on the stability of blended fuels and can cause too much sludge in the separators and filters. If the
blended fuel is not stable, particles can collect on the bottom of the tank.
To keep risks to a minimum, make sure that bunkers from different suppliers and sources are not
mixed in the storage tanks on board. Also be careful when HFO is blended on board to decrease
the viscosity. Paraffinic distillate, when added to an HFO of low stability, can cause the asphaltenes
to collect, which causes heavy sludge.
HFO can contain up to 14% asphaltenes and will not cause ignition and combustion problems in
2-stroke engines if the fuel preparation equipment is adjusted correctly.
12.11.3.9
Pour Point
The operation temperature of the fuel must be kept between approximately 5°C and 10°C above
the pour point to make sure that the fuel can flow easily.
12.11.3.10 Water
The separator and the correct configuration of drains in the settling and service tanks are used to
decrease the water quantity in the fuel. A complete removal of water is highly recommended to
decrease the quantity of hydrophilic cat fines and sodium in the fuel. Sodium is not a natural oil
component, but diesel engine fuel often has sea water contamination, which has sodium. 1.0%
sea water in the fuel is related to 100 ppm sodium.
To get a good separation effect, the flow rate and temperature of the fuel must be adjusted in
relation to the viscosity. For high-viscosity fuels the separation temperature must be increased,
and the flow rate must be decreased in relation to the nominal capacity of the separator. For the
recommended data to operate the separator, refer to the documentation of the manufacturer.
12.11.3.11 Ash and Trace Metals
Fuels with a low content of ash, vanadium, sodium, aluminum, silicon, calcium, phosphorous and
zinc are recommended. High quantities of these materials can increase mechanical wear, high-
temperature corrosion and particles in the turbocharger, exhaust system and boilers.
•
Vanadium and Sodium
Sodium compounds decrease the melting point of vanadium oxide and sulphate salts,
specially when the vanadium to sodium ratio is 3:1. High sodium quantities (as well as lithium
and potassium) at the engine inlet can cause damage to the turbocharger, exhaust system
and boilers. Ash modifiers can correct the effect of high-temperature corrosion and particles.
•
Aluminum and Silicon
Aluminum (Al) and silicon (Si) in the fuel are an indication of catalytic fines (cat fines). These
are particles of hard oxides (round particles of material almost the same as porcelain) which
cause high abrasive wear to pistons, piston rings and cylinder liners. Cat fines are used as
a catalyst in some processes in petroleum refining and can be found in diesel engine fuels.
The most dangerous cat fines are between 10 microns and 20 microns.
X52
AA00-0000-00AAA-030A-A
Operation Manual
Diesel engine fuels
Winterthur Gas & Diesel Ltd.
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Issue 002 2018-11