I have a non-code pressure vessel with a design pressure of 15 psig. The vessel has PSV set at 14.99 psig with a specified backpressure of 6 psig. The backpressure is wrongly specified since the outlet of the PSV is routed to atmosphere. The maximum backpressue the PSV can see is maximum 0.2 psig
1) What are the effects of backpressure on the PSV set pressure?
2) Since there is no backpressure on this PSV; what is the pressure when PSV will start opening? it is 14.99 psig?
3) If in reality, 6 psig backpressure do exists then what pressure the PSV would start relieving, is it at 14.99 + 6 = 20.99 psig. Is this correct?