Pressure Relief Valve Capacity Calculations The following formulas are frequently required in calculating and converting pressure relief valve flow capacities. To calculate the valve capacity at any set pressure for any gas: W = CKAP (sqrt) (M/T) WHERE: W = flow of gas, lb/hr C = constant for gas (function of specific heats) K = coefficient of discharge A = actual discharge area, sq. in. P = (set pressure x 1.10) plus 14.7 psia M = molecular weight T = absolute temp. at inlet (deg. F +460) To Convert from lb/hr to SCFM: SCFM = W x (6.32/M) Where: W = flow of gas, lb/hr M = molecular weight To calculate the valve capacity for air at 60 degrees F: SCFM = 18.33 KAP Where: K = coefficient of discharge A = actual discharge area P = (set pressure x 1.10) plus 14.7 psia Valve Data: Valve Type RXSO Back

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