A ship was alongside in port when the main engine was started, and the oil mist detector gave a warning alarm. When opening up the crank case a hot crankpin bearing was found. The crankshaft was found to be seriously damaged in way of one crankpin, causing the vessel to be put off hire for more than a month before resuming operation.
The original crankshaft was damaged beyond repair, and a new one was fitted, following the manufacturer’s recommendations.
The main medium speed diesel engine was elastically mounted by using rubber mounts. Thus all cooling water, fuel oil and lubricating oil system piping connections to the engine were equipped with rubber expansion joints, in order to allow for some flexibility during operation.
Investigation after the accident revealed that rubber particles of various size had blocked the lubricating oil system, originated from a disintegrated rubber expansion joint of the lubricating oil system.
This could have turned out to be very serious for the vessel if it had happened during operation.
It was confirmed that the manufacturer of such rubber expansion joints has separate specifications for various use of the joints, and the joints are consequently marked with different colour codes, see figure above.
In this case an expansion joint intended for freshwater and seawater cooling systems had been applied for the lubrication oil system from the new-building stage, causing disintegration of the rubber, which caused blocking of the lubrication oil system.
Lessons to be learned
- Specific requirements or limitations for different applications of rubber expansion joints on board may exist, designated by the manufacturer’s colour codes.
- Possible operational consequences by application of rubber expansion joints with wrong colour code, as in this case.
- Colour codes as mentioned above may not necessarily coincide with the generally applied colour codes for freshwater, seawater, fuel oil and lubricating oil systems on board vessels.
Source: DNV
Officer of the Watch 
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