ASME B31.8

ASME B31.8 has design criteria for restrained piping and unrestrained pipinng, respectively buired and above ground piping.

The stress evaluation for buried piping is done for OPE and SUS, and OPE includes all the loads. It is because why EXP is not evaluated sepaeratly like the above ground piping.

Th buried piping design criteria is severer than the above becuase it may be located in where public lives and environmental regurations for hazard and safety.