Steven Levy Enterprises buys and sells new, unused, and used industrial surplus relief valves. Browse our inventory of relief valves available for purchase. A relief valve is a type of safety valve used to control or limit the pressure in a system. A relief valve are divided into pop-type, direct-operated, pilot-operated, and internal relief valves. The primary purpose of a pressure relief valve is for safety of system operators and property protection by venting fluid from an overpressurized vessel. Tell us what surplus relief valves you have for sale or call us at 713-910-4337.