Classification of pipe fittings

　　Generally, we call all kinds of fittings except straight pipes in the pipe system as pipe fittings. But customarily, we call elbow, tee, reducer, cap and various pipe joints pipe fittings. At the same time, we called flange, valve, expansion joint, pipe support, etc respectively.

　　The pipe fitting is mainly subdivided as follows:

　　2.1 It can be divided into three types according to the connection mode between pipe fitting and straight pipe during construction:

　　1) Butt welding pipe fittings (BW)

　　2) Socket pipe fittings (SW)

　　3) Threaded pipe fittings (TH)

　　2.2 According to whether there is a weld on the surface of the pipe fitting, it can be divided into two categories:

　　1) Seamless pipe fittings

　　2) Welded pipe fittings