Interpretation of the working principle of ball valve

Ball valve working principle

Ball valve (ball valve), the opening and closing member (ball) driven by the stem, and rotational movement around the axis of the ball valve valve. It can also be used for the regulation and control of fluids, where the hard seal V ball valve has a strong shear force between the V-shaped ball core and the metal seat of the welded carbide, especially for media containing fibers, tiny solid particles, etc.. The multi-way ball valve in the pipeline not only can flexibly control the media merging, diverging, and switching of flow direction, but also can close any channel and make the other two channels connected. This type of valve in the pipeline should generally be installed horizontally. Ball valve is divided into: pneumatic ball valve, electric ball valve, manual ball valve according to the drive mode.

At present, ball valves are widely used in petroleum refining, long-distance pipeline, chemical, paper, pharmaceutical, water conservancy, electric power, municipal, steel and other industries, occupying a pivotal position in the national economy. It has the action of rotating 90 degrees, and the plug body is a sphere with a circular through-hole or channel through its axis.

Ball valve in the pipeline is mainly used to do cut off, distribution and change the flow direction of the medium, it only needs to use the operation of 90 degrees of rotation and a very small turning torque to close tight. The ball valve is most suitable for use as a switch and cut-off valve, V ball valve.

Ball valve features.

I. Wear resistance.

Because the spool of the hard seal ball valve is alloy steel spray welding, the seal ring is alloy steel overlay welding, so the hard seal ball valve will not produce too much wear and tear when opening and closing. (It has a hardness factor of 65-70).

Second, good sealing performance.

Since the seal of hard seal ball valve is manually grinded until the spool and the seal ring are completely matched before use. So his sealing performance is reliable.

iii. light switching.

Since the seal of the hard seal ball valve uses a spring at the bottom of the seal to make the seal and the spool hold tightly together, so the switch is very light when the external force exceeds the preload of the spring.

Fourth, long service life.

Has been widely used in various sectors such as petroleum, chemical, power generation, paper making, atomic energy, aviation, rockets, and people's daily life.

Features of pneumatic ball valve.

Pneumatic ball valve simple and compact structure, reliable sealing, easy maintenance, sealing surface and spherical surface is often in a closed state, not easy to be eroded by the medium, easy to operate and repair, suitable for water, solvents, acids and natural gas and other general working media, mainly used to cut off or connect the medium in the pipeline, can also be used for fluid regulation and control.

Advantages of pneumatic ball valves.

Pneumatic ball valves compared with other types of valves, with angular stroke output torque, open quickly, smooth and reliable, widely applicable, as well as some of the following advantages.

1, thrust bearing to reduce the stem friction torque, can make the stem long-term operation smooth and flexible.

2、Anti-static function: a spring is set between the ball, stem and valve body, which can export the static electricity generated during the switching process.

3、Since materials such as PTFE have good self-lubrication, the friction loss with the ball is small, so the pneumatic ball valve has a long service life.

4、Small fluid resistance: pneumatic ball valve is one of the smallest fluid resistance among all valve classifications, even if it is a reduced diameter pneumatic ball valve, its fluid resistance is quite small.

5, the stem seal is reliable: because the stem is only rotating movement and not lifting movement, the stem packing seal is not easy to destroy, and the sealing capacity increases with the increase of medium pressure.

6, good sealing performance of the valve seat: the use of polytetrafluoroethylene and other elastic materials made of sealing ring, the structure is easy to seal, and the valve sealing capacity of the pneumatic ball valve increases with the increase in medium pressure.

7, fluid resistance is small, the full diameter of the ball valve basically no flow resistance.

8, simple structure, small volume, light weight.

9, tight and reliable. It has two sealing surfaces, and the ball valve sealing surface materials are widely used in a variety of plastics, good sealing, can achieve a complete seal.

10, easy to operate, open and close quickly, from fully open to fully closed as long as the rotation of 90 °, easy to control from a distance.

11、Easy to maintain, the ball valve structure is simple, the seal ring is generally movable, disassembly and replacement are relatively easy.

12, in full open or fully closed, the ball and seat sealing surface and media isolation, the media through, will not cause erosion of the valve sealing surface.

13, a wide range of applications, diameter from small to a few millimeters, large to several meters, from high vacuum to high pressure can be applied.

14、Because the ball valve has wiping in the opening and closing process, so it can be used in the media with suspended solid particles.

Applicable occasions of ball valve.

①Because ball valves usually use rubber, nylon and PTFE as the seat seal material, its use temperature is limited by the seat seal material. Ball valve shut-off role is to rely on the metal ball in the role of the medium, the plastic seat between the mutual pressure to complete (floating ball ball valve). Seat seal in a certain contact pressure, the local area of elastic plastic deformation. ② And because the seat seal of the ball valve is usually made of plastic, so in the selection of the structure and performance of the ball valve, to consider the ball valve fire resistance and fire prevention, especially in the petroleum, chemical, metallurgical and other sectors, in flammable, explosive media equipment and piping systems using ball valves, more attention should be paid to fire resistance and fire prevention.

③Usually, in double-position adjustment, strict sealing performance, mud, wear and tear, indented channel, rapid opening and closing action (1/4 turn opening and closing), high pressure shut-off (large differential pressure), low noise, cavitation and vaporization phenomenon, a small amount of leakage to the atmosphere, small operating torque, small fluid resistance piping system, the use of ball valves is recommended.

④Ball valve is also suitable for light structure, low pressure cut-off (small differential pressure), corrosive media piping system.

⑤ In the oil pipeline and gas pipeline in the main line to be buried in the ground, you need to use the full diameter welded ball valve.

⑥When it is required to have regulating performance, it is necessary to use ball valve with V-shaped opening of special structure.

⑦ In petroleum, petrochemical, chemical, electric power, urban construction, working temperature above 200 degrees in the pipeline system can be selected metal to metal sealed ball valve.

Operation of the ball valve use.

1）The pipeline and valve must be confirmed to have been flushed before operation.

(2) The operation of the valve is completed by rotating the valve stem according to the input signal size of the actuator: the valve is shut off when rotating 1/4 turn (90°) in the forward direction. The valve opens when it is rotated 1/4 turn (90°) in the opposite direction.

3）When the direction indication arrow of the actuator is parallel to the pipeline, the valve is open; when the indication arrow is perpendicular to the pipeline, the valve is closed.

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