A leading engine maker has acknowledged that it has seen increased liner scuffing with 0.50% sulphur fuels and has not yet established why this is. And this is likely to be the case for all engine manufacturers.
Responding to a question during a webinar last week (5 March), Kjeld Aabo, director of new technologies at MAN Energy Solutions, said there is no indication yet about the cause and “we are very much looking into it and I’m sure that other engine designers are doing the same.”
But he does not believe it is caused by the fuel itself; it is more likely to be related to the lubrication arrangements – perhaps to the lube oil’s base number (BN) and feed rate – or to the engine’s piston-ring arrangement or, more generally, what he termed ‘housekeeping’ of the fuel. At MAN Energy Solutions, “we see so many cases and we are investigating what is actually the cause before we say anything,” he said.
The webinar was the first to be held by the International Council on Combustion engines, known by its French abbreviation, CIMAC, and Mr Aabo chairs its working group on fuels (WG7). Its members are collecting data about this phenomenon and are working “full on to find a concrete conclusion and give a more practical and general recommendation,” he said. The questioner himself provided some information that may prove useful to the WG: it happens with all oil brands and engine types, he said.
During the main part of the webinar, which CIMAC had arranged to provide a briefing about the 2020 sulphur cap, Mr Aabo said that about 90% of engines are now operating on 0.50% sulphur fuel. Based on experience so far, “we know for sure that stability is something that we have to look into [and] that it will be more paraffinic” than previous fuels.
The fuel’s viscosity, density and calculated carbon aromaticity index (CCAI; a measure of its ignition quality) are also different from HFO, so “we have to be aware of what is happening and to do the housework on board according to these new specifications.” And although the new fuels have important differences, “that does not necessarily mean that this is a bad direction to go,” he said.
Charlotte Røjgaard, global head of marine fuel services at Bureau Veritas and secretary of CIMAC’s fuels working group, agreed. She was also speaking in webinar and highlighted a significant benefit from the new fuels. “There is more energy in paraffinic products” – about 3% more, she said – making them “actually quite good fuels” that yield “more energy for your money compared to the high sulphur fuels,” provided temperature is kept under control.
Shealso provided some comparative data between low- and high-sulphur fuels, based on data from the first two months of this year and the corresponding period in 2019. Viscosity and density are lower in low-sulphur fuels and about 25% of samples showed a higher pour-point, because of their paraffinic nature. Micro carbon residue (MCR) is lower for low-sulphur fuels as too is cat fines content, but sediments are about the same, she found, “indicating that the fuels are either unstable in nature or dirty.”
Looking specifically at this year’s data, she found that the proportion of low-sulphur fuels that have been found to be off-spec has halved between January and February, from 4% to 2%. There was also a fall, from about 8% to 5%, of samples that fell within the 95% confidence level of meeting the spec. The amount of sulphur accounted for about half of the samples that were in that borderline situation, with pour-point and sediments also important factors.
Among those that were out-of-spec, about a quarter were because of their sulphur content but “[what was] surprising for us … was to see that 28% of the fuels are out of spec on water [content].”
• Further reading: CIMAC has published a number of relevant documents on its website, including some Joint Industry Guidance on the supply and use of 0.50% sulphur marine fuel, its fuel’s working group’s guideline Marine fuel handling in connection to stability and compatibility and, – published in February – a position paper and two white papers by its Greenhouse Gas (GHG) Strategy Group.
• What is your experience of using 2020-compatible fuels? Have you seen increased engine wear? Have you experienced off-spec fuels? Share your views by emailing me know.
Main image: BV’s tests have shown that the proportion of off-spec fuels has halved between January and February (image: BV)