Water pump cavitation, the manufacturer has been here 4 times and still can't fix it
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The specifications of the two water pumps are 300BWQ800-15-55, and the parameters: Lift 13m, flow 997m3/h, power 55Kw, speed 1850r/min, rated current 103A, operating conditions: The height between the water inlet of the water pump and the water outlet of the pipe (the pipe is vertically upward and then horizontal to the water outlet) is 11m. When the water pump is put into operation, the current displays 106A, and the water pump emits an abnormal sound of cavitation. The pipeline pressure was measured at 0.2Mp when the outlet valve was closed during operation of the water pump. It was inferred that the water pump used was causing cavitation due to too high a head. The solution is as follows: ①, adjust the water pump outlet valve to maintain the normal operating conditions of the water pump and avoid harm to the equipment caused by low-lift and large-flow operations. (The actual situation is that when the water outlet valve is closed four-fifths, the cavitation situation improves, but the vibration at the water outlet valve is severe. ) ② Keep the water outlet valve fully open and cut the water pump according to actual working conditions to reduce cavitation caused by the water pump when the head is low. (After cutting the impeller from 32cm to 30cm, the current when the water pump is running changes from 106A to 76A. When the water outlet valve is closed, the pipe pressure is 0.16Mp when the water pump is running. After cutting the impeller, the water pump still makes a cavitation sound (70dB measured 13m away from the water pump). The abnormal sound is still too loud. How can such a problem be solved? ? ? ? ? ? ? ? ? ?
Have you considered the diameter of the pump's inlet pipe, as well as the height and length of the inlet pipe?
Is your lift not enough? The lift is 13m and the distance is 11m, plus cavitation allowance. I think it’s not enough.
1. The speed you gave is wrong. According to H=v2/2g, the head is about 40 meters at this speed. Your speed should be 980rpm. 2. I don’t know how big the inlet of this pump is. If it is 300, the flow rate at the inlet is 4m/s. This flow rate is quite high for the suction port. 3. What is the immersion depth of the pump, and whether there are vortices on the liquid surface during operation. If there are vortices, air will be brought in.
Is there pressure at the pump inlet? You mentioned in your article, “The actual situation is that when the outlet valve is closed four-fifths of the time, the cavitation situation improves, but the vibration at the outlet valve is severe. ”, it should be that the outlet pressure is insufficient ； Also, is the NPSH of the pump enough? my suggestion: Increase the mesh size of the inlet filter, do not cut the impeller, and try turning off the outlet valve.
Is there a siphon tank? This should be an underground pool, right? If it is an underground pool, there should be insufficient suction flow in the inlet pipe.
It’s best to draw a picture and let everyone analyze it.
Draw a schematic diagram and analyze it to help your understanding.