The term piping refers to the overall network of pipes, fittings, flanges, valves, and other components that comprise a conduit system used to convey fluids. Whether a piping system is used to simply convey fluids from one point to another or to process and condition the fluid, piping components serve an important role in the composition and operation of the system. A system used solely to convey fluids may consist of relatively few components, such as valves and fittings, whereas a complex chemical processing system may consist of a variety of components used to measure, control, condition, and convey the fluids. In the following sections, the characteristics and functions of the various piping components are described.
Pipe and Tube Products
Pressure pipe and tube products are manufactured to a variety of standard specifications of varying designs, employing different manufacturing practices and using a wide variety of materials. The end user of these products must apply the least- cost product suitable for the specified service conditions. Typically, steel and alloy pressure piping is available in cast, wrought, and seam-welded forms. Welded and seamless wrought steel pipe is supplied in standard sizes and wall thickness conforming to ASME B36.10M. Stainless-steel pipe is supplied in standard sizes and wall thickness conforming to ASME B36.19M.
Pressure-tube applications commonly involve external heat applications, as in boilers or superheaters. Pressure tubing is produced to the actual outside diameter and minimum or average wall thickness specified by the purchaser. Pressure tubing may be hot- or cold-finished. The wall thickness is normally given in decimal parts of an inch rather than as a fraction or gauge number. When gauge numbers are given without reference to a system, Birmingham wire gauge (BWG) is implied.
Pressure tubing is usually made from steel produced by the open-hearth, basic oxygen, or electric furnace processes. Seamless pressure tubing may be either hot- finished or cold-drawn. Cold-drawn steel tubing is frequently process-annealed at temperatures above 1200°F (650°C). To ensure quality, maximum hardness values are frequently specified. Hot-finished or cold-drawn seamless low-alloy steel tubes generally are process-annealed at temperatures between 1200°F (650°C) and 1350°F (730°C). Austenitic stainless-steel tubes are usually annealed at temperatures be- tween 1800°F (980°C) and 2100°F (1150°C), with specific temperatures varying somewhat with each grade. This is generally followed by pickling, unless bright annealing was done. #Little_PEng