Everybody likes a quiet pump-it just does its job, leaves you alone, and doesn't break down often. But a noisy pump raises concern. Although the noise is often attributed to cavitations, not every noisy pump is suffering from this problem. Failing bearings, flow turbulence, recirculation, and even a machine's mechanical or electrical geometry can generate noise, any of which may be a more immediate problem than long-term damage from cavitations.
人们都喜欢这样的泵--安静稳定，无故障，正常运行。但嘈杂的泵总会引起人们的关注。虽然噪音常归因于气蚀，但并不是每个嘈杂的泵都归因于它。轴承故障，水流紊动，再循环，甚至是机器的力学或电气几何结构都可能是噪音的起因，但相比于气蚀的长期损害而造成的噪音，前面的任何一种情况都可能是更加紧迫的问题。
Cavitations erodes the suction eye of the impeller without affecting its other surfaces. Disassembly and inspection will confirm if significant cavitations is responsible for pump noise, but the first step is to rule out other potential causes with non-intrusive tests.
气蚀会腐蚀泵叶轮的吸气孔而不影响其表层。通过拆卸和检查能确认，是否有明显的气蚀导致泵噪音，但是第一步是要进行非入侵式测试来排除其他潜在因素。
Rule out bearing noise. 排除轴承噪音
To determine if the noise may be due to failing bearings, listen on the pump volute and bearing housing. An ultrasonic listening device is helpful, but a mechanic's stethoscope will do. If the sound is louder on the volute than on the bearing housing, bearing noise can be eliminated as a source.
噪音是否可能由轴承故障引起，可通过泵蜗壳和轴承箱发出的声音判定。虽说超声波监听装置有用，实际上技工的听筒也可以做到。如果泵蜗壳比轴承箱的声音更大，则可以排除是轴承产生的噪音。
Change suction pressure. 改变吸气压
Next, increase the suction pressure (head) if possible and listen for a decrease in the noise. If suction head can't be increased, reduce it and listen for an increase in noise. Cavitation is directly related to suction head and flow, so changing either of these should cause cavitation noise to change accordingly.
接着，若情况许可，增加吸气压力（压头）可降低噪声。若吸气压头没有增大，减少压力会使噪声更大。气蚀与吸气压头和气流有直接关系，因此改变其中的一部分，均可以相应地改变气蚀噪音。
Check for recirculation. 再循环检查
If suction head changes have little effect on the noise, the source may be recirculation resulting from a discharge flow restriction, perhaps due to a blockage or closed discharge valve. For closed systems without flow-rate instrumentation, verifying flow may not be easy. A portable flow meter attached to the outside of piping will provide accurate data, but such instruments can be expensive.
如果吸气压头变化对噪音的影响很小，则可能是因排放气流限制引起的再循环造成，也可能是排气阀堵塞或被封闭造成。对于没有气流仪表的封闭系统，核对气流量并非易事。连在管道外部的便携流量计可准确测量气流量，可这样的仪器并不便宜。
Another approach is to open a drain valve in the discharge line near the pump and allow flow to exit the system. If this reduces the noise at the pump, the flow through the system is very likely restricted, and recirculation is the source of the noise. Recirculation can damage pump impellers and volutes and subjects the pump to unnecessary vibration. Of course it's also a waste of the energy consumed by the pump.
另一个方法则是打开泵附近的排出管线的排水阀，允许液体流出管道。如果泵的噪音变小了，那么通过管道中的水流很有可能受到了阻滞，再循环则是噪音的来源。再循环会使泵产生多余振动，从而可以损坏泵叶轮和蜗壳。当然，这会缩短了泵的使用寿命。
Determine if the noise is related to mechanical and electrical geometry. 判定噪音是否与力学及电气几何学相关
If changes to neither the suction head nor discharge flow alter the noise characteristics of the pump, the sound is probably mechanical in nature. Mechanical sounds occur at specific frequencies related to the machine's mechanical and electrical geometry. Vibration-analysis techniques can identify and characterize these sounds and their relationship to any mechanical forces.
如果改变吸气压头以及排放气流量均不能改变泵噪音，那么噪音很可能是由机械引起。机械声出现在与力学和电气几何学相关的特定的频率上。振动分析技术可以辨别和描述这些声音，分析出引起的噪音的机械原因。
The most common frequency of sound and vibration in centrifugal pumps is vane-pass frequency, which occurs at the multiple of the number of impeller vanes and the rotating speed. Technicians familiar with pumping machinery may well be able to audibly separate the vane pass and other mechanical sounds from the random noise of cavitations and recirculation.
离心泵最常见的声音振动频率是在多个叶轮叶片数量以及转速中产生的频率。经验丰富泵送设备的技术员通过听觉就能把叶片传递和其他机械声音与来自气蚀和再循环的随机噪音区分开。
In other words 结语
Your noisy pump may be telling you something important. With a methodical approach and through the process of elimination, you can translate its language and avoid pump failure.
嘈杂的泵会告诉你一些重要的信息。使用系统性的方法，通过排除问题的过程，您就可以把这些信息翻译出来，从而避免泵故障。
By Eugene Vogel, Electrical Apparatus Service Association (EASA)
由美国电气设备服务协会的Eugene Vogel供稿 译：陆佩泳（学府咨询集团）
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