有人说自动截止止回阀是美国尼伯科公司最复杂的阀门，理由是对于不同的安装，需要选择适当通径地截止止回阀。
　　It has been said that the automatic stop-check is the most sophisticated valve in the NIBCO line. One reason for this statement is the procedure required to select the proper size stop-check for a given installation.
　　决定阀门通径常用的方法是使其与管道直径相配。但是，对于截止止回阀，这种方法行不通。在许多锅炉安装场合，阀门通径可能甚至应该比管道直径小。在许多情况下，DN200的热水器应该采用DN80的截止止回阀。
　　The obvious way to determine valve size is to match the pipe diameter. For the stop-check this is not correct. In many boiler installations, a valve smaller than pipe size could and should be selected. There are cases where a 3" stop-check should be used on an 8" header.
　　锅炉系统所采用的截止止回阀的通径选择通常由建筑师或工程师决定，但是如果批发商或建筑承包商在选择正确的阀门时有疑问，美国尼伯科销售人员可能可以提供一些帮助。
　　Size specification of the stop-check used on the boiler system is usually done by the architect or engineer, but it should be possible for the NIBCO salesman to assist the wholesaler or contractor in selecting the right valve if there is some doubt.
　　为了确定正确的截止止回阀的通径，需要下列有关的技术参数，饱和蒸汽表压(磅/平方英寸)，和实际所需的正气流量(磅/小时)。然后将这些参数应用到下列表中确定适当的阀门通径。
　　In order to size a stop-check the technical information needed is saturated steam gage pressure in pounds per square inch and actual required steam volume flow in pounds per hour. This information is then applied to the flow rates on the following chart to determine proper valve size.
　　有关我们的自动截止止回阀的另一个技术问题是开启不同通径阀门的阀瓣需要多大的压力？
　　Another technical question that comes up regarding our automatic stop-check is what pressure is required to open the disc on various sizes?
　　开启阀门所需的管路压力是阀瓣/活塞重量和端口直径的函数。例如，DN150的阀门，活塞/阀瓣的重量是21.5磅。开启直径是DN150或28.2平方英寸的面积。因此，开启阀门所需要的最小压力(摩擦力忽略不计)，应该是
　　The line pressure required to open the valve is a function of the disc/piston weight and the size of the port diameter. For instance, on a 6" valve the weight of the piston/disc is 21.5 pounds. The diameter of the opening is 6" or an area of 28.2 square inches. Therefore, the minimum pressure required to open the valve, disregarding friction which is minimal, would be:

　　根据阀门的设计要求，所有通径的阀门的开启都需要0.76psi的阀座压差，前提是阀门安装正确(手轮处于开启位置)，阀门完好无损(例如，阀瓣上的导杆没有弯曲)，没有管线上的外来颗粒导致工作部件无法正常工作的现象发生。
　　Due to the design of the valves, all sizes open with a .76 psi differential across the seat, providing the valve is properly installed (handwheel is in the open position), the valve has not been damaged (for instance, the pilot on the disc has not been bent) and no foreign particles from the line have caused the working parts to become inoperative.
　　如果锅炉没有关闭截止止回阀，则必须防止回流到锅炉上，阀瓣压铁和缓冲活塞，在重力的作用下，能够迅速实现密封，使得蒸汽和冷凝水即使在低压下也不会回流到锅炉里。阀瓣/活塞压铁非常有用，特别是对于低压系统。从美国尼伯科的截止止回阀结构设计中，人们可能会注意到，万一出现由于组装问题或不稳定的热膨胀导致的中心线错位，所安装的阀瓣能够适应阀座区域的要求主动调整密封。这种特征也允许现场维修阀门的阀座，不用担心由于现场维修设备不足导致错误装配。
　　In the event that a boiler does shut down the stop-check must prevent backflow into the boiler, the weight of the disc and dash pot piston, through the force of gravity, promote rapid sealing so steam and condensate cannot backflow into the boiler even at low pressures. The weight of the disc/piston is very helpful, especially in low pressure systems. In the NIBCO design stop-checks, you will note that the disc is mounted to permit the disc to settle into the seat area for positive sealing in case there is any misalignment due to assembly or uneven heat expansion. This feature also permits field repair of the valve seat without fear of misassembly by field mechanics.