internal to the body) and revolution (external axis), the rotation speed can be called spin speed and revolution speed respectively.
Rotor – It is that part of an electrical machine that rotates. It is not necessarily the armature.
Rotor dynamics – It is a specialized branch of applied mechanics concerned with the behaviour and diagnosis of rotating structures. It is normally used to analyze the behaviour of structures such as jet engines and steam turbines. At its most basic level, rotor dynamics is concerned with one or more mechanical structures (rotors) supported by bearings and influenced by internal phenomena which rotate around a single axis. The supporting structure is called a stator. As the speed of rotation increases the amplitude of vibration frequently passes through a maximum which is called a critical speed. This amplitude is normally excited by imbalance of the rotating structure. If the amplitude of vibration at these critical speeds is excessive, then catastrophic failure occurs. In addition to this, turbo-machinery frequently develop instabilities which are related to the internal makeup of turbomachinery, and which is to be corrected. This is the main concern of engineers who design large rotors.
Rotor imbalance – In rotating machinery, rotor imbalance refers to an uneven distribution of mass around the axis of rotation, causing the rotor to vibrate and experience excessive forces during operation.
Rouge finish – It is a highly reflective finish produced with rouge (finely divided, hydrated iron oxide) or other very fine abrasive, similar in appearance to the bright polish or mirror finish on sterling silver utensils.
Rough blank – It is a blank for a metal-forming or drawing operation, normally of irregular outline, with necessary stock allowance for process metal, which is trimmed after forming or drawing to the desired size.
Rough grinding – It consists of grinding without regard to finish, It is normally to be followed by a subsequent operation.
Roughing – It is the initial evacuation of a vacuum system.
Roughing line – It is a line running from a mechanical pump to a vacuum chamber through which preliminary pumping is conducted in the rough vacuum range.
Roughing mill – It is a rolling mill which is used to reduce the thickness of ingots into blooms, billets, or slabs. It is also a rolling mill which is used to reduce the thickness of blooms into billets.
Roughing pump – It is a vacuum pump used for the initial evacuation of a vacuum system.
Roughing stand – It is the first stand (or several stands) of rolls through which a reheated billet / bloom / slab passes in front of the finishing stands.
Rough machining – It is the machining without regard to finish. It is normally to be followed by a subsequent operation.
Roughness – It consists of relatively finely spaced surface irregularities, the heights, widths, and directions of which establish the predominant surface pattern. It is also the microscopic peak-to-valley distances of surface protuberances and depressions.
Rough order of magnitude (ROM) – Rough order of magnitude estimate is a preliminary, approximate cost estimate used in the early stages of project planning when detailed information is scarce, providing a general idea of potential costs for initial decision-making.
Rough-polishing process – It is a polishing process which is having the primary objective of removing the layer of significant damage produced during earlier machining and abrasion stages of a metallographic preparation sequence. Its secondary objective is to produce a finish of such quality which a final polish can be produced easily.
Rough top conveyor belt – The uneven cover rubber surface of this conveyor belt prevents slippage while preventing vibration of, or absorbing and reducing impact to transport materials by providing a cushion effect. This belt is ideal for transporting plywood or packed items.
Round blooms – These are the semi-finished products normally used in the manufacture of seamless pipes. The diameter of these rounds is equal to higher than 180 millimeters.
Round-bottom flasks – These are types of flasks having spherical bottoms used as laboratory glassware. They are typically made of glass for chemical inertness. In modern days, they are normally made of heat-resistant boro-silicate glass. There is at least one tubular section known as the neck with an opening at the tip. Two-necked or three-necked flasks are common as well.
Round flame – It refers to a flame shape which is normally circular or spherical, frequently produced by burners designed to direct the flame towards the centre or a specific area, as opposed to a flat or rectangular flame.
Round lifting magnet – It is built with a centre pole (or core) and a round outer pole concentric with the centre pole. This magnet can be either a permanent magnet or an electro-magnet. The round electro lifting magnet is the most efficient when considering its face area as related to the lift power. Since the outer pole is a consistent distance from the core or centre pole, the result is a uniform magnetic strength over the magnet face area. Black iron pipe or steel tubing is used for outer poles of round lifting magnets, and hot rolled steel round bar stock is used for the centre core of round electro magnets.
