Back pressure regulators perform the opposite of pressure regulators. A back pressure regulator is normally closed while a pressure reducing valve is normally open. Secondly, the back pressure regulator controls upstream pressure (P1), while a PRV controls downstream pressure (P2). Other than that, the valves operate identically. In the normally closed position, upstream pressure is sensed underneath the diaphragm. As P1 increases above the set point, the pressure of the service overcomes the spring force and begins opening the valve. This bleeds off the pressure on the P1 side and maintains the constant upstream pressure.
Many people will refer to BPRVs as relief valves. Although they do perform a relieving function, they are not a snap acting safety relief device. Back pressure regulators regulate. This is an important point and important that BPRVs are not applied where a safety relief valve is required.
Lyle Hamilton, Jordan Valve Project Engineer, and I had the opportunity to present “Back Pressure Regulators 101”, in a Webinar sponsored by Lesman Instrument Company.
This introductory presentation includes Back Pressure Regulator advantages and limitations, basic BPRV applications, pressure build-up, sizing considerations, and more.