Reblading with Rolls-Royce saves fuel

January, 2008

Replacing old propeller blades with modern more efficient versions from Rolls-Royce not only improves fuel consumption but usually also reduces propeller-induced noise and vibration.

Propeller design continues to advance, and when a vessel has been in service for years it can pay the shipowner to invest in a set of new propeller blades. Because of developments in hydrodynamic analysis and blade manufacture, the new blades will be more efficient than the original ones, and it is also likely that wear and tear and repolishing will have altered for the worse critical areas of the blade profile on the existing units.

Rolls-Royce has now carried out numerous reblading jobs, which have resulted in very substantial reductions in fuel consumption and a short payback time. An added bonus is usually a reduction in propeller-induced noise and vibration because of smaller pressure pulses and improved cavitation margin.

Stena has refitted several of its vessels successfully with new Rolls-Royce propeller blades. The first was in 2005, with the upgrading of Stena Germanica operating on the Gothenburg-Kiel route. A reduction in fuel consumption of 10% was achieved, so the sistership Stena Scandinavica was given the same treatment the following year. Since then Rolls-Royce has upgraded the propellers of two more Stena ferries. The work on Trelleborg reduced fuel consumption by 10-12%, while on Stena Nordica the cut in fuel burn has been approximately 17%. Skåne is also being treated to a set of new blades.

Caption: Two vessels that have shown greatly reduced fuel consumption after new propeller blades were fitted: Empress of the Seas and Stenna Nordica (below). (Images courtesy of Stena Line and Royal Caribbean Cruise Lines).

Royal Caribbean International replaced the propeller blades on its cruise vessel Empress of the Seas during drydocking in November 2006. Careful records have been kept, allowing performance before and after reblading to be compared, and any differences in operating profile that might affect the results to be identified and compensated for. Empress of the Seas is a medium-size vessel of about 48,500gt, with facilities for 1,588 to 2,020 passengers depending on the cruise. It was originally built in 1990 and was extensively refitted in 2004.

Speed before and after the new blades were installed is unchanged. In low pitch manoeuvring slightly more throttle is needed for the same thrust but this is as predicted and has no adverse effects.

Based on data from the first nine months after conversion, the reduction in fuel consumption is about 13%, on a like-for like basis for the vessel’s Caribbean cruises ranging from 3 days to 11 days. So far the direct fuel saving amounts to well over 600 tonnes, which also represents a substantial reduction in exhaust emissions. A side benefit is reduced engine running hours. Because the new propellers enable the ship to run at the same speed with less power, the number of engines on line can be cut, and to date the saving in running hours is about 11%.

Geir Lund, Royal Caribbean’s senior superintendent, says he is happy with the outcome: “The vessel performs according to expectations after the re-propellering and we are very satisfied with the results. One important requirement was that there should be no negative impact on guests. The dining room is located aft, and it was vital that the level of vibration should not increase. It is a pleasure to report that vibrations have been greatly reduced, and no increase in noise level observed. Rolls-Royce provided excellent support and assistance during this project, both from the project group and the technicians assisting with the actual installation and related systems adjustments.”

For further information and high resolution images, please contact

Arnfinn Ingjerd, Vice President, Communications - Marine
Rolls-Royce plc
E-mail: arnfinn.ingjerd@rolls-royce.com
Phone: +47 70 01 42 17
Fax: +47 70 01 40 05