Ball valve structure and characteristics
September 18, 2021
(1) ball valve fluid resistance is small, with the lowest flow resistance (in fact, zero) ball valve generally has reduced diameter and non-reduced channel two structures. No matter what kind of structure, ball valve flow resistance coefficient is relatively small. In particular, the so-called full-flow type, that is, the ball valve does not shrink, due to its diameter equal to the diameter of the pipeline, the local resistance loss is only the same length of pipeline friction resistance, that is, in all valves, the valve flow resistance of the smallest. In the rocket launch and its test system, the resistance of the pipeline needs to be as small as possible. There are two ways to reduce the resistance of the piping system: one is to reduce the flow rate of the fluid, for which it is necessary to increase the diameter of the piping and the diameter of the valve, which often has a negative impact on the economic efficiency of the piping system, Liquid hydrogen) is extremely unfavorable; First, reduce the local resistance of the valve, therefore, the ball valve has naturally become the best choice. (2) ball valve opening and closing switch quickly and easily. As the ball valve under normal circumstances only need to turn the handle 90 ° to complete the full open or full close action, it is easy to achieve quick opening and closing. Can achieve fast opening and closing, opening and closing time of some structures only 0.05 ~ 0.1s, to ensure that the test bed can be used in automation systems. Quick opening and closing the valve, the operation without impact. (3) ball valve sealing performance. Currently, the vast majority of valve seat is made of PTFE and other flexible materials, metal and non-metallic materials composed of the sealing pair, commonly known as the soft seal. In general, the soft seal of the seal is easy to guarantee, but also on the sealing surface of the machining accuracy and surface roughness requirements are not high. (4) long service life of the ball valve. As PTFE has good self-lubricating, and the friction and wear of the ball is small, but also because of the ball processing technology improvements, so that the roughness decreases, thus increasing the life of the ball valve. It is reported that the United States WKM company in the test chamber on the life of the ball valve test, switching over 100,000 times. (5) high reliability of the ball valve is mainly because: ① ball and the seat of a pair of seal will not be scratched, abrupt wear and tear and other failures, work will not get stuck (in the absence of lubricant), it can be reliably Application and corrosive media and low boiling point liquid; ② built-in stem structure, eliminating the valve stem under the fluid pressure may be due to the release of the gland and fly out accident risk; ③ anti-static, fire-resistant structure of the ball valve , Suitable for transporting oil, natural gas, gas pipeline. (6) the valve body smooth and more suitable channel for conveying viscous fluid. Slurry, as well as solid particles. (7) It can be reliably used in corrosive media and liquids with a low boiling point because it will not get stuck during operation (when no lubricant is present). (8) Ball-type closure can be automatically positioned in position and can withstand high pressure when closed. (9) Full bi-directional sealing is achieved over a wide range of pressures and temperatures. (10) In the fully open and fully closed, the ball and the seat sealing surface and media isolation, so the high speed through the valve medium will not cause the sealing surface erosion. (11) Compact and light weight, it can be considered the most reasonable valve structure for cryogenic media systems. (12) Body symmetry, especially when welding body structure, can well withstand the stress from the pipeline. (13) Fully welded ball valve, can be buried in the ground, so that the valve parts from erosion, the highest life of up to 30 years, is the ideal oil and gas pipelines valves.
