Ball valve and gate valve are the same type of valve, the difference is that its closing part is a ball, the ball around the valve body center line for rotation to open and close a valve. Ball valve in the pipeline is mainly used to cut off, distribution and change the flow direction of the medium. Flanged ball valve standard GB/T21465-2008 "valve terminology" is defined as: opening and closing parts (ball) driven by the valve stem, and around the axis of the valve stem for rotating movement.
Ball valve advantages
Ball valve is widely used as a new type of valve, it has the following advantages:
1. The fluid resistance is small, and its resistance coefficient is equal to that of the pipe segment of the same length.
2. Simple structure, small volume and light weight.
3. Tighter and reliable, the sealing surface material of the ball valve is widely used with plastic, good sealing, and has been widely used in the vacuum system.
4. Easy to operate, open and close quickly, from full open to full close as long as the rotation of 90°, convenient for remote control.
5. Easy maintenance, ball valve structure is simple, the sealing ring is generally active, disassembly and replacement are more convenient.
6. When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium. When the medium passes, it will not cause the erosion of the valve sealing surface.
7. Wide range of applications, from small to a few millimeters, large to a few meters, from high vacuum to high pressure can be used. This type of valve shall generally be installed horizontally in the pipeline
Classification is introduced
Classification by structure
1. Floating ball valve
The ball of the ball valve is floating. Under the action of medium pressure, the ball can produce a certain displacement and compress on the sealing surface of the outlet end to ensure the sealing of the outlet end. Floating ball valve has simple structure and good sealing, but the ball bears all the load of the working medium and passes to the outlet sealing ring. Therefore, 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 low and medium pressure ball valves.
2. Fix the ball valve
The ball valve of the ball is fixed, pressure does not produce movement. Fixed ball ball valve has a floating seat, by the medium pressure, the seat movement, so that the sealing ring tightly pressed on the ball, to ensure sealing. Usually with the ball on the upper and lower shaft bearing, operation torque is small, suitable for high pressure and large caliber valves. In order to reduce the operating torque of the ball valve and increase the reliability of the seal, in recent years, there has been an oil seal ball valve, both in the sealing surface between the pressure injection of special lubricating oil, to form a layer of oil film, that is, to enhance the sealing, and reduce the operating torque, more suitable for high pressure large diameter ball valve.
3. Elastic ball valve
The ball of a ball valve is elastic. The ball and the valve seat sealing ring are made of metal materials, sealing specific pressure is very large, relying on the pressure of the medium itself has not reached the requirements of sealing, external force must be applied. This valve is suitable for high temperature and high pressure medium. An elastic sphere is made 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 stem to expand the ball and press against the seat to achieve sealing. Loosening the wedge head before turning the ball, the ball returns to its original shape, creating a small clearance between the ball and the seat, reducing friction and operating torque on the sealing face.
Classified by channel location
Ball valve according to its channel position can be divided into straight - through, three - way and right - Angle. The latter two ball valves are used to distribute the medium and change the flow direction of the medium.