Tribological problem solving in medium heavy-duty marine diesel engines part 1: Journal bearings

Tribological problems are extremely common in classical DI (Mechanical Direct Injection Diesels) and those update to CR (Common Rail) technology. These engines are still widely used in Power Generation, Diesel-electric locomotives and Marine applications. The original design of the first prototype, in a few cases, was conceived just after the First World War The marine environment and the continuous increase of performances and TBO provoked several tribological problems that have been partially solved through the years. However, significant improvements are still possible with modern technology in journal bearings, lubrication systems and lubricants. The journal bearing should float before applying load, for this reason start up originated problems cause 90% of the bearings failure. The relative speed between journal and bearing should be over a well-defined value to avoid boundary lubrication. For this reason, compression reduction devices can be used at star or the geometrical compression ratio should be reduced in favour of turbo-charging induced compression. Start velocity should be controlled and the lubrication system should be checked. Finally, a suitable lubricant should be used.