There are three main representation methods:
1) Indicated by the pipe number (Sch):
For carbon steel pipe wall thickness, there are 10 grades: Sch10, 20, 30, 40, 60, 80, 100, 120, 140, 160 (if S is added after the number, it means stainless steel pipe)
For stainless steel wall thickness series, there are four grades: 5S, 10S, 40S, and 80S.
2) Expressed by the weight of the pipe, such as STD (standard weight), XS (thickened pipe), XXS (extra thick pipe)
3) Expressed by the wall thickness of the steel pipe, that is, “pipe outer diameter × wall thickness”, such as φ89X4
The wall thickness of steel pipes cannot be the same everywhere. There is an objective phenomenon of uneven wall thickness in its cross section and longitudinal pipe body, that is, uneven wall thickness. In order to control this unevenness, some steel pipe standards stipulate the allowable index of wall thickness unevenness, which generally does not exceed 80% of the wall thickness tolerance (implemented after negotiation between the supplier and the buyer).