Operational supervision
Partial load operation
A3.06.18.00
M20-M601C
en / 11.12.1997 BA000090 1/2
Ĺ
Partial load operation with heavy fuel
In order to prevent increased wear and tear, pollution of air and exhaust systems and an increased
contamination of the lube oil, the partial load operation has to be carried out with distillate fuel
only.
The distillate fuel provides for an unlimited partial load operation.
The heavy fuel operation is not useful and economic below a rated output of 25 %.
If a heavy fuel engine is working in the lower partial load range in pier to pier operation, the
combustion can be incomplete. After a lengthy operation at very low load, carbon deposits might be
found in the combustion chamber and exhaust gas ducts.
If operation is then to be continued in the upper load range, the load must only be increased
gradually for a period of up to 15 min., for reasons of safety.
If the laod is raised too rapidly, deposits may impair the oil film, damaging the piston and cylinder
liner.
Restrictions for partial load operation on heavy fuel cannot be avoided for some special ships, such
as supply vessels, diver base vessels etc. and for generators, if the low load is run for a lengthy
period, because deposits from combustion residues will then greatly increase.
The graph below represents the restrictions for such cases.
Continuous heavy fuel operation is permitted
above 25 % Pe. Below this range, the heavy
fuel operating time must be limited according
to the load stage, unless the operating
conditions permit a continuation at a high
load stage.
Example:
The engine runs on heavy fuel at Pe = 15 %.
After 4 h, changing-over to destillate fuel is
required or the engine will continue at a Pe
> 70 % if this is possible.
The deposits will burn away in approx.
40 min. and it will be possible to run with
heavy fuel at low load again.
Pe, versus h graph, for engines with two-stage charge air
cooler and HFO-operation. Charge air heated to 60 - 70 °C at
partial load. Centrifugal lube oil purifying for 24 hours/day.
Cleaning run after partial load operation
Cleaning run of engine
Load increase period
approx. 15 min.
Restricted HFO-operation
HFO-operation
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