SCH means the pipe grading of wall thickness, different standards are expressed differently. However, there are three methods(pipe table number, the size of the steel tube wall thickness and pipe weight). 

ANSI B36.10 and JIS standard tube sheet number: Sch l0、Sch 20、Sch 30、Sch 40、Sch 60、Sch 80、Sch 100、Sch 120、Sch 140、Sch 160.