Finnish-Swedish ice class

During the winter months, Finnish and Swedish authorities may declare traffic restrictions in the Northern Baltic Sea in order to ensure that ships operating in the region are capable of navigating in ice-covered waters safely and efficiently.

The Finnish fairway dues, a system of fees charged for using sea lanes to cover the costs of management and icebreaker assistance, also depend on the vessels' ice class.

[1] Ships must fulfill certain design requirements in order to obtain the ice class from the Finnish and Swedish authorities.

It was primarily intended to increase the safety and set a number of requirements for passenger ships operating regularly in winter conditions.

These included double bottom in way of the engines and boilers, construction according to the rules of Lloyd's Register or Bureau Veritas, at least five transverse watertight bulkheads, and sufficient damage stability to survive the flooding of two compartments without sinking.

According to the rules the ships were to pay "ice fees" according to their net register tonnage, classification and strengthening for navigation in ice during the winter season, which began on 1 December and ended on 16 April in the Gulf of Finland and in the Bothnian Sea, and from 1 November until 1 May in the northern parts of the Gulf of Bothnia.

[7] The ice strengthening of the hull was defined as a percentage that was added to the minimum requirements set by the classification societies, such as 45% increase in shell plating thickness.

Shortly after the work started the Swedish Maritime Administration joined and the new regulations, published in 1971, became known as the Finnish-Swedish ice class rules.

Instead of percentages and experience the minimum requirements were based on plastic deformation theory and pressure loads determined from observations of past ice damages in the Baltic Sea.

[6] The current Finnish-Swedish ice class rules were issued in 2021 and are applicable to ships contracted for construction on or after 5 July 2021.

Older ships are generally required to follow either 1971, 1985, 2002, 2008, 2010, or 2017 ice class regulations depending on their contracting or keel laying date.

However, minimum requirement for engine power will become retroactively applicable to ships of ice classes 1A and 1A Super laid down before 1 September 2003 latest at the beginning of the year when 20 years have passed from the delivery of the vessel and ships failing to meet the requirements will have their ice class downgraded.

Product tanker Georg Essberger waiting for icebreaker assistance outside Loviisa in the Gulf of Finland . Its ice class, 1A, fulfilled the minimum requirements of the traffic restrictions at that time and the ship was escorted to port.
Cruiseferries sailing on regular routes between Finland, Sweden and Estonia are usually built to the highest Finnish-Swedish ice class, 1A Super. Due to their high engine power, the cruiseferries do not normally require icebreaker assistance.
When operating alone, pusher Rautaruukki has the same ice class as the integrated tug and barge , 1A Super, but the unpropelled Kalla is downgraded to ice class 3.
Double acting ships capable of independent operation in ice, such as Mastera , could be eligible for the proposed new ice class 1A Super+.