Safety Relief Valves serve the unique function of providing the last line of defense against the dangerous accumulation of excessive pressures within pressure vessels, tanks and piping. They are self-contained and self-operating when other warning and control systems fail to provide the necessary protection. They are typically used on all forms of pressure vessels, heat exchangers, compressed-air receivers, boiler feed-water heaters, and processing equipments. Relief Valves are used at centrifugal and reciprocating pump outlets and on liquid pipelines and hot water heaters.