This is real basic for the person who works with fluid handling systems every day. I need to find where the ASME Code says you protect a system by selecting the fitting with the lowest design pressure (i.e., the weakest link)…or words to this effect.
This is common sense, but I need to cite it. It is either in ASME Code VIII (for sure) and it would help if I could find a cite in ASME B31.1 or B31.3. There must be some guidance on relief set point selection, but where?
Are talking about not using a PRV, or for redundancy in a system that has one. I have VIII on my work computer, I can look through there tomorrow if you haven’t found an answer by then. It’s funny, though, that a lot of the documents I’m pulling up via Google reference LANL (where I work).
Even though it’s in the realm of mechanical failure, chemical guys in general know more about pressure vessel code than mechanical guys. I’m a mechanical guy myself, and only am familiar with the code because I work with a lot of nuclear stuff.
I am a chemical engineer. The question is ill posed really - are you looking for Design pressures ? or set pressure ? or maximum relieving pressure ?
I am assuming that you want the “design pressure” for pressure relief
If that is the case then 322.6.3 (B31.3 2004) says “The design pressure for pressure relief is the maximum design pressure permitted, considering all components in the piping system” and it references Sec VII Div 1 …
I hope the OP knows what he is posting about and the applicability and the limitations of the above standards.
Also to aerodave’s question - design pressures and relief pressures are typically specified by the Process Engineer - aka Chemical Engineer
Bingo! That’s one citation I need. As I posted “I need to find where the ASME Code says you protect a system [i.e., pressure relief] by selecting the fitting with the lowest design pressure [i.e., fitting with lowest MAWP]…” (Granted, yes, I should have said “component” instead of “fitting”.)
As an extra question, I should ask, how does anyone find anything in these Codes? U of D, well known for its Chem Eng Dept, doesn’t even subscribe to an online version of the ASME Code because of the cost. So, how do you find these things?
Could be Chem (I did study more fluid mechanics than my Mech Eng brother but didn’t study any American codes), could be Agro (now those guys know their pipes inside and out)…
I still think you’re wording it wrong,** Jinx**. The maximum design pressure permitted isn’t how you protect the system. The system is protected with PRD (pressure relief devices) such as PRVs, burst disks, isolation valves, etc. The way you’re wording it, you’re not asking how to protect the system, you’re asking what pressures you can subject it to. In safety basis, protecting the system assumes that the pressure gets away from you. The way you’re writing the question makes it sound like you’re selecting a part to intentionally burst to protect something more valuable (a more expensive part, worker injury, etc.)