Tuesday, August 3, 2010

Ball valve structural characteristics and product characteristics


    Ball structural characteristics, as well as the characteristics of different types of ball valve



    (1) ball valve fluid resistance is small, has the lowest flow resistance (in fact, zero)



    Valve generally necking and the indented path channel two kinds of structures. No matter the kind of structure, and valve flow resistance coefficients are relatively small. In particular the so-called full-flow type, that is indented diameter valve, due to its channel diameter is equal to pipe diameter, the local resistance loss is only the same length of pipe friction, that is, all the valves, this valve's flow resistance minimum. In the rocket launcher and the test system, called for the resistance of pipelines as small as possible. Pipeline system to reduce the resistance there are two ways: First, reduce the flow rate, which requires larger diameter and valve diameter, which for economical pipeline system often have a negative impact, particularly for low-temperature delivery system (liquid hydrogen) is extremely unfavorable; First, reduce the local resistance of the valve, so valve naturally becomes the best choice.



    (2) valve open and close switches quickly and easily.



    As the ball valve handle under normal circumstances, only 90 ° rotation is completed fully on or off action, it is easy to open and close fast. Can be realized quickly open and close, open and close some of the structure of time is only 0.05 ~ 0.1s, to ensure that the automation can be used to test-bed system. Fast open and close the valve, the operation of no impact.



    (3) The valve sealing performance is good.



    At present, the vast majority of the seat valve is used elastic materials such as PTFE, metal and nonmetal materials, the composition of the seal pair, often referred to as soft-sealing. In general, soft seal tightness easy to guarantee, but also to seal the surface of machining accuracy and surface roughness requirements are not very high.



    (4) Ball long service life.



    Because PTFE has good self-lubrication, friction and wear with a small sphere, but also because of improvements in processing technology sphere, so that roughness reduced, thus increasing the service life of ball valves. According to reports, the United States WKM companies are experimenting with indoor life test carried out on the ball, switching frequency of more than 100,000 times.



    (5) The valve and high reliability is mainly because:



    ① ball with the valve seat a pair of seal pair does not occur abrasions, rapid wear failure, will not be stuck at work (in the absence of lubricant pm), and it could be reliably applied with the corrosive medium and low boiling liquids;



    ② Built-stem structure, eliminating the stem in the fluid under pressure may loosen the packing gland fly out potential causes of accidents;



    ③ The anti-static, fire-resistant structure, the valve is suitable for transportation of oil, natural gas, gas pipeline.



    (6) The valve body is smooth channel more suitable for conveying viscous fluid. Slurry, and solid particles.



    (7) will not be stuck at work due to (in the absence of lubricant pm), and it could be reliably applied with the corrosive medium and low boiling point liquid.



    (8) ball off pieces can be automatically positioned at the location, and can withstand the pressure differential closure.



    (9) in the larger context of land pressure and temperature, to achieve full bi-directional sealing.



    (10) in the fully open and full closed when the ball and valve seat sealing surface and the dielectric isolation, high-speed through the valve sealing surface of the medium does not cause erosion.



    (11) compact, light weight, it could be considered when the media system for low temperature valve structure of the most reasonable.



    (12) body symmetry, in particular, when the welded body structure, and can well withstand the stress from the pipe.



    (13) Full welded ball valve body can be buried in the ground, so that the valve from erosion within the pieces, the maximum service life of up to 30 years, oil, natural gas pipeline valve ideal. 

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