Ice navigation vessel

Ice navigation vessel is a class of ships specially prepared for independent ice navigation in the waters of the polar seas and for following icebreakers in especially difficult ice conditions.[1] Various registration authorities assign ice classes to vessels based on their technical characteristics.[2] Due to this, ice navigation vessels are usually referred to as ice-class vessels without indicating which class they belong to, but indicating the type of vessel (e.g. ice-class tanker, ice-class cargo ship etc).[3]

Cargo ship navigating in ice, Gulf of Bothnia
Icebreaking bow of the tanker Timofey Guzhenko
MT Alma with bulbous bow and icebreaking stern

Description

The geometry of the hull contours of ice navigation ships is intermediate between the contours of an icebreaker and the shape of a conventional transport vessel. The reliability of any vessel of this type is determined by their ability to withstand the loads acting on them while sailing in ice at a given speed, as well as the loads from compression by ice masses.[4] The target capabilities determine the requirements for enhanced capacity of its engine, the strength of the hull, propellers, propeller shaft and steering gear. It may also include adaptations for functioning in freezing conditions and equipment necessary for navigation in ice.

Double-acting ships
Main article: Double acting ship

One of the varieties of this type of vessels are double-acting ships. To move through the ice, they use the combined effect of the ice-breaking shape of the ship's stern and the effect of the propellers on the ice. These vessels may have the usual bulbous bow and may be capable of moving in ice only astern. An example of such a vessel is a tanker Alma. Since ice sailing astern also eliminates the stress on the hull that occurs when breaking ice in the classical way, this type of vessel has advantages. Due to the icebreaking use of their stern, it is impossible to equip these ships with a conventional rudder and they can only be driven by rudder propellers.

References
  1. "СПГ танкеры: перевозка сжиженного природного газа в Арктике | // LNGas.ru" (in Russian). Archived from the original on 2017-12-31. Retrieved 2017-12-30.
  2. Unified Requirements for Polar Class ships Archived 2012-06-20 at the Wayback Machine. International Association of Classification Societies (IACS), April 2016. Retrieved 2017-03-11.
  3. BySubhodeep Ghosh (January 1, 2021). "Understanding Design of Ice Class Ships // Naval Architecture". Marine Insight - The Maritime Industry Guide. Retrieved 2023-03-15.
  4. "В ледовых условиях" (in Russian). morvesti.ru. Retrieved 2023-03-14.
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