Steam PSV Pipe
Steam PSV Pipe
(OP)
What are the guidelines for sizing steam PSV pipe?
Should I take same approach as for sizing steam piping (since same median will flow through) or there are some other requirements?
Thank you.
Should I take same approach as for sizing steam piping (since same median will flow through) or there are some other requirements?
Thank you.





RE: Steam PSV Pipe
Cheers,
John
RE: Steam PSV Pipe
REFER TO ASME B31.1 APPENDIX II NONMANDATORY RULES FOR THE DESIGN OF SAFETY VALVE INSTALLATIONS
The size and length of the discharge pipe from a steam pressure safety valve is critical.
As the steam leaves the valve it expands. As it moves down the pipe it continues to expand so the velocity increases.
If the velocity reaches Mach 1 the flow rate will be what is called "choked flow". If this flow rate is less than the capacity of the relief valve the require relief flow cannot be attained. The associated equipment could then over pressure and explode.
You must calculate the equivalent length of pipe at which the velocity reaches mach 1. The actual equivalent length of discharge pipe must be shorter than the length required to reach mach 1.
Regards,
D Landis
RE: Steam PSV Pipe