Marine engine lubrication

Abstract

Trunk piston marine engine lubrication, when the engine is fuelled by heavy fuel oil, is effected by a composition of TBN in the range of 20 to 60 comprising a major amount of an oil of lubricating viscosity containing 50 mass % or more of a Group 1 basestock, and respective minor amounts of an overbased metal calcium alkyl salicylate detergent providing 40 to 90 mmol of calcium alkyl salicylate per kg of the composition, and 0.1 to 10 mass %, based on the mass of the composition, of an oil-soluble linear alkyl-substituted phenol. Asphaltene precipitation in the lubricant (black paint), caused by the presence of contaminant heavy fuel oil, is prevented or inhibited.

Description

field of invention [0001] This invention relates to trunk piston marine engine lubricating compositions for medium speed four-stroke compression ignition (diesel) marine engines and the lubrication of such engines. Background of the invention [0002] Marine trunk piston engines typically run off-shore using heavy fuel oil ("HFO"). Heavy fuel oil is the heaviest fraction of petroleum distillates and contains a complex mixture of molecules including up to 15% asphaltenes, defined as being insoluble in excess aliphatic hydrocarbons such as heptane but soluble in aromatic solvents (such as toluene) in the fraction of petroleum distillates. Asphaltene can enter the engine lubricant as a pollutant via cylinders or fuel pumps and injectors, and asphaltene can then precipitate as "black paint" or "black sludge" in the engine. The presence of such carbonaceous deposits on the piston surface can act as an insulating layer, which can lead to the formation of cracks which then propag...

AI Technical Summary

Problems solved by technology

[0006] However, '995 does not address the economics of treating TPEO to suppress "black paint" formation

A considerable cost arises from the detergent soap used, i.e. the amount of detergent other than the alkaline material

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