How to determine the Test medium to be used to test and set PSV's.
How to determine the Test medium to be used to test and set PSV's.
(OP)
I am currently providing third party witnessing at a PSV shop that reconditions and adjust set pressures on PSV's, I am curious to know, how the test medium is determined from Air, Water, Steam. How can i find the specific gravity for say, C4 hydrocarbon or ethelyene or caustic, and how to determine the test medium to be used for each process. This may be a loaded question, but i would like to be pointed in the right code. Been through ASME VIII, PTC 25, ASTM D1298 and of course API 576, and 527.





RE: How to determine the Test medium to be used to test and set PSV's.
RE: How to determine the Test medium to be used to test and set PSV's.
PRV's rated for "lb/hr" are for steam service and test with steam.
PRV's rated "scfm" are for vapor service, and test with air/nitrogen
PRV's rated in gpm are for incompressible flow and test with water.
You also need to be sure that the set-point is for the client's CDTP, if they specified one; not the in-service relieving pressure. The 'cold' part of CDTP gives the set-point at room temperature, thus what a shop test should yield.
NOTE: there is never a CDTP for lb/hr - being tested with steam, the shop test approximates the in-service condition.