Buchi,
For the Relief main headers, generally it is recommended to limit mach no to 0.5 for new plants. for revamp in some projects people go upto 0.7.
For Tail pipes of PSV discharge, we can go upto 0.9.
HI,
What is the maximum source pressure (from the upstream plant) ? if the equipment (separator) is designed for the maximum upstream pressure (say for example 88 barg) then your psv need not be sized for this case, probably only for fire case.
If your source pressure is more than your...