DAS is described in greater detail in section 4.1.3.
Paints for icebreaking ships
The hulls of icebreaking ships are often painted with special paints specifically developed for use in ice. These paints are especially used on the stem and the ice belt, which are in most frequent contact with the ice. One of the purposes of these specialized paints is to protect the shell plates of the hull. The Arctic Ocean poses an exceptionally harsh environment for protecting the shell plates from wearing and corrosion: In ice-covered waters, the shell plates are constantly exposed to contact with ice under intense ice pressure, scraping the paints, while the high concentration of dissolved oxygen in the water accelerates the corrosion rate of the shell. To withstand these tough conditions, the paints for use in ice need to be durable and resistant to peeling, and should also serve to reduce the friction between the hull surface and the ice. When an icebreaking ship is in the process of icebreaking, various forces act on the ship, but friction force between the hull and the ice is one of the most important. Several kinds of paints for particular use in ice with low friction coefficients are being developed and put into use, since ice friction depends heavily on the characteristics of the hull surface. In Finnish and Russian icebreakers, use of stainless-clad steel plates in the ice belt was tested, to improve resistance to wear and corrosion and to reduce the friction between the hull and the ice as well. The stainless-steel surface can provide a paint-free ice belt, but the electric potential difference between two different metals quickens steel part corrosion. Additional anti-corrosion systems were therefore adopted in these cases.
(2) Regulations and classifications of icebreaking ships
Ships are generally divided into a number of categories according to type and function. To ensure the safety of all types of vessels, each vessel is subject to various rules and standards regarding appropriate use of the vessel, the environment and other issues, as established by the classification societies and other organizations. The structural and machinery requirements for icebreaking vessels are established by several classification societies, including the Russian Register of Shipping (RR), Lloyd's Register of Shipping (LR), the American Bureau of Shipping (AB), Norway's Det Norske Veritas (NV) and Nippon Kaiji Kyokai (NK). In addition, responsible government agencies establish rules for the ship and operations in ice with respect to the Baltic Sea, the Canadian Arctic and the NSR. The Baltic Sea is governed by the Finnish-Swedish Ice Class Rules (FSICR), while the Canadian Arctic is regulated by the Canadian Arctic Shipping Pollution Prevention Regulations (CASPPR). Furthermore, Russia has proclaimed the "Regulations for Navigation on the Seaways of the Northern Sea Route." For detailed information on the design and fittings requirements of Russian icebreaking ships, see section 4.3.3.
In these classification society regulations, ice-transiting ships are graded into "ice-strengthened ships" (also called "ice-worthy ships") and "icebreakers" according to the ice conditions they are likely to encounter, the seas they navigate and their icebreaking capability, and appropriate rules are applied for each (Table 4.1-1). Ice-strengthened ships and icebreakers are further divided into several ice classes. The term "ice-strengthened ship" suggests a ship with sufficient durability to withstand the pressure of surrounding ice, which implies that all ice-transiting ships are ice-strengthened ships. In fact, the expression is used to contrast these ships with ships that are capable of serving as icebreakers. Icebreakers are vessels whose purpose is to provide support and emergency assistance for other vessels in ice-infested waters and/or to conduct various monitoring and research tasks, and which are made capable of such service by their durable structure and their function of conducting unescorted operations in ice at any time. Most ice-strengthened ships, in contrast, have cargo holds and are designed to operate under rather easier conditions than icebreakers, satisfying the minimum conditions of specification and outfittings to navigate in ice-covered waters. In a practical sense, however, the regulations to classify the vessels into icebreakers and ice-strengthened ships offer only a rough guideline, and the choice of a ship classification is often dependent on the decision of the ship's owner.
