Bridging to Category II Cylinder Oils


Bridging to Category II Cylinder Oils
A ship's main engine room. © WR studio

Maritime emissions regulations introduced in 2020 caused ship operators to transition to cylinder oils with lower base numbers of 40 and led a market-leading engine manufacturer to develop a new performance specification for them.

But questions remain about the widespread availability of such products, according to speakers at an online webinar last month, and supply issues could create new complications for ship operators.

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IMO 2020 fuel regulations at the start of 2020 led the shipping industry to shift to low-sulfur fuel oils, in turn causing a transition from base number 70 or BN 100 grades cylinder oils to novel BN 40 products.

German ship engine builder Man Energy Solutions “has unfortunately experienced lubricants aiming for low-sulfur fuel applications that have not adequately been able to prevent and manage deposit formulations and cleaning, especially in newer engine types,” Julia Svenson, Man’s fuel and lube research engineer, technology liaison lubricants, for two-stroke marine engines, said Jan. 24 during a webinar hosted by Riviera Maritime Media and titled, “Cylinder oils: how to bridge 40 BN Cat 2 oil requirements.”

Svenson noted the main purposes of cylinder oils are to lubricate, protect and clean. “The number of engine running hours spent in low-sulfur regime has increased significantly compared to pre-2015 values, and that will continue,” she said. “This calls for lubricants that are versatile enough in the formulation to cope with the ever changing fuel variance and engine designs.”

The experience drove the company to a crate a new 40 BN category 2 oil. “Since free movement of the rings is important for an efficient engine operations, we decided we needed to lift the performance up of the cylinder oils,” she said. “In 2020, we introduced a strategy where the aim is to raise the performance levels of cylinder oils by dividing them into two categories: Category I and Category II.” Man did that to motivate the development and usage of cylinder oils that will fit the engines, the fuels and the environmental requirements of the future, she added.

“Category II is the higher performing level, and in order to receive this status, the oil should have excellent overall performance with special focus on cleaning ability,” Svenson noted. “The first cylinder oils to go through the evaluation process were 100 and 140 BN cylinder oils for high-sulfur fuels. The next lubricant grade to be developed and undergo extensive testing is the 40 BN oil – a higher performing Category II BN 40 cylinder oil.” This means a 40 BN cylinder oil that performs equal or better than a 100 BN oil in regards to cleaning, she explained, adding, “Why should we settle for dirtier engines, when we run on at least in theory cleaner fuels?”

She noted that the task of developing the new Category II cylinder oils was and is not trivial, and the work on it and timelines for it were disrupted by the COVID-19 pandemic. “But we carry on,” she said.

Svenson said BN 40 Category II cylinder oils are appropriate to all ship engines and recommended for Man’s B&W two-stroke engines Mark 9 and higher – newer – designs. “There are companies that have successfully passed our main, no-objection test, and suppliers are running confirmation tests as we speak,” she noted. But until the BN 40 Category II oils are available, “we still have to have some patience,” she noted. “Until then, using a good quality 40 BN and Category II 100 BN is the go-to solution.” This must be individually evaluated for each engine and be based upon inspection, she added.

Detergency is the big issue and driver for Category II cylinder oils, according to Adrian Allman, oil content monitor operational development manager for Veritas Petroleum Services. “The main goal is to improve 40 BN cylinder lube oil detergency properties,” Allman said. “With the current 40 BN cylinder lube oils out there, the formulations out there have to change to meet these requirements.”

In the meantime, he said, the recent guidance is to switch back and forth between the high base number products and the 40 base number products. “This is primarily to benefit from the additional detergency which is found in the higher base number products,” he added.

This switching can cause problems with some vessels, he noted. “Some vessels don’t have the storage capability to store both products on board,” Allman said. “There’s also a risk of human error flip-flopping between products, so it’s not ideal. So development of these new products can’t come soon enough for some users.”

Caroline Huot, managing director for Delta Corp. Ship Management, said a major concern of ship owners with new marine lubricants products is availability. “Many vessels are limited capacity in tanks and are tramping to secondary ports where we have seen up to now that the new lubricants were not available for a very long amount of time and sometime never,” she explained.

Supply of the Category II marine cylinder oils is also a concern, she said. “If you are a bulker operator or small tanker operator and are tramping worldwide, the question will be, where will you get your cylinder oils if your tanks do not allow you to reach your full volumes?” she asked. She said another question is whether a ship will have to stop in a main port to obtain the Category II lubricants, or if marine lubricant suppliers will make the investment necessary to make the new lubricant grades available in secondary ports. “That’s a real challenging question for lube oil manufacturers,” Huot said.

There’s a lack of clear guidelines for operators on the new category of cylinder oils and of clarity on what the benefit is versus the additional cost, she said. “If we have to continue switching between Category II and a higher BN cylinder oil, what’s the benefit?” she asked. “Is Category I still acceptable by default? Will insurance of ships accept that Category I is used? Will the benefit of Category II be diluted if you have to alternate due to lack of availability?” These are all questions operators are asking, she said.