Limits For Low Load Running; Recommendation - Man B&W S80ME-C7 Project Manual

MAN B&W
Line 6:
Propeller curve, clean hull and calm weather
– light running, used for propeller layout/design
(i = 3).
Line 7:
Represents the maximum power for continuous
operation (i = 0).
Limits for overload operation
The overload service range is limited as follows:
Line 8:
Represents the overload operation limitations.
The area between lines 4, 5, 7 and the heavy
dashed line 8 is available for overload running for
limited periods only ( hour per 2 hours).
Line 9:
Speed limit at sea trial.
The area between lines 4, 5, 7 and the heavy
dashed line 8 is available for overload running for
limited periods only ( hour per 2 hours).

Limits for low load running

As the fuel injection and exhaust gas valve tim-
ing are optimised automatically over the entire
power range, the engine is able to operate down
to around 5% of the nominal L
MAN B&W ME/ME-C/ME-GI engines
speed.

MAN Diesel

Recommendation

Continuous operation without limitations is al-
lowed only within the area limited by lines 4, 5, 7
and 3 of the load diagram, except for CP propeller
plants mentioned in the previous section.
The area between lines 4 and  is available for
operation in shallow waters, heavy weather and
during acceleration, i.e. for nonsteady opera-
tion without any strict time limitation. After some
time in operation, the ship's hull and propeller
will be fouled, resulting in heavier running of the
propeller, i.e. the propeller curve will move to the
left from line 6 towards line 2, and extra power is
required for propulsion in order to keep the ship's
speed.
In calm weather conditions, the extent of heavy
running of the propeller will indicate the need for
cleaning the hull and possibly polishing the pro-
peller.
Once the specified MCR (and the matching point)
have been chosen, the capacities of the auxiliary
equipment will be adapted to the specified MCR,
and the turbocharger specification and the com-
pression ratio will be selected.
If the specified MCR (and/or the matching point)
is to be increased later on, this may involve
a change of the pump and cooler capacities,
change of the fuel valve nozzles, adjusting of the
cylinder liner cooling, as well as rematching of the
turbocharger or even a change to a larger size of
turbocharger. In some cases it can also require
larger dimensions of the piping systems.
It is therefore of utmost importance to consider,
already at the project stage, if the specification
should be prepared for a later power increase.
This is to be indicated in the Extent of Delivery.
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