Wartsila ?31DF Series Product Manual page 20

2. Operating Ranges
Unloading rate, constant speed engines, 720/750 rpm (DE / Aux / CPP)
Table 2-4
Engine load
[% of MCR]
100
0
Fig 2-5
In diesel electric installations loading ramps are implemented both in the propulsion control
and in the power management system, or in the engine speed control in case isochronous
load sharing is applied. If a ramp without knee-point is used, it should not achieve 100% load
in shorter time than the ramp in the figure. When the load sharing is based on speed droop,
the load increase rate of a recently connected generator is the sum of the load transfer
performed by the power management system and the load increase performed by the
propulsion control.
The "emergency" curve is close to the maximum capability of the engine and it shall not be
used as the normal limit. In dynamic positioning applications loading ramps corresponding to
20-30 seconds from zero to full load are however normal. If the vessel has also other operating
modes, a slower loading ramp is recommended for these operating modes.
In typical auxiliary engine applications there is usually no single consumer being decisive for
the loading rate. It is recommended to group electrical equipment so that the load is increased
in small increments, and the resulting loading rate roughly corresponds to the "normal" curve.
In normal operation the load should not be reduced from 100% to 0% in less than 15 seconds.
If the application requires frequent unloading at a significantly faster rate, special arrangements
can be necessary on the engine. In an emergency situation the full load can be thrown off
instantly.
2-6
Unloading rate
Fast loading
Nominal
[s]
loading
[s]
N/A
0
N/A
60
Unloading rate, constant speed engines, 720/750 rpm (DE / Aux / CPP)
Wärtsilä 31DF Product Guide
Emergency,
diesel opera-
tion only
[s]
0
0
DBAE248994