Properly Size, Select Pressure Relief Valves

Nov. 6, 2020
Last-line-of-defense devices require careful consideration

A pressure relief valve (PRV) is a safety device designed to protect a pressurized vessel or system in case of an overpressure event. An overpressure event refers to any condition that would cause pressure in a vessel or system to increase beyond the specified design pressure or maximum allowable working pressure (MAWP). As relief valves are the last line of defense, they should be independent and highly reliable.

The relief valve is designed to open at a predetermined set pressure. As fluid is diverted, the pressure inside the vessel stops rising and will begin to fall. Once it falls to the valve's reseating pressure, the valve will close. The difference between set pressure and reseating pressure is referred as blowdown.

Similarly, equipment must sometimes be protected against an internal vacuum. In such cases, vacuum relief valves open at a predetermined low pressure limit, admitting air or an inert gas into the equipment to keep the pressure from going too low.

Read the rest of this article from our sister publication Control Global.

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