Routh–Hurwitz stability criterion – It is a criterion for predicting the stability of a system with a given transfer function.
Routine maintenance – It includes those maintenance activities which are repetitive and periodic in nature such as lubrication, cleaning, and small adjustment.
Routing – It refers to the sequence of operations and processes needed to transform raw materials or components into a finished product. It outlines the specific steps, work centres, machines, and resources needed for each operation in the production process.
Roving – It means a number of yarns, strands, tows, or ends collected into a parallel bundle with little or no twist.
Roving ball – It is the supply package offered to the winder, consisting of a number of ends or strands wound to a given outside diameter onto a length of cardboard tube. It is normally designated by either fibre weight or length in yards.
Roving cloth – It is a textile fabric, coarse in nature, woven from rovings.
Royalty – It is the amount of money paid at regular intervals by the lessee or operator of an exploration or mining property to the owner of the ground. It is normally based on a certain amount per ton or a percentage of the total production or profits. Also, it is the fee paid for the right to use a patented process.
R-ratio – It is also called R-factor. In cyclic fatigue testing, It is the ratio of applied minimum stress to maximum stress. When ‘R’ = –1, the cycle is equally compressive and tensile.
Rubber – It is defined as an elastic substance, specifically an elastomer, which is a polymer with the ability to stretch and return to its original shape after being deformed, and can be either natural (like poly-isoprene) or synthetic.
Rubber band – It is a tension spring where energy is stored by stretching the material.
Rubber boot – It is a protective device to prevent entrance of damaging foreign material into the piston actuator seal bushing.
Rubber forming – It is the forming of a sheet metal wherein rubber or another resilient material is used as a functional die part. Processes in which rubber is used only to contain the hydraulic fluid are not classified as rubber forming.
Rubber gasket – It is a flexible, often circular or rectangular, piece of rubber used to create a seal between two mating surfaces, preventing leaks of liquids or gases.
Rubber insulating gloves – These are meant for protecting against electrical shock. These gloves are available to meet different voltage exposures. Lightweight low voltage gloves are for use on voltages under 1,000 volts. Gloves for use on high voltage are of thicker material for the dielectric strength. As the use voltage rating increases so does the glove weight. Rubber gloves are to be visually inspected and an ‘air’ test is to be performed before they are used. Electrical protective equipment is to be subjected to periodic electrical tests. Test voltages and the maximum intervals between tests are to be as per the appropriate standards.
Rubber joining – It is also known as rubber bonding. It is the process of creating a strong and durable connection between rubber and another material (like metal, plastic, or another rubber) using methods like adhesives, vulcanization, or moulding.
Rubber, natural – It consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Types of poly-isoprene which are used as natural rubbers are classified as elastomers. Presently, rubber is harvested mainly in the form of the latex from the Para rubber tree or others. The latex is a sticky, milky and white colloid drawn off by making incisions in the bark and collecting the fluid in vessels in a process called ‘tapping”7’. Manufacturers refine this latex into the rubber that is ready for commercial processing. Natural rubber is used extensively in several applications and products, either alone or in combination with other materials. In majority of its useful forms, it has a large stretch ratio and high resilience and also is buoyant and water-proof.
Rubber-pad forming – It also known as flexible-die forming. It uses a rubber pad or a flexible diaphragm as one tool half, requiring only one solid tool half to form a part to final shape. The solid tool half is normally similar to the punch in a conventional die, but it can be the die cavity. The rubber acts somewhat like hydraulic fluid in exerting nearly equal pressure on all workpiece surfaces as it is pressed around the form block. It is a sheet metal forming operation for shallow parts in which a confined, pliable rubber pad attached to the press slide (ram) is forced by hydraulic pressure to become a mating die for a punch or group of punches placed on the press bed or base-plate. It is also known as the Guerin process. Variations of the Guerin process include the fluid-cell process, fluid forming, and Marforming process.
