2.2 Loading capacity
Controlled load increase is essential for highly supercharged diesel engines, because the
turbocharger needs time to accelerate before it can deliver the required amount of air. A slower
loading ramp than the maximum capability of the engine permits a more even temperature
distribution in engine components during transients.
The engine can be loaded immediately after start, provided that the engine is pre-heated to
a HT-water temperature of min 70ºC, and the lubricating oil temperature is min. 40 ºC.
The ramp for normal loading applies to engines that have reached normal operating
temperature.
2.2.1 Mechanical propulsion
Fig 2-2 Maximum recommended load increase rates for variable speed engines
The propulsion control must include automatic limitation of the load increase rate. If the control
system has only one load increase ramp, then the ramp for a preheated engine should be
used. In tug applications the engines have usually reached normal operating temperature
before the tug starts assisting. The “emergency” curve is close to the maximum capability of
the engine.
Large load reductions from high load should also be performed gradually. In normal operation
the load should not be reduced from 100% to 0% in less than 15 seconds. When absolutely
necessary, the load can be reduced as fast as the pitch setting system can react (overspeed
due to windmilling must be considered for high speed ships).
2-2 Wärtsilä 31 Product Guide - a1 - 18 October 2016
Wärtsilä 31 Product Guide2. Operating Ranges
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