Use the resulting suction effect to reduce the pressure above the Universal Valve

Gate Valve, when the pressure in the protected system rises, an additional force is generated on the sensing element, causing the element to move and open a gap in the Gate Valve channel, and the medium is discharged through the gap. The discharge capacity of the Gate Valve and the service life of its parts , related to the dynamic stability of the Gate Valve operation. The vibration of the Universal Valve will reduce the channel cross-sectional area and discharge capacity of the Gate Valve, and the collision of the Universal Valve with the valve seat and the opening height limiter will damage the sealing surface and other parts of the Gate Valve. , the two-stage full-open Gate Valve is most likely to produce Universal Valve oscillation. The dynamic instability of the Gate Valve operation is mainly caused by the following reasons: the discharge capacity of the Gate Valve exceeds the flow rate of the medium entering the Gate Valve, the spring stiffness is too large, and when the valve is opened, When large back pressure and external dynamic interference occur in the upper chamber of the Universal Valve.

1. Impact on emission capacity
When the following conditions occur, the discharge capacity of the Gate Valve may exceed the flow rate of the medium entering the valve:
① When the passage cross-sectional area of the selected Gate Valve exceeds the cross-sectional area required for calculation.
② When the Gate Valve is installed on a system with changes in emergency displacement.
③When the cross-sectional area of the inlet pipe is not enough, etc.
2. Effect of spring stiffness
Excessive spring stiffness can also be the cause of Universal Valve oscillation. Full-open Gate Valve can achieve full-open discharge depending on the medium recoil force, but when the spring stiffness is too large, this force cannot be used by the spring force to achieve the set opening. height, so the Gate Valve cannot achieve full discharge. This will cause the Gate Valve to return to its seat as soon as it is opened, causing oscillation. If the stiffness is small, the Gate Valve will return to its seat at a very low pressure. In order to eliminate this phenomenon, it should be installed Provide a spring that meets the design, or test several actual groups of springs during design, and determine the most suitable spring through testing.
3. Impact of system back pressure
Similar to the impact caused by excessive spring stiffness, the back pressure generated in the body cavity above the Universal Valve when the Gate Valve is opened may also cause the Universal Valve to oscillate. In order to avoid the generation of large back pressure, for open Gate Valve, the openings in the valve body are used Connect the body cavity above the Universal Valve to the atmosphere. For closed Gate Valve, connect the body cavity above the Universal Valve to the valve body outlet or outlet branch, and use the suction effect generated to reduce the pressure above the Universal Valve.