Ball valve evolved by the plug valve, the opening and closing as a sphere, using ball rao stem axis rotate 90 °, achieve the goal of open and close the valve. Ball valve in the pipeline is mainly used for cutting, distribution, and change the flow direction of medium, the design into a v-shaped ball valve opening, but also has good flow regulating function.
Ball valve is not only simple structure, good sealing, and within a certain range nominal size has small volume, light weight, less material consumption, is one of the fastest growing valves varieties in last decade. Ball valve has a very wide range of USES, the use of varieties and quantity is still large, and the high temperature and high pressure, large diameter, high sealing, long service life, good regulation performance, and a valve multifunctional direction. Its reliability and other performance indexes reach a higher level. With the development of the ball valve, in the foreseeable period, particularly in the oil and gas pipeline, oil refining cracking cracking unit, Marine oil, coal direct liquefaction oil, gas device and will have a wider range of applications in industry.
The advantages of the ball valve is as follows:? Has the lowest flow resistance; A longitudinal because not stuck at work; (in the absence of lubricant) reason can be reliably used in the corrosive medium and low boiling point liquid; ƒ work in high pressure and high working temperature range, can achieve completely sealed; (4) can realize the rapid opening and closing, some institutions of ball valve, the opening and closing time of just 0.5-1 s, to ensure that can be used to test bench of the automation system, the rapid opening and closing valves, no impact on the operation; 5 ball valve closing member can automatically locate on the boundary; 6. Two-way sealing, reliable sealing; All landowners in the full open and full closed, the ball and seat sealing surface and the dielectric isolation, so the high speed won't medium across the valve sealing surface erosion. End up cavity of the medium pressure once made shell material in 38 ℃ 1.33 times the rated pressure, the pipeline of pipeline can be automatic drain into the export or import; Pet-name ruby can be designed to have a fire prevention sealing function; Attending has anti-static function; 11. The design into a v-shaped opening ball ball valve, with good flow regulating function, 12. Organization is compact, light quality, can be thought of as the most reasonable valve system used for low temperature medium agencies; 13. The body symmetry, especially welding body organization, can be a very good bear stress from the pipe; 14. Closed thing that can bear high pressure difference of closed; 15. All welded ball valve, can be directly buried underground, make the internal parts of the valve from erosion, top service life of 40 years, is the most ideal oil, natural gas, pipeline valves.
Because the ball valve has the advantages, so wide range of use: 1. Nominal size from DN8 - DN1600; 2. The nominal pressure from vacuum to PN420 (CL2500); 3. The working temperature from 204 to + 816 ℃.
Ball valve sealing material is the main development polytetrafluoroethylene (PTFE), it is almost for all chemicals is inert, and has a small friction coefficient, stable performance, not easy ageing, using temperature range and good sealing performance of comprehensive characteristics. But the physical properties of ptfe have higher coefficient of expansion, the sensitivity of cold flow and poor heat conductivity, seat sealing surface design must revolve around these features. Seat sealing material, ptfe and packing ptfe, nylon and other materials, when sealing material to harden the reliability of the seal is damaged, especially under the condition of low pressure difference. In addition, synthetic rubber, such as nitrile butadiene rubber can also be used as the seat material, but it is adapt to the medium and temperature range is restricted, in addition, the use of synthetic rubber in the absence of any lubrication easy stuck sphere.
In order to meet the high temperature and high pressure, strong erosion, medium with the demand of working condition of suspended particles, long life, metal sealed ball valve got great development in recent years. Used to adjust flow of v-shaped ball valve has quickly development. Especially in the industrial developed countries, the ball valve is improved, such as used in petroleum, natural gas pipeline on the supporting plate fixed ball institutions of full welded ball valve; High temperature ball valve; V-type regulating ball valve opening; The metal sealing jacket type ball valve and so on, so that the ball valve of the technology for a whole new level.
