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Analysis and selection of the use of gate valve and powder butterfly valve

In the city, construction, enterprise water supply and drainage projects, medium and low pressure valves are widely used, especially low pressure large diameter valves (low pressure valves refer to valves with nominal pressure PN ≤ 1.6MPa), while medium pressure valves (PN2.5-6.4MPa) are more Less, according to the principle and structure classification (international commonly used methods) commonly used valves are powder butterfly valves and gate valves, others are ball valves, check valves, exhaust valves, plug valves, diaphragm valves, pressure reducing valves, regulating valves , mud valve and so on. The following two types of commonly used gate valves and powder butterfly valves are used to provide more product history information for the selection of gate valves and powder butterfly valves.
1, the use of the gate valve:
The gate valve has the longest history of use and is still in use in countries all over the world, especially below DN300mm. It still dominates all kinds of powder butterfly valves. According to the shape of the valve plate and the parallel gate valve and the powder butterfly valve, the wedge gate valve is widely used in the world. The feature is that the pressure difference between the front and the rear of the valve plate forces the valve plate to be pressed on the valve seat on the outlet side, and the sealing property is good, and When fully opened, the pressure loss is small because the powder butterfly valve plate does not remain on the flow path. Used to cut off the media in the pipe.
The powder butterfly valve has a small flow resistance from full opening to intermediate opening, and the flow resistance increases sharply when it is nearly closed. In the larger range, the flow resistance changes little. When the valve is nearly fully closed, the flow rate changes greatly. It must not be used when the valve is close to close. At this time, it is difficult to fine-tune the flow. If the opening of the valve is extremely small, the flow rate at the opening is extremely fast, which will cause cavitation on the underside of the ram, accompanied by fierce vibration noise. The long-term throttling operation often causes the metal of the valve body and the ram to occur. Cavitation. The powder butterfly valve can quickly and efficiently process various powders, which makes the powder butterfly valve market have a better demand. It is mainly used in various industries. Use a powder butterfly valve for a long time. Let's talk about the advantages and disadvantages of the soup powder butterfly valve.
The disadvantage is that the operating torque is large, and the valve body and the valve stem are easily damaged during operation, especially the large-mouth gate valve. The external dimensions and weight are also large. The DN1000 caliber gate valve is about 3200mm high and requires four people to operate. Therefore, the gate valve is generally suitable for small caliber, that is, below DN500.
If the working condition of the gate valve is at the middle opening degree, the valve plate is supported by the guide rails on both sides, and the valve plate is tightly closed when fully closed, and the gap between the valve plate and the guide rail is large and generates vibration in the middle position. Therefore, even in the area where the cavitation incidence rate is low, the valve is throttled for a long time, the guide rail may be deformed, worn or damaged, and since the valve seat is not in full contact, the surface pressure of the contact portion is high, which often occurs. Bite or adhesion, therefore, not suitable for flow control. It should also be noted that when the gate valve is at a small opening degree, the flow rate changes greatly. If the valve is opened and closed urgently, the pressure is sharply increased or a negative pressure is generated, especially when the water hammer is closed when the valve is closed.
On the basis of metal sealing gate valves, rubber soft sealing gate valves have been developed in recent years, which are characterized by:
(1) The sealing performance is not affected by the bending and stretching of the piping.
(2) The sealing surface of the ram is pressed against the valve body to stop the water, and the closing torque is small.
(3) The valve can replace the sealing material and the O-ring while the water is fully opened.
(4) The entire valve plate is lined with rubber, which is resistant to corrosion and does not emit rust water.
(5) There is no recess at the bottom of the valve body, and the fluid passes through the cross section in a straight line, which is not easy to accumulate and is contaminated with foreign matter. Due to its superior function, the international demand (especially in Europe) is increasing rapidly. The soft seal gate valve was invented by the Austrians 30 years ago. It produces more than 500,000 units per year in Europe and is used almost 100%. It is an alternative to hard seal gate valves. The manufacturing caliber is DN500 in Europe and the United States, DN400 is generally used in the United States, and DN1200 is produced in Italy.

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