Ships transporting different liquids have been around for as long as there has been the need to trade between countries and nations. The first liquid transport happened in drums loaded into the ships like any cargo. During the last 120 years as ships have been built of steel/iron it has been possible to transport liquids in tanks built in to the structure of the ships.

During the 20th century cargo ships sailing in ice were assisted seasonally mostly by icebreakers. Most of the liquid transport did not really need any assistance in ice conditions as there was hardly any winter traffic. The continuous need for utilizing oil lead to new territories and the oil discovered in Alaska in the late 1960ies brought up the crude oil transport in ice conditions and Esso started the Manhattan project. This unfortunately did not start the arctic tanker transport. This paper discusses the development history of the propulsion of tankers working in ice conditions.

In the early 1970ies the winter traffic in Finland exploded as the Finnish government decided to keep all the major ports open year-round. This started serious development of ships capable of more independent ice operation. The first propulsion solutions were modifications of well proven technology. We had fixed pitch and controllable pitch propellers connected directly to low speed diesel engines or through a gearbox. In some applications the propeller was equipped with a nozzle. In the 1970ies and 1980ies we were already drafting different tankers with electric propulsion with huge power. However, it was needed a decade more and the development of the propulsion devices from direct shaft lines to azimuth devices to get the propulsion revolution going at full speed.

Today we have available and most commonly used; traditional fixed pitch propellers with conventional shaft lines, mechanical Z-drives and podded propulsors driven by electric motors. The operational profile and mission of the vessel will dictate how the tanker will be furbished.

Most of the new concepts have been tested and developed in conjunction of icebreaker development, where tankers have been closely following. Recently there have been delivered and designed new icebreakers, icebreaking shuttle tankers and LNG carriers. Many of these vessel concepts are relying on podded propulsion system. AZIPOD propulsion has been selected to many of these vessels as it provides excellent ice performance for the vessel, good torque characteristics for the propeller and there already exists proven track record of ice operations. This paper will introduce some outstanding full-scale experience from the revolutionary icebreaking LNG carrier Christopher de Margerie.

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