How to size and set an air compressor safety valve, with the safe discharge capacities of Airpower valves from ¼” to 1¼” BSP at 6 to 12 bar.
Airpower recommend that the safety valve on an air compressor vessel, must be able to discharge at least 25% more than the total output of the compressor(s) pumping into the vessel.
The set pressure of your safety valve must be less than the normal working pressure of the vessel. The pressure must never be able to reach more than 110% of the normal working pressure of the vessel, under any circumstances.
Set the safety valve not more than 0.5 bar above the switch off or offloading pressure of the compressor. The safety valve protects the air vessel as well as the air compressor, from over pressure.
Never install any valve or restriction between inside of vessel and the safety valve. No ball valve or non-return valve.
Make sure the opening from the tank is larger than the opening of the safety valve.
Make sure your safety valve is kept clean and can open freely. No paint or glue on safety valve.
Do not use the safety valve to control the pressure of the compressor. Use an idle running governor or a pressure switch. The safety valve is a safety for in case the idle running governor or pressure switch fails.
The size of the air receiver does not determine the size of the safety valve. A rule of thumb to calculate your 6 to 13 bar electric air compressor output is 100 liter/min per horsepower or 133 liter/min per kW of the compressor.
You can use our customer tools to measure your specific compressor output for a more accurate figure.
Safety valves from ¼” to 1¼” BSP, plus idle running governors and pressure switches.
Capacities are in liter/min. (Divide liter/min by 28.32 to get cfm.)
| Set pressure in bar | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
|---|---|---|---|---|---|---|---|
| Set pressure in kPa | 600 | 700 | 800 | 900 | 1000 | 1100 | 1200 |
| ¼” BSP | 1 360 l/min48 cfm | 1 560 l/min55 cfm | 1 725 l/min62 cfm | 1 947 l/min69 cfm | 2 140 l/min76 cfm | 2 337 l/min83 cfm | 2 530 l/min89 cfm |
| ⅜” and ½” BSP | 3 786 l/min134 cfm | 4 326 l/min153 cfm | 4 866 l/min172 cfm | 5 400 l/min191 cfm | 5 940 l/min210 cfm | 6 480 l/min229 cfm | 7 020 l/min248 cfm |
| ¾” BSP | 5 454 l/min193 cfm | 6 240 l/min220 cfm | 7 000 l/min247 cfm | 7 788 l/min275 cfm | 8 580 l/min303 cfm | 9 360 l/min330 cfm | 10 140 l/min358 cfm |
| 1” BSP | 8 520 l/min301 cfm | 9 720 l/min343 cfm | 10 950 l/min387 cfm | 12 165 l/min430 cfm | 13 380 l/min472 cfm | 14 580 l/min515 cfm | 15 660 l/min553 cfm |
| 1¼” BSP | 15 120 l/min533 cfm | 17 280 l/min610 cfm | 19 440 l/min686 cfm | 21 600 l/min763 cfm | 23 750 l/min839 cfm | 25 920 l/min915 cfm | 28 080 l/min992 cfm |
For example, a ½” BSP safety valve set at 8 bar safely discharges 4 866 l/min (172 cfm), enough for compressors delivering up to about 3 890 l/min.
Refrigerated air dryers from 750 liters/min up to 6500 liter/min ex-stock. Larger ex overseas. Dew point 4°C under pressure. Automatic drain pre and manual drain after filters.
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Screw compressors have no valves or other mechanical forces to cause imbalances unlike piston compressors.
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Airpower keeps universal spare parts for compressors. Pressure switches, non return valves and safety valves are universal to all compressors. Bottom entry filters/ regulators, electric motors and starters can be used for many makes of compressors.
View compressor componentsSend us your vessel size, working pressure and compressor output and we will help you choose the right valve.
