Safety Valves in Saturated Steam Systems

The minimum discharge area of a relief safety valve in a steam system can be calculated as

A = m / (51.5 k_d k_bp P^1/2)                                              (1)

where

A = minimum discharge area (Square Inches)

m = relieving capacity (Lbs. per Hour)

k_d = discharge coefficient - 0.975

k_bp = back pressure coefficient - 1.0 for atmospheric discharge systems

P = relieving pressure (psia) - set pressure (psig) + over pressure (psig) + atmospheric pressure (14.7 psia)