Cut off the regulator to cut off the requirements for regulating valve is the most important the use function of regulator and inner quality. To cut off grade division and standard are shown in table 1. Regulating valve in use meet leakage is one of the most common failure, in addition to the increased leakage caused by intercepting, mostly regulator structure defects and improper selection. 1) Intercepting leakage caused by natural to consider from the trap to increase this problem, see the trap type regulator ( 7. 5) Section. 2) Structure defects caused by leakage increase ( 1) Double sealed valve can not be used as a cut-off valve, double sealing valve, such as two-seater valve, sleeve valve is one of the major drawbacks of leakage. However, many manufacturers are up and down in the sleeve valve made great effort to improve structure to reduce the leakage; Make it evolved into a complicated structure, as shown in figure 4-35. So, brought many disadvantages: parts, poor reliability; Spare parts, maintenance; Cut off the effect is not ideal. In fact, it is design thinking into the erroneous zone, rather than within the 'heart' of the body such complex changes, rather than by the external. Therefore, the author thinks, should choose single type of sleeve Industrial Valves, sealing, seal, reliability problems, maintenance and spare parts problems solved the pocket, the solution the focus of the contradictions into medium to Industrial Valves problems, the unbalanced force increased solve it only with a strong piston actuator. Such apparently by external solution is much easier than through internal complex improvement, this is not so much to problems, as it's a matter of thinking. ( 2) The design of the sealing surface (1) seal face to face: common plunger valve core, the sealing surface for 60 ℃ cant small, small slope, is 60 ℃ the seat width of the small bevel usually at 0. Between 5 mm ~ 2 mm, cant to seal it has to have two good contact, but in fact, it is always under the influence of processing error, such as concentricity, roundness, slope, the sealing effect is not ideal. This kind of valve leakage rate is usually 10, by precision grinding can be up to 10, can achieve a good seal. (2) spherical seal: make use of the valve core seat small cant tangent sphere rotating and fixed, for line contact between them, it's better than the effect of the sealing face to face. Shenyang company launched a fully functional ultra light valve, the spherical sealing butterfly valve is made by this method, the leakage rate can be up to 10, two orders of magnitude greater than that of the sealing face to face can be. ( 3) Sealing material to consider (1) soft seal 'good factory is not working' : soft seal must seal effect is best, but who can guarantee in use after a period of time, the leakage quantity is how many? In the cleaning of pipe installation, system will leave more or less not clean sundry, such as welding slag, iron filings, they through the regulating valve, easy to put the soft sealing material damage, increase the leakage, so 'good factory is not working'. (2) hard seal wear-resistant alloy is the best choice of the cut-off valve surfacing again: this way at the same time considering the sealing and its reliability, although the factory index is 10, short of soft sealing effect, but it is enough to satisfy the requirement of the tight seal cutting, more important is that it can be durable. ( 4) Diaphragm valve poor reliability in the early 50 s, the diaphragm valve is usually as a first choice to cut off the valve, until now, the water treatment system of desalted water control, still use it. Here, is important to note that neither earlier rubber diaphragm valve, or later lining fluorine plastic diaphragm valve, they have a common shortcomings, that is the diaphragm is not reliable, easy to were broken broken, very short service life of the valve. ( 5) Cut-off valve of the optimum order according to the above analysis, we provide optimization of cutting class valves order as follows: (1) fully functional ultra light valve to (2) spherical sealing butterfly valve, 3 to 4 V type ball valve, eccentric valve (5) single seat valve - 6 sleeve valve - > 7) soft seal valve ( O ball valves, line with rubber butterfly valve, rubber diaphragm valve, soft seal single-seat valve) 。
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