Relief Valves
A relief valve is a type of valve used to control or limit the pressure in a system. Relief valves act as a safety measure, relieving excess pressure from equipment failure, process upset, or fire by opening an auxiliary passage to divert the fluid (liquid or gas) away from the pressure vessel. Relief valves are also known as pressure relief valves (PRV), pressure safety valves (PSV), and safety valves.
Industries such as petroleum refining, chemical manufacturing, natural gas processing, and power generation are required by law to protect pressure vessels and related equipment by use of relief valves.
One specialized type of relief valve is known as a vacuum relief valve. As opposed to a normal relief valve, which relieves high pressure, a vacuum relief valve is used to relieve dangerously low pressures, or vacuums, by inserting air or an inert gas.