The status quo and development trend of China's gate valve market
Gate valves have the longest history of use, and are still used in various countries around the world, especially below DN300mm, which still dominate in various types of valves. The characteristic is that the pressure difference between the front and rear of the valve plate forces the valve plate to press on the valve seat on the right side of the outlet, with good sealing performance, and when the valve plate is fully opened, the pressure loss is small because the valve plate does not remain in the flow path. Used to cut off the medium in the pipeline.
The disadvantage is that the operating torque is large, and the valve body and stem are easily damaged during operation, especially large-diameter gate valves. The overall size and weight are also large. The DN1000-diameter gate valve is about 3200mm high and requires four people to operate it. Therefore, the gate valve is generally used in small-diameter, that is, below DN500.
The flow resistance of the gate valve is small from fully open to middle opening, and when it is close to fully closed, the flow resistance increases sharply. In a larger range, the flow resistance changes less. When it is close to fully closed, the flow change is greater. Do not use it when the valve is close to closing. At this time, it is difficult to fine-tune the flow. If the valve opening is extremely small, the flow velocity at the opening is extremely fast, which will cause cavitation on the underside of the gate, accompanied by intense vibration and noise, and long-term throttling operation will often cause the metal of the valve body and gate to occur. Cavitation.
If the gate valve is in the middle opening, because the valve plate is supported by the guide rails on both sides, it fits tightly when fully closed. In the middle position, the gap between the valve plate and the guide rail is large and vibration occurs. Therefore, even in areas where the incidence of cavitation is low, if the valve is throttled for a long time, the guide rail will be deformed, worn or damaged, and because the valve seat is not in full contact, and the surface pressure of the contact part is very high, it will often produce Seizure or adhesion, therefore, it is not suitable for flow control. It should also be noted that when the gate valve has a small opening, the flow changes greatly. If the valve is opened and closed in an emergency, the pressure will rise sharply or produce negative pressure, especially the water hammer when the valve is closed.