Fast load changes must be avoided during transfer from diesel to gas mode.
The “emergency” loading ramp in diesel mode can be used in critical situations, e.g. when
recovering from a fault condition to regain sufficient propulsion and steering as fast as possible.
The emergency ramp can be activated manually or according to some predefined condition,
and there shall be a visible alarm indicating that emergency loading is activated.
In applications with highly cyclic load, e.g. dynamic positioning and manoeuvring, maximum
loading and unloading capacity in gas mode (see figure 2-3) can be used in operating modes
that requires fast response. Other operating modes should have slower loading rates. If the
request is to use this curve intensively a special agreement/contract with end customer is
needed.
Maximum possible loading and unloading can also be required in other special applications.
The engine control does not limit the loading rate in gas mode (it only acts on deviation from
reference speed). If the loading rate is faster than the capacity in gas mode, the engine trips
to diesel.
Electric generators must be capable of 10% overload. The maximum engine output is 110%
in diesel mode and 100% in gas mode. Trip to diesel mode takes place automatically in case
of overload. Lower than specified methane number may result in automatic transfer to diesel
when operating close to 100% output. Load taking ability is also influenced from low methane
number. Expected variations in gas fuel quality must be taken into account to ensure that gas
operation can be maintained in normal operation.
2.2.1 Mechanical propulsion, controllable pitch propeller (CPP)
For successive loading rates and max ramp in variable speed, please contact Wartsila to have
further informations.
2.2.2 Constant speed application
Fig 2-2 Successive Loading & Unloading
The loading rates in gas mode in the diagrams above are to be applied when the gas Methane
Number is ≥ 80. For MN below 80, please contact Wartsila for further information.
DBAD209883 2-3
2. Operating RangesWärtsilä 46DF Product Guide
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