reliefvalve

A relief valve is an automatic pressure-relief device used in fluid systems to protect equipment and people by venting excess pressure when it exceeds a predetermined setpoint. It is designed to limit the maximum operating pressure and prevent equipment damage, process upsets, or hazardous releases.

Most relief valves are spring-loaded; other designs are pilot-operated or lever-actuated. In operation, when system pressure reaches the setpoint, the valve opens to discharge fluid and reduce pressure. Once the pressure drops below the reseat or reset point, the valve closes again.

Types and usage: The terms relief valve and safety valve are often used interchangeably, but some industries distinguish a safety valve as a rapid pop-action device and a relief valve as a spring-loaded valve that can provide controlled relief. In boiler and pressure-vessel practice, both may be required to comply with codes.

Applications: Relief valves are used on boilers, pressure vessels, compressors, pipelines, hydraulic systems, refrigerant equipment, and gas storage or handling systems to prevent overpressure.

Design considerations: Key parameters include the set pressure, relieving capacity (the maximum flow rate the valve can pass when open), relieving medium (gas, steam, vapor, or liquid), backpressure, installation orientation, material compatibility, and venting arrangement. Valves are selected and tested according to standards such as the ASME Boiler and Pressure Vessel Code, API 520/521, and ISO 4126.

Maintenance and testing: Regular inspection, calibration, and periodic functional testing are required to ensure reliability. Damaged, corroded, or stuck valves should be repaired or replaced to maintain system safety.