1) Adjustment of opening pressure
① Before the Gate Valve leaves the factory, its opening pressure should be adjusted one by one to the setting value required by the user. If the user proposes a spring working pressure level, the factory adjustment should generally be made according to the lower limit of the pressure level.
② Before installing the Gate Valve on the protected equipment or before installation, the user must readjust it at the installation site to ensure that the set pressure value of the Gate Valve meets the requirements.
③ Within the spring working pressure level range indicated on the nameplate, the opening pressure can be adjusted by changing the spring compression amount by rotating the adjusting screw.
④ Before rotating the adjusting screw, the valve inlet pressure should be reduced to less than 90% of the opening pressure to prevent the valve disc from being driven to rotate when the adjusting screw is rotated, thereby damaging the sealing surface.
⑤ In order to ensure the accuracy of the opening pressure value, the medium conditions during adjustment, such as medium type, temperature, should be as close as possible to the actual operating conditions. When the type of medium changes, especially when the accumulation state of the medium is different, the opening pressure often changes. As the operating temperature increases, the cracking pressure generally decreases. Therefore, when adjusting at normal temperature and using it at high temperature, the set pressure value at normal temperature should be slightly higher than the required opening pressure value. How high it is is related to the valve structure and material selection, and should be based on the manufacturer's instructions.
⑥Conventional Gate Valve are used when additional back pressure is fixed. When adjusting the opening pressure after inspection, the setting value should be the required opening pressure value minus the additional back pressure value.
(2) Adjustment of discharge pressure and return pressure
① To adjust the valve discharge pressure and reseating pressure, an action test must be carried out with the valve reaching the full opening height. Therefore, it can only be carried out on a large-capacity test device or after the Gate Valve is installed on the protected equipment. The adjustment method varies depending on the valve structure.
②For the structure with recoil plate and
Universal Valve adjusting ring, the Universal Valve adjusting ring is used for adjustment. Unscrew the fixing screw of the adjusting ring and insert a thin iron rod or other tool from the exposed screw hole to move the gear teeth on the adjusting ring to make the adjusting ring rotate left and right. When the adjusting ring is rotated counterclockwise to the left, its position increases, and both the discharge pressure and the return pressure will be reduced. On the contrary, when the adjusting ring is rotated clockwise to the right, its position decreases, and both the discharge pressure and the return pressure will increase. Every time you adjust, the range of adjustment circle rotation should not be too large. After each adjustment, the fixing screw should be tightened so that its end is located in the groove between the two teeth of the adjusting ring, which can prevent the adjusting ring from rotating and produce no radial pressure on the adjusting ring. For safety reasons, the inlet pressure of the Gate Valve should be appropriately reduced before turning the adjustment ring to prevent the valve from suddenly opening during adjustment and causing an accident.
③ For structures with upper and lower adjustment rings, the adjustment is more complicated. The Universal Valve adjusting ring is used to change the size of the channel between the valve disc and the adjusting ring, thereby changing the degree of pressure accumulation in the chamber between the valve disc and the adjusting ring when the valve is initially opened. When the Universal Valve adjustment ring is raised, the degree of pressure accumulation increases, thereby reducing the proportional opening stage of the valve and reaching sudden rapid opening faster. Therefore, raising the Universal Valve adjustment ring can reduce the discharge pressure. It should be noted that the Universal Valve adjustment ring cannot be raised too close to the valve disc. In that case, leakage at the sealing surface may cause the valve to suddenly open prematurely, but because the medium pressure is not enough to keep the valve disc in the open position at this time, the valve disc will close again immediately, so the valve will jump.
(3) Lead seal
After the adjustment of the Gate Valve is completed, it should be sealed to prevent arbitrary changes in the adjusted condition. When renovating a Gate Valve, note the position of the adjusting screw and adjusting ring before disassembling the valve to facilitate adjustment after the reconditioning. After readjustment, it should be sealed again.
