Relief Valves Key Terms

Learn about the types of relief valves available

By Terri Deno

A relief valve is a valve used to limit pressure in a specific tank or pipe system. This valve is used in systems where pressure is built up through fire or equipment failure. The pressure is relieved when the valve is adjusted or released, letting the pressurized gas or liquid flow out of the system into a separate tank. Most relief valves are made to open automatically when a specific level of pressure is reached. Once the pressure level returns to normal in the main system, the relief valve will close again.

Flare header, relief header

The relief header, also known as a flare header, is the piping system used to relieve pressure from the main system. When a relief valve is opened, the excess liquid or gas is released into the relief header and eventually out into the atmosphere.
Try: John M. Campbell provides information about the common problems associated with relief headers in pressure relief systems.

Balanced pressure relief valve

A balanced pressure relief valve is a spring loaded valve that works to minimize the impact on the valve's performance due to back pressure.
Try: Integrated Publishing provides information on the poppet-type selector valve, which is made in unbalanced and balanced versions.

Conventional pressure relief valve

A conventional pressure relief valve is a spring loaded valve. It releases automatically when changes to the back pressure on the valve occur.
Try: Chemical & Process Technology provides information on the impact of back pressure on the conventional types of pressure relief valves.

Maximum allowable working pressure

The maximum allowable working pressure is the highest level of pressure allowed inside the system at a set temperature. This is the level of pressure that determines the need for relief devices for protection.
Try: The Engineering Toolbox provides a chart that determine the maximum allowable working pressure for carbon steel piping systems.

Pilot operated pressure relief valve

A pilot operated pressure relief valve is a system where a main and auxiliary valve work together to relieve pressure. The auxiliary valve controls to main valve.
Try: Tyco Valves and Controls provides information on a number of pilot operated pressure relief valve models for flowing and no-flow tank systems.

Required discharge area

The required discharge area for a pressure relief valve is the calculated area of pressure that determines the size of the valve used.
Try: Rockwood Swendeman provides calculations to perform in order to determine the flow area and the size of the relief valve needed for a particular system.