Gaskets and Their Types...

Gaskets and Their Types The cost of leaky joints in a steel plant can be staggering. Gaskets perform an important role in the prevention of fluid leakage from pipes and equipment parts in the steel plant. A gasket is a compressible material, or a combination of materials, which when clamped between two stationary members prevents the passage of the media across those members. The gasket material selected must be capable of sealing mating surfaces, resistant to the medium being sealed, and able to withstand the application temperatures and pressures. Generally, gaskets are called upon to affect a seal across the faces of contact with the flanges. Permeation of the media through the body of the gasket is also a possibility depending on material, confined media, and acceptable leakage rate. A gasket is normally placed in between two objects in order to prevent leakage of any kind of the pressurized or not pressurized media. Most important is the compression set of a gasket to adapt to flange irregularities and to any dimensional changes of the flange system caused by temperature changes during operation. Gaskets are used to create a static seal between two stationary members of a mechanical assembly and to maintain that seal under operating conditions which may vary dependent upon changes in pressures and temperatures. If it is possible to have perfectly mated flanges and if it is possible to maintain an intimate contact of these perfectly mated flanges throughout the extremes of operating conditions, then the gaskets are not required.  However this is virtually impossible because of the following. Size of the flanges and/or the vessel Difficulty in maintaining extremely smooth flange finishes during handling and assembly Corrosion and erosion of the flange surfaces during operations Large number of flanged joints needed...

Crushers and Their Types...

Crushers and Their Types A crusher is a multi dimensional machine which is designed to reduce large size materials into smaller size materials. Crushers may be used to reduce the size, or change the form of waste materials so they can be more easily disposed of or recycled, or to reduce the size of a solid mix of raw materials (as in the case of ore), so that pieces of different composition can be differentiated for separation. Crushers are normally low speed machines that are designed for breaking large lumps of ores and stones, even aving a size with a diameter of over one and half meter. The purpose of crusher is to reduce the size of the materials for making them usable in construction or industrial use, or for extraction of valuable minerals trapped within a ore matrix. Crushing is the process of transferring a force amplified by mechanical advantage through a material made of molecules that bond together more strongly, and resist deformation more, than those in the material being crushed do. Crushing devices hold material between two parallel or tangent solid surfaces, and apply sufficient force to bring the surfaces together to generate enough energy within the material being crushed so that its molecules separate from (fracturing), or change alignment in relation to (deformation), each other. There are four basic ways to reduce a material, namely (i) impact, (ii) attrition, (iii) shear, and (iv) compression. Most crushers employ a combination of all these crushing methods. Impact – In crushing terminology, impact refers to the sharp, instantaneous collision of one moving object against another. Both objects may be moving, or one object may be motionless. There are two variations of impact, namely (i) gravity impact, and (ii) dynamic impact. Material dropped onto a hard...

Steel Reinforcement Bars and its Important Characteristics...

Steel Reinforcement Bars and its Important Characteristics Steel reinforcement bar is also known as rebar, reinforcing bar, reinforcing steel and reinforcement steel. It is a versatile constructional material which is widely used in the construction industry for making of the reinforced concrete. Reinforcement concrete (RC) is a composite material made up of concrete and some form of reinforcement – most commonly steel rods, bars, wires or mesh of steel rods and steel wires. The steel reinforcement bars usually consists of such shape and size that they may easily be bent and placed in the concrete so as to form a monolithic structure. The properties of thermal expansion for both steel and concrete are approximately the same. This along with excellent bendability property makes steel the best material as reinforcement in concrete structures. Another reason steel works effectively as reinforcement is that it bonds well with concrete. When passive reinforcement (steel bars) is employed, the structure is known as reinforced concrete structure. In pre-stressed concrete structure, the reinforcement (steel wire) is stressed prior to subjecting the structure to loading, which may be viewed as active reinforcement. Passive steel reinforcing bars, also known as rebars, should necessarily be strong in tension and, at the same time, be ductile enough to be shaped or bent. Steel rebar is most commonly used as a tensioning devise to reinforce concrete to help hold the concrete in a compressed state. Concrete is a material that is very strong in compression, but virtually without strength in tension. To compensate for this imbalance in a concrete slab behavior, reinforcement bar is cast into it to carry the tensile loads. The surface of the reinforcement bar may be patterned to form a better bond with the concrete. Reinforced concrete gets its strength from...