Alpha Adaptive Cylinder Oil Control (Alpha Acc); Working Principle; Typical Dosage (G/Kwh); Specific Minimum Dosage With Alpha Acc - Man B&W S50ME-B9.3-TII Project Manual

MAN B&W

Alpha Adaptive Cylinder Oil Control (Alpha ACC)

It is a wellknown fact that the actual need for
cylinder oil quantity varies with the operational
conditions such as load and fuel oil quality. Con-
sequently, in order to perform the optimal lubrica-
tion – costeffectively as well as technically – the
cylinder lubricating oil dosage should follow such
operational variations accordingly.
The Alpha lubricating system offers the possibility
of saving a considerable amount of cylinder lubri-
cating oil per year and, at the same time, to obtain
a safer and more predictable cylinder condition.
Alpha ACC (Adaptive Cylinder-oil Control) is the
lubrication mode for MAN B&W two-stroke en-
gines, i.e. lube oil dosing proportional to the en-
gine load and proportional to the sulphur content
in the fuel oil being burnt.

Working principle

The feed rate control should be adjusted in rela-
tion to the actual fuel quality and amount being
burnt at any given time.
The following criteria determine the control:
•
The cylinder oil dosage shall be proportional to
the sulphur percentage in the fuel
•
The cylinder oil dosage shall be proportional to
the engine load (i.e. the amount of fuel entering
the cylinders)
• The actual feed rate is dependent of the operat-
ing pattern and determined based on engine
wear and cylinder condition.
The implementation of the above criteria will lead
to an optimal cylinder oil dosage.

Specific minimum dosage with Alpha ACC

The recommendations are valid for all plants,
whether controllable pitch or fixed pitch propellers
are used. The specific minimum dosage at lower-
sulphur fuels is set at 0.6 g/kWh.
MAN B&W 98-26 engines
After a running-in period of 500 hours, the feed
rate sulphur proportional factor is 0.20 - 0.34 g/
kWh × S%. The actual ACC factor will be based
on cylinder condition, and preferably a cylinder oil
feed rate sweep test should be applied.
Examples of average cylinder oil consumption
based on calculations of the average worldwide
sulphur content used on MAN B&W two-stroke
engines are shown in Fig. 9.02.01a and b.

Typical dosage (g/kWh)

1.20
1.10
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
0 0.5
Fig. 9.02.01a: ACC = 0.20 g/kWh × S% and BN100 cyl-
inder oil – average consumption less than 0.65 g/kWh
Typical dosage (g/kWh)
1.20
1.10
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
0 0.5
Fig. 9.02.01b: ACC = 0.26 g/kWh × S% and BN100 cyl-
inder oil – average consumption less than 0.7 g/kWh
Further information on cylinder oil as a function of
fuel oil sulphur content, alkalinity of lubricating oil
and operating pattern as well as assessing the en-
gine wear and cylinder condition is available from
MAN Diesel & Turbo, Copenhagen.
MAN Diesel
1 1.5 2 2.5
1 1.5 2 2.5
9.02
Page 2 of 6
3 3.5 4
Sulphur %
178 61 196.1
3 3.5 4
Sulphur %
178 61 184.0
198 76 14-4.1