A relief valve works by reducing the pressurized fluid via an open path. As fluid begins to rise, the force from that pressure is applied to the bottom of the spool or poppet. Which then encourages the relief valve to open slowly while maintaining pressure downstream. Relief valves experience pressure rise from load pressure, back pressure, and the energy required to flow through the valve.

Relief valves are based on two types of operation: pilot-operated valves and spring-loaded valves. Programmed to open and close via a spring mechanism, spring-loaded valves open automatically when the pressure reaches an excessive level, releasing the material inside the vessel. The typical spring-loaded valve can be controlled in numerous ways, such as a remote or control panel.
 

Pilot-operated valves work by combining the primary main valve with self-actuated auxiliary pressure relief valves, also known as the pilot control. The pilot control responds to the pressure in the system and then decides the opening and closing of the main valve.

A relief valve is designed to release excess pressure that builds up in equipment and piping systems. Their purpose is to prevent significant damage that may occur to the system or even cause injury to operators. In the case of an overpressure event, a relief valve can release elevated force before it becomes extreme; it does so by using a steel spring to automatically open when the pressure is detected unsafe for the application. It’s vital the valve is consistently maintained and operates at all times to ensure it offers complete protection.