SL2023-738/IKCA Sampling of scavenge drain oil Adjust feed rate factor in service

Controlling wear rates and good cylinder conditions are essential for optimising component service life and overhaul intervals. New guidelines for iron (Fe) content and base number (BN) of the scavenge drain oil. Guiding intervals for sampling and advise on interpretation of the results.

The cylinder condition must be monitored by performing a monthly visual inspection through the scavenge air ports and by acquiring a scavenge drain oil analysis (SDA) from an accredited laboratory every third month or 1,500 running hours. In addition, it is recommended to supplement the laboratory SDA by doing onboard SDAs at short intervals (100–200 running hours).

By monitoring the cylinder condition closely, the cost of ownership
can be reduced by:
– Optimising the cylinder oil feed rate
– Wear control
– Optimising overhaul intervals

Drain oil iron content
The iron content in the drain oil depends on fuel sulphur content, cylinder oil grade and feed rate, engine type, and engine condition.

Tables 2 and 3 show guiding drain oil values for total iron content and magnetic iron content, respectively, for the four wear categories. These values correspond to a feed rate of 1.0 g/kWh. An iron content obtained at a given feed rate must be corrected to reflect the content at 1.0 g/kWh, considering the same iron quantity (absolute wear).

See Equation 1 and the following example.
FeCorr1.0 = FeAct ∙ FRAct Eq. (1)
Example: An iron content (FeAct) of 35 ppm at feed rate (FRAct) 0.80 g/kWh corresponds to 28 ppm at feed rate 1.0 g/kWh

Summary
New guidelines for iron (Fe) content and base number (BN) of the scavenge drain oil. Guiding intervals for sampling and advise on interpretation of the results.