Dynamic balancing

[WalidAbid]

Dear All,
We have a 90kW electrical motor. we overhaul the motor by replacing the bearing, dust seals, stator cleaning...
this was done because of bearing damage.

The stator and stator shaft seems to be OK without any crack, wear or damage.
Could you please advise whether a dynamic balancing for the rotor is needed or not?
when such balancing is needed?

thank you in advance.

 

[MikeHalloran]

Unbalance is one possible cause of bearing damage, that you have not eliminated by merely replacing the failed bearings.

Balancing the rotor may turn out to be unnecessary, but until you spin it, you won't know that, so it's cheap insurance.



Mike Halloran
Pembroke Pines, FL, USA

 

[WalidAbid]

we are talking about motor for air blower.
the bearings were replaced before in January 2014.
last week, we found abnormal sound on the motor and we dismount to check the reason when we found that the bearing lock nut was little loosen, which explain the damage of the balls bearing cage.

 

[MikeHalloran]

No, a loose lock nut does not explain damage inside the bearing.

It only suggests that no one bothered to fit a French lock or other secondary retaining mechanism to the lock nut, and possibly did not bother to seat the bearing properly.

What was the exact nature of the bearing cage damage?


Mike Halloran
Pembroke Pines, FL, USA

 

[davidbeach]

Or, was the lock nut loosened by the vibration that also damaged the bearing.

 

[petronila]

Hello WalidAbid,

The bearing failures are complex and some times is very hard to find easier the causes. Only tell you that you can analize the replaced bearings and compare with figures tabulated by manufacturers like Fag, INA, SKF.

You can cut the bearings in two halves and after cleaning compare with patron figures.

Also, regarding the information provided by you I don´t see that you are speaking about vibration analysis performed in the motor so with out the spectrums and vibration levels is not possible determine if the problem overcome from fan-rotor balancing.

If you have doubts about it the better solution could be peform a rotor-fan dynamic balancing.

Also check lubrication and enviromental conditions( dust, mist and dirty) looking for something abnormal.

http://www.schaeffler.com/remotemed...ownloads_24/barden_bearing_failures_us_en.pdf

Best Regards,

Carlos

 

[jraef]

Just out of curiosity, is this motor run from a VFD?


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