We evaluate each installation and provide a detailed view of potential savings. Upgrading with Promas Lite could be even more efficient. Fitting old controllable pitch propeller hubs with modern more efficient blades not only improves fuel consumption, but can also reduce propeller induced noise and vibration.
Propeller design techniques continue to improve, and when a vessel has been in service for some time it can often pay to invest in a new set of propeller blades.
Due to advances in hydrodynamic analysis and blade manufacture the new blades will be more efficient than the old ones, which will also be suffering from normal wear and tear. If the vessel has changed its operational profile the gains can be even higher.
Rolls-Royce has carried out numerous reblading jobs that have resulted in substantial reductions in fuel consumption and short payback times, with a subsequent reduction in emissions. An added bonus is usually a reduction in vibration and propeller induced noise.
Ships are studied to see if new propeller blades will pay off – contact your local Rolls-Royce service centre if you have a candidate vessel and determine the potential savings.
Stena has successfully refitted new blades on several of its vessels. Although initial analysis by Stena and Rolls-Royce indicated fuel savings of around 8% would be achieved, the overall result has been around 10% on the Stena Germanica, operating on the Gothenburg-Kiel route.
In practice the ship can maintain its schedule using only one engine per side instead of two. The additional advantages are that the level of redundancy is increased and maintenance costs cut. Sister ship Stena Scandinavica was subsequently given the same treatment.
New blades were then fitted to two more ferries which resulted in Trelleborg recording a fuel consumption reduction of 10-12%, while on Stenna Nodica the cut in fuel burn has been approximately 17%.
Royal Caribbean International replaced the blades on the 48,500gt cruise vessel Empress of the Sea’s. Careful records were then kept allowing performance before and after to be accurately compared. Speed before and after the blade change is unchanged. In low pitch manoeuvring slightly more throttle is need for the same thrust, but this is as predicted.
The reduction in fuel consumption is around 13% on a like-for-like basis when on cruises that range from 3-11 days. A side benefit is reduced engine running hours as the new blades enable the ship to run at the same speed with less power. The number of engines on line can be cut, with a saving in running hours of around 10%. Vibration was also reduced with no increase in noise levels.