AWT Weather Routing/Routeing: Applied Weather Technology

Does Fixed RPM Actually Deliver Reduced Fuel Consumption?

by George Schlinkert

Attaining optimum fuel consumption on a voyage is a complex issue. In liner shipping, vessels are, ideally, to maintain the schedule with minimum fuel consumption. Is this attained by setting a fixed RPM for a voyage? Or, is it most favorable to consider a full set of parameters? AWT offers a service that provides both the optimum route and speed setting in combination to realize reduced fuel consumption, as both depend on each other.

AWT takes into consideration the full set of parameters to determine the speed setting, including the season and sailing area, weather forecast, remaining voyage time and the vessel’s speed reserve. Furthermore, AWT accounts for potential power reductions in unavoidable heavy weather conditions ahead.

The AWT solution lets ship Captains know the speed-loss to be expected during the voyage and suggests a calm sea speed setting. AWT updates the speed suggestion on a regular basis. As a result, ship Captains and Chief Engineers can then operate their vessel in the most safe and efficient manner.

What is the advantage of the approach adopted by AWT? The propeller slip of a vessel is highest in heavy weather. In these circumstances, maintaining higher RPM rates in heavy weather is often impossible, as it may result in ship and cargo damages. Besides, the conversion of power to speed is at its minimum efficiency. And given safety considerations, a Captain has two courses of action when vessel motions become excessive. Either he must adjust the RPM or the heading of the vessel. A Captain’s only choice would be to alter the vessel’s course with an accompanying increase of distance.

Accounting for potential power reductions in advance ensures that the suggested speed settings are reliable, realistic and consistent. Hence, AWT’s method is not only fuel-efficient in good weather, but it has been well proven in situations where the vessel encountered heavy conditions. The AWT suggested calm sea speed setting takes into account all parameters, even potential power reductions for safety reasons, to provide maximum fuel efficiency.