原文：
密封性能 　　 阀门的密封性能是指阀门各密封部位阻止介质泄漏的能力，它是阀门最重要的技术性能指标。阀门的密封部位有三处：启闭件与阀座两密封面间的接触处；填料与阀 杆和填料函的配和处；阀体与阀盖的连接处。其中前一处的泄漏叫做内漏， 也就是通常所说的关不严，它将影响阀门截断介质的能力。对于截断阀类来说，内漏是不 允许的。后两处的泄漏叫做外漏，即介质从阀内泄漏到阀外。外漏会造成物料损失，污染环境，严重时还会造成事故。对于易燃易爆、有毒或有放射的介质，外漏更 是不能允许的，因而阀门必须具有可靠的密封性能 流动介质 　　 介质流过阀门后会产生压力损失（既阀门前后的压力差），也就是阀门对介质的流动有一定的阻力，介质为克服阀门的阻力就要消耗一定的能量。从 节约能源上考 虑，设计和制造阀门时，要尽可能降低阀门对流动介质的阻力 启闭力和启闭力矩 　　 启闭力和启闭力矩是指阀门开启或关闭所必须施加的作用力或力矩。关闭阀门时，需要使启闭件与发座两密封面间形成一定的密封比压，同时还要克服阀杆与填料之 间、阀杆与螺母的螺纹之间、阀杆端部支承处及其他磨擦部位的摩擦力，因而必须施加一定的关闭力和关闭力矩，阀门在启闭过程中，所需要的启闭力和启闭力矩是 变化的，其{zd0}值是在关闭的最终瞬时或开启的最初瞬时。设计和制造阀门时应力求降低其关闭力和关闭力矩。 启闭速度 　　 启闭速度是用阀门完成一次开启或关闭动作所需的时间来表示。一般对阀门的启闭速度无严格要求，但有些工况对启闭速度有特殊要求，如有的要求迅速开启或关 闭，以防发生事故，有的要求缓慢关闭，以防 产生水击等，这在选用阀门类型时应加以考虑。 动作灵敏度和可靠性 　　 这是指阀门对于介质参数变化，做出相应反应的敏感程度。对于节流阀、减压阀、调节阀等用来调节介质参数的阀门以及安全阀、疏水阀等具有特定功能的阀门来 说，其功能灵敏度与可靠性是十分重要的技术性能指标。 　　 使用寿命 　　 它表示阀门的耐用程度，是阀门的重要性能指标，并具有很大的经济意义。通常以能保证密封要求的启闭次数来表示，也可以用使用时间来表示

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译文：
Sealing performance Valve valve sealing performance is part of the sealing ability to prevent media leaks, it is the most important technology valve performance. Sealing valve has three parts: opening and closing pieces and valve seat sealing surface between the two contact points; stem and stuffing box packing and distribution and office; body and bonnet connection. Which is called before a leak within the leak, also known as loose relationship, it will affect the ability of the valve cut off media. For the truncated valve, the internal leakage is not allowed. Leakage after the two called the leak, that media leaks from the valve to the valve outside. Leakage will result in material losses, environmental pollution, will result in serious accidents. The explosive, toxic or radioactive medium, leakage is allowed, and therefore must have a reliable valve sealing performance Mobile Media Medium flow through the valve will generate pressure loss (both before and after the valve pressure difference), that is, the flow valve on the media have a certain resistance, medium to overcome the resistance of the valve, it takes some energy. From the conservation of energy considerations, the design and manufacture of valves, to minimize the resistance of the valve on the flow medium Stop force and the opening and closing torque Stop force and the opening and closing torque is necessary for the valve to open or close the force or torque applied. Close the valve, the need to open and close the two pieces with the fat seat sealing surface of the seal formed between certain specific pressure, but also to overcome the stem and the packing between the stem and the nut thread between the stem end of the Bearing friction and other friction parts, which must exert a certain moment of closing force and closing the valve in the opening and closing process, the need to stop force, and opening and closing moments of change, and its maximum is close to the final instant or open the initial transient. Design and manufacture of valve closing force should seek to reduce and close the moment. Hoisting speed Opening and closing speed is an opening or closing the valve action to complete the time required to represent. Generally open and close the valve speed without strict requirements, but some conditions have special requirements on the opening and closing speed, if the requirements of rapidly turned on or off, to prevent accidents, and some asked slowly shut down to prevent water hammer and other produce This should be in the selection of valve types to be considered. Sensitivity and reliability of action This refers to the valve for the medium parameters, and make the appropriate degree of sensitivity. The throttle valve, reducing valve, regulating valve used to adjust the valve and safety valve medium parameters, the trap has a specific function such as valves, its function is very important to the sensitivity and reliability of technical performance indicators. Life It said that the durability of the valve, the valve is an important performance indicators and has great economic significance. Usually guarantee the number of seals required to open and close that can also be used to indicate the use of time