Status quo and development trend of our country's gate
Gate valves use * long history, until now the world is still in the application, especially under DN300mm, still dominate in the various types of valves.
Is characterized by pressure before and after the valve plate errand valve plate force pressure on the export on the right side of the seat, sealing better, and fully open, because the valve plate not stay on the flow, pressure loss is small.
Used to cut off the media in the pipeline.
The downside is operating torque, operation is easy to make the valve body, valve stem damage, especially large-diameter gate valves.
Overall dimensions and weight is big also, DN1000 caliber gate of about 3200 mm high, need four operations, so gate generally used in small diameter, namely below DN500 use.
The opening of the gate valve from fully open to the middle valve flow resistance is small, close to full close flow resistance has increased dramatically.
Larger scale, small flow resistance change, when close to full close, a great changing flow, do not close the valve closing, then it is difficult to flow of fine-tuning.
If the valve opening, fast opening velocity, gate underside causes cavitation, accompanied by the fierce vibration and noise, throttling operation for a long time, often can make the valve body and disc metal cavitation occurs.
If gate valve working condition in the opening, middle, valve plate because it is depend on both sides of the guide rail support, full close cooperate closely, while the middle position, the valve plate and guide rail gap big and vibrate.
Therefore, even in a lower incidence of cavitation area, for a long time to make the valve throttling operation guide can also occur malformation, abrasion or damage, and because the seat is not * * contact, the contact parts of the surface pressure is very high, often produce a bit corrosion or adhesion, therefore, should not be used for flow control.
Also note that gate in small open degree, change of flow, and if an emergency opening and closing of valve, can cause a sharp rise in pressure or produce negative pressure, especially when close the valve of water hammer.
Gate valve in our country the status quo and development trend of the mechanical and electrical products in the face of huge cost pressure domestic valve industry in China are in urgent need of high precision technical support