1. By the construction of the gate, they can be divided
1) Parallel Sluice Gate: A gate valve with sealing surfaces parallel to the vertical centerline, meaning the two sealing surfaces are mutually parallel.
In parallel slide gate valves, structures with thrust wedges are commonly used, featuring double-sided thrust wedges between the two gate plates. These valves are suitable for low-pressure medium and small bore (DN40-300mm) gates. There are also designs with springs between the gate plates, which generate pre-tension, beneficial for the sealing of the gate plates.
2) Wedge Gate Valve: A type of gate valve with sealing surfaces at an angle to the vertical center line, forming a wedge shape between the two sealing surfaces.
The sealing face inclination angles typically include 2°52′, 3°30′, 5°, 8°, 10°, etc., with the size of the angle primarily depending on the medium's temperature. Generally, the higher the working temperature, the larger the angle should be to reduce the likelihood of wedging during temperature changes.
In wedge gate valves, there are single, double, and elastic plates to choose from. Single plate wedge gateGate valveThe structure is simple and reliable to use, but it requires high precision for the sealing face angle, making it difficult to process and maintain. There is a high likelihood of wedging during temperature changes. Double wedge gate valves are commonly used in water and steam medium pipelines. Their advantages include lower precision requirements for the sealing face angle, less likelihood of wedging due to temperature changes, and the ability to compensate for wear on the sealing face with gaskets. However, this structure has many parts, which can easily stick together in viscous media, affecting the seal. More importantly, the upper and lower baffles are prone to rust over long-term use, and the gate may easily fall off. The elastic wedge gate valve, with its simple structure and reliable operation like the single wedge gate valve, can also produce slight elastic deformation to compensate for deviations in the sealing face angle during the processing, improving the workability, and is now widely adopted.
2. Gate valves can be further divided according to the construction of the valve rod.
1) Clear Stem Gate Valve: The valve nut is located on the valve cover or bracket. To open or close the gate plate, rotation of the valve stem nut is used to lift or lower the valve stem. This design is beneficial for lubrication of the valve stem and offers clear opening and closing, hence it is widely used.
2) Submerged Ball Valve: The valve nut is inside the valve body, in direct contact with the medium. The ball valve is opened or closed by rotating the valve stem. The advantages of this structure include: the height of the ball valve remains constant, thus requiring less installation space, suitable for large-diameter valves or those with limited installation space. This structure requires a position indicator to indicate the opening and closing degree. The disadvantages are: the valve stem thread cannot be lubricated and is directly exposed to medium erosion, making it prone to damage.
