PSV After Regulator
PSV After Regulator
(OP)
Could someone please help my aging memory. . ..
We always require a PSV downstream of a pressure regulator because downstream components are not rated for regulator inlet pressure. Failure scenario is wide-open regulator failure, simple sizing calculation.
I've seen "requirements" in Fisher gas regulator literature, and Sarco steam regulator literature. I also think that I saw an API, CGA or ISA requirement in a Code document, but I haven't been able to get my hands on it because I don't remember which Code it was. I do know that B31.3 301.2.2(c) requires consideration of ". . . failure of control devices."
Does anyone know of a Code document that explicitly requires pressure relief downstream of a regulator? The client wants to have a Code citation for this requirement on oxygen and hydrogen systems.
We always require a PSV downstream of a pressure regulator because downstream components are not rated for regulator inlet pressure. Failure scenario is wide-open regulator failure, simple sizing calculation.
I've seen "requirements" in Fisher gas regulator literature, and Sarco steam regulator literature. I also think that I saw an API, CGA or ISA requirement in a Code document, but I haven't been able to get my hands on it because I don't remember which Code it was. I do know that B31.3 301.2.2(c) requires consideration of ". . . failure of control devices."
Does anyone know of a Code document that explicitly requires pressure relief downstream of a regulator? The client wants to have a Code citation for this requirement on oxygen and hydrogen systems.
Larry





RE: PSV After Regulator
RE: PSV After Regulator
To answer your code question directly: it is good practice to do this, and many A/E firms or users will include the requirement in their internal piping standards. I have never seen it in a code.
RE: PSV After Regulator
You really didn't state specifically what equipment downstream of the regulator you are trying to protect and of course you know not to apply the code requirements intended for one type of equipment to a different type, then....
If you are dealing with piping, I would just backup a little in B31.3 and it would seem that B31.3 301.2.2(a) is quite clear that
"(a) Provision shall be made to safely contain or
relieve (see para. 322.6.3) any pressure to which the
piping may be subjected."
In the case of a pressure vessel, refer your client to ASME Sec VIII, Div 1, UG-125.
The list of codes could go on and on...
For piping systems, maybe you don't have a lot of scenarios you have to consider but don't let yourself get hung-up on the short list of examples in B31.3 301.2.2(c), be sure you are looking at anything and everything that can cause you problems.
RE: PSV After Regulator
Larry
RE: PSV After Regulator
Thanks.
RE: PSV After Regulator
best wishes,
sshep
RE: PSV After Regulator
Larry
RE: PSV After Regulator
J. Alton Cox
www.delucatest.com