This current environment of the shipping business is pressuring operators to economize and aggressively reduce operating expenses, including fuel and lubricant consumption.

Aside from a trend toward slow-steaming and reduced loads to save on fuel consumption, newer engine designs are further enhancing fuel efficiency, which can affect combustion conditions and, consequently, the performance requirements for additives and engine lubricants.

Traditionally, marine lubricants have been blended from Group I base stocks, which offer better solvency for polar and aromatic materials, to tolerate contamination from exposure to high-sulfur fuel oils. Due to factors such as rationalization and higher production costs compared to Group II base oils, Group I production is being scaled back. As Group I capacity declines and is replaced by Group II, it is important that lubricant and additive systems be designed to perform in both types of base oils.

Emissions Constraints

The IMO has worked for decades to reduce the harmful environmental impacts of shipping operations, developing regulations to minimize local and global air pollution and human health issues. A global sulfur cap in marine fuels was first established in 2005 at 4.5 percent weight of sulfur and reduced to 3.5 percent in 2012.

Since 2005, the designation of more Emission Control Areas has further restricted the use of heavy fuel oils in selected geographic zones, including the Baltic Sea, the European North Sea, North American coastal waters, the Caribbean and, most recently, a few selected river basins in Asia-Pacific. ECAs initially had a sulfur limit of 1 percent by weight, but their cap has been reduced to 0.1 percent.

In 2008, the IMO established a target date of 2020 to implement a new global limit at 0.5 percent weight of sulfur, recognizing the need to review the impacts and likely availability of low-sulfur fuels. It committed to the 2020 implementation date in October 2016, though some stakeholders had expected a delay to 2025 to allow further study.

The IMOs Marpol 2020 regulation will trigger a significant reduction of heavy fuel oil use, expanded use of distillates and liquefied natural gas fuels, as well as a new category of fuels introduced to the market to meet the 0.5 percent weight of sulfur specification. Heavy fuel oils are the bulk of fuels used in the marine industry, with the remaining 20-25 percent of the market served by distillates containing 0.1 weight percent or less sulfur, according to analysis from consultancies such as Wood Mackenzie, PIRA Fuel Outlook and Marine and Energy Consulting.

These 0.5 percent sulfur fuels do not exist today, and its hard to predict what they will look like. They could be refinery products with more robust sulfur removal treatment, or they may be blends of existing heavy fuel oils with low-sulfur distillates in ratios that yield an aggregate of 0.5 percent sulfur.

Fuels Influence Lubes

It seems reasonable to assume there will not be a single solution and there will be different ways to meet the IMO requirement, such as continued use of high sulfur fuel (3.5 percent or higher) in combination with effluent scrubbers as an alternate mitigation technique; converting operations to work with refined low-sulfur fuels or blended low-sulfur fuels; and a wider use of alternate fuels such as liquid natural gas.

The eventual selection by individual operators will involve trade-offs among price differentials between fuel grades, availability of compliant fuels and early investment in LNG engines or scrubber-equipped vessels. Lubrication will therefore be more complex due to the variety of fuels that might be employed.

The number of possible solutions to choose from could require unique combinations of additives and base oils for each operating regime. In some cases, new additives and lubricant formulations will need to be commercialized to meet the operating needs of engines consuming the new fuel types.

Lubricant suppliers and additive companies will need to provide a broad portfolio of solutions. Chevron Oronite notes that by 2020, there will be significant demand for lubricants designed to work with new hybrid blended fuels or further refined fuels meeting the 0.5 percent sulfur requirement in two-stroke crosshead engines and four-stroke trunk piston engines.

Different Strokes

For two-stroke crosshead engines, the marine cylinder lubricant runs down the cylinder liner and is consumed with the fuel. It serves two primary functions: It neutralizes acids to prevent corrosion and provides detergency to prevent deposit formation on the cylinder wall.

When the lubricant is injected into the cylinder, the base provided by the additive neutralizes acids formed during combustion. Base number is a measure of the acid neutralization power of the lubricant. For operation with heavy fuel oils (2 percent to 3.5 percent weight or higher sulfur), engine manufacturer guidelines have called for cylinder oils with BNs between 70 and 100, and 40 BN cylinder lubes for 1 to 2 percent weight of sulfur fuels.

With cleaner fuels, there is less demand for acid neutralization, but a simple down-treat (lower BN or lower feed rate) will not be adequate to prevent engine deposits. Engine designs for cleaner fuels or LNG operation will also have different operating conditions, and the application of the typical 70 BN lubricant will not be acceptable across all operating regimes.

Oronite projects that two-stroke engines will continue to need 70 to 100 BN lubricants for use in vessels with scrubbers or where cheaper 3.5 percent sulfur fuels are used because of limited availability of compliant fuels. There will also be increased use of existing 25 and 40 BN cylinder oils that are already used with 0.1 percent sulfur fuels or LNG fuels, because these fuel types will be more widely used. Lubricants with 15 to 40 BN will supplant a significant portion of the current higher-BN cylinder lubricants in 2020 as ship operators switch from predominantly heavy fuel oils to hybrid fuels and distillates.

For four-stroke trunk piston engines, low-sulfur fuels are in wider use already compared to the two-stroke market. There will be significant uncertainty in the TPEO market about the consistency and quality of hybrid fuel blends of heavy fuel oil and distillates.

There could be large variation in the compatibility and handling properties of fuels from different sources. The use of new hybrid fuels and operating regimes may also increase severity or introduce new challenges for lubricants to address, such as cylinder liner lacquering or oxidative stability.

Four-stroke trunk piston engines will need 20 to 60 BN TPEOs for use in vessels that continue to operate with 3.5 percent sulfur fuels if compliant fuels are limited, and will have higher usage of existing 5 to 20 BN products that are already common in ships that use 0.1 percent sulfur fuel or LNGs. Oronite forecasts that 12 to 30 BN lubricants will replace a large amount of high BN lubricants in four-stroke trunk piston engines as operators switch to alternate fuels.

Tasks and Timelines for New Additives

Commercialization of new additive and lubricant technology ultimately depends on formal acceptance and approval by marine engine builders. In the marine industry, there are no industry-wide performance or analytical tests for commercial use. OEMs require demonstration in the field to grant approval of the lubricant to support the engine warranties and claims. The duration of an approval field test is between 4,000 and 6,000 operating hours, or six to 12 months.

There is a natural progression of scale-up activities to screen and demonstrate lubricant formulations, starting with laboratory bench tests using analytical tools and representative bench performance measurements designed to mimic engine and field conditions, then prototype engine testing in test stands (representing anything from a few days to weeks of operation), and finally blending quantities of lubricant test candidates to be used in an operating commercial vessel.

There are costs to supply sufficient lubricants for the test phase, paying for periodic field inspections, and replacement of spare parts. This could require investing between $300,000 and $600,000 per field test.

Additive and lubricant suppliers typically invest two to four years to develop and demonstrate product formulations based on existing chemistry and commercial blending components. If an application requires invention of new chemistry for a special performance attribute, development time could stretch four to six years. Therefore, the pre-work and development to identify new lubricant technologies for the post-2020 marine fuel sulfur cap era needs to be in progress right now.

Dick Wolpert is a marine product line specialist at Chevron Oronite, where he has worked since 1997. He has led projects to construct facilities for commercial production of new chemical additives, including several marine detergents in Oronite additive products. Wolpert can be contacted at richard.wolpert@chevron.com