Stainless steel flange ball valve features and classification
December 20, 2018
The ball valve and the plug valve are the same type of valve, only the closing member of which is a ball, and the ball rotates around the center line of the valve body to open and close a valve.
The ball valve is mainly used in the pipeline to cut, distribute and change the flow direction of the medium. Ball valve is a new type of valve widely used in recent years, which has the following advantages:
1. The fluid resistance is small, and its resistance coefficient is equal to the pipe length of the same length.
2. The structure is simple, small in size and light in weight.
3. It is compact and reliable. At present, the sealing surface material of the ball valve is widely used in plastic and has good sealing performance. It has also been widely used in vacuum systems.
4. The operation is convenient, the opening and closing is rapid, and the rotation is 90° from full opening to full closing, which is convenient for long-distance control.
5. The maintenance is convenient, the ball valve has a simple structure, and the sealing ring is generally movable, and the disassembly and replacement are relatively convenient.
6. When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, and the medium does not cause erosion of the sealing surface of the valve.
7. Wide range of applications, from small to a few millimeters, up to a few meters, from high vacuum to high pressure can be applied.
Ball valves have been widely used in petroleum, chemical, power generation, paper, atomic energy, aviation, rocket and other departments, as well as people's daily lives.
The ball valve can be divided according to the structure:
1. The ball of the floating ball valve is floating. Under the action of the medium pressure, the ball can generate a certain displacement and press on the sealing surface at the outlet end to ensure the sealing of the outlet end.
The floating ball valve has a simple structure and good sealing performance, but the load of the ball subjected to the working medium is all transmitted to the outlet sealing ring, so it is necessary to consider whether the sealing ring material can withstand the working load of the spherical medium. This structure is widely used in medium and low pressure ball valves.
Second, the ball of the fixed ball valve is fixed, and does not move after being pressed. The fixed ball valve has a floating valve seat. After the medium pressure, the valve seat moves, so that the sealing ring is pressed against the ball to ensure the seal. Usually mounted on the upper and lower shafts of the ball, the operating torque is small, suitable for high pressure and large diameter valves.
In order to reduce the operating torque of the ball valve and increase the reliability of the seal, oil seal ball valves have appeared in recent years, and the special lubricating oil is injected between the sealing faces to form an oil film, which enhances the sealing performance and reduces the operating torque. It is more suitable for high pressure and large diameter ball valves.
Third, the ball of the elastic ball valve ball valve is elastic. Both the ball and the seat ring are made of metal material, and the sealing pressure is very large. The pressure of the medium itself cannot meet the sealing requirements, and an external force must be applied. This valve is suitable for high temperature and high pressure media.
The elastic sphere is made by opening an elastic groove at the lower end of the inner wall of the sphere to obtain elasticity. When the passage is closed, the wedge of the valve stem is used to open the ball and press against the seat to seal. Before the ball is rotated, the wedge head is loosened, and the ball is restored to its original shape, so that a small gap occurs between the ball and the valve seat, which can reduce the friction and operating torque of the sealing surface.
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