Dear All,

API 520, 4.4.1.1 gives a formula for calculation of relief valve thrust for compressible fluids with critical steady state flow. Assuming that the outlet piping is very short, or none at all, how does one best determine the value to use for P, the static pressure within the outlet at the point of discharge?
another thing, formulas from Crosby is supposed to be based on API 520 but there result has big difference. Why did they differ in their result? (its a BIG difference in result.)

Result is based on reaction force calculation of the two standard reference.

please advise.
thanks