Types and advantages of ball valves

Ball valve and plug valve are the same type of valve, only its closure is a sphere, the sphere rotates around the centerline of the valve body to open and close. 
The ball valve is mainly used to cut off, distribute and change the flow direction of the medium in the pipeline. Ball valve is a new type of valve which has been widely used in recent years. 

It has the following advantages: 

1. The fluid resistance is small, and the resistance coefficient is equal to the pipe segment of the same length. 

2. Simple structure, small size and light weight. 

3. Tight and reliable, at present, the sealing surface material of ball valve is widely used in plastic, good sealing, and has been widely used in vacuum system. 

4. Easy to operate, quick to open and close, from full open to full off as long as the rotation of 90 °, convenient for long-distance control. 

5. the maintenance is convenient, the structure of the ball valve is simple, the sealing ring is generally active, and it is convenient to disassemble and replace. 

6. when fully open or closed, the sealing surface of the sphere and seat is isolated from the medium, and the sealing surface of the valve will not be eroded when the medium passes through. 

7. a wide range of applications, small to a few millimeters, large to a few meters, from high vacuum to high pressure can be used. 

Ball valve has been widely used in petroleum, chemical industry, power generation, papermaking, atomic energy, aviation, rocket and other departments, as well as people's daily life. 
Ball valves can be divided according to their structure: 

Floating ball valve. 
The sphere of the ball valve is floating. Under the action of 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 the advantages of simple structure and good sealing, but the load of the sphere bearing the working medium 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 sphere medium. This structure is widely used in medium and low pressure ball valves. 

Fixed ball valve. 
The ball of the ball valve is fixed and does not move under pressure. Fixed ball valves are equipped with floating seats, under the pressure of the medium, the seat moves, so that the sealing ring tightly pressed on the sphere to ensure sealing. Usually equipped with bearings on the upper and lower shafts of the sphere, the operation torque is small, 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, in recent years, the oil seal ball valve has appeared, which not only injects the special lubricating oil between the sealing surfaces to form a layer of oil film, not only enhances the tightness, but also reduces the operating torque. It is more suitable for high pressure and large diameter ball valve. 

Elastic ball valve. 
The ball of the ball valve is elastic. The sphere and seat sealing ring are made of metal material, the specific pressure of the seal is very large, depending on the pressure of the medium itself has been unable to meet the requirements of the seal, external force must be applied. This valve is suitable for high temperature and high pressure medium. 
An elastic sphere is an elastic slot at the lower end of the inner wall of the sphere to obtain elasticity. When closing the passage, use the cuneiform head of the stem to open the sphere and press the seat to seal. Loosen the cuneiform head before turning the sphere and restore the sphere to its original shape, resulting in a small gap between the sphere and the seat, reducing friction and operating torque on the sealing surface.