Identifying bearing defects using vibration analysis is not going to improve plant reliability. To do this we have to look at the root cause of the defect and take action to prevent the same problem re-occurring in the future.
Here is a nice example from a large ID Fan, after a 3 month shut down of the plant. The fan was restarted, straight away an outer race defect was picked up on the Fan NDE bearing by an RMS engineer.
The damaged bearing was planned in for replacement. At RMS we are always trying to find the root cause so the bearing was cleaned and inspected. You can clearly see the bearing has suffered from corrosion whilst the fan was stationary. Spalling has started to occur in one area.
In this case the root cause of the problem was that the fan was not rotated during its 3 month shutdown. This allowed corrosion to take place within the bearing leading to a defect upon start-up. Plans are now in place for future shutdowns to rotate the shafts to eliminate this type of defect.