Pressure reducing valve is widely used in fire water supply and automatic sprinkler system. Today, Xiaobian and everyone learn the working principle of pressure reducing valve and its setting requirements.
Working principle
1. Pilot reducing valve
By changing the throttling area, the flow rate and kinetic energy of the fluid in the pipeline system change, resulting in different degrees of pressure loss, to achieve the purpose of decompression inside the pipeline, through careful control and regulation, let the valve internal pressure fluctuation and spring force to reach a balance, and finally make the valve pressure in the pipeline to keep within a certain range of error constant.
Pilot pressure reducing valves use hydraulic operating principles to achieve control. Pilot pressure reducing valve as a local pressure change adjustment and throttling components, by adjusting the inlet pressure, reduce it to a set outlet pressure range, and then with the energy of the medium itself, let the outlet pressure automatically maintain stability valve.
2. Proportional pressure reducing valve
Proportional pressure reducing valve is a kind of pressure reducing valve in accordance with the numerical proportion to control the pressure after the valve, the ratio of the pressure before the valve and the pressure after the valve is 2:1,3:1, etc. The pressure after the valve changes with the change of the pressure before the valve. The pressure after the valve does not remain constant, but only maintains a certain ratio with the pressure before the valve. When the pressure before the valve increases, the pressure after the valve increases proportionally. When the pressure before the valve decreases, the pressure after the valve decreases proportionally, and the pressure ratio between the inlet and outlet of the reducing valve remains unchanged.
二、Setting requirement
1. The reducing valve shall be set in front of the entrance of the alarm valve group. When two or more alarm valve groups are connected, the spare reducing valve shall be set up.
2.The inlet of the reducing valve should be set up a filter, the diameter of the filter mesh should not be less than 4 mesh /c square meters ~ 5 mesh /c square meters, the flow area should not be less than 4 times the cross-sectional area of the pipeline.
3. Filter and pressure reducing valve before and after the pressure gauge, gauge dial diameter should not be less than 100mm, the maximum range should be 2 times the design pressure.
4. A control valve should be installed before the filter and after the pressure reducing valve.
5. The pressure test drain valve should be set up after the pressure reducing valve.
6. The reducing valve shall be provided with a flow detection test interface or flowmeter.
7. Vertical installation of pressure reducing valve, water direction should be downward.
8. Proportional pressure reducing valve should be installed vertically, adjustable pressure reducing valve should be installed horizontally.
9. The reducing valve should have a device that protects or locks adjusting accessories.
10. The pipe section connected with the reducing valve should not be blocked or blocked.
note：
1）The performance of the reducing valve requires that the direction of water flow cannot be changed. Proportional pressure reducing valve, if the direction of the flow changes, the pressure reduction into a pressure boost; Adjustable reducing valve, if the flow direction is reversed, can not work, reducing valve into a check valve. Therefore, the installation should be strictly in accordance with the direction indicated by the reducing valve.
2）It is required to install a filter on the water inlet side of the reducing valve, which is mainly to prevent debris in the pipe network from flowing into the reducing valve, blocking the pilot valve path of the reducing valve, or depositing on the movable parts in the reducing valve, affecting its action and causing the reducing valve failure. Installing the control valve before and after the reducing valve is mainly to facilitate the maintenance and replacement of the reducing valve. During the maintenance and replacement of the reducing valve, the drainage time of the system and the influence range of water shutdown are reduced.
3）Proportional pressure reducing valve spool for cylinder piston type structure, working location sealing is sealed by the valve spool jacket rubber seal ring and valve body. Vertical installation, the valve core and the valve body sealing contact surface and force is more uniform, is conducive to ensure the reliability of its working performance and prolong the service life. Such as horizontal installation, the valve core and valve body due to the reason of gravity, easy to cause the lower contact is tight, increase friction resistance, affect the decompression effect and service life. When the installation is horizontal, the single breathing hole is downward, and the double breathing hole is horizontal, mainly to prevent external debris from blocking the breathing hole, affecting its performance.
4）Installation of the pressure gauge, mainly in order to debug can check the pressure reducing valve decompression effect, in use at any time to check the water supply pressure, pressure reducing valve decompression after the pressure is in line with the design requirements, that is, the working state of the pressure reducing valve is normal.
Pressure reducing valve commissioning
1. The dynamic and static pressure of the valve front and back of the reducing valve should meet the design requirements.
2. The discharge flow of the reducing valve should meet the design requirements. When the discharge flow is 150% of the design flow, the dynamic pressure behind the valve should not be less than 65% of the rated design working pressure.
3. Reducing valve in small flow, design flow and design flow 150% of the noise should not be significantly increased.
4. The difference between static and static pressure behind the test reducing valve should meet the design requirements.
Pressure reducing valve maintenance
1. The water discharge test shall be carried out once a month for the reducing valve group, and the pressure before and after the reducing valve shall be detected and recorded. When the design value is not met, the debugging and maintenance measures shall be taken to meet the requirements of the system.
2.The flow and pressure of the reducing valve should be tested once a year.
