Dear all,

I got some piping system which consist of several relief valves (6-8 relief valves).
These relief valves was install from upstream main pipe and blow to downstream main pipe, then blow to atmosphere.
I need to know which node I can input force. Force are calculated according to API520.

In my opinion, it shall be on the each relief valve. Is it correct?

Any comment, please.
Best regards
PP.

Forces everywere!!!
(do a search on this forumn).
Also its pretty important how you are going to define a short or long distance because forces wont cancel out on a long distance.
If the prv discharge lines relieve into a relatively large header (ie the area of the header pipe is greater than the square of the run pipe) then this can be assumed to be an open system. but this intern means a net thurst on the discharge pipe mentering the header.
It is statistically impossible for all relief valve to open at the same time, so don't have all the forces acting at once, but it is highly probably for these prv to be open at the same time, which means allowing for large almalgamated thrust forces acting on the header.
Dont forget about the fire case. (relief forces during fire, when pipe is hot)
Dont use springs.
dont use large gaps on restrains, but you MUST model the gaps acurratly!
have the pipe well supported.
prepare for alot of load cases
If you are unsure, have your calc checked by A.N.Other (or Coade).
Absolutely make sure that under all circumstances
the pipework is analyised properly. Ie be in no doubt about your solutions. it is better to have an overengineered Relief system than have damage due to pipe failure.
Good luck
In the event of an accident, your head will be on the chopping block

Dear all
Actually I think I shall consider the worst case that set pressure of relief valve are the same pressure so it will be operated at the same time.

I have more questions..
1. For the total reaction force is also summary of force from each relief valve, isn't it?
2. The node which located this total force must be the last elbow before open end.

Multi valve release is complex and needs detailed
thought.

sounds like you have a multitude of PRV's protecting the same line, which i have never encountered and struggle to understand.

If you want detail analysis for the reaction force of PSVs in the closed system, the only solution is to run time history.

I think you should have your flow solved by a process eng. He can tell you how many and in wich order the valves are going to relieve. In that way you will now wich is the worst case, and once the flow is solve you will know where are the forces and when are acting.
Normally piping stress engineers go an extra mile and try to solve problems that, from its nature, requires more than one area of expertise in order to find the proper answer. We have to remember that we are (normally) part of a team and don’t have all the knowledge.

Regards,