Elimination of centrifugal pump cavitation measures
..........................................................................................................................................................................................................................

Abstract: This paper describes the water of a dredging project designed to build the # 3 blowing mud boat, as the red pump and pipeline pump does not match the pump so that the work flow in large areas, to run when cavitation, after the modified line and to reduce The installation of pumps and so on a high degree of measures to address this problem.
Key words: red pumps; pipeline system; measures
Key words: TH3 Document code: B
 
If the centrifugal pump is installed or used improperly, it is possible to cavitation occurred. Once cavitation, the performance will decline, reducing water, the impeller speed up the damage will be accompanied by vibration and noise, and other serious, even pumps do not work. Therefore, to avoid occurrence of pump cavitation. Zhejiang North Water, a dredging company's blowing mud boat # 3 (commonly known as ship Xini) for the use of red mud pieces of red pumps, pipes and pumps as a result does not match the pump so that the work flow in large areas, not only motor Overloading, and pump cavitation occurred, affecting the normal work after Gaixiao the outlet pipe and install pumps to lower the height of the solution to the problem.
     1. Cavitation situation
     The use of red mud on board pump model 8Sh-13, rated flow Qn = 288m3 / h; rated head Hn = 41.3m; electric power Pn = 55kw. After the completion of the ship, to be measured in accordance with the parameters for the pumps: HA = 24.4m; QA = 400m3 / h. In the test run in the red pumps and found that every time after running a short time, out on the water, unstable and sustained over time, the situation become worse and worse. This shows that have taken place inside the pump cavitation and gradually increase. At this point, the operator had to open the release valve of the pump, only interrupted from time to time in order to make the gas flush stability.
     2, cavitation of the reasons
     Red pumps in the pipeline system, although the location of the installation of the pump is not high (the installation of a high degree of pump axis hg = 0.6m), not long water pipe (a long tube sections L1 = 8.5m), but due to the shorter outlet pipe, water loss Small, combined with a high degree of low flush (from the surface of the water outlet height h = 2m), so that the pump in a large flow area, entrance of the pump is relatively lower than the vacuum at the time of vaporization of the local pressure caused by the cavitation.
     3. Measures to improve
To change the current status of this operation is usually available three ways to deal with that is to replace the new pumps, piping and changing the frequency deceleration.
By contrast, decided to adopt the third change is more simple and economic programs.
     Specifically the original water by Dg = 200mm diameter changed to 150mm, the same length; exports in the first flush from the original diameter Dg = 120mm changed to 100mm; a high degree of pump installed from the original 0.4 changed hg = 0.6m m, and the remaining unchanged. The transformation took only two days.
     After the change, the real test vessel. First measured value of the pump head of the HA, re-search features curves of the pump, pump flow was at this time QA = 340m3 / h, by the calculation that the flow pump in the vacuum aspiration value is less than allowed. Therefore, no pump cavitation.
     In later work, in the first flush of water normal circumstances, and each time the replacement of packing seals, are not found to have the impeller cavitation signs.