MAIN ENGINE CROSS HEAD BEARING DAMAGE :
The cross head bearing of No. 3 unit was to be opened up for survey. The bottom nuts were opened up and the piston was turned to lock the cross head with the lock pin provided, to the guides. While trying to remove the top half shells, it was found that the bearings and the shells got stuck, and not coming out of the bolts. Turned on the reverse direction, and tried to remove, still the bearing halves were stuck. It was decided to open the cylinder head and to remove the piston. Piston was removed, and the bearing top halves removed. Found the bearing damaged heavily, hence the bearing halves were renewed. Bottom half was also partially damaged, hence bottom half was also changed.On re-assembling, it was noticed that bearing was not going freely. Bolts were taken out, and found them bent. Bolts were also renewed and the unit was boxed back.
The probable reason for this may be that during the previous survey, while boxing up, the bolts would have been hammered inside instead of aligning both halves properly.
Lesson learnt :
while doing overhauling or assembling after repairs, check manuals and do as guided in that. Also check that before fitting the bolts, whether surfaces are properly aligned and that holes are matching. Bolts have to go in freely even though they may be tight fit. Hammering has to be avoided at any cost.