Rubber, synthetic – It is an artificial elastomer. It consists of polymers which are synthesized from petroleum by-products. Synthetic rubber, just like natural rubber, has several uses in the automotive industry for tyres, door and window profiles, seals such as O-rings and gaskets, hoses, belts, matting, and flooring. It offers a different range of physical and chemical properties which can improve the reliability of a given product or application. Synthetic rubbers are superior to natural rubbers in two major respects namely thermal stability, and resistance to oils and related compounds. It is more resistant to oxidizing agents, such as oxygen and ozone which can reduce the life of products like tyres.
Rubber wheel – It is a grinding wheel made with a rubber bond.
Rubber wheel abrasion test – It measures a material’s resistance to wear by simulating sliding abrasion conditions using a rotating rubber wheel and dry sand, quantifying wear as volume loss.
Rubbing (polishing) – It is a macro- or microscale fractographic feature resulting from relative movement of two crack faces. It is common in fatigue loading.
Rubbing bearing – It is a bearing in which the relatively moving parts slide without deliberate lubrication.
Rubble trench foundation – It is a type of foundation which uses loose stone or rubble to minimize the use of concrete and improve drainage. It is considered more environmentally friendly than other types of foundation since cement manufacturing needs the use of large quantities of energy. However, some soil environments are not suitable for this kind of foundation, particularly expansive or poor load-bearing (less than 0.1 MPa) soils. A rubble trench foundation with a concrete grade beam is not desired for earthquake prone areas.
Rube Goldberg machine – It is a chain reaction–type machine or contraption intentionally designed to perform a simple task in an indirect and (impractically) overly complicated way. Normally, these machines consist of a series of simple unrelated devices, The action of each triggers the initiation of the next, eventually resulting in achieving a stated goal.
Rubidium (Rb) – It is a chemical element having atomic number 37. It is a very soft, whitish-grey solid in the alkali metal group, similar to potassium and caesium. It has a density higher than water. Natural rubidium comprises two isotopes namely 72 % is a stable isotope 85Rb, and 28 % is slightly radioactive 87Rb, with a half-life of 48.8 billion years. The colour of its emission spectrum is deep red. Rubidium’s compounds have various chemical and electronic applications. Rubidium metal is easily vapourized and has a convenient spectral absorption range, making it a frequent target for laser manipulation of atoms. Rubidium ions have similar properties and the same charge as potassium ions.
Rub mark – It is a large number of very fine scratches or abrasions. A rub mark can occur by metal-to-metal contact, movement in handling, and movement in transit.
Rub, tool – It is a surface area showing a scratch or abrasion resulting from contact of the hot extrusion with the press equipment or tooling or, in the case of multi-hole dies, with other sections as they exit the press.
Rudder – It is a primary control surface which used to steer a ship, boat, submarine, hovercraft, airship, or other vehicle that moves through a fluid medium (normally air or water).
Ruggedness – It normally refers to the ability of an equipment, component, or a sintered part to withstand harsh conditions, impacts, or stresses without significant deformation or failure, implying a robust and durable component.
Rugged systems – These are hardware which are designed to operate reliably in harsh environments, featuring enhanced durability and resilience to withstand extreme conditions like dust, water, temperature fluctuations, and physical impacts, making them suitable for demanding applications.
Rugosities – These are also known as asperities. These are the small-scale irregularities on a surface. These are the minute imperfections on a seal face or surface of a mating ring that are the result of normal surface finishing processes. Rugosities, their shapes, sizes, and mechanical properties are the basis for developing several theoretical models for friction, lubrication, and wear behaviour.
Rule of mixtures – It is a method which is used to estimate the properties of composite materials by combining the properties of their individual components, providing a weighted average of the constituent properties.
Rules of thumb – These are empirical relationships developed from practical experience. In design, these are frequently used to improve ease of manufacture or to relate performance to costs. Rules of thumb can be very useful when employed by an experienced person, but they can easily be misinterpreted or misused by less experienced personnel.
