Pop test is carried out on pyrolysis furnace of an ethylene plant. The furnace itself is a 1500 psig steam generator. Pop test is to ensure the PSV will relieve at the set pressure and able to resit properly. This is carried out when the furnace is on hot standby without any hydrocarbon.
For new furnaces, there are chances the PSV cannot resit. On older furnaces, the PSV may be passing badly that it will relieve prematurely.
We carry out pop test for our co-gen HRSG as well for the same reasons. But at 600 psig, the likelihood of failure is lower.