原文：
动态特性 虽然有些传统因素仍很重要，但它们仅仅偏重于阀的“静态”性能。实际上它们是在“工作台”上对阀进行测量所获得的结果，但这样的结果很难说明阀门在实际运行条件下将会表现出什么样的性能。传统理论认为，仔细调节静态因素将会使阀（从而也使整个回路）获得良好的性能。然而，现在我们认识到情况并非总是如此。 研究人员和生产商进行的成千上万次性能检查证明，多达50%的在用阀(其中有许多是通过考虑传统因素而选择的)对于优化控制回路性能未能产生多大效果。后继研究表明，阀的动态特性对于降低流程易变性起了很重要的作用。在许多关键的流程中，不同的阀门降低流程易变性的幅度即使相差1%也能够大幅度提高生产效率并减少废物，从而可取得超过100万美元的经济效益。很显然，这样的经济效益使我们xx可以否定传统的做法，即只根据阀的最初购买价格来决定是否购买。 其次，传统的看法总是认为，流程优化的改进总是来自于控制室控制仪表的升级。但是，测试数据表明，在使用相同控制仪表的条件下，阀的动态特性能够对回路性能产生显著的影响。如果控制阀的精度只能达到5%，那么，花费大量的钱去配置一套其控制精度可达到0.5%的高级控制仪表系统并不能起到多大作用。 阀门类型 在寻找一种与使用场合相匹配的阀门时，首先应考察一下4种基本型式的节流控制阀，即笼式球阀、旋转浮球阀、偏心阀与蝶形阀。 笼式球阀的调整片形式的种类非常广泛，因此能够满足大多数应用场合的需求，从而使它成为各种阀中的{sx}。笼式球阀调整片有很多种，包括平衡调整片、非平衡调整片、弹性座调整片、受约束调整片及全尺寸调整片等。在许多情况下，一种阀体的各种调整片配置是可以互换的。 笼式球阀也有若干缺点。一是该阀的尺寸受到限制（通常为16英寸）;二是与同等规格的视线阀（如浮球阀或蝶形阀）相比，其容量比较低;三是售价较高，特别是大口径的笼式球阀。然而，在降低流程易变性方面，笼式球阀具有优异的性能，常常足以弥补这些缺陷。 旋转浮球阀的流量比同等口径的笼式球阀大。虽然旋转浮球阀的控制范围大于笼式球阀，但仍然优于大多数其他类型的阀。旋转浮球阀的允许压力降和允许温度范围比笼式球阀小。通常它们的压力降上限为7.0x105kg/m2，适合于在温度低于398℃的场合使用。浮球阀不适用于易起空泡的液体，而且在用于压力降较高的气体中时，常常可能发出较大的噪声。 偏心阀比浮球阀的摩擦更小，价格更低。特有的结构设计使其对于流程易变性的控制更xx。这一点从fisher公司的新产品bv500可见一斑。除此之外，偏心阀的优缺点与浮球阀相差不大。 按阀的性能来衡量，蝶形阀属于低档阀。蝶形阀的流量大，价格{zpy}，而且有多种不同的口径。但是，蝶形阀的特性曲线只有等比例特性曲线一种，这就大大限制了蝶形阀降低流程易变性的性能。由于这一原因，蝶形阀只能用于负载固定不变的场合中。虽然蝶形阀有多种不同的口径，并且可以用大多数铸合金来制造，但蝶形阀不符合ansi关于面对面尺寸的要求，也不适用于易起空泡的流体或噪声较大等场合。

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译文：
Dynamic characteristic Although some traditional factors are still important, but they are only biased towards the valve "static" performance. In fact they are in the "table" on the valve to measure the results obtained, but it is difficult to explain the results of the actual operating conditions the valve will show what kind of performance. Traditional theory holds that the static factors will carefully adjust the valve (and hence in the loop) for good performance. However, we recognize that not always the case. Researchers and manufacturers to check the performance of thousands of times that, up to 50% of the valves (many of which are chosen by considering the traditional factors of) control loop for optimizing the performance failed to produce much effect. Follow-up studies have shown that the dynamic characteristics of the lower valve process has played an important role in volatility. The key process in many different valves reduce process variability even if the difference between the rate of 1% can significantly increase productivity and reduce the waste, which can get more than one million U.S. dollars in economic benefits. It is clear that the economic benefits of this so that we can negate the traditional approach, that is only the initial purchase price under the valve to decide whether to buy. Secondly, the conventional wisdom is always that the process optimization for control room control is always meters from the upgrade. However, the test data show that the control devices using the same conditions, the valve's dynamic performance on the circuit performance can have a significant impact. If the precision control valves can only reach 5%, then spend a lot of money to configure a set of control precision can reach 0.5% of the advanced control and instrumentation systems can not play much. Valve type Use the search for a match withthe valve, should first look at four kinds of basic types of throttle control valve, that is, cage ball, rotating ball valve, eccentric butterfly valve and valve. Caged ball valve to adjust the type of film form is very wide, to meet the needs of most applications, making it the first choice for a variety of valves. Cage-type valve adjustments There are many films, including film balance adjustment, non-balance adjustment film, flexible seat trim tab, adjust the sheets and bound full-size adjustment films and so on. In many cases, a body of various trim tab configuration is interchangeable. Cage Ball also has some drawbacks. First, the size of the valve is limited (usually 16 inches); second line of sight with the same size valve (such as the floating ball valve or butterfly valve) compared to the relatively low capacity; Third, higher prices, especially large diameter cage ball. However, reducing process variability, the caged ball valve with superior performance, often enough to make up for these deficiencies. Rotating ball valve flow diameter cage than the same ball great. Although the rotating ball valve's control over the cage valve, but still better than most other types of valve. Rotary floating ball valve allows the pressure drop and allow the valve temperature range than a small cage. Usually their maximum pressure drop 7.0x105kg/m2, for temperature lower than 398 ℃ of occasions. Floating ball valve does not apply to trade from the cavity of the liquid, and in the higher pressure drop for gas, it is often possible to issue large noise. Floating ball valve eccentric valve friction than smaller, lower prices. Unique structural design to control for more accurate flow volatility. This new product from the fisher's bv500 evident. In addition, the eccentric and the floating ball valve or less the same advantages and disadvantages. Measured by the performance of valves, butterfly valves are low-end valve. Butterfly valve of the flow rate, cheapest, and a variety of different caliber. However, the butterfly valve characteristic curve characteristic curve is only proportional one, which greatly limits the flow butterfly valves reduce the volatility of performance. For this reason, Butterfly valves can only be used for load fixed occasion. Although the butterfly valve has many different caliber, and can use most of the cast alloy to produce, but ansi butterfly valve does not meet the requirements of size on the face, does not apply easily from the cavity of the fluid or noisy places such as .