Run chart – It is also known as a run-sequence plot. It is a line graph which displays data in a time sequence, allowing users to visualize trends, shifts, or cycles in a process over time. Frequently, the data displayed represent some aspect of the output or performance of a manufacturing or other organizational process. It is hence a form of line chart.
Run-in – In tribology, it is an initial transition process which is occurring in newly established wearing contacts, frequently accompanied by transients in coefficient of friction, wear rate, or both, that are uncharacteristic of the given tribological system’s long-term behaviour. It also means to apply a specified set of initial operating conditions to a tribological system in order to improve its long-term frictional or wear behaviour, or both. The run-in can involve conditions either more severe or less severe than the normal operating conditions of the tribo-system, and can also involve the use of special lubricants and / or surface chemical treatments. In seals, run-in is the period of initial operation during which the seal-lip wear rate is highest and the contact surface is developed.
Run-in roller table – It is the approach roller table to the rolling mill cooling bed. It is normally provided with individually driven horizontal rollers which are gradually inclined to match the incline of the run-in roller table. The approach table is normally designed to operate faster than the finishing speed of the bar being rolled in order to create a gap between the divided materials at the shear prior to entering the brake slide to the cooling bed. The run-in table rollers are also individually driven and inclined at the same angle as the brake slide. The brake slide lifts the cut bar off the run-in table rollers to allow braking of the cut bar under friction before being discharged onto the first notch of the cooling bed. A hydraulic cylinder cushions the cut bar against the brake slides while lowering it for a smoother control. The entry section of the run-in table is equipped with drop down walls to prevent the larger bar from sliding down the brake slide before the previous bar is discharged.
Runner – It is a channel through which molten metal flows from one receptacle to another. It is the portion of the gate assembly of a casting which connects the sprue with the gate(s). It is also the parts of patterns and finished castings corresponding to the portion of the gate assembly. In a blast furnace, runner is the channel in the cast house for directing of liquid products. Hot metal runner is refractory lined and directs hot metal from trough to the hot metal ladle while slag runner directs liquid slag to slag granulation plant, or to slag pot, or to slag pit.
Runner box – It is a distribution box which divides molten metal into several streams before it enters the casting mould cavity.
Runner mass – It is the refractory material used for preparing of runner before the cast is opened in a blast furnace. It is normally water based.
Runner system – It is also called gating. It is the set of channels in a mould through which molten metal travels to the mould cavity. It includes sprues, runners, gates, and risers.
Running-in – It is the process by which machine parts improve in conformity, surface topography, and frictional compatibility during the initial stage of use. Chemical processes, including formation of an oxide skin, and metallurgical processes, such as strain hardening, can contribute.
Running maintenance – It includes those maintenance activities which are carried out while the equipment is running and it represents those activities which are performed before the actual preventive maintenance activities take place.
Runoff – It is the flow of water from land to the ocean caused by rainfall which exceeds the soil’s ability to absorb it. It can have both positive and negative impacts, such as damaging infra-structure and vegetation or providing a source of fresh water in arid areas.
Run-of-mine – It is a term which is used loosely to describe ore or coal average grade. It describes ore or coal which has been mined but not yet processed. It can also refer to the unsorted product of a mine.
Run-out – It is the unintentional escape of molten metal from a mould, crucible, or furnace. It is also an imperfection in a casting caused by the escape of metal from the mould.
Run out roller table – These are normally chain-driven roller table at the end of the cooling rake. Run out roller table is provided to transport the pack of the bars to the cold shear.
Run-to-failure – Run-to-failure is a failure management strategy which allows an equipment item to run until failure occurs and then a repair is done. This maintenance strategy is acceptable only if the risk of a failure is acceptable without any proactive maintenance tasks.
Runway – It consists of the rails, beams, brackets, and framework on which the crane operates.
Runway beam – In the context of overhead cranes, a runway beam is a long, horizontal structural beam which provides the foundation and path for the crane to travel, typically made of steel, and supports the crane and its lifted loads.
Runway rail – It is the rail which is supported by the runway beams on which the crane travels.
