PSV Sizing
PSV Sizing
(OP)
How do I determine if a PSV will still be at maximum relief capacity if reset? There are two sets of PSVs, ones currently set at 500psig and need to be reset 475psig and ones that are set from 1210 to 1290 psig and need to be reset to 1100psig. I also have a PSV that is set at 445 psig and one that is at 600 psig that need to be reset to 475psig and 1100psig respectively but I didn't know if they could be set higher than what it was rated for or if it just had to be replaced. The PSVs need to be able to relieve 6.2 mmcf.





RE: PSV Sizing
If you are in a VR state, a Code shop may be required to make the change.
RE: PSV Sizing
RE: PSV Sizing
RE: PSV Sizing
In the US you commonly can size a PSV using either the API orifice areas and API discharge coefficients or the ASME areas and ASME discharge coefficients (the ASME capacity is the valve's tested capacity less 10%). The two approaches will give you similar but not identical results. I've seen some significant differences in the smaller orifice sizes.