WinGD W-X82, Operation Manual

Page: 156 / 548

Operation
0710 − 1/A1
Winterthur Gas & Diesel Ltd.
2/ 12
Heavy fuel oil must be treated in an applicable fuel treatment plant.
When bunkering, it is possible that the fuel suppliers will report only some of the
values given in the Quality Specifications. Frequently, only the density and maximum
viscosity is given. This makes the analysis of a fuel difficult, thus it is important to get
a full certificate of analysis with each bunker.
The supplier must guarantee the stability of the fuel, i.e. resistance to the formation of
sludge. Also, the fuel must not have a corrosive effect on the injection equipment and
must not contain used lubricating oil or chemical waste.
If possible, oils from different bunkers must not be mixed because there is a risk that
the fuels will have different compositions (e.g. this can cause fouling of filters or too
much sludge, which will overload the fuel preparation equipment). Fresh bunkers
must always be put into empty tanks and not on top of old bunkers.
2. Heavy Fuel Oil
Diesel engine fuels include many different petroleum products from gas oil to Heavy
Fuel Oil (HFO). Gas oil is made from crude oil by distillation and processing. HFO is
the remaining material after distillation of the crude oil. To get the necessary viscosity,
the material is mixed with lighter, less viscous components. Modern refineries also
apply a secondary conversion process, such as viscosity breaking (visbreaking) and
catalytic cracking to get a higher yield of lighter products. The remaining products are
mixed to get HFO.
Viscosity is usually used to identify diesel engine fuels. The viscosity is shown in
mm
2
/s, referred to as centistokes (cSt) and measured at 50
_
C. The fuels are
classified in accordance with ISO 8217 and the latest revision is the fourth edition
dated 15 June 2010.
Viscosity itself is not a quality criterion. To make an analysis of the fuel quality (to
make sure that the fuel is applicable for use in a diesel engine), refer to the properties
such as those given in the Table 1.
To make an estimate of the ignition properties of a distillate diesel fuel, the CETANE
number (standardized engine test) or the CETANE index (calculation) were used. The
ignition and combustion properties are very important for medium and high-speed
engines. For low-speed diesel engines, the ignition properties are not very important.
Note: Some very poor fuels that are not frequently found can have important
ignition properties.
Very good supervision, engine maintenance and fuel treatment equipment is
necessary when fuel with properties near the maximum limits are used. Fuel
preparation that is not sufficient and poor quality fuels cause overhauls to be more
frequent and thus, an increase in the cost of maintenance.
The values in the column Bunker limit (ISO 8217:2010 RMK700) show the minimum
quality of heavy fuel as bunkered, i.e. as supplied to the ship/installation. Good
operation results come from commercially available fuels that are in the ISO 8217
limits. But the use of fuel with metal, ash and carbon contents and a lower density can
have a positive effect on overhaul periods. These effects can improve combustion
and exhaust gas composition as well as a decrease in wear.
The fuel as bunkered must be processed before it goes into the engine. It is
recommended that you refer to the related specifications of Winterthur Gas &
Diesel Ltd. for the design of the fuel treatment plant. The minimum centrifuge capacity
is 1.2 x CMCR x BSFC / 1000 (litres/hour), which is has a relation to 0.21 l/kW. The
fuel treatment must remove sludge and decrease catalyst fines and water to the
recommended engine inlet limits.
2017 − 08
Diesel Engine Fuels