Safety Valves and Relief Capacity

Maximum safety valves free air relief capacity

The table below can be use to determine the maximum relief free air capacity of safety valves:

The relief capacity of a safety valve depends on the

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

A 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.

As a "rule of thumb" it is common to set the relief pressure 10% above the working pressure of the system.

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