Pressure Relief Valves

Marine pressure relief valves are used in piping systems where pressure must be discharged in a controlled manner once a predefined operating limit is exceeded. Typical applications include fuel, water, fire protection, pumping packages, and closed-loop systems where overpressure can load piping, mechanical equipment, gaskets, seals, and instrumentation beyond allowable limits.

This category includes the Cla-Val 50M, 50M-2, and 50M-5. The Cla-Val 50M is a pilot-operated modulating pressure relief valve with spring-loaded adjustable relief control. It is applied in gasoline and jet fuel distribution systems where relieving action must occur at a defined set pressure and remain stable under variable flow conditions.

The Cla-Val 50M-2 is intended for back pressure sustaining or pressure relief duty in constant-pressure pumping systems and is available in flanged configurations to MIL-F-20042 Class 150 or Class 250. Its suitability should be evaluated against the pump curve, system flow variation, suction and discharge pressure conditions, and the need to prevent unwanted recirculation, chatter, or repeated cycling near the setpoint.

The Cla-Val 50M-5 is a remote sensing pressure relief valve for marine fuel oil transfer systems on surface vessels. It is available in globe pattern from 1-1/2” to 8”, and in angle pattern at 8”, with flanged versions to MIL-F20042 Class 150/250 and union-style valves to MIL-F1183. Remote sensing arrangement should be assessed in relation to line losses, sensing point location, and response stability.

Selection should consider set pressure, allowable overpressure, required relieving capacity, process medium, viscosity, temperature, end connection, available differential pressure, and elastomer compatibility. Maintenance should focus on pilot lines, strainers, restriction orifices, diaphragm condition, seat leakage, and adjustment spring integrity, with verification of actual opening pressure under operating conditions.