What are the structural forms of ball valves?
Ball valve and plug valve is the same type of valve, only its closing part is a ball, the ball is rotated around the center line of the valve body to achieve the opening and closing of a valve. Ball valves are 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, ball valve and plug valve is the same type of valve, only its closing part is a ball, the ball around the center line of the valve body for rotation to achieve the opening and closing of a valve. Ball valves are 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 the pipe segment of the same length.
2. Simple structure, small size, light weight.
3. Tight and reliable, the sealing surface material of the ball valve is widely used in 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 degrees, easy to 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 seat is isolated from the medium, and the medium will not cause the erosion of the sealing surface of the valve.
7. Wide range of application, small diameter to a few millimeters, large to a few meters, from high vacuum to high pressure can be applied.
Ball valves have been widely used in petroleum, chemical, power generation, paper making, atomic energy, aviation, rockets and other departments, as well as People's Daily life.
Ball valve can be divided according to the structure:
First, floating ball valve
Ball valve ball is floating, under the action of medium pressure, the ball can produce a certain displacement and tight pressure on the outlet sealing surface to ensure that the outlet is sealed.
The structure of the floating ball valve is simple and the sealing is good, but the load of the ball bearing the working medium is all passed to the outlet sealing ring, so 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.
Second, trunnion mounted ball valve
The ball of the ball valve is trunnion and does not move after pressure. Trunnion mounted ball valves are equipped with floating seat, under the pressure of the medium, the seat is moved, so that the sealing ring is firmly pressed on the ball to ensure sealing. Bearings are usually installed on the upper and lower shafts of the ball, and 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, both in the sealing surface pressure injection of special lubricating oil to form a layer of oil film, that is, to enhance the sealing, but also reduce the operating torque, more suitable for high-pressure large-caliber ball valves.
Third, elastic ball valve
The ball of a ball valve is elastic. The ball and the seat sealing ring are made of metal materials, the specific pressure of the seal is very large, and the pressure of the medium itself can not meet the requirements of the seal, and external forces must be applied. This valve is suitable for high temperature and high pressure media.
An elastic sphere is an elastic groove opened at the lower end of the inner wall of the sphere to obtain elasticity. When the channel is closed, use the wedge head of the stem to expand the ball and press the seat to seal. The wedge head is loosened before the ball is turned, and the ball is then restored to its original shape, so that there is a small gap between the ball and the seat, which can reduce the friction and operating torque of the sealing surface.
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.