Mitsui Delivers Big Ore Carrier With M a n y Energy-Saving Features

The 197,060-dwt ore carrier Asakasan Maru, built at the Chiba Works of Mitsui Engineering & Shipbuilding Company (MES), was delivered recently to joint owners Mitsui O.S.K. Lines and Sawayama Kisen Kaisha, Ltd. The big vessel has an overall length of 984.25 feet, beam of 164 feet, depth of 79 feet, and full-load draft of 58.5 feet. She is powered by a slow-speed Mitsui/ B&W 7L80MCE diesel engine with a maximum continuous output of 20,700 bhp at 80.8 rpm. On sea trials the ship attained a speed of 16.35 knots.

A special feature of the new ore carrier is the superstructure located aft, which is shaped like a compact, streamlined tower. Such towershaped superstructures have been used by MES in the past for the construction of only four vessels— three tankers built in 1965 for Fred Olsen of Norway, and another in 1968 for Anders Wilhelmsen & Company, also of Norway. Reflecting the current increasing need for energy efficiency in ships, use of this unusual type of superstructure to reduce air resistance is now attracting renewed interest.

The Japan Marine Machinery Development Association, taking note of the advantage of this superstructure design, in 1981 set up a research subcommittee to study the resistance of offshore structures to wind pressures. As the effects of the tower-shaped superstructures had not been fully assessed in numerical terms, the subcommittee carried out research and investigation in various aspects, both theoretically and experimentally.

Participating in this research project, MES was commissioned to conduct an experimental study on the effect of reduced resistance on compact, streamlined superstructures on ships. With the cooperation of her co-owners, such a superstructure was incorporated into the design of the Asakasan Maru.

A Mitsui ATG-V turbogenerator system (mixed-pressure turbine system) is installed for maximum utilization of the waste heat of the main engine exhaust. The ship is also equipped with a thyristor convertor- invertor type shift generator (that can be used as an emergency propulsion motor), and a power management system for maximum effective utilization of the turbogenerator's output.

Other energy-saving features include a Mitsui Integrated Duct Propeller, a reaction rudder, and extensive use of high-tensile steel in the hull structure. The hull bottom and waterline area are coated with selfpolishing antifouling. Windlasses, mooring winches, and deck washing system are fitted with remote control systems with a view to reducing the crew's workload. The engine control room and cargo control room are integrated for more rational performance of the duties of both.

The engine room is designed for unmanned operation, and has obtained NK's "MO-A" notation. •

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