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Low Sulphur Fuel Operation
MAN B&W low speed engines can op-
erate on both heavy fuel oils (HFOs)
with a varying amount of sulphur, marine
diesel oil (MDO) and marine gas oil
(MGO). All fuels are specified in accordance
with ISO 8217 and CIMAC recommendation
21. Also biofuels (with separate
fuel specification) are now used on
MAN B&W low speed engines.
Local and international restrictions on
sulphur emissions are the reason why
an increased focus on low sulphur fuels
is seen today. Sulphur emissions can
be limited in two ways:
By making rules for a maximum
amount of sulphur in the fuel. Fig. 52
shows the “road map” for such legislation
globally and locally in so-called
SECAs (Sulphur Emission Control
Areas)
By applying abatement technologies
on board the vessels allowing the
vessels to continue operating on a
high sulphur content HFO. The driving
force for such technologies is the large
price difference between various HFOs
and distillates, see Fig. 53.
When running on low sulphur fuels, a
number of issues of interest in relation to
operational aspects can be mentioned.
Many of these are dealt with in detail in
our Service Letter, SL09-515/CXR, Ref.
[3]. These issues are discussed one by
one in the following.
Catfines in Low Sulphur HFOs
From a large number of bunker analyses,
it can be seen that there is a tendency
towards a higher amount of
catfines in fuels with lower sulphur con-
US$ per Ton
1300
1100
900
700
500
300
100
26 Service Experience of MAN B&W Low Speed Diesel Engines
MEPC 57 IMO & CARB Fuel-Sulphur Content Limits
Equivalent methods may be used as altemative
Global 4.5→3.5→0.5
SECA 1.5→1.0→0.1
Global
CARB MGO 1.5→1.5→0.1 (DMA)
CARB MGO 2.0→0.5→0.1 (DMB
SECA
CARB Phase 1
CARB Phase 2
2000 2005 2010 2015 2020 2025
Year
5
4,5
4
3,5
3
2,5
2
1,5
1
0,5
0
Fig. 52: Sulphur reduction ‘road map’
US$ per Ton
End of Period
July 2009
MDO
380 CST
85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 A M J J A S O N D J F M A M J J A S O N D J F M
Fig. 53: Cost difference: HFO vs. distillates
March 2010
tents. This requires increased focus on
optimal function of the fuel treatment
plants on board vessels operating on
low sulphur fuels.
Cylinder Lubrication and Low
Sulphur Fuels
It is well-established that MAN B&W
low speed engines, to a certain degree,
need cylinder oil feed rates proportional
to the sulphur content in the fuel. This is
due to the fact that we prefer to have a
controlled amount of cold corrosion on
Jan 2012
2008 2009 2010
the cylinder liner wall. However, we also
have other requirements for lubrication
apart from controlling the acid neutralisation.
These requirements presently
put a minimum limit to the feed rate of
0.6 g/kWh. Fig. 54 illustrates the degree
of over-additivation when operating on
various cylinder oils (various BN numbers),
and it can be seen that the need
for lower BN cylinder oils will persist as
fuel sulphur content limits are tightened.