Rupture – It refers to the sudden breaking or bursting of a material or structure under stress. It frequently occurs after a period of creep or under high tensile forces.
Rupture disk – A rupture disk is a safety device which acts like a safety valve to protect against excessive pressure buildup in a system. However, the disk shatters when its maximum pressure is reached and is to be replaced each time it activates.
Rupture stress – It is the stress at failure. It is also known as breaking stress or fracture stress. Unless otherwise specified, rupture stress is calculated on the basis of original area for axial loading.
Rust – It is a visible corrosion product. It is applied only to ferrous alloys. It is an iron oxide, which is a normally reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron (III) oxides (Fe2O3.nH2O) and iron (III) oxide-hydroxide [FeO(OH), Fe(OH)], and is typically associated with the corrosion of refined iron.
Rust inhibitors – These are also known as corrosion inhibitors. These are substances which reduce or prevent the oxidation (rusting) of metals by forming a protective barrier or reacting with corrosive elements.
Rust-preventive coatings – These are removable coatings which are used to protect the surfaces of iron, steel, coated or galvanized products, and other alloys. Some compounds also protect non-ferrous metals, such as aluminum, brass, and copper. Coatings of these compounds are to be considered temporary, since their function is to protect surfaces during storage, handling, shipping, and fabrication. An additional application can be necessary after parts are fabricated. In some cases, the coating can need to be removed before fabrication or assembly.
Rust-preventive compounds – These are a combination of basic materials, inhibitors, and specialty additives. They vary in physical characteristics, depending on the properties needed and the quantity of protection needed at corrosion sites. A corrosion cell is like a battery, which has a cathode (-), an anode (+), and an electrolyte (liquid in cells). By coating the corrosion sites (anodes and cathodes) on a surface, rust-preventive compounds prevent contact with electrolytes, such as oxygen and moisture-containing materials. A rust-preventive compound can consist of only one or a combination of these four basic parts namely a carrier, a film former, polar materials, and specialty additives. For example, the rust protection offered by film formers such as grease, petroleum jelly, and low-melting-point waxes, can be improved by the addition of a polar material, which has an affinity for steel and attaches to steel surfaces like a magnet.
Rust staining – It is the reaction between exposed inter-metallic layers (specifically the iron portion of the layers) with oxygen, which cause mild red or brown staining.
Ruthenium (Ru) – It is a chemical element having atomic number 44. It is a rare transition metal belonging to the platinum group. Like the other metals of the platinum group, ruthenium is unreactive to most chemicals. Ruthenium is normally found as a minor component of platinum ores. Ruthenium is used in wear-resistant electrical contacts and thick-film resistors. A minor application for ruthenium is in platinum alloys and as a chemical catalyst. A new application of ruthenium is as the capping layer for extreme ultraviolet photomasks.
Rutherford back-scattering spectrometry (RBS) – It is an analytical technique which is used in materials science. Sometimes referred to as high-energy ion scattering (HEIS) spectrometry. Rutherford back-scattering spectrometry is used to determine the structure and composition of materials by measuring the backscattering of a beam of high energy ions (typically protons or alpha particles) impinging on a sample.
Rutherford scattering – It is a general term for the classical elastic scattering of energetic ions by the nuclei of a target material.
r-value – It is also called the Lankford coefficient or the plastic strain ratio. It is the plastic strain ratio of sheet metal intended for deep-drawing applications. It is a measure of the resistance to thinning or thickening when subjected to either tensile or compressive forces in the plane of the sheet i.e., it is the ability to maintain thickness as the material is drawn. It is the ratio of the true width strain to the true thickness strain at a particular value of length strain. Strains of 15 % to 20 % are normally used for determining the r-value of low carbon sheet steel. Like n-value, the ratio will change depending on the chosen reference strain value.
R-value – In fatigue testing, it is the stress ratio determined by the minimum stress in the stress cycle divided by the maximum stress. For a completely reversed stress cycle, R = -1.
RZ powder – It is the reduced iron powder made from the scale of pig iron.
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