The ball valve is a valve with a ball as a closing component, which is mainly composed of a valve body, a valve seat, a ball body, a valve stem, a handle (or other driving devices, such as electric actuators, pneumatic actuators or hydraulic actuators). The valve stem rotates around the axis of the ball valve. It is mainly used to cut off, distribute and change the flow of the medium in the pipeline. A number of flanged ball valves Q41F have been provided, which are widely used in major urbanized factories in China and exported to the international market. 

 According to the structure, it can be divided into: 

I. Floating ball valve 

The ball of the ball valve is floating. Under the action of medium pressure, the sphere can produce a certain displacement and press on the sealing surface of 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 working medium of the ball bearing 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. This structure is widely used in medium and low pressure ball valves. 

II. Fixed ball valve 

The ball of the ball valve is fixed and does not move under pressure. 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 pressed tightly on the sphere to ensure the sealing. Bearings are usually installed on the upper and lower shafts with balls, and the operating torque is small, which is suitable for high-pressure large-caliber valves. In order to reduce the operating torque of ball valves and increase the availability 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. It is more suitable for high-pressure large-caliber ball valves. 

III. Elastic ball valve 

The ball body of the ball valve is elastic. The ball body and the valve seat sealing ring are made of metal material, and the sealing specific pressure is large. According to the pressure of the medium itself, the pressure cannot meet the sealing requirements, and external forces must be applied. This valve is suitable for high-temperature and high-pressure media. The elastic sphere obtains elasticity by opening an elastic groove at the lower end of the inner wall of the sphere. When closing the channel, use the wedge of the valve stem to expand the sphere and press the valve seat to achieve sealing. Before rotating the sphere, release the wedge first, and the sphere will return to its original state, so that there is a small gap between the sphere and the valve seat, which can reduce the friction and operating torque of the sealing surface.