Safety relief valves are a critical safety device that must be used on all compression systems. These valves prevent catastrophic failure of the essential pressure equipment and piping. All receivers must be equipped with a safety relief valve that is rated to open at a pressure no higher than the maximum rating on the receiver’s name plate. The valves must be equipped with a manual actuator. Compression pumps should be equipped with safety relief valves to prevent costly damage to the internals of the pump in the event of a control failure. Safety valves should be inspected on a regular basis and verified in accordance with the manufacturer’s recommendations. Valves that are found to be leaking, in poor condition, excessively dirty, missing the manual actuator, or showing any damage should be replaced immediately. The afflicted valve should be discarded or sent back to the manufacturer for overhaul and requalification. Safety valves are generally not adjustable and are delivered by the manufacturer at a preset pop-off pressure.
Figure shows a typical safety relief valve. The OD of the poppet is considerably larger than the orifice size. This oversize design allows the valve to open at a high pressure and remain open until the pressure has dropped to a considerably lower pressure, usually about half of the valve’s popoff pressure. To determine the close pressure of a safety valve, simply turn off your compressor and manually actuate the valve. The pressure of the system when the valve stops flowing is the close pressure.