Smooth operator

摘要

Switching to ultra-low sulphur (0.1%) fuel brings an added layer of complications to shipboard operations in and out of ECAs. In addition to ensuring that their vessels make the switch to the distillate well in time (usually ISO 8217 Fuel Grade DMA with 0.1% S max specified), operators must also match their fuel to the appropriate lubricant. Less sulphur inthefuel means that there is a corresponding reduction in sulphuric acid produced along the cylinder liner when water from the condensation and sulphur from the fuel interact. In a way, this resolves the issue of cold corrosion, which required operators to use a lubricant with a high base number (BN; alkalinity value) to counteractthe acid. It moved manufacturers away from the 'one size fits all' lubricantto more of a twin approach of high end (100BN) and mid range (40BN) lubricants for large two-stroke engines. The fact that distillates require a much lower alkalinity to match the sulphur level has resulted in a new generation of low BN cylinder oils.