'Backpressure' will affect the performance of a Conventional spring loaded Pressure Relief Valve (PRV). How 'backpressure' affect Conventional PRV ? Backpressure is the sum of the superimposed and built-up backpressures. Backpressure is pressure result of both superimposed backpressure caused by other sources and built-up backpressure due to the relief flow during 'relieving' mode. Superimposed backpressure may be constant or variable.īuilt-up backpressure is the increase in pressure at the outlet of a pressure relief device that develops as a result of flow after the pressure relief device (PRD) opens ('relieving' mode).īackpressure is the pressure that exists at the outlet of a pressure relief device (PRD) as a result of the pressure in the PRD discharge system. Pressure control valve (PCV), pressure relief valve (PRV), etc.

Superimposed backpressure is the result of pressure in the discharge system coming from other sources i.e. Superimposed backpressure is the static pressure that exists at the outlet of a pressure relief device (PRD) at the time the device is required to operate ('Ready-to-operate' mode). It is important to make the defintion clear prior to any discussion. In many event, understanding of this 'backpressure' creates a lot of confusion among engineers in operation, design, vendor, manufacturer, etc.

' Relieving' mode is PRV disc away from seat allowing fluid passing the PRV valve nozzle when the inlet pressure (Pi) is higher than PRV set pressure (Ps).Īs PRV may be in Ready-to-operate and Relieving mode, the 'backpressure' exist at different modes will vary. ' Ready-to-operate' mode is the PRV's disc keeping PRV in closed position when inlet pressure (Pi) is lower than or equal to PRV set pressure (Ps). A pressure relief valve (PRV) in ' Ready-to-operate' mode and ' relieving' mode during plant operation will expose to different type of pressure.

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