The recent introduction of the International Maritime Organization (IMO) emissions cap of 0.5 percent on marine fuels, has triggered changes to the way operators fuel their vessels and added complexity to the correct selection of marine lubricants.
For operators choosing to adopt low sulphur fuel oil as a route to compliance, the majority of IMO compliant fuels with a sulphur content below 0.5 percent will typically be of residual nature. When entering an Emission Control Area (ECA), vessels will still need to switch to a 0.1 percent sulphur fuel. Another option is to install an Exhaust Gas Cleaning System (EGCS), more commonly known as a scrubber. This removes sulphur emissions from the exhaust gases to the same level as a 0.5 percent fuel allowing for continued use of high sulphur fuel oil of 3.5 percent, or even higher. Operators should be aware that some port authorities have restricted the use of scrubbers, so compliant 0.5 percent sulphur fuels will still be required. Where ECA restrictions are in place, a fuel of 0.1 percent should be used when transiting the zones.
Follow these steps to help ensure best practise before switching fuels:
- Choose a reputable supplier for your bunker fuel that complies with ISO specifications, ensuring compatibility will result in reliable performance and minimise downtime.
- Clean and maintain bunker tanks to avoid mixing compliant low sulphur fuel with any high sulphur fuel remaining in remaining in the tank.
- Check supplier recommendations before mixing any fuels to ensure compatibility.
- Ensure you are using the correct lubricant for the fuel used.
- Use DOT.FAST® drip oil analysis to optimize cylinder oil feed rate and guard against cat fines.
- Use FAST™ oil analysis to ensure optimal performance from your engine.
Lubricant matching for two-stroke main engines
Chevron Marine Lubricants has conducted over 75,000 hours of field tests in 21 applications across a wide range of bunker fuels including IMO compliant 0.5 percent sulphur fuel blends likely to be used post-2020. For the majority of vessels opting for compliant 0.5 percent sulphur fuel, Chevron recommends Taro® Ultra 40, designed for the optimal balance of lubrication and neutralization for your engine and provides the flexibility to be used when burning 0.1 percent fuels in ECA areas.
Cylinder lubricants with a base number (BN) between 70 and 140 are ideal for use with high sulphur fuels, but using them in conjunction with a lower sulphur, IMO compliant fuel will typically introduce excessive alkalinity in the combustion chamber, which can lead to the formation of harmful deposits if used for a prolonged period. In a few cases, for example if an engine currently requires a minimum BN of 100 or 140 as a result of higher-than-average sulphuric acid condensation in the combustion chamber, a higher feed rate or BN lubricant may be recommended. Dual fuel engines may require closer investigation into actual operating conditions before a cylinder oil recommendation can be made.
The Taro® Ultra range from Chevron Marine Lubricants
Lubricant matching for four-stroke engines
For medium speed, four-stroke trunk piston engines, the engine lubricant does not provide direct cylinder lubrication in the same way as a cylinder oil. Trunk Piston Engine Oils (TPEOs) remain in the crank case and are designed to provide neutralising capability and thermal stability as well as dispersancy. Before selecting a lubricant, it is important to establish if the fuel being used is distillate or residual, as the nature of the fuel impacts the ideal quality of the lubricant in the sump tank. Refer to the fuel ISO specifications for clarification, or contact your technical services representative for advice.
The Delo®, Taro® DP and Taro® XL range from Chevron Marine Lubricants
To ensure continued smooth performance and prevent over feeding the engine, balancing the cylinder oil BN and feed rate is critical when switching fuels. The market-leading DOT.FAST® Service from Chevron Marine Lubricants provides on-board analysis of drip oil samples, immediately indicating to crew if there is an imbalance in the oil quality and identifying engine wear. For a complete picture on all lubricated equipment on board your vessel, the FAST program provides comprehensive, technically verified reports of used samples studied at our global laboratories.
Always consult your technical services representative when switching to a different fuel or lubricant program.