Pressure Relief Valve Function and Features

The Pressure Relief Valve or called pressure safety valve  is a valve mechanism for the automatic release of a gas from a boiler, Pressure Vessel, or other system when the pressure or temperature exceeds preset limits. It is part of a bigger set named Pressure Safety Valves (PSV) or Pressure Relief Valves (PRV). The other parts of the set are named Relief Valves, safety relief valves, pilot-operated safety relief valves, low pressure safety valves, vacuum pressure safety valves.

Pressure Relief Valves or pressure safety valve were first used on steam boilers during the industrial revolution. Early boilers without them were prone to accidental Explosion. 

Pressure Relief Valves (pressure safety valve )also evolved to protect equipment such as pressure vessel (fired or not) and heat exchangers. Safety valveterm should be limited to compressible fluid application (gas, vapor, steam). 

The two general types of protection encountered in industry are thermal protection and flow protection. For liquid-packed vessels, thermal relief valves are generally characterized by the relatively small size of the safety valve necessary to provide protection from excess pressure caused by thermal expansion. In this case a small valve is adequate because most liquids are nearly incompressible, and so a relatively small amount of fluid discharged through the relief valve will produce a substantial reduction in pressure. 

Flow protection is characterized by safety valves that are considerably larger than those mounted in thermal protection. They are generally sized for use in situations where significant quantities of gas or high volumes of liquid must be quickly discharged in order to protect the integrity of the vessel or pipeline. This protection can alternatively be achieved by installing a High Integrity Pressure Protection System (HIPPS)