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

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The discussion centers on troubleshooting catastrophic failures of a new submersible pump used in a sewage system, which has replaced a 20-year-old model. Despite having the same specifications, the new pumps are experiencing severe damage, with the outer casing blowing apart and signs of burning at the ground connection. The electrical system remains unchanged, and line monitoring has only revealed normal voltage dips during startup. Participants suggest that overheating may be a potential cause, possibly due to incorrect voltages or insufficient cooling, leading to insulation breakdown and electrical faults. The situation remains perplexing, with no clear mechanical issues identified in the pumps themselves.
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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.
 

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