Regulations and care
Heavy fuels
A4.05.07.02
M20-M601C
en / 15.12.1997 BA000170 4/5
Ĺ
Notes to the specification of the permissible limits:
The equipment of the engine and the fuel treatment system are decisive for the determination
of the permissible heavy fuel grade.
There may be restrictions, for instance, if the engine has no cylinder lubrication, the exhaust
valve seat rings have no cooling or the pistons are of the monobloc aluminium type. Fuels to
CIMAC-A10 are to be used in such cases. Caterpillar / MaK should be contacted if necessary.
A high vanadium content accelerates corrosion on the exhaust valves, and this must be taken
into account when fuelling in the Caribbean area.
It will frequently happen in the near future that the limits of the Caterpillar / MaK heavy fuel
specification are reached owing to a general change on the fuel market. If it is intended to take
such fuels for a lengthy period of time and the owners have no experience with this, we
recommend to contact Caterpillar / MaK first.
The sodium and water content should be kept as low as possible after the separator (water less than
0.2 % weight).
The ash content determines the mechanical wear. So preference should be given to heavy fuel with
a low ash content.
Mixing of fuel components to obtain the desired viscosity should be done in suitable mixing
appliances before bunkering.
A separate filling of the two components into the ship bunker as well as the use of mixed compon-
ents that are incompatible can cause a great deal of trouble.
If there are mixing facilities on board ship the compatibility of the components must be assured by
the supplier.
The technical development in handling of crudes has led to a noticeable increase in the proportion
of fuels from new refining processes (catalyst cracking, visbreaking) with which mixing presents
more of a problem than with the established heavy fuels. It is therefore preferable to bunker ready
mixed fuels.
Note
In the residues from catalyst cracking there can be catfines which lead to extensive engine wear if
they are not separated out very carefully.
The flash point of the heavy fuel must be above 60 °C in accordance with the requirements of the
classification societies.
In any case a sample of the heavy fuel should be taken while bunkering. Analyses can be carried out
by Caterpillar / MaK against payment of costs incurred or by the fuel supplier.
Heavy fuel operation makes necessary the use of a medium alkaline lubricating oil in accordance
with our recommendation of lubricating oil brands (A4.05.
08.00).
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