The Finnish-Swedish ice class is an ice class assigned to a vessel operating in first-year ice in the Baltic Sea and calling Finnish or Swedish ports. Ships are divided into six ice classes based on requirements for hull structural design, engine output and performance in ice according to the regulations issued by the Finnish Transport Safety Agency (TraFi), which overtook the responsibilities of the Finnish Maritime Administration in 2010, and the Swedish Maritime Administration.
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Traffic restrictions in the Baltic Sea during winter months are based on the Finnish-Swedish ice classes. These restrictions, imposed by the local maritime administrations, declare the minimum requirements for ships that are given icebreaker assistance, for example "ice class 1A, 2000 DWT". Finnish fairway dues, a system of fees charged for the use of sea lanes to cover the costs of management and icebreaker assistance, also depend on the vessels' ice class. Since ships of lower ice classes generally require more assistance during the winter months, their fairway dues are considerably higher than those of ships of the highest ice classes.[1] For this reason the majority of ships regularly calling Finnish ports are built to the highest ice classes. In the beginning of 2008, 47% of the Finnish tonnage were of ice class 1A Super.[2]
Many international classification societies have incorporated the Finnish-Swedish ice class rules to their own rulebooks and offer ice class notations that are recognized by the Finnish and Swedish authorities. Since the ice class rules have been revised and amended several times over the years, a list of equivalent ice class notations is used to assign the correct official ice class for older vessels when they visit Finnish and Swedish ports.[3] Although mainly used in the Baltic Sea, the Finnish-Swedish ice classes and the equivalent ice class notations from classification societies are sometimes used when discussing ships operating in other ice-infested seas of the world.
While the Finnish-Swedish ice classes can be assigned to icebreakers for the purpose of collecting fairway fees, the rules are intended primarily for merchant ships operating under icebreaker escort. Because the engine output and the level of ice-strengthening in ships designed to operate independently in ice-infested waters, especially in the presence of multi-year ice, usually exceeds the requirements of the Finnish-Swedish ice class rules, the classification societies use different ice class notations, such as the IACS Polar ice classes, for icebreakers. The two highest Finnish-Swedish ice classes, 1A and 1A Super, are somewhat equivalent to the two lowest Polar classes, PC7 and PC6, respectively.[3]
Ships of the highest Finnish-Swedish ice class, 1A Super, are designed to operate in difficult ice conditions mainly without icebreaker assistance while ships of lower ice classes 1A, 1B and 1C are assumed to rely on icebreaker assistance. However, even ships of the highest ice class are assumed to require icebreaker assistance from time to time. In addition there are ice class 2 for self-propelled steel-hulled ships with no ice strengthening that are capable of operating independently in very light ice conditions and class 3 for vessels that do not belong to any other class such as unpropelled barges and ships built of wood.[4] The Finnish-Swedish ice classes are usually spelled with roman numerals in official context and legislation.[5]
Ships must fulfill certain design requirements in order to obtain the ice class from the Finnish and Swedish authorities. The design requirement for ice class 1A Super is a minimum speed of 5 knots in a broken brash ice channel with a thickness of 1.0 metre (3.3 ft) in the middle and a consolidated (refrozen) ice layer of 0.1 metres (3.9 in). Ice classes 1A, 1B and 1C have lower design requirements corresponding to non-consolidated ice channels with a thickness of 1.0, 0.8 and 0.6 metre (3.3, 2.6 and 2.0 ft) in the middle, respectively. While the ice class rules provide equations to calculate the minimum engine power based on the ship's main dimensions and hull shape, more exact calculations or ice model tests resulting in lower minimum engine power can also be approved, but in such case the ice class can be revoked if the experience of the ship's performance in practice motivates this. In addition the ice strengthening of the ship's hull must be adequate to allow safe operation in open sea conditions corresponding to a level ice thickness not exceeding 1.0 m (3.3 ft) for ice class 1A Super, 0.8 m (2.6 ft) for 1A, 0.6 m (2.0 ft) for 1B and 0.4 m (1.3 ft) for 1C. Again the rules provide tables and formulas to determine the minimum scantlings of the hull.[4] The latter requirement is sometimes mistaken for the minimum required icebreaking capability of the vessel.
Since even ships of ice class 1A Super are assumed to rely on icebreaker assistance from time to time, a research was conducted recently about introducing a new ice class exceeding all existing ice classes, 1A Super+, for ships capable of independent operation in all ice conditions and therefore reducing the need of icebreaker assistance in some ports. These ships could also be granted "icebreaker status" and their higher operating costs could be partially covered by government subsidies from the same funds that are used to cover the cost of icebreaker assistance.[2] As of 2011[update] the new ice class has not been implemented in the Finnish-Swedish ice class rules.
The current Finnish-Swedish Ice Class Regulations were issued in 2010 and apply for ships contracted for construction on or after 1 January 2012.[6]