Characteristics and classification of the ball valve

Ball valve evolution and the working principle of the ball:

       Ball valve is evolved from the plug valve. It has the same rotation of 90 degrees of action, the difference is that the plug body is a sphere, a circular through the channel through its axis. The ratio of the sphere to the passage opening should be such that when the ball rotates 90 degrees, the sphere should be present at the inlet and the outlet, all of which cut off the flow.

The application and characteristics of ball valve:

     Ball valves are generally considered to be most suitable for direct opening and closing, but recent developments have designed the ball valve to provide for throttling and control of flow. Ball valve is mainly applied to water, solvents, acids and natural gas and other general working medium, but also for the working conditions of poor media, such as oxygen, hydroge n peroxide, methane and ethylene.

Ball valve is mainly used to do cutting, distribution and change the direction of flow of media in the pipeline. Ball valve is widely used in recent years, a new type of valve, which has the following advantages:

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

    2. Simple structure, small size, light weight.

    3. Tight and reliable, the ball valve sealing surface material widely used plastic, sealing, and in the vacuum system has also been widely used.

    4. Easy to operate, open and close quickly, from full open to fully closed as long as the rotation 90 degree, easy remote control.

    5. Easy maintenance, ball valve structure is simple, the seals are generally active, demolition and replacement are more convenient.

    6. In the fully open or fully closed, the ball and seat sealing surface and medium isolation, the media through, it will not cause corrosion of the valve sealing surface.

    7. Applicable to a wide range from small to a few millimeters in diameter, large to a few meters, from high vacuum to high pressure can be applied.

         Ball valve has been widely used in petroleum, chemical, power generation, paper, atomic energy, aviation, rockets and other departments, as well as people's daily lives.

The ball valve can be classified by structure as followed:

     1. Floating ball valve

     Ball valve ball is floating, in the medium pressure, the sphere can produce a certain displacement and pressed on the export side of the sealing surface, to ensure that the export side of the seal.

     Floating ball valve structure is simple, good sealing, but the ball to bear the working medium load all passed to the export ring, so to consider whether the material can withstand the ball ring ball medium work load. This structure is widely used in low pressure ball valve.

2. The fixed ball valve

     The ball of the ball is fixed, do not move after compression. Fixed ball valve with a floating seat, subject to media pressure, the valve seat to move, so that the ring pressed on the ball to ensure that the seal. Usually with the ball on the upper and lower shaft with bearings, operating 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 there has been oil seal ball valve, both in the sealing surface pressure between the injection of special lubricants to form a layer of oil film that enhance the tightness, but also reduce the operating torque , More suitable for high-pressure large-diameter ball valve.

3.Elastic ball valve

     The sphere of the ball valve is elastic. Ball and seat seals are made of metal materials, sealing a great pressure to rely on the media itself has been less than the pressure of the sealing requirements, you must exert external force. This valve is suitable for high temperature and high pressure medium.

     Elastic sphere is in the lower end of the inner wall of the ball to open an elastic groove, and get elastic. When closing the channel, with the stem of the wedge-shaped head so that the ball up and the valve seat pressed to seal. Before turning the ball first release the wedge-shaped head, the ball will be restored to its original shape, so that the ball and the valve seat between a small gap, can reduce the sealing surface friction and operating torque.

Ball valve classification according to its channel position can be divided into straight-through, three-and-right angle. The latter two ball valves are used to dispense media and change the flow direction of the media.