Relief valve after a regulator: mandatory?
Relief valve after a regulator: mandatory?
(OP)
Here's the situation: a new regulator is to be installed on a nitrogen line that feeds several vessels (and no other users!) for pressure transfer and line purging. EACH ONE of the vessels thus fed has a dedicated relief device that is appropriate for the vessel in question. Thus: I don't believe that a relief valve immediately after the regulator is necessary. However, I can't cite a source offhand for this judgment, nor am I absolutely sure this is the case. (I've always heard of a rule of thumb that a pressure reducing regulator should be followed by a relief device under any circumstances.)
Opinions? And appropriate code citiations? Thanks very much.
Opinions? And appropriate code citiations? Thanks very much.





RE: Relief valve after a regulator: mandatory?
RE: Relief valve after a regulator: mandatory?
Good luck,
Latexman
RE: Relief valve after a regulator: mandatory?
For older models, it is common for the upstream side to be rated for the body (say 400#)
then the downstream side be rated based on the diaphragm (say 250#).
So the PSV setting has nothing to do with vessels, equipment or piping but instead the PSV protects the regulator diaphragm.
RE: Relief valve after a regulator: mandatory?
There are some legitimate instances where a relief valve is absolutely necessary, as some component is not adequately protected against regulator failure by other relief valves or by design- usually because there is a valve between them which is probably there to be closed from time to time.