The so-called pipe fittings are the parts that connect pipes into pipelines. According to the connection method, it can be divided into four categories: socket-type pipe fittings, threaded pipe fittings, flanged pipe fittings and welded pipe fittings. Mostly made of the same material as the tube. There are elbows (elbow pipes), flanges, tee pipes, cross pipes (cross heads) and reducers (large and small heads). Elbow is used where the pipe is turned; flange is used for the parts that connect the pipe to the pipe, what is the connection to the end of the pipe, what is the pipe fitting The place where the children gather; the reducer is used where two pipes of different diameters are connected.