Wtirtsilti Delivers Advanced Icebreaker To Finnish Board Of Navigation

The icebreaker Otso (shown), ordered in March 1984 by the Finnish Board of Navigation, was delivered recently by Wartsila's Helsinki Shipyard. She is the first of two technologically advanced icebreakers of a new type. The second vessel was ordered in December 1985 and is scheduled for delivery in January 1987.

Christened by Finnish Premier Kalevi Sorsa, the Otso and her sister ship will replace three icebreakers of the Karhu Class, which are all more than 25 years old and too small to assist today's much larger merchant vessels. The Otso was handed over by Martin Saarikangas, managing director of the Helsinki Shipyard, and accepted on behalf of the Navigation Board by Jan-Erik Jansson, director general.

Compared with the Urho Class icebreakers built in the mid-70s, the Otso has a 21.33-foot shorter waterline but a beam 1.3 feet wider. This allows efficient assistance to the bigger ships in use today. The design draft is only 24 feet, less than the Urho Class, making a larger number of harbors accessible to the new icebreaker. The Otso has an overall length of 324.8 feet, beam of 79.4 feet, and maximum draft of 26.25 feet.

The forward propellers common in recent Baltic icebreakers have been replaced by Wartsila's patented air-bubbling system. This and the absence of forward propeller bosses decreased the reisistance encountered by the vessel in ice. The ice resistance has also been reduced by modification of the hull shape and the use of compound plate with a surface layer of stainless steel in the ice zone. These features, together with application of epoxy paint to the underwater surfaces, will keep frictional resistance low for longer periods than could be achieved by the methods used previously.

The general arrangement of the Otso differs considerably from that found on earlier icebreakers. The diesel generators are placed on the upper deck, below the helicopter deck, resulting in simpler cable and piping systems. The heavy fuel tanks are placed amidships well away from the hull plating, which decreases the risk of pollution.

A new feature in comparison with earlier Finnish icebreakers is the "power station" type of machinery, in which no auxiliary units are needed. This is an economical arrangement as the vessel can run entirely on heavy oil, which is cheaper than diesel fuel.

The main machinery comprises four Wartsila Vasa 16V32 diesel engines, each developing 7,320 bhp, driving propulsion motors developed and manufactured by Kymi- Strombery Oy. The motors are of an advanced AC type, in which the rpm is regulated by altering the AC frequency.

The machinery can be started and supervised from the wheelhouse using a computer-assisted control system.

The control consoles in the wheelhouse are placed far out on the bridge wings, from which there is nearly 360-degree visibility. The computer-assisted radar system can also supply information on the speed and course, and data on the fairway can be fed into it in advance.

Crew accommodations have been designed to provide sufficient rest and recreation even under arduous working conditions. All cabins are located in the superstructure, which decreases the noise of breaking ice coming from the hull. Each of the 28 crewmembers has a separate cabin.

Separate messes and dayrooms are provided for the officers, crew, and catering personnel, and the ship has two saunas and a gymnasium.

For free literature on the facilities available at Wartsila shipyards.

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Other stories from March 1986 issue


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