Importance

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Abstract

A pressure relief system includes a relief valve for selectively discharging process media from a pressure vessel, a pilot valve for controlling the relief valve, and an isolation system for isolating the pilot valve from the process media. The pilot valve has an inlet port, a control port in communication with a dome chamber of the relief valve, and a discharge port. The isolation system includes an accumulator such as a piston-type or bladder-type accumulator, a source of pressurized control fluid, a pressure regulator, and a check valve. The accumulator has an interior chamber with an inlet in communication with an inlet of the relief valve and an outlet in communication with the inlet port of the pilot valve. An isolator such as a piston or bladder divides the interior chamber into a first portion and a second portion and prevents flow therebetween to isolate process media (located in the first portion) from control fluid (located in the second portion). The isolator is movable in response to fluid pressure in the first and second portions to transmit pressure changes of process media in the first portion to control fluid in the second portion. The source of pressurized control fluid is in communication with both the accumulator outlet and the pilot valve inlet port so that the control fluid does not drop below a predetermined pressure level. The pressure regulator is located between the source of pressurized control fluid and both the accumulator outlet and the pilot valve inlet port. The check valve is located between the pressure regulator and both the accumulator outlet and the pilot valve inlet port.

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First Claim