MAN lube blending unit in service tests

The automated cylinder oil mixing (ACOM) system consists of three small tanks holding low base number (BN), high BN and blended oils. Based on the optimal cylinder oil feed rate factor and sulphur of fuel currently in use, ACOM blends cylinder oil to the appropriate BN and calculates the lowest possible optimum feed rate.

The ACOM unit replaces the heating tank currently placed before the engine and eliminates the need for a day tank for cylinder oil, with the base oils being taken directly from cylinder oil storage tanks. After prototype stage, controls for the ACOM unit will be integrated into the electronic control system of MAN’s ME engines and controlled from the main operating panel.

The first ACOM unit to undergo service testing has been installed on a 26,000dtw oil tanker with a MAN B&W 6S50ME-B8 main engine for more than six months without technical issues. A second ACOM system has also started its service test in a vessel with a MAN B&W 5S60ME-C8.2 main engine.

In a paper presented at CIMAC Congress in June, MAN Diesel & Turbo used an operational case from containership owner Costamare, which is trialling the unit, to highlight the need for ACOM.

“Most of the Costamare vessels trade regularly in sulphur emission control areas and switch to either gas-oil or hybrid fuel with less than 0.1% sulphur. At the same time the vessels switch from BN100 to BN25 cylinder oil. Some vessels trade in South America and bunker low sulphur HFO with sulphur percentages typically ranging from 1-1.5%. Ideally, such fuels require third cylinder oil with a BN of around 40. That would require three grades of cylinder oils, which logistically is difficult.”

As well as potentially saving significant cylinder oil consumption and optimising cylinder condition, the ACOM unit will also ensure a quick changeover process from high to low BN or vice versa, as it operates constantly with only a small mixing volume.

MAN has so far been testing the unit with oils up to BN100. But the company noted that BN140 oils – beyond the usual BN range of cylinder lubricants – could allow minimum feed rate to be maintained at higher sulphur levels.

“Calculations show that this will be a good business case for high sulphur fuels as lube oil dosage can be lowered, and at the same time the ACOM system may protect the engine from possible bore-polish as the BN will be reduced at lower sulphur contents.” the company added.

As a result, MAN reported that it has been testing several brands of BN140 cylinder oils.