Pressure Relief Valves are used to protect equipment and personnel from damage or injury due to overpressure of piping systems and pressure vessels. These valves are available in various sizes, materials, pressure classes and types of inlet and outlet connections.
Pressure Relief Valves are generally used on liquid duty and an allowance is made for an increase in pressure over the set point -at least 10%, to achieve the required capacity.
Pressure Safety Valves are generally used on gases and steam and are typified by rapid opening and a lower increase of pressure over the set point to achieve required discharge capacity.
Sizing is generally calculated according to pressure, flow rate and number of other influencing factors.
Valves for boilers and pressure vessels are covered by Australian Standard (AS 1271) and International code (API 526) and care should be made in selecting a valve that complies and is marked accordingly.