How to eliminate centrifugal pump cavitation
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Cavitation Elimination Centrifugal Pump Cavitation Centrifugal pumps can cause cavitation if installed or used improperly. In the event of cavitation, the performance will be reduced, the amount of water reduced impeller damage accelerated, but also accompanied by vibration and noise, in severe cases, even the pump can not work. Therefore, pump cavitation should be avoided. In Northern Zhejiang Province, a dredging engineering company 3 # blow dredger (commonly known as suction dredge) used on the red mud pump for flushing mud, because the pipeline does not match the pump, the pump work in the large flow area, not only the motor Overload, and cavitation in the pump, affecting the normal work, after a smaller outlet pipe and reduce the pump installation height to solve this problem. 1. Cavitation conditions Flush pump models used on the mud boat 8Sh-13, the rated flow Qn = 288m3 / h; rated head Hn = 41.3m; motor power Pn = 55kw. After the completion of the ship, according to the measured pump parameters obtained: HA = 24.4m; QA = 400m3 / h. During the trial operation of the flushing pump, it was found that the amount of water discharged was not stable every time it was started up, and the situation became worse with the passage of time. This situation shows that the pump cavitation has occurred and gradually increased. At this point, the operator had to open the pump deflation valve, only intermittently deflated to flush stability. 2. Cause of Cavitation In the flushing pump piping system, although the installation position of the pump is not high (the pump shaft installation height is hg = 0.6m) and the suction pipe is not long (the pipe length is L1 = 8.5m) Shorter, less hydraulic loss, combined with lower flush height (outlet height h = 2 m from surface) causes the pump to work in a large flow area with a relative degree of vacuum at the pump inlet lower than the local vaporization pressure at that time, thus causing Cavitation. 3. IMPROVEMENTS To change the existing operating conditions, there are three general solutions that can be used to replace a new pump, reduce speed and change lines. By contrast, the decision to adopt the third alternative is simpler and cheaper. The specific approach is to change the original outlet diameter from Dg = 200mm to 150mm, tube length unchanged; flushing head outlet diameter from the original Dg = 120mm to 100mm; pump installation height from the original hg = 0.6m to 0.4 m, the rest unchanged. This transformation took only two days. After the change, conducted a real ship test. First measured the pump head value HA', check the pump characteristic curve, was the pump flow QA' = 340m3 / h, the pump was calculated that the suction vacuum degree is less than the allowable value. So the pump does not cavitation. In later work, flushing the water situation is normal, and every time you replace the seal packing, did not find signs of impeller cavitation.