Thanks for the replies and the interesting links. Engines that seem to suffer the worst (in my experience) are medium speed, around the 4000 - 5000 kw power range and 750 rpm. The popular belief is that the change to Ultra Low Sulfur fuel (less than 10 ppm) in 2009 has led to lacquering becoming a big issue. There may be some truth in this but I have always believed it is more related to incorrect loading, overcooling and/or improper combustion (poor atomisation, timing or calibration of pumps).
I have worked on engines that have been switched to different lub oils to try and combat lacquering. Generally these anti-lacquer oils have a lower TBN to account for the lower sulfur content. In my experience this has not helped. There are also additives than can be added to the fuel which are supposed to prevent lacquer build-up and remove deposits, however I have no experience of whether they work or not.
In all my cases of engines with high lacquering, the oil consumption steadily increases as the honed surface gets 'filled in' by the lacquer. Often this leads to high crankcase pressure and an increase of soot production in the lub oil. The ships often pick this up as high viscosity during their tests. I even know of ships that only bunker in ports that supply high sulfur diesel (outside of NZ) in an effort to try and prevent lacquering!
I just wondered if this was a common issue around the world or just isolated to a few ships here?
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