we had a major failure on a Head bearing elevator that had collapsed(spherical bearing with taper sleeve) , The bearing was found in this condition(see attached pictures), although it was covered in thick black (carbon like) grease, very dry. some of the rollers where still intact and they don't seem to be that badly worn. a few points to note is that:
- The taper lock ring wasn't found inside, yet the lock nut still had a piece bent over and looks like it was snapped off
- the outer race has a crack that starts on the edge and works down the middle of the race.
- The inner race has worn unevenly
- the Lock Nut was found off the taper sleeve.
- remnants of the cage were found.
I've been asked to identify what caused this issue to prevent it failing again in the future.
What I believe has happened is that the taper sleeve has not been properly tightened on the shaft. so its been allow enough movement to vibrate. When the bearing is on the shaft too loose it will tend to vibrate a lot more. This in turn disrupts the oil film thickness and the bearing will tend to run hotter which then creates greater running clearances which in turn creates more vibration. Loss of metal due to fretting, caused by the vibration, again, loosens everything up. eventually its gotten hot enough for the oil to drain out of the grease, leaving the thickener which has then solidified.
Any advice from guys who may have seen this before or maybe have another idea would be greatly appreciated.