A brief discussion on Gate Valve common sense and its application in thermal systems of power plants

August 23, 2024

There are a large number of pipelines in thermal systems of power plants, and these pipelines have different uses. If each pipeline and the connected equipment are to meet the operation needs of the thermal system, it is necessary to scientifically select the valve to be used. According to the function of the system, the appropriate valve should be selected to connect between the pipeline and the equipment, so as to meet the needs of the system function. Based on many years of experience, here is some common sense about Universal Valve, and which systems can be used in thermal systems of power plants.

1. Classification of Universal Valve

Universal Valve can be divided into wedge-type Universal Valve and parallel Universal Valve according to the sealing surface configuration. Wedge-type Universal Valve can be divided into: single gate, double gate and elastic gate; parallel Universal Valve can be divided into single gate and double gate. According to the thread position of the Valve Stem, it can be divided into two types: rising stem Gate Valve and concealed stem Gate Valve.

The Gate Valve includes a Gate Valve body and a gate plate. The gate plate has two sealing surfaces. The two sealing surfaces of the commonly used Gate Valve form a wedge shape. The wedge-shaped Gate Valve is a wedge-shaped Gate Valve. The single gate plate type is a single gate plate, and the double gate plate type is a Gate Valve with two gate plates. The gate plate of the wedge Gate Valve can be made into a whole, called a rigid gate plate; it can also be made into a gate plate that can produce a slight deformation to improve its processability and compensate for the deviation of the sealing surface angle during the processing process. This gate plate is called an elastic gate.

Parallel Gate Valve means that the gate plates of the Gate Valve are parallel. Similarly, the gate plates are divided into single gate plates and double gate plates.

The stem head of the rising stem Gate Valve will rise and fall when opening and closing the valve, that is, the movement of the valve stem can be seen (no rotation, only rise and fall). The so-called concealed stem Gate Valve stem will only rotate and not rise and fall when opening and closing the valve.

2. Working principle and characteristics of Universal Valve

The Gate Valve's opening and closing parts are gates, and the movement direction of the gate is perpendicular to the direction of the fluid. The Gate Valve can only be fully opened and fully closed, and cannot be adjusted or throttled. There are two types of Gate Valve seals: self-sealing and forced sealing. The sealing surface can be sealed only by the medium pressure, that is, the sealing surface of the gate can be pressed against the valve seat on the other side by the medium pressure to ensure the sealing of the sealing surface. This is self-sealing. Forced sealing means that when the Gate Valve is closed, the gate must be pressed against the valve seat by external force to ensure the sealing of the sealing surface.

When the gate lifts the height equal to 1:1 times the valve diameter when the valve is opened, the fluid passage is completely unobstructed, but this position cannot be monitored during operation. In actual use, the top of the valve stem is used as a mark, that is, the position that cannot be opened, as its fully open position. In order to consider the locking phenomenon caused by temperature changes, it is usually opened to the top position and then retracted 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 gate (i.e., the stroke).

Author:

Mr. Jim

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798905845@qq.com

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