Part 8 – System Protection

Protection Devices

Spring-loaded safety valves are always installed on the delivery side of an air compressor and between each stage on multi-stage machines

Safety valves are set to open at a pressure slightly above the standard maximum. They should also have sufficient capacity to prevent the pressure from rising above the safe value for the portion of the system they are installed to protect. Regular testing and servicing is included as part of he routine maintenance for the whole system.

The relief capacity of a safety valve depends on the following criteria:

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

Safety valves must be capable of relieving the capacity of the connected compressor(s) at operating pressure. If the operating pressure is right below the relief pressure of the valve, the valve may start leaking. As a “rule of thumb” it is common to set the relief pressure 10% above the working pressure of the system.