Operation
0270−1/A1
Winterthur Gas & Diesel Ltd.
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Change-over from Diesel Oil to Heavy Fuel Oil and Back
1. General
Continuous operation with heavy fuel oil (HFO) is recommended for engines and
plants. You must only change from HFO to marine diesel oil (MDO) if necessary, for
example when:
D The engine is flushed before maintenance
D The heating plant is set to off in the dry dock
D There are environmental conditions.
To make sure that the change-over is safe, see the paragraphs that follow:
2. Recommended Viscosity at Inlet to Fuel Pumps
For the temperature necessary to make sure that the fuel upstream of the inlet to the
fuel pumps is at the correct viscosity, see the 0710−1 Diesel Engine Fuels,
paragraph 3.1, Viscosity / Temperature Diagram.
A viscosimeter controls the temperature increase of the fuel.
Note: While the engine has stopped, fuel flows through the fuel pumps, fuel rail
and fuel pressure control valve and then flows back to the fuel system.
3. Change-over from MDO to HFO
See 0720−1 Fuel Treatment and Fuel System, Fig. 1 Schematic Diagram − Fuel
System.
3.1 Plant Side
To change from marine diesel oil MDO to HFO, you must make sure that the
automatic change-over unit (16) is in the correct position. When the position of the
automatic change-over unit (16) is changed, HFO and MDO are mixed in the mixing
unit (21).
The viscosimeter controls the end-heater (23), which keeps the fuel temperature at
the necessary viscosity. You must make sure that the fuel temperature increases
slowly (i.e. the temperature increase must be a maximum of 2_C each minute).
Note: It is possible that sudden temperature changes can stop the movement of
the fuel pump plungers.
1) Make sure that the heating for the fuel filter (24), fuel supply and fuel return pipes
is set to on until the fuel is at the necessary temperature.
Note: The temperature is shown on the thermometer upstream of the inlet to
the fuel pumps
2) Do a check of the fuel pressure downstream of the low pressure feed pump and
at the fuel pump inlet (see Operating Data Sheet 0250−1).
3.2 Engine Side
The trace heating on the engine (fuel pressure pipes and fuel rail) must be set to on
when there is a change-over from MDO to HFO in the plant. All covers of the rail unit
must be closed.
If the engine room is cold, you must set to on the trace heating approximately one
hour before the change-over.
Before you stop the engine, the change-over procedure must be fully completed. This
prevents a mixture of MDO and HFO in the fuel rail, which can cause viscosity
problems during the next engine start.
It is recommended that for the change-over, the fuel is at the necessary temperature
and the CMCR load is not more than 75%.
Operation
2015-03
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