I have a question regarding the structure of gate valves

This post was last edited by ylb913 on 2015-11-21 at 11:56. 1. Gate valves with visible stems are more commonly used; their structure is generally well-known to those who have used them. Gate valves with hidden stems are used less frequently. 1) Straight-stem gate valve: The valve stem nut is located on the valve cover or bracket; to open or close the gate, the valve stem is raised or lowered by rotating the valve stem nut. This structure is beneficial for lubricating the valve stem, and it provides a clear indication of the degree of opening and closing; therefore, it is widely used. 2) Hidden stem gate valve: The stem nut is located inside the valve body and is in direct contact with the medium. Opening and closing the gate plate is achieved by rotating the valve stem. The advantage of this structure is that the height of the gate valve remains constant, thus requiring less installation space; it is suitable for large-diameter gate valves or those with limited installation space. Such a structure must be equipped with an opening/closing indicator to show the degree of opening or closing. The disadvantage of this structure is that the valve stem threads are not only unable to be lubricated, but also are directly exposed to the erosion by the medium, making them prone to damage. 2. The gate of a wedge-type gate valve can be made as a single piece, known as a rigid gate ； It is also possible to create a gate valve disc that can undergo slight deformation, in order to improve its workability and compensate for any deviations in the angle of the sealing surface that occur during processing; such a gate valve disc is called an elastic gate valve disc. ——In wedge gate valves, there are single-plate, double-plate, and elastic-plate types. The single-plate wedge gate valve has a simple structure and reliable performance, but it requires high precision in the angle of the sealing surface; it is difficult to manufacture and maintain, prone to jamming and scuffing, and there is a high likelihood of wedging due to temperature changes. The double-plate wedge-type gate valve has a relatively complex structure and is widely used in pipelines for water and steam media. Its advantages are: it requires less precision regarding the angle of the sealing surfaces, temperature changes are less likely to cause wedging, and gaskets can be used as a compensation when the sealing surfaces wear out. However, this type of structure has many parts, and it tends to stick together in viscous media, affecting the seal. More importantly, the upper and lower baffles are prone to rusting over time, causing the gate plates to fall off easily. The structural feature of the elastic gate wedge gate valve is an annular groove around the edge of the gate, which provides the gate with appropriate elasticity. It combines the advantages of a simple structure and reliable performance typical of single-gate wedge gate valves; moreover, it can undergo slight elastic deformation to compensate for any deviations that occur during the machining of the sealing surface, thereby improving the manufacturability of such valves. As a result, it is now widely used.

The information upstairs is very detailed; elastic gate valves are now widely used in oil pipelines.