决定阀门操作的力主要有三种：推力，扭矩和边缘拉力。下面简要介绍确定某个阀门三种力所用到的公式。参阅第3页至第7页，了解与测定美国太平洋闸阀、截止阀和截止止回阀的推力、扭矩和边缘拉力相关的参考数据。这些内容也包括碳钢阀门在最大或一半的冷工作压力下压差的扭矩。
　　The three major forces involved in valve actuation are thrust, torque and rimpull. Below is a brief description and formula used to determine each of the three forces for a particular valve application. See pages 3 through 7 for reference data to be used with Pacific gate, globe and stop-check valves to determine thrust, torque and rimpull for a particular application. These pages also show torque for differential pressures at full and half maximum cold working pressure for carbon steel valves.
　　推力是阀门在开启和关闭时阀座上产生的纯粹线性推力或拉力。推力可以按照下列阀门和应用条件进行测定：
　　Thrust is the purely linear push-pull force involved in seating and unseating a valve. It is determined using the following valve and application criteria:

1. – 阀门阀座直径。
   如果不知道阀门阀座的直径，则可以将端口直径作为阀座直径进行估算。
   – The valve seat diameter.
   If the valve seat diameter is not known, the port diameter can be assumed to be the seat diameter for estimating purposes.
2. – 通过阀门阀座的最大压差。
   测定阀门阀座的最大压差的最常用方法是将最大设计或工作压力作为上游的压力值P1，然后假定下游压力值P2为0 PSIG.
   – The maximum differential pressure across the valve seat.
   The most common method of determining maximum differential pressure across the valve seats is to assign the maximum design or operating pressure the upstream value P1 and assume a downstream pressure P2 of 0 PSIG.
3. – 阀门阀杆直径。
   –The valve stem diameter.

　　这些用来计算推力的因素是下列力的合力。推力的计算单位是磅。
　　These criteria are used in the thrust calculation which is the sum of the following forces. Unit of measure is Ibs. of thrust.

　　* 例子：DN150, 150磅闸阀，阀座直径6英寸, 阀杆直径为1¹/₈英寸，最大压差为100 PSIG.
　　* Example - 6" 150 Ib. gate valve, seat diameter 6", stem diameter 1¹/₈", maximum differential pressure 100 PSIG.

　　阀门运行推力只是阀门阀杆行程力的90%，因此测算阀门推力时，要加上阀杆负载和阀杆填料摩擦力。
　　Valve running thrust which represents 90% of the travel of the valve stem can be determined by adding stem load and stem packing friction.

　　扭矩是一种旋转力。使用中的闸阀和截止阀配置由驱动螺母驱动的梯形螺纹升降阀杆，此时，推力就由纯粹的线性力转换成扭矩，利用螺纹的机械性能来实现线性运动。用来将推力转换成扭矩的阀杆系数是阀杆和驱动螺母(轭架套管)上的梯形螺纹的函数。第3页至第7页包括美国太平洋闸阀、截止阀和截止止回阀的阀杆系数。一旦计算出启闭阀门时的阀座推力，则扭矩也可以从下列公式得到：
　　Torque is a rotary force. For gate and globe valve applications which have acme threaded rising stems driven by a drive nut, torque is conversion of thrust from a purely linear force, utilizing the mechanical advantage of a screw to achieve linear movement. The stem factor used to convert thrust to torque is a function of the acme thread characteristics of the valve stem and drive nut (yokesleeve). Pages AA-3 thru AA-7 contain stem factors for Pacific gate, globe and stop-check valves. Once seating or unseating thrust has been calculated, the torque can be obtained by the formula:

扭矩 = 推力 x 阀杆系数
Torque = Thrust x Stem factor

*例子：DN150, 150磅闸阀
推力 = 2072.2
阀杆系数 = 0。0099
扭矩 = 2072.2 x 0.0099 = 20.5英尺·磅
*Example: 6" 150 Ib. Gate valve
Thrust = 2072.2
Stem factor = .0099
Torque = 2072.2 x .0099 = 20.5 ft. Ibs.

　　利用上列公式，用阀座推力替代运行推力，就可以计算出阀门的运行扭矩。
　　Valve running torque can be calculated utilizing the above formula substituting running thrust for seating thrust.
　　边缘拉力是指在操作阀门时必须施加在手轮边缘的力。边缘拉力是利用扭矩来计算的。在计算手轮边缘拉力时，需要下列资料：
　　Rimpull is the force which must be applied to the rim of the handwheel during operation of the valve. Rimpull is calculated using torque. The following information is required to calculate handwheel rimpull: