In ASME B16.11 Threaded and Socket Welded Fitting rating shown as Class 2000lb, 3000lb, ..etc. Anybody knows where did this class designation come from?
Read the forward in ASME B16.11. In 1960 the standard addressed threaded fittings and plugs covered by MSS SP-49/50. The wording was upgraded in 1972. Consider checking old copies of MSS 49 and 50.
