Ice class
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Ships with an Ice Class have a strengthened hull to enable them to navigate through sea ice.
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[edit] History
The first requirements for merchant ships to be escorted by icebreakers were set in in Finland in 1890, after winter traffic to the port of Hanko was started. In the past, different classification organizations had different standards, rules, and ice classes. Converting between the Baltic and Arctic systems is not usually done. Recently, the two different class systems have been defined by the IACS and the IMO.
[edit] Significance of Ice Class
Not all ships are built to an ice class. Building a ship to an ice class means that the hull must be thicker, and more scantlings must be in place. Sea chests may need to be arranged differently depending on the class. Sea bays may also be required to ensure that the sea chest does not become blocked with ice. Most of the stronger classes require several forms of rudder and propellor protection. Two rudder pintles are usually required, and strengthened propeller tips are often required in the stronger ice classes. More watertight bulkheads, in addition to those required by a ship's normal class, are usually required. In addition, heating arrangements for fuel tanks, ballast tanks, and other tanks vital to the ship's operation may also be required depending on the class.
[edit] Arctic classes
The American Bureau of Shipping has a system of ice classes which includes classes A5 through A0; B0, C0, and D0. A5 class is the strongest built of the classes, with D0 being the weakest. All other major classification societies have a similar system of ice classes, and converting between ice classes is relatively easy. In most cases only the names of the classes are changed and the specifics of the Arctic class are identical. ABS Class A5 is the only Arctic Class that may act independently in extreme Arctic waters with no limitations. Other classes are subject to limitations on time of year, required escort (always with a vessel of higher ice class) and ice conditions.
The ABS database includes hundreds of Arctic Ice Classed ships, including many Arctic Research Vessels,[1] and the entire productions of certain shipyards.
[edit] Baltic ice classes
The Baltic Ice Classes consist of 5 classes. Classes 1A, 1B and 1C were created in 1932. In 1972 new Swedish-Finnish rules extended the classification with the new class "1A Super". In addition, there is a weaker ice class named "Class II". Like the Arctic Ice Classes, different classification societies may assign different names for these classes, however, the restrictions and requirements of each class are the same regardless of the name given by the society.
Class II is the class offering the least protection from ice. Class 1A Super is the strongest class: ships in this class can navigate in "extremely difficult ice-conditions", meaning they can navigate in ice 1 meter thick with the help of an icebreaker. Most ships that are built for the Baltic Sea, including cruiseferries are at least Ice Class 1A.
[edit] IACS Polar Classes
The International Association of Classification Societies published a set of Unified Requirements for Polar Class Ships[2]to complement the IMO Guidelines for Ships Operating in Arctic Ice Covered Waters. This will effectively unify the ice classes for all IACS member societies. Seven Polar Classes are proposed in the requirements, abbreviated as PC1 through PC7[3]
[edit] References
- Ice Classes & Requirements - Swedish Maritime Administration
- Approximate correspondence between Ice Classes of the Finnish-Swedish Ice Class Rules (Baltic Ice Classes) and the Ice Classes of other Classification Societies - Finnish Maritime Administration
- GENERAL SPECIFICATIONS FOR MARINE AND AERIAL SUPPORT VESSELS (several Arctic/Polar classed vessels)
- ABS Rules for Steel Vessels 2007, Part 6- Optional Items and Systems
Eyres, David J. Ship Construction. 1st ed. Elsevier, 2007. 36-39.
