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Noknroll

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I have a submerged sump pump driven by a long vertical shaft direct coupled to a vertical motor.
attached spectrum shows elevated axial vibration at 0.53 orders. measured at motor DE bearing
my question is if I had shaft whip would this show something like what I have here? or would it be synchronous?
shaft whip.png

OLi

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Is that where the axial bearing is or is that on top? What does it look like NDE? No change radial?
Is the sump of the variation that fill up with material and mess up the flow or is it nice and of good size
never giving any flow problems? Any variation of or with water level?

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Curran919

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Is this an API VS1 type (example)?

Shaft whip is common on the line shaft bearings that run the length of the shaft. Clearances are not considered and they tend to wear pretty quickly in many cases. As this excitation occurs below grade, vibration tends to remain on the pump column. You will only see subharmonic vibration on the above-grade components (i.e. the motor) if there is a coupled mode and that mode is in resonance with the whip.

But then I would expect to just see radial vibration on the motor. Axial vibration? That is strange, I never see vertical pumps with significant axial vibration unless there is a problem with the foundation or something catastrophic going on in the motor.
OLi

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Reply with quote  #4 
Or the pump wheel "bounces" on the muck gathered on the sump floor? Or just suffering from the changed flow path in the same situation.
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Noknroll

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Reply with quote  #5 
Curran
Yes it's the type in your example
Oliv
I believe both bearings are deep groove, the sump is very big 10 x 10 metres x 6 deep so no flow issues
This is one of six pumps, each one is run individually for data collection, 2 of the other pumps have elevated 1 X radial. The pump in OP is the only one with sub synch axial vibration
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