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So I have a submersible pump (Which I do not use submerged but just connect hose to both ends) who's output is consistently falling. While guessing for the causes I am tempted to blame one instance where I had connected it to a high pressure source with flow rates higher than the pump's itself. Can such a scenario affect Pump's condition?

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  • $\begingroup$ is it drawing in air? which collects at a high point? $\endgroup$
    – Solar Mike
    Nov 4, 2022 at 11:23
  • $\begingroup$ @SolarMike How do I know if its drawing in Air? It does make slight gurgling noise sometimes. But its regular sound was much stronger which isn't there anymore. $\endgroup$ Nov 4, 2022 at 11:27

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The dominant failure modes in motors are bearing failure (lube problems), or insulation breakdown. Both can be accelerated by poor cooling. thus, this being a submersible-pump it may not be sueded for not being submersed. Due to the lack of cooling fins.

there is a chance that the bearing seals distorted and let water thru to the bearings when you had the pump connected to the high-pressure source. there is a probability that the bearing on the pump side of the motor is shot.

Did you also check if there isn't any debris left in the pump housing. and did you check if the impeller still is in one piece.

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A pump of that type is intended to be cooled by immersion in the fluid it is pumping. If it is not cooled, the resistance of the windings will go up, the current through them will go down, and the torque applied to the impeller will go down- and the pump output will decrease. Can you feel it getting hot?

Also, can you tell how fast the motor is spinning if you run it dry for a couple of seconds?

By the way, that seems to be an absurdly expensive pump for its rated specs!

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  • $\begingroup$ Would a membrane pump be better? I have been looking at this piece robu.in/product/… for some time, but as this pump might need to pump milk, I was told diaphragm pumps might not be able to pump something of viscosity of milk. $\endgroup$ Nov 5, 2022 at 6:12
  • $\begingroup$ A diaphragm pump like that one will pump milk without problems. The main difficulty you will experience is that for food service, any pump must be contaminant-free and capable of repeated disassembly for sterilization. you MUST specify a pump suitable for food and beverage service. $\endgroup$ Nov 5, 2022 at 6:50
  • $\begingroup$ I agree it needs to be ROHS. if I am correct then the water contact parts of this pump are plastic, then it should be ROHS and hence food grade. $\endgroup$ Nov 5, 2022 at 9:46

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