Well Pump Failure

[rami dave]

After two weeks of operating a submersible well pump , a sudden decrease in the water flowrate is occured. the flowrate was about 160m3/hr , and then it decreased to 120 m3/hr. the decrease is not related to the drawdown of water level in the well , the well pump was running with VFD system. after trying to increase the frequency/rpm from 50Hz to 55Hz . nothing is changed and the flowrate still the same without any increase and stay at the same value 120m3/hr !!! did any of you have the same type of failure , and prior to pullout the pump , do pou have any suggestions or expecation for this type of failure , taking into consideratio that the current values are normal !!! your help is highly appreciated ???

The well pump is installed at deep setting - about 500m . assuming that we may have blockage at the suction side of the pump or the check valve above the pump is not working properly (3m above the pump) , can this blockage cause this decrease and constant flow after trying to raise up the frequency value from 50 Hz to 55 Hz , I thought that increasing the RPM will increase the flow although we may have blockage ?????

any of your inputs and expectations for the cause of this sudden decrease in flow is highly appreciated .....

 

[Valveman]

Flow rate increases proportionally to the RPM. So a 10% increase in speed, should only give you a 10% increase in flow. The fact that it worked for two weeks then suddenly went to reduced flow rate, makes me think that you spun off an impeller or two. Could even be a broken pump shaft. Blockage on the intake screen usually happens gradually, not all of a sudden. And if you are certain that the pumping level is still above the pump, it is most likely a pump problem.

I also do not understand why the current would still be normal, as current should reduce with the flow rate. A submersible at 500m running on a VFD could have all sorts of problems. I am guessing resonance from the VFD broke the pump shaft in half. The half that is still connected to the motor is using less amps and delivering less flow, while the part that is broken off is binding up and causing the current to seem normal.