World Wide Icebreakers
An icebreaker is a ship that is intended to break ice in order to escort merchant vessels, do ice management or carry out some other special task in ice. Usually these kinds of vessels are pure icebreakers, ice breaking supply vessels or cruise ships (modified usually from icebreakers). The borderline between different vessels is not exact. The definition of an icebreaker is not very clear - even if a towing notch is usually deemed to be required from an icebreaker - and thus also the fleet of icebreaking supply vessels and research vessels with an icebreaking capability should be included. The supply vessels are intended to operate in various tasks at offshore oil and gas fields and thus they are not intended to be used in escort duties - this is reflected for example in that these supply vessels do not have a towing notch. An example of the necessity for an icebreaker to have a notch is given by the addition of a notch into the Estonian icebreaker EVA-316. The bridge of a supply ship is not suitable for escort operations as a large sector visibility astern is required for icebreakers.
The ice breaking performance reflects the capability of the ship in ice. This breaking performance does not necessarily make a good icebreaker. The requirements for a good icebreaker include a sufficient speed in the ice conditions of the operational area (in the Gulf of Bothnia for example 10-12 knots in 80 cm thick ice) and good manoeuvrability in ice for escort operations. Additionally it can be observed that even a technically good icebreaker is not performing well in escort services if the crew cannot use all the capability invested into their ship. The experienced icebreaker crews indicate short escort times and larger escort speeds. The average escort speed is one of the main measures of a good, smooth winter navigation system. The ice breaking capability and the bollard pull help in assessing the capability of a ship in escort operations.
Among modern European sea-going icebreakers with non-traditional solutions as to the hull shape and rudder-propeller system one should distinguish Swedish icebreaker Oden built in 1988. The icebreaker has a simplified box-like form of hull with a flat stem and a wider, in comparison with main hull, forward end changing in the bottom wedge and making a cleaner wider channel as well as improving the maneuverability of the icebreaker. Besides, to raise the icebreaking capability, icebreaker Oden is equipped with powerful water washing and fastacting heeling systems. To reduce the circulation radius of the icebreaker special side attachments were used, which abut against ice when icebreaker is heeling creating additional turning moment. On the icebreaker a motor-reduction unit with two nozzle controllable pitch propellers is used.
Among the largest foreign icebreakers built during last 30 years there were American icebreakers Polar Star and Polar Sea of the same type constructed in 1976-1977 with a combined propulsion unit consisting of a diesel-electric and afterburner gas turbine installation and Japanese icebreaker Shirase of 1982 construction with a diesel-electric unit of 26 500 kW. On icebreakers of the Polar Star type for the first time in the practice of icebreaker building controllable pitch propellers were used, power being directly delivered form gas turbines via reduction gear to propeller shafts. These icebreakers are used mainly for the research in the Arctic and also, as icebreaker Shirase, for the supply of Antarctic stations.
Specially for the Antarctic, Finland delivered to Argentine in 1978 a twin- shaft icebreaker Almirante Irizar with a diesel electric plant of 14 MW. One should mention as well German research icebreaking ship Polarstern built in 1982 and used for Arctic and Antarctic expeditions. This ship has icebreaking hull shape close to a traditional one with forward end in the form of a concave wedge, motor reduction unit with a power of about 15 MW and two nozzle CPP. Particular feature of the hull shape of Polarstern, as of a ship designed for long transits in open water, is presence of a box-like keel 1 m high protruding beyond the basic line and playing the role of a passive stabilizer.
For carrying out conventional icebreaking works on the escorting of ships in the Arctic and freezing seas Canada for the period in question completed its fleet by a series of three icebreakers of the Pierre Radisson type with a diesel-electric plant of about 13 MW and one icebreaker Henry Larsen, also with a traditional diesel-electric unit of about 18 MW, but with an AC propeller drives. In the mid-seventies Sweden and Finland have set in operation icebreakers of the Finnish construction of the Atle type having four-shaft diesel-electric propulsion units with two stern and two bow propellers.
