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 widely used in recent years, it has the following advantages:
1. The fluid resistance is small, and its resistance coefficient is equal to that of pipe sections of the same length.
2. Convenient operation, rapid opening and closing, only need to rotate 90° from fully open to fully closed, which is convenient for remote control.
3. Convenient maintenance, simple structure of the ball valve, the sealing ring is generally movable, it is convenient to disassemble and replace.
4. Simple structure, small size and light weight.
5. It is tight and reliable. At present, the sealing surface material of the ball valve is widely used in plastics with good sealing performance, and it has also been widely used in the vacuum system.
6. When fully open or fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, and the medium will not cause erosion of the valve sealing surface when the medium passes.
Ball valves have been widely used in petroleum, chemical, power generation, papermaking, atomic energy, aviation, rockets and other sectors, as well as people's daily life. According to the structure of the ball valve can be divided into:
Forged steel fixed ball valve
The ball of the ball valve 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 moves, 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-caliber ball valves.
Elastic ball valve
The ball of the ball valve 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 channel, 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 ball, and the ball will return to its original shape. A small gap appears between the ball 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.
Hard seal floating ball valve
The ball of the ball valve is floating. Under the action of the medium pressure, the ball 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. Therefore, 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. Ball valves are widely used in irrigation systems, mainly at the inlet of branch pipes. The ball valve has a simple structure, small size, and low resistance to water flow. The disadvantage is that it opens or closes too fast, which will produce water hammer in the pipeline (the pressure will increase when the water speed in the pipeline changes suddenly). Therefore, it is not appropriate to use ball valves on the main pipes, and can be used for flushing on the stem and branch pipes or at their ends, with a good flushing and drainage effect.
Ball valves are divided into O-shaped ball valves and V-Shaped Ball Valves. O-type ball valve adopts floating structure, the core is precision casting, the surface is hard chromium plated, the valve seat is made of reinforced polytetrafluoroethylene, the flow channel mouth is the same as the pipe diameter, the flow capacity is very large, the flow resistance is very small, and there is no Leakage, generally used as on-off valve, especially suitable for high-viscosity, fiber-containing, granular media; V-shaped ball valve adopts a fixed structure, with a V-shaped cut on the ball core, which can achieve proportional adjustment, and the flow characteristic is approximately equal percentage.
According to different process equipment, it can be composed of high pressure internal thread ball valve and forged steel three-piece hard-sealed ball valve. For high-pressure internal thread ball valve to achieve proportional adjustment, a valve positioner must be equipped, and forged steel three-piece hard-sealed ball valve must achieve proportional adjustment. Must choose electronic electric actuator or equipped with servo amplifier, etc.
The Male Threaded Ball Valve butt-welded ball valve is a valve that uses a sphere with a circular channel as the opening and closing part, and the sphere rotates with the valve stem to realize the opening and closing action. The opening and closing part of the external threaded ball valve butt welded ball valve is a holed sphere, which rotates around the axis perpendicular to the channel to achieve the purpose of opening and closing the channel. Ball valves are mainly used to open and close pipelines and equipment media.