The back pressure valve operates by utilizing the force of an internal spring: when the system pressure is lower than the set pressure, the diaphragm blocks the pipeline under the force of the spring; when the system pressure is higher than the set pressure, the diaphragm compresses the spring, opening the pipeline and allowing the fluid to pass through the back pressure valve. The structure of the back pressure valve is similar to that of a check valve, but the opening pressure is higher, ranging from 0.1 to 1.0 megapascals.
In situations where the pressure in a pipeline or equipment container is unstable, the back pressure valve can maintain the required pressure in the pipeline, allowing the pump to output flow normally. Additionally, in cases where a siphon effect may occur at the pump outlet due to gravity or other factors, the back pressure valve can reduce the flow and pressure fluctuations caused by the siphon effect. For volumetric pumps such as metering pumps operating under low system pressure, over-delivery may occur. To prevent such problems, it is necessary to maintain a back pressure of at least 0.7 bar at the outlet of the metering pump, which is generally achieved by installing a back pressure valve at the outlet of the metering pump.