Particular feature of the last decade of the XX-th century in the field of icebreaker building was further improvement of conventional hull lines and rudder-propeller systems as well as the construction of new icebreakers of multipurpose type. The latters during winter period provide for the escorting of ships in freezing seas and in summer serve as supply vessels of offshore drilling rigs. As an example of that may be the construction in Finland of icebreaker Fennica which was put into operation in 1993. The second icebreaker of this type Nordica was delivered in 1994. It is envisaged to use these ships not only for icebreaking operations in winter in the Baltic Sea, but also as offshore supply vessels in the North Sea during summer period. Such purpose predetermined rigid requirements to ensure, along with high ice performance, good seaworthiness and maneuverability in open water. Accordingly, a combined icebreaking and seaworthy hull shape of the new ship was elaborated and two azimuthing propellers with a power of 7 500 kW each specially manufactured by Aquamaster-Rauma were used as a main propulsion rudder unit. Besides, three bow thrusters with a ship's dynamic positioning were installed. Thanks to the possibility of directing propeller jet sideways the icebreaker was capable of making the channel with a width much larger than that of the icebreaker proper.
In 1998 the shipyard Aker Finnyrds Oy delivered to the Finnish Maritime Administration a new multipurpose icebreaker Botnica having smaller dimensions and power in comparison with icebreakers of the Fennica type (see table 2.2), but is equipped with Azipod propulsion system. The icebreaker is designed to escort ships in winter principally in the Gulf of Finland. In summer, she, as Fennica, serves as an offshore supply vessel in the North Sea. Besides, drilling equipment may be installed aboard the ship. Her functions include operations on rescue, patrolling and escorting of ships, oil spills combating.
In 1999 the polar diesel-electric icebreaker WAGB-20 Healy built in New Orleans at shipyard Avondale Industries to order of the US Coast Guard was put into operation. Along with its direct purpose, icebreaker Healy is constructed for the research works in high latitudes. Icebreaker Healy has a traditional improved hull shape permitting to work practically under any ice conditions keeping acceptable seaworthiness. Being a research ship the icebreaker is equipped with laboratories and living spaces for the accommodation of 50 scientists. On the icebreaker there is also a helipad with a hangar for a board helicopter. This icebreaker is the last one of the sea-going icebreakers built in the XX-th century.
In the Soviet Union, a whole series of nuclear ice breakers was constructed. The first- of the series, the ice breaker "Lenin," which displaced 16,000 tons was built in 1957. The nuclear power plant produced 44,000 hp., which permitted the ship overcome ice a few meters thick at a speed of 2 knots. The speed in open water was 18 knots. Even more high-powered icebreakers, such as "Sibir' ", "Arktika" and "Rossiya" are now in operation.
In 1988, the USSR launched the first nuclear ice-breaking cargo vessel, "Sevmorput' ", with a nuclear power plant capable of delivering 40,000 hp and a freight-carrying capacity of 33,000 tons. The vessel is about 300 m long, with a beam of 32.2 m. She is intended for transportation in Arctic regions. The "Sevmorput" nuclear powered lighter-aboard container carrier is the only icebreaking nuclear powered freight ship in Russia.
The operation of icebreakers to support maritime trade is usually included in the infrastructure given by the port state. The icebreaker support is given in Finland by the Merenkulkulaitos (Finnish Maritime Administration), in Sweden by Sjöfartsverket (Swedish Maritime Administration), in Estonia by Veteede Amet (Estonian Maritime Administration), in Latvia by by the Port of Riga, in Denmark by the Danish navy, in the USA by the US Coast Guard, in Canada by the Canadian Coast Guard and in Japan by the Japanese Navy i.e. the Self Defence Force in Japan. In Russia the state offers the ice breaking services through the state company RosMorPort but there is also some private ice breaking services. An example of private ice breaking services is given by Gazprom icebreaker that were intended to assist the oil export from the Prirazlomnaja oil field. There does not exist economic competition anywhere in the world in ice breaking services as there does not exist any free icebreakers to participate in the competition. Only in the Okhotsk Sea there exists some competition in offering offshore supply services.
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