Author(s): Arnor Jensen; Basile Bonnemaire; Sveinung Loset; Kare G. Breivik; Karl U. Evers; Ola Ravndal; Vegard Aksnes; Trine Lundamo; Christian Lonoy
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Abstract: A new concept for offshore offloading in ice-infested waters is tested in the Large Ice Tank at the Hamburg Ship Model Basin. The test scale was 1:24, and the model was equipped with propulsion and a dry mooring system. The concept, Arctic Tandem Offloading Terminal (ATOT), comprises two units; a moored offloading icebreaker (OIB) and an offloading tanker moored in tandem. The three basic operational modes of the ATOT are; the OIB moored alone, close loading mode and distant loading mode. These modes are related to the following physical environmental conditions: 1) the OIB moored alone in severe ice conditions, 2) close loading in medium and heavy ice conditions, 3) distant loading mode in light ice conditions and open water. The system is disconnectable making it promising for year-around operation in challenging environments such as the Eastern Barents and Kara Seas. The OIB is connected to a sub-surface turret mooring and riser system while the tanker is moored on a dry mooring through deck winches on the OIB. The OIB is a purpose designed vessel for operation in ice with azimuth propulsion units fore and aft with an installed power of 20-40 MW depending on the ice conditions to operate in. The sub surface mooring system of the OIB contains a heavy duty spread mooring system with a preliminary horizontal station keeping load capacity up to 40 MN. The mooring system will be connected via a quick disconnectable turret system to the OIB. During the summer of 2007 a series of model testing of the concept was performed showing promising capabilities.
Year: 2008