WÄRTSILÄ WARTSILA 20, Product Manual, Page: 14 / 178

2.3.1 Mechanical propulsion
Fig 2-3 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.
If minimum smoke during load increase is a major priority, slower loading rate than in the
diagram can be necessary below 50% load.
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).
2-4 Wärtsilä 20 Product Guide - a13 - 6 September 2016
Wärtsilä 20 Product Guide 2. Operating Ranges