Safety Relief Valves - Capacity vs. Pressure

Maximum safety valve free air relief capacity. Displays the relationship between valve diameter, gauge pressure, and maximum relieving capacity of free air in CFM.

Valve Diameter (inches)50 psi100 psi150 psi200 psi250 psi300 psi350 psi400 psi500 psi600 psi800 psi1000 psi1200 psi1600 psi2000 psi2400 psi
1/4122027333843485361708497109128147160
3/817273644515865728395115133149176197215
1/220324251596774111129147177205230270304330
3/437597896112127141176224232242346386423474518
15894124152178202224248286324390450500586
1 1/484135180221259293325352400443509
1 1/2114186248302354400444478528568634
2189306410501592668741
2 1/22824576137508809981114
33936388561050123013981557

Safety Relief Valve Selection Guidelines

Factors Affecting Relief Capacity:

  • Relief discharge area
  • Compressibility factor of the actual gas
  • Temperature of the gas
  • Geometry of the safety valve

Important Considerations:

  • A safety relief valve must be capable of relieving the capacity of the connected compressor(s) at operating pressure
  • The relief pressure cannot be set higher than the maximum rated working pressure of any equipment in the system
  • If the operating pressure is right below the relief pressure of the valve, the valve may start leaking

Rule of Thumb:

Set the relief pressure 10% above the working pressure of the system.

Unit Conversion:

  • 1 inch = 25.4 mm
Safety Relief Valves - Capacity vs. Pressure | MEPKit Engineering Tools | MEPKit