What Is a Fitting?
Fittings are methods of joining members of a structure, such as buildings or machinery, or their joints.
It is a generic term for structures used to join parts and components of various sizes of pipes, machines, and buildings, and exists in a variety of materials, shapes, and names, depending on its use.
Types of Fittings
Fittings can be broadly divided into those used for equipment piping in all fields and those used for connecting rotating parts in the field of mechanical engineering.
Piping fittings include couplings, ferrules, and nipples that make straight connections between pipes, elbows and vents that change the direction of fluid flow, crosses and cheeses that create mergers and branches, increasers and sockets that change pipe size or length, and caps and plugs that seal the ends of pipes.
In addition to welded fittings, there is a wide variety of connection styles, including threaded, flanged, and pinched fittings. Even basic malleable iron fittings can be classified into white, black, and resin-coated fittings, depending on the surface treatment and type. Other widely used materials include corrosion-resistant stainless steel fittings, brass fittings, bronze fittings, plastic fittings, and PVC fittings.
In the field of mechanical engineering, fittings, couplings, and joints are used to connect rotating bodies, such as a drive shaft and a driven shaft, to transmit mechanical power and absorb mounting errors and vibration.
Fittings are used when the axes of the two shafts to be connected are coincident, deflection shaft couplings are used when the axes are difficult to align or to mitigate vibration and shock, and oldham couplings are used when the two shafts are not parallel to each other .
Fittings such as rotary joints and swivel joints, which form a flow path for water, air, oil, etc. between a pipe and a rotating shaft, are also called rotary joints.
Fittings Dimensions
The outside diameter dimensions of piping fittings are expressed in terms of nominal diameter. There are two types of nominal diameters: A, which is a millimeter dimension, and B, which is an inch dimension, but both are not the same as the inner or outer diameter.
Materials of Fittings
This section describes the materials used in the major types of fittings.
1. Black Fittings
Fittings used for general piping are often made of malleable cast iron (cast iron that can be deformed by heat to some extent) and are suitable for use with many fluids such as water, oil, steam, and air.
2. White Fittings
Unlike black fittings, white fittings have a plated surface (hot-dip zinc) and are used for cooling water, industrial water, etc., in addition to the fluids for which black fittings can be used.
3. Stainless Steel Fittings
Fittings made of stainless steel, which, as the name suggests, has excellent resistance to rust and corrosion, are used for piping in sites where hazardous substances are handled (general chemical facilities, nuclear power plants, flue gas desulfurization equipment, hydrogen sulfide and chloride).
4. Brass Fittings
Fittings made of brass (an alloy of copper and zinc) and used in familiar applications such as toilet water pipes and flushing pipes.