A recent joint project between Stone Marine Propulsion and Danish shipowner Norden has resulted in a significant improvement in the fuel efficiency.
The project involved three 32,500DWT bulk carriers contracted from the Jiangmen Nanyang Shipyard as part of an ongoing series of ships. One was equipped with the series' original engine configuration, but the other two were fitted with slower-turning main engines to improve fuel consumption. However, to maximise potential improvements, all three vessels were fitted with Stone Marine's new high-efficiency NPT propeller. This provided an opportunity to obtain full scale performance results comparing previous ships in the class fitted with the original machinery and propeller, to one fitted with an NPT propeller.
Sea trial results were very encouraging. During project planning the gain from the NPT design was conservatively assessed at 3 percent, but the shipyard's trial reports show a much larger than expected improvement – approximately 6 percent. While other factors, such as differences in hull condition and measurement accuracy, may have influenced the trial results, the expected gain in efficiency appears to have been achieved, and probably exceeded.
Norden will be monitoring the long-term performance of the ships in service to confirm the results, and trial results for the vessels with the slower turning main engine and NPT propeller should be available shortly.
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