止回阀
CHECK VALVES

1. 止回阀适用于具有适度高流速的应用场合。但是，为了优化工作性能，这些阀门应该工作在具有足够的流量以充分开启阀门的流量范围内，而且，流量又不能过大，不能产生过分湍流和压降。任何一种极端都可能损坏阀门的内部构件，缩短使用寿命。
   Check valves are suited for moderately high velocity applications. For optimum performance, however, these valves should operate within a flow range sufficient to hold the valve open fully, but not so high that it produces excessive turbulence and pressure drop. Either extreme may damage valve internals, and shorten operating life.
2. 应该避免应用在经常出现流向逆转或流体间歇性中断的应用环境中。止回阀的安装位置应该距离弯管和其它导致流向转变的装置至少5倍管道直径长度的地方，这样可能会最大程度减少甚至消除大多数安装中可能出现的问题。如果这样做是不可能的，则可能要将最大流速降低50%.
   Service involving frequent flow reversals or fluid pulsations should be avoided. Locating check valves no closer than five pipe diameters from elbows and other flow diverting means can minimize or eliminate problems in most installations. Where this is not possible, it may be necessary to reduce the maximum velocity by as much as 50%.
3. 如果流体噪音过大，则通常意味着出现气穴现象。
   Excessive fluid noise is usually an indication that cavitation is occurring.
4. 止回阀通常安装在水平管道或者流向朝上的垂直管道上。如果阀门应用在垂直管道上，这应该清楚指定。
   Check valves are normally designed for installation in horizontal pipe runs or in vertical lines where flow is up only. When valves are used in vertical pipe runs, this should be clearly specified.
5. 如果应用环境比这些推荐更加严酷，请在使用前咨询美国太平洋阀门公司，以了解进一步的信息。
   If severe conditions are outside these recommendations contact Pacific Valves for further information prior to use.

美国太平洋阀门所适用的标准
PACIFIC VALVES CODES AND STANDARDS

　　美国太平洋阀门公司在阀门的设计和制造过程中，结合了多年的研究和开发成果和所有类型阀门的实际应用经验，采用优质的材料和工艺和现代化的制造方法和设备，确保阀门的可靠性和一致性。美国太平洋阀门公司的阀门结构符合下列标准的最新版本的要求：
　　API – 美国石油协会
　　MSS – 美国阀门和连接件行业制造商标准协会
　　ANSI – 美国国家标准协会
　　ASME – 美国机械工程师协会
　　Years of research and development, together with practical experience in reconditioning all types of valves, have gone into the design and manufacture of Pacific valves. High quality material and workmanship, combined with the modern manufacturing methods used in producing these valves, is your assurance of a dependable, uniform product. Pacific valves are designed in accordance with applicable requirements of the latest edition of the following standards.
　　API – American Petroleum Institute
　　MSS – Manufacturers' Standardization Society of the Valve and Fittings Industry
　　ANSI – American National Standards Institute
　　ASME – American Society of Mechanical Engineers