PSV relief header sizing

[Dammi77]

Hello Everyone ,
I'm trying to size a relief header to which three PSVs are connected on a gas compression package . I'm using the max capacity of the largest PSV (MMSCFD) and sizing the header for 0.7 Mach velocity .
Should I use the simple flow rate equation Q=V*A to find the pipe dia. or there is some more in depth equation that I should be using , since this is a compressible flow .
Thanks for your help in advance .

 

[BigInch]

You may need to size for all combined relief flows. Why just the maximum?
You cannot use incompressible flow equations for high pressure gas.

 

[EmmanuelTop]

The same query was posted here:

http://www.eng-tips.com/viewthread.cfm?qid=384153

Please avoid duplicate posting - usually you'll get half of the answers.

Dejan IVANOVIC
Process Engineer, MSChE