GL prepares for the Arctic


Moves to exploit resources within the Arctic Circle, and the fact that ice cover is melting has led to the opening up of the Northern Sea route, and in consequence an increase in the number of ice class vessels required to operate in demanding conditions, writes Sandra Speares.


Dennin, the “tanker market especially, has seen the number of vessels with some kind of ice class balloon over the last five years. Other sectors, be they fishing, even expeditionary tourism, will also be developed, but the main focus for ice class at present is in vessels associated with oil exploration, extraction and transport.” As Dennin explains: “Preparing a vessel


A


to operate in ice-covered waters requires a great deal of attention, many if not all of the features of the vessel will have to be changed in some way. Te hull structure must be designed to resist the global and local ice loads characteristic of its ice class. “The extent and magnitude of local


ice loads for the different hull areas and appendages depend on the various ice interaction scenarios upon which the design of


the ship is based. The


uncertainty associated with ice loads is relatively high compared to sea loads and so the design of the ship structure has to incorporate some strength reserve to limit damage from accidental overloads. Higher material grades suitable for low temperatures have to be used and special abrasion-and corrosion-resistant coatings are required.” Key machinery needs to be designed for


operation in ice, he says, with particular emphasis placed on the ice loads on propellers and the entire propulsion line. Not only do engine output requirements need to be established for independent or escorted operations, but deck and auxiliary machinery systems also have to be designed taking snow, ice and the expected low temperatures into account. Other pieces of equipment including


deck machinery and steering gear have to operate in low ambient temperatures, he explains. Ballast tanks above the waterline need to be heated and vent pipes, sea


The Naval Architect January 2012


ccording to class society Germanischer Lloyd’s business manager for polar shipping Justus


GL takes a closer look at ice classification.


chests, intake and discharge pipes and associated systems have to be designed so that blockage or damage due to freezing or ice and snow accumulation is avoided. Even electrical installations and safety systems require special attention. When operating in hostile climatic


conditions, loss of essential services or control systems could be catastrophic. Emergency batteries have to be protected from low temperatures and the danger of explosion when gas ventilation is restricted by the accumulation of ice or snow, Dennin says. Te basic arrangement of an ice class ship has to take into account special subdivision and stability requirements due to icing, damage and/ or ramming, as well as accommodation and escape measures, and anchoring and towing arrangements. Given the expense of providing salvage


and towage services in such inhospitable conditions,


ensuring maximum


redundancy for any ship operating in Arctic or Antarctic waters is vital, and whether or not salvage companies will


decide to provide services in these conditions will depend on whether the demand is there. Operation of ships in polar waters


has been extensively discussed at the International Maritime Organization (IMO) design and equipment subcommittee this year, and further discussion is expected at the next DE meeting in February 2012. The International Association of


Classification Societies (IACS) will be putting in a paper to the next meeting, which Paul Sadler of IACS says will be considering the format of the new Polar Code including its goals and prescriptive requirements. IACS has already submitted a number


of papers to the IMO on issues like powering requirements for ice class vessels operating in polar waters, ice certificates and descriptions of polar classes, which Mr Sadler says have been taken forward in working group meetings. Polar classes, for example take into account whether the ship is operating


35


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