The working principle of pneumatic ball valve is to make the valve unblocked or blocked by rotating the valve core. Pneumatic ball valve has the advantages of light switch, small volume, large diameter, reliable sealing, simple structure and convenient maintenance. The sealing surface and spherical surface are often in closed state and are not easy to be eroded by medium, so it is widely used in various industries.
Pneumatic ball valve and plug valve belong to the same type of valve, only its closing part is a ball. The ball rotates around the center line of the valve body to open and close. Pneumatic ball valve in the pipeline is mainly used to cut off fast, distribute and change the flow direction of medium.
1、 Floating pneumatic ball valve
The ball of pneumatic ball valve is floating. Under the action of medium pressure, the ball can produce a certain displacement and press tightly on the sealing surface of the outlet end to ensure the sealing of the outlet end.
The floating pneumatic ball valve has simple structure and good sealing performance, but the load of the ball bearing working medium is transferred to the outlet sealing ring, so whether the sealing ring material can withstand the working load of the ball medium should be considered. This structure is widely used in medium and low pressure ball valves.
2、 Fixed ball pneumatic ball valve
The ball of pneumatic ball valve is fixed and does not move under pressure. Fixed ball valves are equipped with floating valve seat. Under the pressure of medium, the valve seat moves and the sealing ring is pressed tightly on the ball to ensure sealing. Usually, bearings are 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 pneumatic ball valves and increase the reliability of sealing, 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 operating torque, which is more suitable for high pressure and large diameter ball valves.
3、 Pneumatic ball valve with elastic ball
The ball of pneumatic ball valve is elastic. Ball and valve seat seal ring are made of metal materials, the sealing specific pressure is very large, the pressure of medium itself can not meet the requirements of sealing, so external force must be applied. This valve is suitable for high temperature and high pressure medium.
Elastic sphere is to obtain elasticity by opening an elastic groove at the lower end of the inner wall of the sphere. When the channel is closed, the wedge head of the valve stem is used to make the ball open and press the valve seat to achieve sealing. Before rotating the ball, loosen the wedge head first, and then 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 can be divided into straight through type, three-way type and right angle type according to its channel position. The latter two kinds of ball valves are used to distribute medium and change the flow direction of medium.