METHANOL ENGINE LUBES GAIN SERVICE EXPERIENCE

Newly developed 40 BN lubricants will gain service experience with the growing uptake of methanol dual-fuel 2-stroke engines

Gulf Marine was the first lubricant manufacturer to receive MAN Energy Solutions’ Cat II 40 BN no-objection-letter (NOL) in August 2021, and by May 2022, the company was supplying it to customers – again claiming an industry first as the earliest supplier of Cat II 40BN cylinder oils to the marine industry. Others, including Castrol, Chevron, ExxonMobil, Shell and TotalEnergies Lubmarine, have followed since then, and MAN released a service letter in August 2022 presenting the Cat II 40 BN cylinder oils which have shown excellent overall performance in MAN B&W two-stroke engines, especially when focussing on cleaning ability.

MAN introduced Cat II performance levels in 2020. Extensive testing has been completed in partnership with lubricant manufacturers to meet the standards set by MAN for 40 BN, 100 BN and 140 BN cylinder oils. Cat II 40 BN lubricants were tested at same feed rate as 100 BN.

“It was difficult for all involved, but finally we – the industry –succeeded in achieving 40 BN cylinder oils that performs equal or better than a 100 BN oil in regards to cleaning,” says Dr Julia Svensson, Senior Research Engineer, Fuel & Lube, at MAN.

“Operation on low sulphur fuels is the most predominant way of operating today, and fuel-efficient engines with high pressures and temperatures require lubricants with matching performance. To secure an acceptable TBO (Time Between Overhaul), it is important to ensure that piston rings, top lands, ring grooves and piston crowns are clean. These lubricants will also decrease the risk of ash deposit build-up in EGR and SCR NOx compliant Tier III-systems.”

The new lubricant formulations are suitable for all of MAN B&W 2-stroke engine types and are recommended for MAN B&W two-stroke engines with Mark 9 and higher, including ME-GA engines. However, even though MAN’s Cat II lubricant certification relates to its modern engines running on a range of fuels, much of the testing and experience gained so far has involved LNG rather than methanol dual fuel engines.

Over the three years of research and development for the Cat II formulations, the popularity of MAN’s methanol dualfuel ME-LGIM engines has increased, and the range of bore sizes has expanded. MAN’s ME-LGIM reference list, starting with two tankers in 2016, has now included a range of vessel types including container ships and bulk carriers. In February 2023, long-term MAN licensee, Mitsui E&S Machinery, won another contract to supply a MAN B&W 6G50ME-LGIM engine for a 65,700dwt bulk carrier slated for construction at Tsuneishi Shipbuilding.

Currently 101 ME-LGIM engines are on order or in service, with 20 of them already operating on the water today, gaining in excess of 200,000 operational hours on methanol. Svensson expects close scrutiny of the performance of the Cat II 40 BN lubricants in these engines over at least the next 12 months, but she is not expecting problems. “We need service testing, to get the oil onboard and have the crews onboard inspecting the engines,” she said. “We are grateful for the support we have already received from shipowners and operators and from the lube oil industry.”

Building on previous experience with the Horizon 2020 project Hercules-2 where WinGD successfully demonstrated combustion of alcohol-based fuels on its test engine, the engine designer is currently running a methanol engine development program focusing on application from 2024. WinGD’s development program includes a systematic testing sequence beginning with intensive combustion property investigations on their one-of-a-kind Spray Combustion Chamber, followed by component and systems performance verification, finally leading to full scale validation on their lab engines.

“Methanol is a low viscosity fuel with relatively poor ignition properties when compared to traditional diesel,” said Bartosz Rozmyslowicz, Senior Expert Fuels & Lubricants, at WinGD. “Potential improper fuel combustion might lead to mixing of methanol with lubricant which would decrease oil lubricity and lead to increased wear. However, when proper ignition control measures are taken, all fuel should be fully consumed and no interactions between methanol and cylinder lubricant should exist. Additionally, due to the 2-stroke concept, the combustion chamber is separated from the crankcase by the gland box, which prevents mixing of methanol with system oil.”

Previous lab engine tests with alcohol-based fuels demonstrated no piston running issues while using commercially available cylinder lubricating oils. Nevertheless, WinGD will continue collaborating with major lubricant suppliers to ensure the readiness and high quality of cylinder oils for its future methanol engines.

8 MAN ES’ ME-LGIM engines (such as the 6 cylinder G50 version pictured) have gained over 200,000 operational hours on methanol