I do not have experience on frame 1 but I think you should check some information and answer for yourself that:
1. The leakage oil just happen at Bearing #3 or at all bearings?
Total 4 bearings, All bearings Checked , only bearing#3 found with Babbitt material lost. other 3 bearings found normal.
2. Have you checked the oil drain piping for any plug/stuck?
Yes Checked , no obstruction or Plugging observed.
3. there is buffer air supplied to labyrinth seal, isn't it? if any, have you checked the buffer air lines?
Yes, Seal air has been taken from 10th stage of Axial Compressor, air supply lines have been checked and found normal for required seal air pressure.
4. How about oil vapour system?
Please elaborate further on this??
5. Have you checked the bearing temp? when is it increased? the same for vibration?
If the fire happen in the moment of GT running, i think that the oil leakage happen from internal (if from external, i believe someone seen and announced).
Fire smoke has been observed in exhaust duct of GT, soon after GT enclosure was opened and fire was seen, in 1st thought, LO Pump was shutdown and fire was removed, once LO Pump Started again, the fire happened again then again the L.O Pump was shutdown and fire removed. Fire is for sure due to L.O leakage , but still mystery from where the Oil leaked and how the fire caught? and how the L.O penetrated at LP rotor bucket and formed coking/tar since L.O Pressure is lesser than the Turbine Pressure??
The bearing look like running under too high temp. The oil under high temperature (over 200oC) will form coke.
The bearing#3 damage looks secondary damage due to fire and dry running of LP rotor (since L.O pump was stopped)
How the fire happened , still dont know??