According to the current standard of the steel tube couplers used in the scaffolding system, the minimum weight of the rectangular

coupler shall be 2.2g and that of the butting coupler shall be 2.5g.

While the standard weight of the swivel coupler shall be 2.5 as well. If the torque force of the rectangular coupler is 900N·M, the working

temperature shall be no bigger than 4℃, and for the tensile strength of the button coupler is 4.0N, the distance shall be no bigger than

2.0mm. There are also some rigorous requirements on the scaffolding couplers’ surface.

There shall be no cracks, looses or dent on the couplers and the opening space between the cover plates and the bases shall be bigger

than 49mm or 52mm. The depth of the concaves and the convexes on the couplers surface shall be no bigger than 1mm.