Double Acting Technology (DAT)
During winter tests of the Artic tanker UIKKU, it was found that a ship with an Azipod and well designed stern generally performs much better in heavy ice condition when going astern. This conclusion led to the stern-first ice-breaking concept developed by Kvaerner Masa Yard, s Arctic Technology Centre (MARC) in order to combine the best of open water performance with superior ice navigation capabilities. In the DAT design, the vessel has its bow optimised for open water conditions, with stern designed to break the ice. This design is possible only when the rudder is replaced with an azimuthing propulsion unit – the Azipod. With this design, the vessel has a performance in open water, which is equal to that of any other vessel and with icebreaking characteristics superior to those of any icebreaker.
Two ice-strengthened, Azipod-equipped supply ships ARTICBORG and ANTARTICBORG delivered for the Caspian Sea service in 1998 were the first newbuildings to implement the double-acting concept. In 2002 and 2003, the concept moved into commercial shipping when two Aframax Artic tankers TEMPERA and MASTERA were built. The combined icebreaker/offshore supply/support ship FESCO SAKHALIN built by Aker Finnyard in 2005, is the first large example of an icebreaker built according to the double-acting principle.
Further step in DAT concept are two 70 000dwt shuttle tankers that will be built at Admirality Shipyards in St Petersburg for delivery at the end of 2007 and 2008. Each will have an overall length of 260m, breadth of 34m and draught of 13.6m. The diesel-electric power plant consists of four main diesels providing 25MW total power, split between twin pod drives, each of 8.5MW.