Change drives lubricant development

The pace of change in the marine industry over the last 10 years has been remarkable, but that journey is by no means over. The pressure that the current economic environment is placing on ship owners and charterers, coupled with upcoming legislation and the drive for even more fuel efficient vessels, means that there is still considerable change to come.

This in turn poses interesting challenges to the oil companies that need to anticipate in advance, what these legislative changes might mean for engine hardware and therefore what the lubricants will need to cope with. Shell uses a technology roadmapping process to assess how these changes will shape the lubricant needs of customers. At present, it is clear that the IMO NOx Tier II requirements and the tuning of engines for fuel efficiency are resulting in engine hardware changes such as introduction of two-stroke Miller timing, turbocharger cut out, waste heat recovery, longer stroke and higher combustion pressure at part load. These measures are significantly increasing the corrosion tendency of engines. Whilst it is generally recognised that these issues arise due to engine hardware changes, the lubricant suppliers are increasingly being asked to help by providing higher performance products.

“This is where a fundamental knowledge about what is actually happening on the liner wall is key,” explains Jerry Hammett, marine technology group manager, Shell Technology Centre Hamburg. “By understanding the oil stress and how it is impacted by these hardware changes, formulations can quickly be developed to help manage these challenging operational and engine hardware needs”.

He goes on to explain his belief that this approach, which is built on real data and actual measurements of wear performance, clearly surpasses a purely theoretical approach based on calculations and an understanding of older, more conventional technologies.

For example, if you only look at theoretical calculations for the viscosity grade for marine two-stroke engines, it is easy to draw a conclusion that an SAE50 grade is the right solution and indeed this viscosity grade has served the market well for many years. However, Shell’s work on ring spray sampling clearly shows that the oil on the cylinder liner thickens rapidly in the used condition and is always of a higher viscosity than fresh oil. In practice, the actual viscosity in service is significantly higher than that of the fresh oil. In fact, it can be concluded that an SAE40 fresh oil grade is optimal as in service it is closest to an SAE50 viscosity grade, around which the engines are typically designed.

It is interesting to note that the actual viscosity grade in service of an SAE50 is significantly higher, suggesting that there could potentially be issues with transport of the lubricant and insolubles debris, resulting in deposit formation and poorer wear performance. This may be even more critical given the much greater stress recent engine hardware changes are putting on the cylinder oil.

In addition to the engine hardware challenges that are very real for customers now, there is more imminent change on the horizon. The fuel sulphur specification in an ECA, which will reduce to 0.1% from 1 January 2015, will require all vessels to move from a low sulphur residual fuel to a distillate type fuel. Whilst the specification limit is 0.1%, there is general consensus that in many locations, the fuel supplied may be the same as an automotive diesel, given supply chain constraints around the number of different fuel grades that can be managed simultaneously. This effectively means that the fuel sulphur levels could be as much as 100 times less than the specification limit, i.e. 10ppm sulphur. It is also anticipated that LNG fuels, which are effectively zero sulphur, will increasingly start to penetrate the market place. At fuel sulphur levels this low, it is unlikely that any oil company will be able to develop a cost- and performance-effective wide range oil to cover both ECA and global requirements. Shell says it is already well progressed in developing a product suitable for this application.

To conclude, recent engine hardware changes to enable vessels to save fuel and meet upcoming emissions legislation, coupled with the upcoming changes in fuel sulphur limits result in the need for continued focus on ensuring that the right cylinder oils are available in the marketplace. According to Shell, the company’s fundamental knowledge of oil stress and ongoing interactions with the OEMs mean that it is placed to deliver products that meet the needs of customers, both now and in the future.