There are many elements or we can call accessories in the scaffolding system, including the steel tubes, the couplers, the base plates and scaffolding planks.
The couplers, including the stage couplers, can use the materials of pressed steel with a mechanical property no lower than KTH300—08. The pressed couplers can not have any cracks or air holes. The binding surface between the couplers and the steel tubes shall be cohesive without any gaps to make sure the flexible parts will be able to move when the tubes are tied to the couplers. The two swivel surfaces of the swivel couples shall have a gap less than 1mm. When the couplers clamp the steel tubes, the minimum distance of the opening holes shall be no less than 5mm. All the couplers shall be certified with Quality Certificate, Production Certificate, and Professional Testing Unit Report.
The distance from the center joints of the couplers to the diagonal tubes shall be no bigger than 150mm and top of the diagonal tubes shall be added with a safety coupler. And all the holes shall be full planked with thick board.