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Assembly of Engine - RA Power Solutions

We were reported regarding failure of alternator bearing of Yanmar 6N18(A)L/V marine engine during the sailing of vessel near Mombasa. The ship staff removed the alternator bearing and observed damage of babbitt white metal lining. They informed us regarding this failure.

Damage Alternator Bearing

Damage Alternator Shaft With Deep Bearing Marks

We as a service provider immediately deputed our two senior technicians having valid CDC with latest calibrated instruments and onsite portable grinding machine. Following is the sequence of events:

Inspection of Alternator Bearing of White Metal Babbitt

I) The alternator bearing was visually inspected by our technicianS and it was observed that white metal was removed from different locations of inner diameter of alternator bearing.
II) The displacement of white metal from the alternator bearing created deep depression on the inner diameter of the bearing.
III) In some locations, the damage of white metal was so serious that steel lining was clearly visible.
IV) The outer steel casing was subject to crack check by MPI. No crack or abnormality was observed.
V) The profile of main critical areas of alternator bearing  was checked and no change in profile was observed.

Based on the above preliminary examination, RA Power Solutions technicians decided to 
repair the alternator bearing by rebabbitting process.

Alternator Bearing Under Inspection

Alternator Bearing Under Machining

Inspection of Alternator Shaft:

Alternator shaft having a diameter of 100 mm of Yanmar 6N18(A)L/V marine engine was thoroughly inspected by our technicians and following are the main observations:

I) On visual inspection deep bearing line marks were observed on bearing sitting area of alternator shaft.
II) The surface finish on bearing sitting area of alternator shaft was found rough.
III) The dimensional inspection of Alternator shaft was conducted to check the taper and ovality.
Following were the observation

      A) Minimum diameter observed 99.74
      B) Maximum diameter observed 99.96 mm
      C) The ovality of 0.22 mm was observed

IV) The alternator shaft was subject to hardness check by portable hardness tester . The hardness was observed within the limits.
V) The alternator shaft was also subject to MPI for crack detection. No cracks were observed.
VI) Run out of alternator shaft was checked and was observed within limits. Hence there was no loss of alignment.

Considering the above observation, RA Power Solutions technicians decided to undertake the repair of alternator bearing and to undertake repair of alternator shaft.
Alternator Bearing After Rebabbitting Under Inspection

Yanmar Engine for Repair and Overhauling

Following steps were taken to execute the repairs:

Repair of alternator shaft of Diesel engine Yanmar 6N18(A)L/V

I) The on site grinding and polishing of alternator shaft, bearing sitting diameter having length of 120 mm was undertaken by portable, lightweight on site grinding and polishing machine. After grinding following size of alternator shaft was maintained:
       A) Minimum diameter 99.28mm
       B) Maximum diameter 99.30mm
II) The bearing sitting diameter of alternator shaft was also subject to fine polishing , surface finish of less than 0.2micrometer in terms of RA value was maintained.

Diesel Genrating Sets

Alternator Shaft Grinding Under Progress

Repair of Babbitt White Metal Bearing

I) Immediately on inspection of alternator bearing it was decided to air freight the alternator bearing to RA Power Solution works near New Delhi, India.
II) The rebabbitting of alternator bearing was undertaken with the centrifugal process and all the quality norms were strictly followed.
III) The bearing inner diameter was machined and polished. The inner diameter bore was maintained between 99.48 to 99.50 mm keeping the oil gap of 0.20 mm approx.
IV) After maintaining above parameters and going through the final inspection, bearing was air frightened and connected to the vessel.

Following checks were undertaken at the time of fitment of Alternator Bearing:

I) Alternator bearing after fitment was subject to blue matching
II) The blue matching was maintained to 91 %
III) The oil gap between the alternator bearing and alternator shaft was checked by lead wire and oil gap ranging between 0.18 mm to 0.20 mm was observed.
IV) The movement of the shaft was checked after fitment of 
white metal babbitt alternator bearing and was observed free without any obstruction.
Grinding of Alternator Shaft

Polishing of Alternator Shaft

Engine was commissioned and is performing satisfactorily.

RA Power Solutions with experience of more than forty years in the field of repair, maintenance and overhaul of high capacity Marine Diesel engines has team of experienced technicians with modern latest breed of instrumentation for inspection and equipments for execution of repair. All the repairs undertaken by us are guaranteed for satisfactory performance. We are respected for our sincerity and are well known for reasonable prices for the repair services offered by us in comparison to our competitors based in Europe.

For any further information, please email us on 

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