Troubleshooting 3-Phase Pump Failures: Causes and Solutions | Expert Tips

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Discussion Overview

The discussion centers around troubleshooting catastrophic failures of a 3-phase submersible pump used in a sewage system. Participants explore potential causes of the failures, including electrical issues and overheating, while sharing observations and experiences related to pump performance and failure modes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes the catastrophic failures of new pumps that are rated similarly to an older model, suggesting potential electrical faults related to the case ground connection.
  • Another participant questions the nature of the "explosions," asking for clarification on whether they originate from the material being pumped or the pump's electrical system.
  • A participant confirms the pump's application in a sewage system and describes the physical damage observed, indicating signs of burning or arcing at the ground connection, which they believe points to an electrical fault.
  • One participant speculates that overheating could be a cause of failure, suggesting that it might be due to incorrect voltages or insufficient cooling, leading to insulation breakdown and potential arc faults.
  • Another participant raises the possibility of cavitation as a cause of the explosions but later acknowledges that it may not apply in this case.

Areas of Agreement / Disagreement

Participants express differing views on the cause of the pump failures, with some suggesting electrical faults and others considering overheating. There is no consensus on the exact cause, and the discussion remains unresolved.

Contextual Notes

Participants have not provided specific details about the operating conditions or the exact nature of the electrical system beyond the basic specifications. There are indications of potential issues with voltage and cooling, but these remain speculative.

livewireca
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Here's the situation. We have tried to replace a "non-clogging Submersible" pump that has been in service for 20+yrs and are experiencing catistrophic failures. The new pumps are the same rating as the old (as far as nameplate data goes) and nothing has changed to the electrical system. The electrical feed consists of a wye-delta transformer to give 240VL-L, with a tap off of one of the windings to give 120L-N... leaving C phase as the bastard-leg. However this should have no impact on the pump as it is 240V 3phase. The pumps housing are being blown apart and it appears that source of the "explosions" may be coming from the case ground connection, but it is difficult to tell. We've gone through 3 pumps from two manufacturers. We've also just added line monitoring to check for harmonics, voltage & current etc. And have only noticed so far that the voltage dips during startup, which is normal. These pumps run for a length of time before failing. Here is the nameplate specs from one pump:
5HP, 208/230V, 3ph, 60Hz, 1750RPM, FLA 17.0/16.0, Ins.Class B, Code B D, Impeller Dia 7.00
And some info from the supply panel that feeds the pumps (located btw the pole transformer and pump):
3.7kW-5HP, 1745RPM S1, 3ph, 60Hz, Yser460/Y//230KV 6.8/14A cos 0.81
Any information would be greatly appreciated as we are scratching our heads with this one.
 
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What exactly are you using the pump for? My background in electrical is minimal (hence I lurk on these threads for learning purposes :)) but I do a lot of work with large hydraulic systems and have seen all kinds of pump failures in this area.
You're also quite vague on what these 'explosions' are. Are they orginating in the material being pumped or from somewhere in the pump electrical system? You say they originate from the case ground connection but arent sure.
 
The pump is used in a sewage system, and this is why we require a non-clogging design. The "explosions" are hard to descibe. I haven't witnessed what has happened, and have only viewed the condition of the pump(s) when they have been taken out of service due to failure. The outer case of these pumps that have failed have large pieces missing as if the side has been blown off. One of the pumps shows the ground that went to the case showing signs of burning/arcing and points to when the case used to be... In my opinion it appears to be an electrical fault of some kind. There doesn't appear to be any problem at the mechanical end of these pumps.
 
Okay, I see what you mean. I just hear a 'submersible' pump and 'explosion' and I automatically think some type of caviation phenomenon occurring. Doesnt seem so in this case.
 
Stop serving beans.
 
If I had to hazard a guess, I'd say overheating was a likely culprit. Whether this heating is due to incorrect voltages or insufficient cooling, I can't say. I'm imagining what's happening here is the unit gets all hot inside, the insulation begins to break down and BLAMMO you get an arc fault blast.