The chemical equipment refers to the process piping used for the downstream processing equipment of refining ethylene. There are carbon steel pipes and stainless steel pipes (seamless and welded): the commonly used carbon steel pipes are made of 20# (GB/T8163) and 20G (GB5310). 20g and 20# (GB9948) are rarely used. If it is used for Class A pipes, it must be 100% UT; the steels commonly used for stainless steel pipes are generally 304, 316L, 316Ti, etc.