1. Floating ball valve
The sphere is floating. Under the action of the medium pressure, the sphere can produce a certain displacement and press tightly on the sealing surface of the outlet end to ensure that the outlet end is sealed.
The floating ball valve has a simple structure and good sealing performance, but the load of the working medium on the ball 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.
2. Fixed ball valve
The sphere is fixed and does not move when pressed. The fixed ball valve is equipped with a floating valve seat. After receiving the pressure of the medium, the valve seat will move, so that the sealing ring is pressed tightly on the ball to ensure 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 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 enhances the sealing performance and reduces the operating torque. , It is more suitable for high pressure and large diameter ball valves.
3. Resilient ball valve
The sphere 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 media.
The elastic sphere is made by opening an elastic groove on the lower end of the inner wall of the sphere to obtain elasticity. When closing the passage, use the wedge-shaped head of the valve stem to expand the ball and press the valve seat to seal. Loosen the wedge-shaped head before rotating the sphere, and the sphere will return to its original shape, 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.
Ball valves can be divided into straight-through type, three-way type and right-angle type according to their channel position. The latter two ball valves are used to distribute the medium and change the flow direction of the medium.
Its many characteristics make the ball valve widely used in petroleum, chemical industry, power generation, papermaking, atomic energy, aviation, rockets and other departments, as well as people's daily life.
