Pneumatic ball valve is a kind of pneumatic valve, including hard-sealed pneumatic ball valve, pneumatic O-shaped cut-off ball valve, soft-sealed pneumatic ball valve, wafer type pneumatic ball valve, pneumatic floating ball valve, pneumatic three-way ball valve, pneumatic flanged ball valve, etc. According to the different balls, it can be divided into floating ball pneumatic ball valve, fixed ball pneumatic ball valve and elastic ball pneumatic ball valve.
1. Floating pneumatic ball valve: The ball of the stainless steel pneumatic ball valve is floating. Under the action of the medium pressure, the ball can produce a certain displacement and be pressed on the sealing surface of the outlet end to ensure the sealing of the outlet end. The floating stainless steel 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.
2. Fixed ball pneumatic ball valve: The ball of the stainless steel 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 with 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, oil-sealed ball valves have appeared in recent years. 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 operation. torque, more suitable for high-pressure and large-diameter ball valves.
3. Elastic ball pneumatic ball valve: 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.