What can cause failure of bearing bushes inside a motor? How to detect the onset of their failure before the damage spreads to other parts of the motor eg mechanical seal, rotor etc ?

Can you clarify what type of bearing and what part failed?

Both drive and non-drive motor journal bearings which were obliterated with rotor bearing locations having suffered serious radial score damage and diameter reduction and the Graflon bearing bushes were themselves completely worn out. These bearings are water-cooled.

Lower thrust bearing pads have some radial markings but can be reused.

Which scenario is likely to occur first for the same motor:
1) Bearing fails first and followed by mechanical seal?
2) Mechanical seal fails first and followed by bearing failure?

The mechanical seal has ceramic vs carbon faces. What can cause the ceramic face to be broken?

The bearing material has been ground to powder.

First, I'll make the assumption that this is a vertical shaft machine and that the mechanical seal is below the bearing(s). I don't know the statistics so I won't bother to guess the most likely scenario. However, I think you should concentrate on the possible causes of the bearing failure even though it might be a result of the seal failure.

To me, mechanical seals have always had a certain "delicate/sensitive" quality to them and a finite life. On the other hand, it is my perception that journal bearings tend to be a little more robust and their failure the result of something in addition to its normal service(shaft currents, overload, misalignment, lack of lubrication, etc.).

I would suggest temperature and, perhaps, vibration monitoring to detect the onset of "bad things" happening to a journal bearing. The seal mfr may need to answer reasons for a broken ceramic face but I'm wondering why ceramic instead of carbon faces. Does the application require them? What is the application?

Regards, Hokeith

Yes, you guess right it's a vertical submersible motor directly-coupled to the pump.
However, the mechanical seal is on top of the top journal bearing & secured to the motor top piece.

First I focus on why the bearing failed but somebody said that the bearing is most likely to fail after something else has failed. So now your view supports this notion. Thus, I'm focusing on why the mecahnical seal failed.

The application is seawater lift pump.

Are you asking why the ceramic face failed but not the carbon face?

Vibration monitoring is not possible because the pump set is submersible. Temp of motor windings is monitored by RTD but no readings stored.

This message has been edited. Last edited by: Josh,