Report to the Engineering Superintendent concerning abnormal cylinder liner wear during the past six months, explaining the possible causes, the immediate action taken to deal with the problem and the action as Chief Engineer, intend to take in order to reduce the risk of future incidents.
Report to the Engineering Superintendent
During a recent overhaul of No.2 cylinder, the liner wear rate was found to be increasing, and well above the normal and acceptable level of 0.1mm/1000 hours. In order to determine whether this wear was affecting only No 2 cylinder, liner measurements were also taken from No.5 cylinder, which has been recently overhauled. This cylinder also exhibited a rise in liner wear rates, similar to those measured from No 2 cylinder.
Possible Causes Remedies for Abnormal Cylinder Liner Wear
Visual examination of both the liner surfaces did not show any obvious damage. Investigations were carried out to check:
- Cylinder oil injection rates (found to be normal and the same for the past 18 months)
- Cylinder liner temperatures (all temperatures were normal and steady at the required 85 degrees)
- Fuel oil viscosity (this has been maintained between 13 and 15 cSt)
- Piston ring specification (the same rings have been in use for over 5 years)
- Fuel oil quality. The vessel has changed bunker supplies 9 months ago when the trading area changed. Although usage of the fuel has not presented any other operational difficulties to date, the quality of the fuel could be a possible cause of these high liner wear rates.
As per shore analysis for fuel oil, fuel contaminants were within limits, but the sulphur levels in the fuel were between 3.4 and 3.9%, which are higher than the recommended levels for the grade of cylinder oil presently used on-board. To counteract any further corrosive wear of the liners, the cylinder oil dosage rate was increased on all cylinders by 25%, and awaited the recommendations of the lubricating oil supplier for advise regarding possible use of a higher TBN grade of cylinder oil.
A report is attached showing measurements of the liner to date. All liners will be monitored for wear monthly over the next six months. Please note that at present total liner wear is still acceptable, but should this level of liner wear continue, then the liners would require replacement in less than two years.