The opening and closing parts of the
Gate Valve are plug-shaped discs, the sealing surface is flat or conical, and the disc moves linearly along the center line of the fluid. The movement of the
Valve Stem can be either lifting rod type or lifting rotating rod type.
Universal Valve are only suitable for full opening and full closing, and adjustment and throttling are not allowed.
The Gate Valve is a forced sealing valve, so when the valve is closed, pressure must be applied to the disc to force the sealing surface to not leak. When the medium enters the valve from below the disc, the resistance that the operating force needs to overcome is the friction between the stem and the packing and the thrust generated by the pressure of the medium. The force to close the valve is greater than the force to open the valve, so the diameter of the valve stem should be larger, otherwise the valve stem will bend.
In recent years, since the emergence of self-sealing valves, the medium flow direction of the Gate Valve has changed from the top of the disc to enter the valve cavity. At this time, under the action of the medium pressure, the force to close the valve is small, while the force to open the valve is large, and the diameter of the valve stem can be reduced accordingly. At the same time, under the action of the medium, this type of valve is also tighter. my country's valve "three-in-one" regulations have stipulated that the flow direction of Universal Valve should be from top to bottom.
When the Gate Valve is opened, when the opening height of the valve disc is 25% to 30% of the nominal diameter, the flow rate has reached a maximum, indicating that the valve has reached the fully open position. Therefore, the fully open position of the Gate Valve should be determined by the stroke of the valve disc.
