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HOW DOES GATE VALVE WORKS?
Created on 2024.08.05
The gate has two sealing faces, and the two sealing faces of the most commonly used wedge gate valve form a wedge, and the wedge angle varies depending on the valve parameters and is typically 5 degrees. The gate plate of the wedge gate valve can be made into a whole, which is called a rigid gate; It can also be made into a ram that can produce a slight amount of deformation to improve its manufacturability and make up for the deviation of the sealing surface angle in the processing process, which is called an elastic ram.
When the valve is opened, the flow of the fluid is completely unobstructed when the ram lift height is equal to 1:1 times the valve diameter, but this position cannot be monitored during operation. In actual use, it is marked by the apex of the stem, that is, the position that cannot be opened, as its fully open position. In order to consider the lock-up phenomenon due to temperature changes, it is usually opened to the apex position, and then reverted back 1/2~1 turn as the position of the fully open valve. Therefore, the fully open position of the valve is determined by the position of the ram (i.e. the stroke).
When the gate valve is closed, the sealing surface can only rely on the medium pressure to seal, that is, the sealing surface of the ram plate is pressed to the valve seat on the other side by relying on the medium pressure to ensure the sealing of the sealing surface, which is self-sealing. Most gate valves are forcibly sealed, that is, when the valve is closed, the ram should be forcibly pressed against the valve seat by external force to ensure the tightness of the sealing surface.
If the gate plate of the gate valve moves in a straight line with the valve stem, it is called the lifting rod gate valve (also called the open rod gate valve). Usually there is a trapezoidal thread on the lifting rod, which changes the rotary motion into a linear motion through the nut at the top of the valve and the guide groove on the valve body, that is, the operating torque into the operating thrust.
In terms of structural form, the main difference is the form of the sealing element used. According to the form of sealing elements, gate valves are often divided into several different types, such as: wedge gate valve, parallel gate valve, parallel double gate gate valve, wedge double gate gate valve, etc. The most commonly used forms are wedge gate valves and parallel gate valves.
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