IMO 2020 will change the market for marine lubricant additives. Anticipated fuel challenges mean that more advanced additive chemistries will be needed to protect engines. That applies to the 2020 shift happening now as well as to future changes in the marine fuel market.
As reported in the October issue’s Lube-Tech article, Why BN alone is not the answer when formulating cylinder oils for 0.5% sulphur fuels, the newly available VLSFOs are expected to feature widely varying fuel characteristics due to the diversity of blend stocks and refinery processes that will be used to create the compliant 0.5% sulphur blends. Among the factors that could be affected are combustion characteristics and stability. There is also concern in the shipping market that new fuels will not be widely compatible, making it more challenging to handle fuels from different suppliers or even from different refineries owned by the same supplier.
The anticipated wide range of fuel characteristics and potential instability of VLSFO blends will increase the deposit handling capability demanded from cylinder lubricants, while the low sulphur content will reduce the requirement for acid neutralisation. Conventional high-sulphur HFO has required high BN and strong deposit handling, but low-sulphur fuels need low BN lubricants that maintain the deposit handling performance of higher BN oils.
High BN detergents have dominated cylinder lubricant formulations as they deliver the acid neutralisation needed for HFO and help to keep the high-temperature surfaces of the engine clean of deposits. Reducing these high BN detergents for the lower neutralisation needs of 0.5% sulphur fuels without rebalancing the formulation with extra deposit control additives would severely impact the lubricant’s cleanliness performance.
To provide more protection at low BN, additive chemistries that are new to the marine market are needed. Tested against several VLSFO formulations, a BN40 lubricant with dispersant balanced against more typical detergents demonstrated improved deposit control performance over detergents alone. Crucially, that performance is delivered independently of high alkalinity.
While BN40 lubricants have been available on the
marine market for some years, the legacy products were not designed for the challenges of new VLSFOs. They are therefore unlikely to be able to handle the deposits that could be formed if concerns over instability and other troubling fuel characteristics are realised. As a ship’s lubricant tanks can hold five to eight months’ worth of cylinder lubricant, switching from an underperforming lubricant can be costly and inconvenient. Ship operators should instead aim to be confident that their originally selected oil will perform as required.
Switching back and forth between lubricants is not an ideal scenario for ship owners. Operators would be better off choosing a lubricant designed to offer the protection they need and then monitoring their engines carefully and adjusting the feed rate as required.
High-sulphur fuel will not disappear entirely from the marine market. Around 3,000 vessels are expected to comply with the 2020 regulation by using scrubbers, which remove sulphur from exhaust gas. This allows ship operators to continue burning HFO, which is expected to be cheaper than VLSFO, after the sulphur cap is introduced.
High-sulphur HFO means that engines require a high base cylinder lubricant of at least BN70. In recent years, some modern engine designs – particularly those with ultra-long stroke and a very wide bore – have suffered from cold corrosion, which has necessitated the use of oils with an even higher basicity of up to BN140. Scrubbers are generally only feasible on big, new vessels; exactly the type of ships Continued on page 12
LUBE MAGAZINE NO.154 DECEMBER 2019 11
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