INTERMEDIATE SHAFT B EARING FAILURE :
On joining the vessel, found workshop involved in renewing 2 nos. intermediate shaft bearings. Also noticed that no root cause analysis had been done & there were other instances of the same bearings being renewed in the near past also. The bearings were taper roller bearings on chock fasting.On sailing out, noted that all bearings were running hot & the vessel also had the practice of cooling these bearings externally. After 15 days, one of the bearings renewed gave way & the second bearing also failed after a week. A detailed study of all the log books from inception was done & the following noted. 1. Right from the time of the sea trial, the bearings had been running hot and the guarantee engineer had somehow brought down the temperatures by putting shims under the chock fasting of various bearings and the then Chief Engineer had logged this in the logbook. Despite this, the ship had been taken over by ONGC without any complaints.
After a detailed study, the office was informed to check the following.
1)Suspected all bearings bad.
2)Suspected journal area of all bearings less in dia.
3)Suspected shafts bent.
4)Suspected alignment wrong.
Initially the management co, was reluctant to take up the Job, as the vessel will be off-hired. Better sense prevailed and the management reluctantly took up the job as the job entailed both high cost and time.
Mazagon Dock, Bombay who took up the job, found all the defects as exactly projected by the ship staff. 4 Nos. bent shafts were straightened and shafts were built up & machined in the journal area. Alignment of the shafts were done and all four shafts were fitted with new bearings. It was also noted during the progress of the job that the manual had prescribed 3.8 kgs of grease for each bearing, which was found to be wrong. The bearings required only @ 2 Kgs of grease for efficient air circulation & cooling.
The Korean yard had initially goofed up the alignment and it was compounded additionally by the extra grease in the bearing, which was aggravating the problem with high temperature and thereby deforming and affecting the alignment further.