Lubmarine Warning on High Sulphur Fuels

Maritime lubricants supplier Lubmarine says despite the likely implementation of European regional caps on sulphur content of marine fuels ship operators need to remain vigilant when dealing with high sulphur fuels. Claude Ouvrier-Buffet, technical manager of Total Lubmarine, says, "When all eyes are on the implications of impending regional caps on the sulphur content of marine fuel oils, it seems odd to be asking what effect very high sulphur fuels will have on engine lubrication. Yet despite an imminent new world-wide sulphur cap of 4.5 per cent, and lower regional limits of 1.5 per cent or less, there are areas of the world where fuel sulphur content is climbing. Owners and engineers need to pay attention to the possible effects." "Typical heavy fuels today have a sulphur content of around 3 per cent," says Ouvrier-Buffet. "And typically owners use BN 70 lub oils, which provide the right alkalinity to match the fuel sulphur level. But the sulphur content of the fuel is a function of the crude it comes from, and fuels supplied in the Caribbean, for example, may have substantially higher sulphur levels. Paradoxically, as owners adjust to the idea of having to change lub oils to lower BN numbers, that is, with lower alkalinity, to cope with strict fuel sulphur limits in Europe, they will still have to cope with burning very high sulphur fuels in other areas. Sulphur contents up to 4.5 per cent will be permitted by IMO Annex VI. Some owners have already been offered fuels with sulphur contents over 4 per cent." Lubmarine advises that the most important step is to increase monitoring of the engine performance and increase monitoring of the condition of the piston crown and the ring pack through the scavenge ports. Lub oil feed rates should not be increased initially, as this may lead to increased deposits on the top land and also in the grooves. "Too much lub oil interferes with the circulation of the lubricant behind the rings leading to lub oil stagnation and deposits," explains Ouvrier-Buffet. "Although the BN70 oils are matched to current average sulphur levels, and if the sulphur level is reduced owners need to switch to lower BN oils, the reverse is not normally true. There is no mathematical or direct link between the BN of the oil and the sulphur content of the fuel, as performance of the lub oil depends also on the engine design, and the ignition and combustion quality of the fuel." "If high sulphur fuel is to be burned regularly, then the best answer may be to switch to a lub oil with a BN higher than 70. But this step should only be taken after a period of monitoring the engine burning the higher sulphur fuel and after discussion with the engine manufacturers and lub oil suppliers," he concludes." "Unfortunately there is no one simple remedy to the problems of high sulphur fuels."