Relief valves open the input port to the exhaust port when a specific pressure differential (ie. setpoint) is achieved. A diaphragm provides area for pressure supplied from the input port to act against the spring force. When the force of the input pressure exceeds the spring force, the valve opens. The valve stays open until the input pressure drops below the setpoint.

Ports can be supplied with straight or barbed fittings. A single barbed version is available when the exhaust port does not require a barb.