Cylinder oil consumption monitoring is one of the main drivers for fleet performance management. Savings between 4% and 7% are regularly found, but some cases see up to 25%.
Fleet performance management targets an entire vessel’s efficiency and improvement. The first measurable indicator (and most important factor for success) is reducing fuel oil consumption. High global fuel oil prices have an impact on the lubes as well. Thus, the cylinder oil consumption for two-stroke prime movers is worth reviewing.
The analysis of ECO Insight data revealed 4–7% savings in cylinder oil consumption of our customers’ fleets over time. These savings were calculated by comparing a reference period close to the implementation of ECO Insight and after its implementation (Q1 2018)
Dry Cargo fleet
Calculating these fuel savings is a somewhat manual process. First, the reported measurement must be monitored and compared to target figures. The target ranges are 1–1.6 g/kWh for a conventional lubricator and 0.5–0.9 g/kWh for an advanced lubricator. Average figures can be checked on a monthly basis and Performance Center customers are sent vessel-specific alerts on a daily basis.
Over consumption is not only expensive, as a lot of unused oil escapes in the scavenge area, but it can have other negative technical impacts. For example, excess lube oil can result in piston rings sticking in the ring groove, preventing rotation and combustion gas blow by. Under consumption must also be avoided to: (a) maintain an oil film between the piston rings and cylinder liner, (b) avoid corrosion by sulfur content in fuel oil and (c) clean the cylinder liner of combustion residue.
Fine-tuning the lubricator is a continuous process that can be re-initiated by crew and those technically responsible when the values are out of range. Visual inspection of the cylinder liner and piston condition through the scavenging ports is important, specifically to ascertain the effect of changes in cylinder oil feed rate or cylinder oils. Lubrication rate may increase after changing the cylinder liner and piston or due to the demand on the sulfur content in fuels. If two or more lubricants are not in stock, the lubricator must be adjusted when sailing within and outside of sulfur emission control areas (SECA). For example, lubricants with a base number of BN70 to BN100 for fuels with a sulfur content of 3.5% have been used in the past. Today and in the future, BN40 (or below) is likely used for fuels with a sulfur content of 0.1–0.5%.
Even with the IMO’s 2020 sulfur cap, different cylinder oil lubricants will continue to support various fuel qualities on globally trading vessels.
Unlike most other vessel performance levers, which focus on fuel consumption, lubes consumption is on a ship owner’s account and the savings will benefit them directly. An additional benefit is the lubes reduction itself and the reduction of engine maintenance when the feed rate is optimized.