Pressure relief valve principle and construction type analysis

Pressure relief valve principle and construction type analysis

The pressure relief valve is a special device that automatically reduces the working pressure of the pipeline. It reduces the higher water pressure in the pipeline before the valve to the level required for the pipeline behind the valve. Pressure reducing valves are widely used in high-rise buildings, urban water supply networks, water pressure areas, mines and other occasions to ensure that the water supply system in the water supply system to obtain appropriate service water pressure and flow. Since the water leakage rate and the degree of waste are almost proportional to the water pressure of the water supply system, the pressure reducing valve has an improved system operating condition and potential water saving effect, and the water saving effect is about 30% according to statistics.


There are many types of pressure reducing valves, and conventionally, there are membrane type, inner spring piston type and the like. The basic principle of the pressure reducing valve is to reduce the water pressure by the local resistance of the flow passage in the valve to the water flow. The range of the water pressure drop is automatically adjusted by the pressure difference between the inlet and outlet of the membrane or the piston connected to the valve flap. In recent years, some new type of pressure reducing valves, such as fixed ratio pressure reducing valves, have appeared. The construction principle is shown in Figure 14.2-2. The principle of constant pressure reduction is to use the water pressure ratio control of the floating piston in the valve body, and the pressure reduction ratio at the inlet and outlet ends is inversely proportional to the ratio of the piston area on the inlet and outlet sides. The pressure reducing valve works smoothly without vibration; there is no spring in the valve body, so there is no spring corrosion and metal fatigue failure; the sealing performance is good and does not leak, so the pressure is reduced (when the water flows) and the static pressure is reduced (the flow rate is 0 o'clock); especially during decompression without affecting water flow.

The pressure reducing valve usually has various specifications such as DN50 to DN100. The working pressures before and after the valve are <1 MPa and 0.1 to 0.5 MPa, respectively, and the error of the pressure regulating range is ±5% to 10%.

It should be noted that although the water flow has a large head loss through the pressure reducing valve, it is still energy-saving in general due to the reduction of water waste and the reasonable distribution of the system flow and the improvement of the system layout and working conditions.