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Pneumatic ball valves have been widely used in power generation, papermaking, petroleum, chemical industry, atomic energy, aviation, rockets and other departments, as well as people's daily life. Next, MSTN will share with you the working principle and classification of pneumatic ball valves.
The pneumatic ball valve only needs to use the pneumatic actuator to rotate the air source by 90 degrees and a small torque to close tightly. The completely equal valve body cavity provides a low resistance, straight-through flow path for the medium. It is generally considered that the ball valve is most suitable for direct opening and closing. The main feature of the ball valve is its compact structure, easy operation and maintenance, suitable for general working media such as water, solvent, acid and natural gas. It's one of types of valves used onboard ship or in sewage treatment plant. It's also suitable for media with harsh working conditions, such as oxygen, hydrogen peroxide, methane and ethylene. The ball valve body can be integral or combined.
(1) Fixed ball
The ball of the pneumatic ball valve is fixed and does not move after being pressed. The fixed ball valve has a floating valve seat. After being pressurized by the medium, the valve seat moves, so that the sealing ring is tightly pressed on the ball to ensure the sealing. Bearings are usually installed on the upper and lower shafts of the ball, and the operating torque is small, which is suitable for high-pressure and large-diameter valves. In order to reduce the operating torque of the pneumatic ball valve and increase the reliability of the seal, the oil-sealed ball valve has appeared, that is, a special lubricating oil is injected between the sealing surfaces to form an oil film, which not only enhances the sealing performance, but also reduces the operating torque. Suitable for high pressure and large diameter ball valves.
(2) Floating ball
The ball of the pneumatic ball valve is floating. Under the action of the medium pressure, the ball can produce a certain displacement and be pressed against the sealing surface of the outlet end to ensure the sealing of the outlet end. The floating pneumatic ball valve has a simple structure and good sealing performance, but the load of the ball bearing the working medium is all transferred to the outlet sealing ring, so it is necessary to consider whether the sealing ring material can withstand the working load of the ball medium. This structure is widely used in medium and low pressure ball valves.
(3) Elastic ball
The ball of the pneumatic ball valve is elastic. Both the ball and the valve seat sealing ring are made of metal materials, and the sealing specific pressure is very large. The pressure of the medium itself cannot meet the sealing requirements, and external force must be applied. This valve is suitable for high temperature and high pressure medium. The elastic sphere is obtained by opening an elastic groove at the lower end of the inner wall of the sphere to obtain elasticity. When closing the channel, use the wedge head of the valve stem to expand the ball and press the valve seat to achieve sealing. Before turning the ball, loosen the wedge head, and the ball will return to its original shape, so that there is a small gap between the ball and the valve seat, which can reduce the friction and operating torque of the sealing surface.
Pneumatic ball valve is a ball valve equipped with a pneumatic actuator. The execution speed of the pneumatic actuator is relatively fast, and the fastest switching speed is 0.05 seconds/time, so it is usually called a pneumatic quick cut-off ball valve. Pneumatic ball valves are usually equipped with various accessories, such as solenoid valves, air source treatment triples, limit switches, positioners, control boxes, etc., to achieve local control and long-distance centralized control, and the valve can be controlled in the control room. , do not need to go to the scene or bring manual control at high altitude and dangerous, which saves human resources as well as time and safety to a great extent.
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