PSV sizing calculator – blocked gas discharge

This is a sample of the PSV sizing calculator. To access the working calculator, please sign up for free membership trial.

Pressure Safety valve sizing calculator for blocked outlet of a vapor filled vessel.

Set pressure barg
Accumulation %
Back pressure barg
Coefficient of discharge Kd (max=0.975)
Rupture disk upstream to PSV ?
Gas flowrate kg/hr
Gas temperature 0C
Isentropic coefficient k
Molecular weight
Gas density kg/m3
Compressibility factor (z)
Relieving pressure barg
Required discharge area cm2

The calculated area is the minimum orifice area required to allow the discharge of liquid. The actual orifice area is the next higher available area. Following table presents the standard orifices with their designating letters and corresponding area. For sizing of a PSV on liquid filled vessel, refer to EnggCyclopedia's PSV sizing calculator for blocked liquid outlet.

Area (cm2) Designating letter Valve size (inch)
0.71 D 1D2 / 1.5D2 / 1.5D3
1.26 E 1E2 / 1.5E2 / 1.5E3
1.98 F 1.5F2 / 1.5F3
3.25 G 1.5G3 / 2G3
5.06 H 1.5H3 / 2H3
8.3 J 2J3 / 3J4
11.86 K 3K4 / 3K6
18.49 L 3L4 / 4L6
23.2 M 4M6
28 N 4N6
41.2 P 4P6
71.2 Q 6Q8
103 R 6R8 / 6R10
168 T 8T10


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