Engine cleanliness now the main challenge for marine lubricants

Author Erik Hoffman and Catherine Caulfield

Interview with Serge Dal Farra, marketing manager at Total Lubmarine, which blends marine lubricants in 65 locations and supplies more than 1,000 ports across the world.

Preventing deposit build-up in ship engines has become the main challenge for marine lubricant manufacturers since the majority of the global shipping fleet switched to low-sulphur fuels this year, Total Lubmarine’s Serge Dal Farra says. Before the 0.5pc sulphur cap, the main concern for cylinder lubrication was to neutralise corrosive acids formed during the combustion of high-sulphur fuel oil (HSFO).

The International Maritime Organisation’s (IMO) 0.5pc sulphur cap ushered in a range of 0.5pc sulphur fuel oil blends with varying viscosity, density, pour point and concentration of catalytic fines. Choosing a compatible lubricant that compensates for these varying specifications is now essential to avoid engine fouling and costly repairs.

The detergency of a lubricant is a measure of its ability to carry soot and particles away from moving engine components and seals, preventing sludge formation. Detergency has become particularly important because of the increased risk of sediment that can result from mixing HSFO and gasoil to produce compliant 0.5pc blends.

Marine fuel testing firm Veritas Petroleum Services (VPS) issued seven alerts about excess sediment levels during the last week of 2019 and first three weeks of 2020. This was the highest frequency of marine fuel alerts about a single fuel quality issue, VPS said. Fuels with high sediment levels are at greater risk of becoming unstable and forming sludge deposits in the fuel tanks and injection systems. In the worst cases, sludge deposits can block filters and cause engine damage.

It is recommended to test the lubricant every four weeks, Dal Farra said. The iron level of the lubricant is analysed to check for engine wear and lubricant performance. By testing the level of viscosity of the lubricant after use, it is possible to determine if the base number and feed rate of the lubricant is appropriate and sufficient.

Base number (BN) is the measure of alkalinity that neutralises corrosive sulphuric acids formed during combustion of the fuel. A high-sulphur fuel requires a lubricant with a high BN (BN 70-140), and a low-sulphur fuel a lubricant with a low BN (BN 25-60), or even more for demanding engines.

Refiners began production of 0.5pc fuels in 2019 to meet IMO’s sulphur cap deadline on 1 January this year. This provided a narrow window for engine manufacturers to work on lubricant formulations with base oil producers. A ship sails for about 5,000 hours/yr, while a marine lubricant requires 4,000 hours of testing, which made the schedule tight. But it soon became apparent that BN 40-60 would go well along with the new 0.5pc sulphur blends, Dal Farra said.

Total Lubmarine’s BN 40 and Talusia Universal BN 57 lubricants have been approved by original equipment manufacturers (OEMs) MAN Energy Solutions and WinGD, which make ship engines. Total ensures consistency across 65 blending locations by producing concentrates that are blended with base oils that are readily available in those regions.

Group II base oils are being increasingly used in low BN lubricants compatible with low-sulphur fuels. Lower levels of basic additives reduced the requirement for solvency that Group I base oils were favoured for. Since 2015, over 3mn t/yr of new Group II capacity has been added globally. Increased capacity has provided security of supply in all key markets. Increased availability has narrowed the discount of Group I, making Group II more attractive from a cost perspective.

Major blenders such as Total, Shell and Chevron are using Group II or plan to increase the use of Group II in marine lubricants. Global manufacturer Lukoil continues to blend using Group I base oils but has increased the detergency of its BN 40 marine lubricant. Some producers have OEM approvals for formulations using either Group I or Group II base oils. This allows blenders with the flexibility to choose which base oil is most appropriate based on supply and cost.