HFO pipes shall be properly insulated. If the viscosity of the fuel is 180 cSt/50°C or higher, the pipes must
be equipped with trace heating. It shall be possible to shut off the heating of the pipes when operating on
MDF (trace heating to be grouped logically).
Starting and stopping
In diesel mode operation, the engine can be started and stopped on HFO provided that the engine and the
fuel system are pre-heated to operating temperature. The fuel must be continuously circulated also through
a stopped engine in order to maintain the operating temperature. Changeover to MDF for start and stop is
not required.
Prior to overhaul or shutdown of the external system the engine fuel system shall be flushed and filled with
MDF.
Changeover from HFO to MDF
The control sequence and the equipment for changing fuel during operation must ensure a smooth change
in fuel temperature and viscosity. When MDF is fed through the HFO feeder/booster unit, the volume in the
system is sufficient to ensure a reasonably smooth transfer.
When there are separate circulating pumps for MDF, then the fuel change should be performed with the
HFO feeder/booster unit before switching over to the MDF circulating pumps. As mentioned earlier, sustained
operation on MDF usually requires a fuel oil cooler. The viscosity at the engine shall not drop below the
minimum limit stated in chapter Technical data.
Number of engines in the same system
When the fuel feed unit serves Wärtsilä 34DF engines only, maximum one engine should be connected to
the same fuel feed circuit, unless individual circulating pumps before each engine are installed.
Main engines and auxiliary engines should preferably have separate fuel feed units. Individual circulating
pumps or other special arrangements are often required to have main engines and auxiliary engines in the
same fuel feed circuit. Regardless of special arrangements it is not recommended to supply more than
maximum two main engines and two auxiliary engines, or one main engine and three auxiliary engines from
the same fuel feed unit.
In addition the following guidelines apply:
•
Twin screw vessels with two engines should have a separate fuel feed circuit for each propeller shaft.
•
Twin screw vessels with four engines should have the engines on the same shaft connected to different
fuel feed circuits. One engine from each shaft can be connected to the same circuit.
Feeder/booster unit (1N01)
A completely assembled feeder/booster unit can be supplied. This unit comprises the following equipment:
•
Two suction strainers
•
Two fuel feed pumps of screw type, equipped with built-on safety valves and electric motors
•
One pressure control/overflow valve
•
One pressurized de-aeration tank, equipped with a level switch operated vent valve
•
Two circulating pumps, same type as the fuel feed pumps
•
Two heaters, steam, electric or thermal oil (one heater in operation, the other as spare)
•
One automatic back-flushing filter with by-pass filter
•
One viscosimeter for control of the heaters
•
One control valve for steam or thermal oil heaters, a control cabinet for electric heaters
•
One thermostatic valve for emergency control of the heaters
•
One control cabinet including starters for pumps
•
One alarm panel
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Product Guide Wärtsilä 34DF - 3/2012
Product Guide
6. Fuel System
