译文：
7、为什么切断阀应尽量选用硬密封？ 切断阀要求泄漏越低越好，软密封阀的泄漏是{zd1}的，切断效果当然好，但不耐磨、可靠性差。从泄漏量又小、密封又可靠的双重标准来看，软密封切断就不如硬密封切断好。如全功能超轻型调节阀，密封而堆有耐磨合金保护，可靠性高，泄漏率达10-7，已经能够满足切断阀的要求。 8、为什么套筒阀代替单、双座阀却没有如愿以偿？ 60年代问世的套筒阀，70年代在国内外大量使用，80年代引进的石化装置中套筒阀占的比率较大，那时，不少人认为，套筒阀可以取代单、双座阀，成为第二代产品。到如今，并非如此，单座阀、双座阀、套筒阀都得到同等的使用。这是因为套筒阀只是改进了节流形式、稳定性和维护好于单座阀，但它重量、防堵和泄漏指标上与单、双座阀一致，它怎能取代单、双座阀呢？所以，就只能共同使用。 9、为什么说选型比计算更重要？ 计算与选型比较而言，选型要重要得多，复杂得多。因为计算只是一个简单的公式计算，它的本身不在于公式的xx度，而在于所给定的工艺参数是否准确。选型涉及到的内容较多，稍不慎，便会导致选型不当，不仅造成人力、物力、财力的浪费，而且使用效果还不理想，带来若干使用问题，如可靠性、寿命、运行质量等。 10、为什么在气动阀中活塞执行机构使用会越来越多？ 对于气动阀而言，活塞执行机构可充分利用气源压力，使执行机构的尺寸比薄膜式更小巧，推力更大，活塞中的O型圈也比薄膜可靠，因此它的使用会越来越多。

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原文：
7, why use a hard shut-off valve should be closed? Shut-off valve required leakage as low as possible, soft-sealing valve leakage is the lowest cut off the effect is good, but not wear and poor reliability. From the leakage volume is small, sealed and reliable double standards, not as hard on the soft sealing off sealing off well. As a full-featured ultra-light control valve, sealing the heap are wear-resistant alloy protection, high reliability, leakage rate of 10-7, has been able to meet the shut-off valve requirements. 8, why sleeve valves instead of a single, two-seat valve does not wish fulfilled? 60 years came sleeve valve, 70 years large-scale use at home and abroad, and 80 years the introduction of the sleeve valve petrochemical plant accounted for a larger proportion of that time, many people think that the sleeve valve can replace a single, two-seat valve , to become the second-generation product. By now, is not the case, single-seat valves, seat valves, sleeve valves have been the same use. This is because the sleeve valve is throttling the form of improved stability and maintenance of better than single-seat valve, but it's weight, aiming to halt and leakage targets with single-seat valve in line, how can it replace the single-seat valve it? So, the only shared use. 9, Why is selection is more important than the calculation? Calculation and selection of comparison, the selection should be much more important, much more complex. Because the calculation is a simple formula, which itself does not lie in the accuracy of the formula, but rather by the given parameters are correct. Selection related to the contents of the large, slightly careless, would lead to selection of properly, not only causes human, material, financial waste, and using results are not satisfactory, the use of bringing a number of issues, such as reliability, life, running quality. 10, why in the pneumatic valve in the piston executing agencies will be more and more? For the pneumatic valve, the piston executing agencies may make full use of gas supply pressure, so that the executing agency of the size smaller than the membrane, a greater thrust piston in the O-ring and reliable than the film, so its use will become increasingly more.