Marine Installation Manual
2021-08
4-21
4 Ancillary Systems
4.3 Lubricating oil systems
X72DF
Cylinder oil
For normal operating conditions, a high-alkaline marine cylinder oil with a vis
-
cosity of SAE 50 and a minimum kinematic viscosity of 18.5 cSt (mm
2
/s) at
100 °C is recommended. The alkalinity of the oil is indicated by its BN.
Cylinder lubricants of intermediate BN (50
<
BN
<
60 mg/KOH/g) may be used
if the performance is regularly monitored and the lubricating oil feed rate is ad
-
justed to avoid a low piston underside BN. Residual BN which is too low can
lead to excessive corrosive wear and scuffing.
Base number of
cylinder lubricating oil
The Base Number (BN) of the cylinder lubricating oil must be selected depending
on the total sulphur content of the fuel burnt. The higher the sulphur content in
the fuel, the higher the BN requirement for the cylinder lubricating oil.
Consequently, for gas operation and low sulphur diesel operation, a low BN cyl
-
inder lubricating oil must be supplied, whereas a high BN cylinder lubricating oil
is required when the engine is running on fuels with higher sulphur content.
In fuel sharing mode, with liquid fuel of higher sulphur content, the total sulphur
content depends on the fuel share ratio (see section
1.3.3 Operation in fuel sharing
).
Since the introduction of the global limitation of sulphur content in fuels (the
global cap of 0.50 % sulphur m/m), the maximum required BN is limited. This
permits the use of certain BN 40 to 60 cylinder lubricating oils which are capable
and approved of for handling both modes, gas and diesel mode operation, with a
single grade cylinder lubricating oil.
Alternatives to finished
cylinder oils
The cylinder lubricating oil can also be blended/mixed on board. Multiple con
-
cepts for blending/mixing cylinder oil on board are available.
The validated additives and oils which can be used for this purpose can be found
in the document
Lubricants
, which is provided on the WinGD webpage under
the following link:
For additional information please contact the oil supplier.
Another solution to have the needed BN value available is to mix lubricating oils
of different BN values.
Changeover between cylinder lubricating oils
There are in general two possibilities to changeover between the cylinder lubri
-
cating oils: A manual changeover or an automatic changeover.
iCAT changeover unit
(see
In case the automatic changeover alternative is selected, the engine will be
equipped with an automatic changeover unit called the iCAT (Integrated Cyl
-
inder lubricant Auto Transfer). The iCAT automatically selects the appropriate
low- or high BN cylinder lubricating oil, matching with the sulphur content of
the gas and/or liquid fuel supplied.