Ishikawajima-Harima Heavy Industries (IHI) has developed a large-size Contra-Rotating Propeller (CRP) System that can be used for Panamax type 4000 TEU class to 10,000 TEU class container ships. IHI retro-fitted the first large size CRP on 37,000 dwt bulk carrier in 1989 and then delivered a similar system for 259,000 dwt VLCC in 1993. In both cases, energy savings of 14%-15% were confirmed during the years of service of these vessels, together with high reliability of the system.
The latest CRP system for container ships is based on the technology proven in the above two vessels. However, this time on a larger scale providing twice as much transmission torque as that of a VLCC. In the recent years, larger size, high-speed container ships reached 6000 to 7000 TEU class. The market trend suggests the growing need for even a larger size in excess of 8000 TEU. However, diesel engines available today are not powerful enough to serve such large container ships of 10,000 TEU class with the required cruising speed, calling for undesired and uneconomical twin-engine, twin-screw configuration. If the newly developed CRP system is adopted, a single engine/single-screw container ships of 10,000TEU with the required service speed of 25 knots become feasible.
CRP system requires additional investment costs, but the fuel saving advantage is such that with today’s fuel costs, the initial investment can be recovered within 2.5 to 3 years. The larger the power, such as in container ships, the larger is the fuel saving effect. Furthermore, the initial investment for the CRP system is lower than a cost to provide a twin screw/twin engine arrangement.