The medium diameter welded pipe production lines (ranging from 8 to 26 inches) initially utilized the opposed roller forming method. However, since the advent of the row forming method in the 1970s, the row roller forming method has become the mainstream for medium diameter welded pipe production lines. After the 1990s, almost all such lines, with exceptions only being the five newly built 12-inch lines by Taiwan's Keng An company that used the opposed roller forming method and the two 8-inch lines supplied by Japan to the United States and Europe that adopted the FF forming method, employed the row roller forming method.
There are three primary processes within the row roller forming method for medium diameter welded pipe production lines: the full row roller forming method, the semi-row roller forming method, and the straight-edge row roller forming method. The main manufacturers of these lines include France's DMS, Austria's VAI, and Germany's SMS-Demag. In the last five years, these three companies have manufactured five newly built ERW lines worldwide. The primary products of these lines include pipeline tubes, structural tubes, and casing pipes.
