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Working Principle of Gate Valve

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Working Principle of Gate Valve

The opening and closing parts of gate valves are flashboards. The movement direction of flashboards is straight with the fluid direction. Gate valves can only be fully opened and closed, and cannot be adjusted or throttled. The ram has two sealing surfaces. The two sealing surfaces of the most commonly used mode ram valve form a wedge shape. The wedge angle varies with the valve parameters, usually 5, and 2 52' when the medium temperature is not high. Wedge gate valve gate can be made into a whole, called rigid gate; It can also be made into a ram with slight deformation to improve its manufacturability and compensate for the error of sealing surface angle during processing. This ram is called an elastic ram. When the gate valve is closed, the sealing surface can be sealed only by the medium pressure, that is, the sealing surface of the gate plate is pressed to the valve seat on the other side by the medium pressure to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves are forced to seal, that is, when the valve is closed, the gate plate should be pressed against the valve seat by relying on strong external force to ensure the sealing performance of the sealing surface. The gate of a gate valve moves linearly with the valve stem. It is called a lifting rod gate valve, also known as an open rod gate valve. Usually there is trapezoidal thread on the lifting rod, and through the nut at the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is, the operating torque is changed into operating thrust. When the valve is opened, when the height of the ram is equal to 1: 1 times the valve diameter, the fluid passage is completely unblocked, but this orientation cannot be monitored during operation. In actual use, the apex of the valve stem is taken as the mark, i.e. the fixed position is taken as its fully open position. In order to consider the locking phenomenon caused by temperature change, it is usually to turn back 1/2-1 turn at the position of opening the apex as the position of fully opening the valve. Therefore, the fully open position of the valve shall be confirmed according to the position of the ram, i.e. the stroke. In some gate valves, the valve stem nut is arranged on the gate plate, and the handwheel rolls to drive the valve stem to roll so as to raise the gate plate. This type of valve is called rotary rod gate valve, or hidden rod gate valve.