If the centrifugal pump is not installed or used properly, the cavitation erosion may occur. Once cavitation occurs, the performance will decrease, the water volume will decrease, impeller damage will accelerate, vibration and noise will be accompanied, and even the pump will not work. Therefore, the cavitation of the pump should be avoided. In a water conservancy dredging engineering company 3# suction dredger (commonly known as suction dredger) used for flushing pump broken mud, because the pipeline and pump does not match the pump work in large flow area, not only the motor overload, and pump cavitation, affecting the normal work, after a small change the water outlet pipe and reduce the pump mounting height to solve this problem.
1. Cavitation erosion
The type of water pump used on the dredger is 8Sh-13, rated flow rate Qn=288m3/h, rated lift Hn=41.3m, motor power Pn=55kw. After the ship is built, the parameters of the pump are: HA=24.4m; QA=400m3/h. In the trial run, it is found that when the running time is not too long after start-up, the output of the flushing pump is unstable, and the situation is worse and worse as time goes on. This shows that the pump has been cavitation and gradually aggravated. At this point, the operator has to open the pump's vent valve, only intermittently and intermittently in order to stabilize the water. Stainless steel chemical pump
Two. The cause of cavitation erosion
In the flushing pump pipeline system, although the pump installation position is not high (the axis of the pump mounting height is hg=0.6m), the suction pipe is not long (pipe length L1=8.5m), because of the water outlet pipe is short, small hydraulic loss, coupled with low height (flushing water outlet from the surface height of H = 2m), the pump in the work the flow area of the pump inlet relative to the vacuum is lower than when the local vaporization pressure, thus causing cavitation.
Three. The improvement measures should change the existing operating conditions. There are three kinds of methods that can be used to change the new pump, the frequency conversion and the change of the pipeline. By contrast, the decision to adopt third changes is more simple and economical.
The original water outlet pipe diameter is changed from Dg=200mm to 150mm, the length unchanged; flush head outlet diameter is modified from Dg=120mm to 100mm; the pump installation height is modified from hg=0.6m to 0.4m, the rest unchanged. The transformation took only two days.
After the modification, a real ship test was carried out. The first measured pump lift value HA ', and then check the characteristic curve of pump, as the pump flow QA' = 340m3/h, the calculation of the flow pump suction vacuum degree is less than the allowable value. So there is no cavitation in the pump.
In the later work, the water outlet of the flush head was normal, and no signs of cavitation erosion were found when the seal was replaced each time.
- Close This Page
- Recommendation：
- Browse：
