Recently I had a client who made alterations to a pressure vessel (PV) in an ammonia refrigeration process that required the PV to be re-certified. The state where this PV resides is a “coded state”, meaning they have adopted ASME Code for the PVs within the state. So, the contractor making the alterations had scheduled the Authority Having Jurisdiction (AHJ) (in this case it was an insurance agent) to be present for the state inspection following the alteration(s). And this is where the state PV code and PSM/RMP practices part ways…
The contractor making the PV alteration has a company policy to pressure test the PV to 50 psi after the alterations are complete and is done by inserting a rubber plug into the open nozzle. The insurance inspector witnessed the contractor to pressurize the vessel to 50 psi as a means to “test” the integrity of the alterations. For the life of me, and those more “in the know” than I, we have no idea where the 50 psi came from. I can only assume this is done when piping to and from a PV is not complete and where the inspector has a propensity for visual inspections. The state code for PV’s does allow the inspector a lot of latitude in how he/she validates the alteration/repair of the PV, but it is amazing that the AHJ allowed only 50 psi, knowing the normal pressure in this vessel could be in the 105-190 psi range on the summer months; so, 50 psi does not even come close to be “normal operating pressure”, much less the MAWP!
So here is the language from the state PV code and the NBIC (as referenced by the state code)