Source：Time：2021/09/07Views：267
Gate valve refers to the valve whose closing part (gate) moves along the vertical direction of the center line of the passage. The gate valve in the pipeline can only be used for full open and full close cut-off, not for regulation and throttling. Gate valve is a valve with a wide range of applications. Generally, it is selected for cutting-off devices with a diameter of DN ≥ 50mm, and sometimes gate valve is also selected for cutting-off devices with a small diameter.
The ram has two sealing surfaces. The most commonly used mode is that the two sealing surfaces of the ram valve form a wedge. The wedge angle varies with the valve parameters, usually 50. When the medium temperature is not high, it is 2 ° 52 '. The gate of wedge gate valve can be made into a whole, which is called rigid gate valve; It can also be made into a ram that can produce slight deformation to improve its manufacturability and make up for the deviation of the angle of the sealing surface in the processing process. This kind of ram is called elastic ram.
When the gate valve is closed, the sealing surface can be sealed only by the medium pressure, that is, the sealing surface of the gate valve can be pressed to the valve seat on the other side by the medium pressure to ensure the sealing of the sealing surface, which is self sealing. Most gate valves are forced sealed, that is, when the valve is closed, the gate shall be forced to the valve seat by external force to ensure the tightness of the sealing surface.
The gate of the gate valve moves in a straight line with the valve stem, which is called lifting rod gate valve (also known as rising rod gate valve). Generally, there are trapezoidal threads on the lifting rod. Through the nut at the top of the valve and the guide groove on the valve body, the rotary motion is changed into linear motion, that is, the operating torque is changed into operating thrust.
When the valve is opened, when the lifting height of the ram is equal to 1:1 times the valve diameter, the fluid channel is completely unblocked, but this position cannot be monitored during operation. In actual use, the vertex of the valve stem is used as the mark, that is, the position that cannot be opened is used as its fully open position. In order to consider the locking phenomenon caused by temperature change, it is usually opened to the peak position and then turned back 1 / 2-1 turn as the position of fully open valve. Therefore, the fully open position of the valve is determined according to the position of the RAM (i.e. stroke).
1. Gate valves are usually used for open close applications and cannot be used for throttling applications.
2. The gate valve is usually installed on the horizontal pipe with the valve stem vertically upward. It can also be installed on the vertical pipe or the horizontal pipe with the valve stem not vertically upward. However, special structure may be required according to the size of the valve diameter, application environment and material. If the purchased valve is to be installed in a special way, the direction of the valve shall be specified when ordering To.
3. For the application environment where the temperature exceeds 260 ℃, it is recommended to use flexible or split wedge to prevent the wedge from being stuck due to thermal expansion. This may occur when the valve is cold closed and then hot opened.
4. When used in high-speed fluid (turbulent) or thermal cycle applications, in order to avoid loosening, the threaded seat ring should be lock welded to the valve body. Please specify when ordering.
5. After closing the gate valve, the valve stem should rotate slightly (1 / 8 to 1 / 4 turn) to release the valve stem load. This allows the valve stem to expand slightly without jamming or damaging the valve and affecting the closing effect.
6. If the seat ring mounting lug is removed, the highly integral shut-off gate valve can be used in hot water outlet or piping system with soft iron. Please specify when ordering.
7. If the pump station uses valves that are not limited by the site, there are many sundries in the water and are easy to block important positions, it can use hand-operated and electric gate valves; on the contrary, it can use butterfly valves, especially in the pump house reconstruction project, so as to effectively use the space of the original pump house and improve the water supply (discharge) under the premise of unchanged area of the original pump house.