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1, why cut-off valve should try hard seal? Cut off the valve requires the lower the better leakage, soft-sealing valve leakage is the lowest, of course, cut off the effect, but not wear-resistant, poor reliability. From the leakage is small, sealed and reliable double standards, the soft seal cut off as good as the hard seal cut off. Such as full-function ultra-light control valve, sealed and piled with wear-resistant alloy protection, high reliability, leakage rate of 10-7, has been able to meet the requirements of shut-off valve. 2, why double seal valve can not be used as a shut-off valve? Double-seat valve spool has the advantage of force balance structure, allowing large pressure, and its prominent drawback is that the two sealing surfaces can not be a good contact at the same time, resulting in large leaks. If it is artificially and purposely used to cut the occasion, apparently ineffective, even for it made many improvements (such as double seal sleeve valve), is not desirable. 3, why double seat valve easy to oscillate when working? For single core, when the medium is open type, the valve stability is good; when the medium is flow closed, the valve stability is poor. Double-seated valve has two spools, the lower spool in the flow closed, the valve spool is open, so that work in a small opening, the flow-closure valve spool is easy to cause the valve vibration, which is the double-seat valve Can not be used for a small degree of work reason. 4, what is the difference between the straight-run valve anti-blocking performance, anti-blocking valve performance good? Straight stroke valve spool is a vertical throttling, and the medium is the level of flow in and out of the valve cavity flow path must turn around the flip, so that the valve flow path becomes quite complex (inverted shape, such as "S"). In this way, there are many dead zones that provide space for the precipitation of the medium over time, causing clogging. Angle valve stroke direction is the horizontal direction, the media into the level, the level of outflow, easy to clean media away, while the flow path is simple, medium precipitation space is also small, so the anti-blocking performance of the angular stroke valve. 5, why the straight stroke adjustment valve stem thin? It involves a straightforward stroke adjustment valve mechanical principle: sliding friction, rolling friction small. Straight travel valve stem up and down movement, the packing a little bit tight, it will be very tight stem package, resulting in greater backlash. To this end, the valve stem is designed to be very small, packing and PTFE friction coefficient is often small PTFE packing, in order to reduce backlash, but the problem is sent stem thin, easy to bend, filler life is short. Solve this problem, the best way is to travel with the valve stem, which is the type of angular travel control valve, the valve stem than the straight travel valve stem thick 2 to 3 times, and the choice of long life graphite packing, stem stiffness Good, long filler life, but the friction torque on the contrary, small backlash. 6, why the angular stroke valve cut off the larger pressure? Angle stroke valve cut off the larger pressure differential is because the media in the valve core or valve plate together on the torque generated by the rotating shaft is very small, therefore, it can withstand greater pressure. 7, why the sleeve valve instead of single, double seat valve but did not get it? Sleeve valves, introduced in the 1960s, were extensively used both at home and abroad in the 1970s. The percentage of sleeve valves in petrochemical plants introduced in the 1980s was large. At that time, many people thought that sleeve valves could replace single and double seat valves , Become the second generation product. Until now, not so, single-seat valve, seat valve, sleeve valve are the same use. This is because the sleeve valve is only improved throttle mode, stability and maintenance better than a single seat valve, but its weight, anti-blocking and leakage indicators with the single, double seat valve, how can it replace single, double seat valve What? So, can only be used together. 8, why the desalted water medium using rubber lined butterfly valve lined diaphragm valve life is short? Desalinated water medium contains a low concentration of acid or alkali, they are more corrosive to rubber. Rubber is corrosive performance of expansion, aging, low strength, with rubber lining butterfly valve, diaphragm valve are poor results, its essence is caused by rubber intolerance. Liner rubber diaphragm valve improved corrosion-resistant performance of fluorine-lined diaphragm valve, but lined with fluorine diaphragm valve can not withstand the collapse of the upper and lower folded, resulting in mechanical damage, valve life shorter. Now the best way is to use special ball valve water treatment, it can be used to 5 to 8 years. 9, why the piston actuator in the pneumatic valve will be more and more? For pneumatic valves, the piston actuator can take full advantage of the air pressure, the actuator size smaller than the film, the thrust greater piston in the O-ring is also more reliable than the film, so its use will be more and more many. 10, why selection is more important than calculating? Calculation and selection comparison, the selection is much more important, much more complex. Because calculation is just a simple formula calculation, it does not depend on the accuracy of the formula itself, but on the accuracy of the given process parameters. Selection involves more content, a little carelessness, it will lead to improper selection, not only resulted in human, material and financial waste, and the use of results are not satisfactory, bringing a number of use problems, such as reliability, life expectancy, operation Quality and so on.
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