原文：
当阀门为改变流量而开大或关小时，流体液柱动能的变化会造成管路中静压的瞬时变化。在液体中这种静压的瞬时变化常常随之引起管路振动，产生像锤击声音，因而得名为水击。这种压力的瞬时变化不是沿着整个管路同时立即发生的，而是从变化的起始点逐渐扩散开的。例如，当在管路一端的阀门快速关闭时，只有阀门部位的液体分子能立即感受到阀门的关闭。然后液体分子中积聚的动能压缩液体分子并使相邻的管壁胀大，其部分的液柱仍以原来的速度流动一直到液柱平静为止。 压缩区向管路进口端扩张的速度是均匀的，并且等于管路内液体的声速。当压缩区到达进口管路末端时，所有液体就处于静止状态，但压力高于正常的静压。这个压差在这时产生了一个向相反方向的液流，从而解除了静压的升高和管壁的胀大。当这一压降波到达阀门时，整个液柱又重新处于正常静压之下，但液柱继续向进口管末端流动，从而从阀门处开始产生了一个低于正常压力的压力波。当这个压力波往返一周后，就恢复了正常的压力和起始的液体流动方向。这种往返一直要重复到由于摩擦和其他原因使液体动能耗尽为止。 在使用D／e之比为35的钢管和水介质时，压力波速度约为l200m／s(约4000ft／s)。当瞬时速度变化为lm／s时，静压的增量为l．2MPa；如果是英制lft／s时，约为501bf／in 2。 当阀门不是快速关闭，但其关闭时间是在压力波往返一次所需的时间2L／a之内时(L为管路的长度)，{dy}次返回的压力波不能抵消紧接着流出的压力波，这时的压力升值类似阀门快速关闭时的压力升值，这种速度的关闭叫快速关闭。 如果阀门关闭时间大于2L／a，返回的压力波抵消了一部分流出的压力波，{zd0}的压力上升就减小，这种速度的关闭称为慢速关闭。 如果是由于泵停止运转而引起的冲击压力，那么在计算该冲击压力时，必须把泵的性能参数和电流切断后泵速度的变化量考虑进去。 数学运算只能计算出简单情况的冲击压力值。较复杂的水击问题过去是使用压头速度曲线的图解方法来解决。由于这一问题变得更为复杂，图解就更麻烦，而且又很难保证精度。但是利用计算机就可较方便地解决这个复杂问题，而且精度很高。 更慢地关闭阀门可以避免由关闭阀门所造成的过的冲击压力。为了达到{zg}的阀门关闭速度，同时又不致造成过分的冲击压力，就必须使阀门关闭时产生均匀的流速变化率。在泵设施中，止回阀关闭时的冲击压力不像关断阀关闭时的冲击压力那样容易控制。止回阀是靠流动介质来操作，关闭速度要由阀门结构和滞止液柱的减速特性来决定。如果介质向前的流速为零时阀门仍是部分开启，则回流的流束会将阀门使劲关上。由于回流造成的阀门突然关闭就产生了一个冲击压力，这个冲击压力就加在由正向流束的减速早已产生的冲击压力上。泵停止后，在液柱开始停滞之前，压力波必须传递到折回点，然后根据这一点的压力和液位来确定介质停滞的速度。因此，当止回阀与折回点间的距离较长，而折回点上的液位和压力较低时，该系统就可使用关闭较慢的止回阀。相反，如果止回阀与折回点问的距离较短，折回点压力较高，回流几乎是立即产生，则需要使用关闭速度极快的止回阀。在安装有多只泵的系统中，当有一只泵突然失效，就会产生立即回流的情况。

“ Valves hit the water running ”是由提供的阀门行业新闻，译文仅供参考。另外，中国气动阀门网还提供相关产品搜索： 、 、 、 、 等。

译文：
When the valve is opened to change the flow of the large or off hours, the fluid kinetic energy changes of fluid column will cause instantaneous changes in static pressure pipeline. Static pressure in the liquid that is often transient changes caused by pipeline vibration followed produce sounds like a hammer, which was called water hammer. This instantaneous change in pressure along the entire pipeline at the same time not occur immediately, but gradually spread from the starting point of change open. For example, when one end of the valve in the pipeline shut down quickly, only the valve position can immediately feel the liquid molecules close the valve. Then the kinetic energy of liquid molecules in the accumulation of compressed liquid molecules adjacent to the wall and to swell, its still the original part of the liquid column flow rate to the liquid column has been quiet so far. Compression zone expansion to the pipeline inlet velocity is uniform and equal to the velocity of fluid pipes. When the compressed area to reach the end of the import pipeline, all the liquid at rest, but the pressure is higher than the normal static pressure. The pressure at this time produced a flow in the opposite direction, thereby lifting the increase of static pressure and wall swell. When this wave reaches the valve pressure drop, the entire liquid column is again under normal static pressure, but the plume continues to flow to the inlet tube end to the valve from the beginning to have a lower than normal pressure of the pressure wave. When the pressure wave from a week later, on the restoration of the normal fluid pressure and initial flow direction. Such travel has to repeat to the other reasons due to fluid friction and kinetic energy depletion. Using the D / e ratio of 35 steel and water media, the pressure wave speed is about l200m / s (about 4000ft / s). When the instantaneous rate of change is lm / s, the static pressure of the increment for the l. 2MPa; if British lft / s was around 501bf/in 2. When the valve is not a quick closing, but closing time is a pressure wave from the time required for 2L / a time within the (L is the length of the pipeline), the first return of the pressure wave can not offset the outflow of the pressure wave followed , then the pressure of appreciation of the rapid closure of the valve similar to the pressure of appreciation, this is called rapid closure of the closing speed. If the valve closing time is greater than 2L / a, return to partially offset the pressure wave out of the pressure wave, the largest increase in the reduced pressure, such as slow speed of closure of the closure. If the pump stops running because of the impact caused by the pressure, then calculating the impact of stress, must pump performance parameters and the current cut off after the pump speed variation into account. Simple math can calculate the value of impact pressure situation. More complex problem of water hammer is the use of punch velocity over the last curve graphic method to solve. As this problem becomes more complex, more trouble diagrams, and it is difficult to guarantee accuracy. However, you can use the computer more convenient to solve this complex problem, and high precision. More slowly close the valve can be avoided by the closure of the valve had caused the shock pressure. In order to achieve the maximum valve closing speed that will not unduly impact pressure, the valve must be closed to generate a uniform flow rate of change. Facilities at the pump, check valve closes off the impact of pressure like the impact of the pressure valve closes as easy to control. Check valve is to operate through mobile media, the closing speed to the valve structure and the stagnant liquid column to determine the deceleration characteristics. If the media ahead of the flow rate is zero part of the valve is still open, the return flow valve will shut the beam. Since returning to the sudden closure of the valve caused by a shock pressure generated, the impact pressure on the increase in positive flow from the beam produced by the deceleration shock pressure on already. Pump stops, the plume began to stagnate before the pressure wave must be delivered to the returning point, and then that pressure and level to determine the media speed of stagnation. Therefore, when the check valve and turn back a long distance between points, while the returning point of the liquid level and pressure is low, the system can use slower valve closing. On the contrary, if the check valve and turn back from the point of asking short, reverting to the point of pressure is high, almost immediate return, you need to use the extremely fast valve closure. How to install the pump in the system only when there is a sudden failure of the pump will produce an immediate return to the situation.