A pressure relief valve is a safety device that has been designed for protecting a pressurized vessel or system during an overpressure event. By an overpressure event, any condition that would cause pressure in a system or vessel to increase more than the specified design pressure or the maximum allowable working pressure. The main purpose of a Pressure Relief Valve is to protect the life and property by venting fluid from an overpressurized vessel. Several pneumatic, electronic and hydraulic systems are available today for controlling the fluid system variables like temperature, pressure, and flow. Each of these systems needs a power source of a type like electricity or compressed air for operating. A pressure relief valve needs to be capable of operating at almost all times mainly during any sudden period of power failure when system controls become nonfunctional. The main source of power for pressure relief is the process fluid. Whenever a situation arises which causes the pressure inside a vessel or system to increase to an alarming level, the pressure Relief Valve may be the only device that is remaining for preventing a catastrophic failure. The reliability is mainly related to the complexity of the device. It is important for the design of the Pressure Relief Valve to be simple.
At a predetermined set pressure, the Pressure Relief Valve needs to be open, flow a determined capacity at a specific overpressure, and then close down when the pressure returns to a safe level. Pressure Relief Valves needs to be designed with materials that are compatible with several process fluids from simple air and water to the most corrosive media. They are also needed to be designed to operate in a consistently stable and smooth manner on a variety of fluids and fluid phases.