Operation
0750−1/A1
Winterthur Gas & Diesel Ltd.
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It is necessary to find the safe value for continuous operation on fuel oil with a low
sulphur content (of between 0.0% m/m and 0.5% m/m) and a low BN cylinder
lubricating oil (between BN 15 and BN 25) for each engine. To find this safe value,
you monitor the piston underside samples and do regular checks of the pistons,
piston rings and cylinder liners for excessive deposits, corrosion and wear.
Fig. 2 shows data for fuel oil with a sulphur content in the range of 0.5% m/m to
3.5% m/m and cylinder lubricating oil with a base number between BN 40 to BN 100.
Fig. 2: Piston Underside, Scrape-down or Drip Oil Analysis Interpretation
Note: There are smooth transitions between the different areas shown in Fig. 2.
Fig. 2 shows the operation ranges for engines with chrome ceramic piston rings and
fully honed cylinder liners installed. It shows the relation between the piston underside
total oil iron content and the residual BN. If necessary, the cylinder lubricating oil BN
and/or feed rate must be adjusted to prevent excessive corrosion or magnetic iron in
the piston underside oil.
For engines with chrome ceramic piston rings installed, the chromium content of the
piston underside oil shows if there is corrosion or wear in the engine.
D A chromium content less than 25 mg/kg shows small corrosion or wear in the
engine.
D A chromium value more than 25 mg/kg shows corrosion or wear in the engine.
The lifetime of the piston rings and the cylinder liners can decrease.
D The chromium value must not be more than 25 mg/kg for a longer period.
Note: Engines with cast iron or non-chrome ceramic piston rings installed, can
have a much larger total iron level than engines with chrome ceramic
piston rings under usual operation conditions.
2017−08
Lubricating Oils
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