Safety Relief Valves Capacities

Safety valves and maximum free air relief capacities

Safety valves maximum relief free air capacities:

Maximum Relieving Capacity of Free Air (ft3/min)
Valve
Diameter (inches)
Gauge Pressure (psi)
5010015020025030035040050060080010001200160020002400
1/4 12 20 27 33 38 43 48 53 61 70 84 97 109 128 147 160
3/8 17 27 36 44 51 58 65 72 83 95 115 133 149 176 197 215
1/2 20 32 42 51 59 67 74 111 129 147 177 205 230 270 304 330
3/4 37 59 78 96 112 127 141 176 224 232 242 346 386 423 474 518
1 58 94 124 152 178 202 224 248 286 324 390 450 500 586
1 1/4 84 135 180 221 259 293 325 352 400 443 509
1 1/2 114 186 248 302 354 400 444 478 528 568 634
2 189 306 410 501 592 668 741
2 1/2 282 457 613 750 880 998 1114
3 393 638 856 1050 1230 1398 1557

The relief capacity for a safety valve depends on

  • the relief discharge area
  • the compressibility factor of the actual gas
  • the temperature of the gas
  • the geometry of the safety valve

A safety relief valve must be capable of relieving the capacity of the connected compressor(s) at operating pressure. Note that the relief pressure can not 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.

A "rule of thumb" is to set the relief pressure 10% above the working pressure of the system.

Related Topics

  • Heating - Heating systems - capacity and design of boilers, pipelines, heat exchangers, expansion systems and more
  • Gas and Compressed Air - Gas properties, capacities of pipelines, sizing of relief valves - air, LNG, LPG and more
  • Control Valves and Equipment - Sizing and dimensions of control valves & equipment in steam and condensate systems

Related Documents

Tag Search

Search the Engineering ToolBox

- "Search is the most efficient way to navigate the Engineering ToolBox!"

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your SketchUp model with the Engineering ToolBox - SketchUp Extension/Plugin - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!

Translate the Engineering ToolBox!
About the Engineering ToolBox!

Support the ToolBox

If you find the Engineering ToolBox useful and want this website to be available tomorrow - and the days after tomorrow - enable ads or make a contribution!

Contribute to the Engineering ToolBox

close