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Back to SSG 08
Built in China for world wide service with focus on calls in icy waters. Photo: ICS
Gotland Carolina: Built for ice
The Gotland Carolina is the first vessel in a series of twelve 53,000 tonnes medium range product tankers with ice class 1 A Super to be delivered.
She is the first of four vessels owned by Rederi AB Gotland to join a pool of vessels under the management and operation of Danish Torm. Extensive testing has optimised her hull for a life in ice.
Many identical vessels
The ice classed vessels will be operating world wide on both the spot market and on charter contracts in a pool of ice classed vessels.
Out of the twelve sisters, Rederi AB Gotland’s four vessels join six vessels owned by Torm and the last two by other companies. Since there are so many identical vessels in the same pool, Torm can choose what vessel to use on every loading.
“We have been cooperating with Torm on our previous vessels the Torm Anna and the Torm Anna Marie, and are very happy with this strategy”, says Anders Larsson, Technical Manger at Rederi AB Gotland.
The Gotland Carolina flies the Danish DIS flag and was built accordingly, to meet all requirements set up by the Danish International Register of Shipping.
“The future will show that this type of ice classed vessels will be in demand, since the new oil fields are more and more remote”, says Mikael Andersson, Rederi AB Gotland’s site manager at Guangzhou Shipbuilding International (GSI) in China, where the vessels are built.
“We have built these vessels in close cooperation with GSI, Torm, DNV and the Swedish Maritime Administration. We started by making model testing at HSVA, Hamburg Ship Model Basin, to find out what kind of engine we needed.”
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Godmother Ann-Marie Åström with her daughter Carolina, who lends her name to the Gotland Carolina. Photo: ICS |
The alternative to do model testing would have been numerical calculations but they have their limitations. In the case of Gotland Carolina and her sisters, model testing proved itself worth the effort. Traditionally, on smaller vessels, horse power has been the answer to cope with ice.
“The model testing made it clear to us that we could go for an engine with 3,500 kW less than the numerical calculations showed us. This granted our wish to have a vessel also suited for conditions outside the ice season.”
No NOx-reducing equipment
Even though the Gotland Carolina was built for icy conditions, the average time an ice classed vessel really operates in ice might be as low as ten percent of her life time.
The 11,340 kW Wärtsilä, seven cylinder main engine installed in the vessel, has not been fitted with any NOx-reducing equipment, such as catalytic converters.
“No, we have no such installations but we meet all IMO-requirements and since we have Wärtsilä’s flex engine we can use all different types of fuel and easily meet all future requirements”, says Mikael Andersson.
Less ice in cooling pumps
Since the Gotland Carolina and her sisters were specifically designed for icy waters, not only the engine size had to be considered, but also smaller things such as cooling water pumps.
“Back in the day when I was sailing, we always had problems with the cooling water pumps sucking up a lot of ice, clogging the cooling system. Since the icy water is cold anyway the engine doesn’t really need that much cooling but the pumps were still running all the time. Now on the new vessels we have installed frequency controlled pumps, that only runs when the engine really needs cooling, this means we don’t unnecessarily clog the cooling system with ice.”
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Already in February the Gotland Carolina got to feel the ice, when she called Vitino on the White sea to load natural gas condensate. The model testing showed the vessel is capable of doing 4.5 knots in 25 centimetres of level ice without the assistance of an icebreaker. The ice class 1A Super requires vessels to be able to do 5 knots behind an icebreaker in one metre of broken ice. This vessel has proven to be capable of propelling her 55,000 cubic metres of cargo in up to seven segregations, at 15 knots in broken White sea-ice.
“To achieve optimal thrust at low speed, which is the case in ice, we choose a controllable pitch propeller.”
The main propeller is specially designed to handle heavy ice, and to add manoeuvrability a 1,200 kW bow thruster was chosen rather than a more conventionally sized 800 kW.
With only one main engine and one propeller one could argue that the vessels do not have the same redundancy that a vessel with double and independent power lines has, but Mikael Andersson does not agree.
“We have four auxiliary engines and generators, so in case of a blackout we have the same redundancy and can quickly restart the main engine.”
At the end of March Rederi AB Gotland took delivery of the second vessel in the series, the Gotland Sofia. Today, the manning of the ever growing world fleet is a great problem and to get sufficient numbers of officers you need to educate new officers. Officers in training need training onboard real ships and therefore cabins for cadets are essential.
“We have 29 cabins onboard and the crew will be 23 or 24, so there are cabins enough for cadets, and Torm has a training program where these vessels will be included.”
//Fredrik Davidsson
Latest update 18-04-2007 11:43
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No 22/2008
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No 21/2008
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2007
