Couplers can be classified into several groups including right angular couplers, swivel couplers, joint pin couplers and base boards. The mechanical capacity has been clearly regulated in GB15831-1995 “tubular scaffolding system with couplers”, which is made and determined according to the bearing load of scaffoldings.

The external working load can be ranked in 3 degrees: 1 2 and 3 kn/m². Couplers made of welded iron can satisfy the working load limits of 3kn/m². Swivel couplers: used in the scaffolding system as ledger braces and the connection joints between double standing posts in high constructions and buildings. The ledger braces play an important role in assuring the stability and sturdy structure in the whole scaffolding system.

What’s more, they can also deliver the longitudinal braking force from the trolleys on scaffolding boards and the lateral force from the wind working loads; hence, there should not be any skid for couplers under a working force of 10kn and should be kept as good if working under a load of 17kn.