the manufacturers usually do not set the pressure relief value in advance when the pressure relief valve leaves the factory, but loosen the adjusting screw on the guide valve, so that the spring is in a free state, for the convenience of storage and transportation.
the setting of pressure relief value is accomplished by twisting the adjusting screw on the pilot valve.
the setting steps are as follows:
a. pull the adjusting screw on the pilot valve out to the force free state of the pilot valve spring. b. start the fire pump to discharge water from the pressure relief valve.
c. gradually screw in the pilot valve adjustment screw, and the pressure indicated by the pressure gauge on the valve body gradually increases.
d. when the pressure of the compaction meter rises to the pressure relief value of the system design, the setting is completed. tighten the lock nut on the adjusting screw. this pressure value is the working point of the pressure relief valve. open the drain valve on the outlet pipe of the fire pump and observe whether the working point of the pressure relief valve is stable.
the pressure relief value (working point) of the pressure relief valve shall be determined according to the design working pressure of the fire water supply system and the appropriate residual star. this is because the relief valve has a range of pressures during opening and closing. for example, the pressure relief value of the pressure relief valve in a fire water supply system of an engineering is set as 1.0mpa. when the system pressure rises to 0.9mpa, the pressure relief valve is still closed. when the pressure relief valve exceeds 0.9mpa, it gradually opens and water flows out. when the pressure rises to 0.95mpa, the pressure relief valve opens and the star increases, and a small amount of water flows out. when the pressure rose to 1.0mpa, the pressure relief valve opened more, with large water outflow.
after that, if the drainage meteor continues to increase, as long as mercury is within the scope of the pressure relief valve, the system pressure will not rise, the pressure gauge pointer of the pressure relief valve will remain unchanged at the position of 1.0mpa. with the increase of water consumption, the pressure relief valve will close automatically. when the system pressure drops to 0.9mpa, the relief valve is completely closed. therefore, the relief valve opening and closing process - generally within 0.1mpa range. in other words, the pressure relief valve should be designed to exceed the working pressure of the system by 0.1mpa.
a. the pressure relief valve can be installed horizontally or vertically. pay attention to the flow direction of the valve body.
b. if the discharge pipe of the pressure relief valve passes a long (> 20m), the diameter of the discharge pipe should be enlarged to a larger range than that of the pressure relief valve to prevent backpressure caused by poor discharge and ensure stable pressure of the system pipe network.
c. in the process of system pressure test, if the test pressure is higher than the nominal pressure level of the pressure relief valve, the control valve before the pressure relief valve should be closed to avoid damage or failure of the pressure relief valve.
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