The overview of a gate valve

A gate valve is one of the most common types of valves in isolation valves. A gate valve can be found in every refinery, chemical plant, power station and industrial enterprise production facility, and its sizes range from DN6 to 4200. The main purpose of selecting the gate valve is to cut off the fluid. It is for this reason that gate valves are often referred to as "cutoff" valves or "block" valves. Gate valves are generally used in fully open or fully closed operation. When a gate valve is fully opened, the pressure drop through the gate valve is very small; when a gate valve is fully closed, it has good pressure sealing performance. When the gate valve is closed, almost no leakage occurs due to the cooperation of the valve disc and the seat ring. However, certain leaks may occur when the back pressure is very low (usually not less than 0.34 bar, lbar equals 105 Pa). Another advantage of the gate valve is that it is normally slow to be opened and closed. This feature prevents damage to the piping system due to the water hammer of the fluid.

Only flow characteristics of full bore ball valves can be equal to flow characteristics of gate valves among many common types of valves. Symmetrical design structures and peer-to-peer seals allow the gate valve to intercept the flow of media from either direction. Gate valves can also be made of a variety of materials. Small brass gate valves with a size of DN15 can be found on the shelves of hardware stores, and special alloy gate valves can also be found in nuclear islands of nuclear power plants. The main limitation of the gate valve is that it cannot be applied to throttling conditions. When the gate valve is used in throttling conditions, the fluid often has a very high flow velocity near the valve seat, which can cause erosion. Also, when the gate valve is partially opened, the valve disc will swing under the influence of the media, resulting in damage to the sealing pair. In general, the sealing surface of the valve seat and valve disc of the gate valve is more easily worn than that of the globe valve. And it is difficult to restore the wear by grinding and polishing methods.

Because the structural characteristics of the gate valve are very suitable for large-scale devices, the application of the gate valve is wider and developing toward the high temperature and high pressure environment. The maximum diameter of the gate valve has reached DN4200. The high-pressure gate valve with a pressure of PN320 has been widely used in the ammonia plant. The working pressure of the gate valve used for the drilling of oil and gas wells is as high as 138 MPa. Flexible valve seats and flexible floating valve seats have begun to be applied to enable gate valves to be used for inlet, outlet, double inlet and outlet seals. At present, a gate valve has shorter service life than that of the other valves. How to increase the service life is also an important issue for the development of the gate valve.

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