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PORV are also called pilot-operated safety valve (POSV), pilot-operated pressure relief valve (POPRV), or pilot-operated safety relief valve (POSRV), depending on the manufacturer and the application. Technically POPRV is the most generic term, but PORV is often used generically (as in this article) even though it should refer to valves in ...
Pilot valves are useful because they allow a small and easily operated feed to control a much higher pressure or higher flow feed, which would otherwise require a much larger force to operate; indeed, this is even useful when a solenoid is used to operate the valve. Pilot valves are often used in critical applications (e.g., emergency and SIS ...
An example of safety valve is a pressure relief valve (PRV), which automatically releases a substance from a boiler, pressure vessel, or other system, when the pressure or temperature exceeds preset limits. Pilot-operated relief valves are a specialized type of pressure safety valve.
A relief valve DN25 on cooling water pipe from heat exchanger Schematic diagram of a conventional spring-loaded pressure relief valve. A relief valve or pressure relief valve (PRV) is a type of safety valve used to control or limit the pressure in a system; excessive pressure might otherwise build up and create a process upset, instrument or equipment failure, explosion, or fire.
On September 24, 1977, the relief valve for the reactor pressurizer failed to close when the reactor, running at only 9% power, shut down because of a disruption in the feedwater system. [ 17 ] This incident later became a precursor to the Three Mile Island accident , in which a pilot-operated relief valve also became stuck open, leaking ...
In fact, the light when on only indicated that the PORV pilot valve's solenoid was powered, not the actual status of the PORV. [40] While the main relief valve was stuck open, the operators believed the unlighted lamp meant the valve was shut. As a result, they did not correctly diagnose the problem for several hours. [41]