Data driven cylinder condition strategies

The next big engine problem you’ve never heard of? Mixing paraffinic and aromatic fuels. Ship owners taking on stable residual fuels are protected from asphaltene – heavy particles within the fuel that have the potential to create sludge – by the fuel’s aromatic properties, which keep the horrid stuff suspended in solution. But if the ship later tops up its tanks with distillate fuels, the mixing of highly paraffinic distillates with the aromatic heavy fuel oil will trigger instability in the fuel, which would cause asphaltene to drop out and could block lines, filters and purifiers.

Until now, the problem has been only a sporadic one for the shipping industry. But with the IMO’s global sulphur cap fast approaching, the prospect of ships mixing residual and distillate fuels is very real indeed. According to Iain White, global field engineering manager, ExxonMobil, it is just one of many challenges the industry must manage before the regulation comes into force on 1 January 2020.

Arguably the most straightforward route to IMO emission compliance is to use low-sulphur fuels. According to some estimates, from 2020 industry consumption of around 4 million barrels per day will switch from currently used heavy fuel oil which can contain sulphur up to 3.5% to compliant 0.5% sulphur fuel. But with around 15 months to go, there remains little visibility on the exact make-up of the new low-sulphur fuels that refiners will need to produce to meet this demand.

White predicts that, at major ports, low-sulphur residual fuel blends will be more commonly available. At more remote ports without easy access to refineries, ships will likely have to rely on distillate blends, which will be readily available due to demand from markets beyond shipping.

UNINTENDED IMPACTS

The likelihood of having distillates in your tank as well as residual fuels will increase unless ship owners manage what they are bunkering very carefully. The nature of those fuels will also change, says White.

“With today’s residual and distillate fuels you know what you’re getting,” he notes. “In the future, some refiners will blend these fuels to the 0.5% sulphur limit but may pay less attention to density and viscosity. These factors will be well within specification, but they have an impact on ignition characteristics as well as storage and handling.”

One characteristic of new fuels that can be predicted is an increase in cat fines, the potentially engine-damaging aluminium and silicon particles that are left in low-sulphur fuel streams as a result of catalytic cracking at refineries. These fuel streams are employed in the marine industry today, White acknowledges. But this is likely to increase post 2020.This means a need for increased filtration, separation and cylinder condition monitoring. In the future, these streams are likely to be attractive to refiners aiming to create low-sulphur blends. Their use is therefore expected to become both more widespread and more difficult to trace.

Ship owners will need to get to grips with these challenges very quickly indeed. White suggests that there will be limited information on what kinds of low-sulphur fuels will be available until the middle of 2019. By then, owners will have only a handful of months to prepare for compliance. And White is not convinced that owners have fully considered what compliance means.

“By 1 January 2020 ships need to be compliant. Before then they need to have taken on 0.5% sulphur fuel and to have put it in clean tanks. Any non-compliant fuel in the tanks will push up the sulphur content, and I don’t expect port state control will be lenient. And from 31 March 2020 there will be a carriage ban on non-compliant fuel, so all high-sulphur fuel will need to be gone by then.”

UNCHARTED TERRITORY

The challenges will not stop in 2020. White explains that monitoring cylinder condition afterwards will be even more important given that the use of low-sulphur fuels (and therefore lower-alkalinity cylinder oils) in modern two-stroke engines aside from the limited information gathered from those vessels in ECAs is relatively uncharted territory. Today, such engines mainly run on high-sulphur fuel oils and so deploy cylinder oils with a high base number (BN) to counter cold corrosion, the scourge of today’s ultra-long stroke engine designs. While lower sulphur fuels are likely to reduce the incidence of cold corrosion, there has been little experience to date on how else they may affect engine condition when combined with the new fuel formulations.

“Less sulphur may well mean less cold corrosion,” says White, “but that doesn’t help me to understand where I should set my feed rate. That’s where the discussion comes around to monitoring – to keep a close eye on how these new fuels are performing, what the impact is on cylinder condition and what that means for optimising cylinder oil.”

With all these challenges ahead, it is no surprise that ExxonMobil is reminding customers not to forget the importance of cylinder condition monitoring as they embark on their new, sulphur-compliant fuelling regimes. New technology is helping the company to improve its monitoring programme, says White.

“Cylinder condition monitoring is driven by data in two ways,” he says. “First, by analysing historic information operators can benchmark the current performance of their vessels. And second, having monitored so many vessels over the years we can compare engines of similar designs to plot trends, potentially enabling us to identify issues before they become problems.”

But optimising feed rates is not as simple as checking what has worked on similar engines, White admits. Different engines have different requirements based on their current condition and operating profiles, as well as their tunings – White notes that in the age of slow steaming virtually every engine is rated differently from the moment it leaves the shipyard, with a corresponding difference in lubrication requirements.

IMPROVED TESTING

If data is helping to improve how ship operators can use the results of cylinder monitoring, other technological advances are helping to make that monitoring easier. Historically, ExxonMobil has provided onboard engineers with three tests to perform on scrapedown oil – testing for iron wear, corrosion and residual base number. On a large, ten-cylinder engine, such testing could mean an engineer spending most of a day on a tedious, laborious task.

The company recently launched new onboard equipment that provides read-outs for iron content and residual base number in a matter of seconds. The system, which deploys X-ray fluorescence (XRF) technology, sends the results to the cloud, from where ExxonMobil runs them through its algorithms and sends a report back to the ship owner, showing the results, highlighting trends and offering guidance where needed.

These advances are part of the industry’s move to embrace the potential of digitalisation to improve maintenance and reduce costs. The Motorship’s fifth roundtable with ExxonMobil, titled ‘Data driven cylinder condition strategies for a complex future’, will explore ship operator perspectives on the challenges they face and how digitalisation within the cylinder lubrication sector can help them face those challenges.

The invitation-only event takes place on 5 September and will be the subject of an in-depth report in a subsequent issue of The Motorship.