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October 2011 www.sname.org/sname/mt VESSEL REPORT: PLATFORM SUPPLY VESSEL VESSEL REPORT Norway was among the first countries to take concrete measures to combat global warming. The Kyoto agreement was signed in 1998 and ratified by the Norwegian gov- ernment in 2002, and environmental awareness was high on the nations agenda as the new millennium began. It is not surprising, therefore, that when Eidesvik Offshore ASA, the Norwegian shipping group, began planning a new platform supply ves- sel (PSV) with Wärtsilä Ship Design, sustainability and a minimized carbon footprint were key items of discussion. This is not surprising, as the vessel was to be chartered to Statoil, the Norway-based inter- national energy company that routinely follows the policies of the Norwegian government. Viking Energy , designed by Wärtsilä Ship Design and built by Kleven Verft in Norway, was deliv- ered in 2003. e most tangible result of the design discussions was that it was tted with four 6-cylin- der Wärtsilä 32DF dual-fuel engines, making it the worlds rst PSV to be powered by liqueed natural gas (LNG). However, the engines can also use die- sel oil as a backup fuel, thus providing valuable fuel exibility benets. e switch between fuels can be made automatically without loss of power, ensuring safe operation of the vessel at all times. This dual-fuel capability means that when run- ning in gas mode, emissions of nitrogen oxides (NO X) are reduced by 85% compared to diesel operation. is is because the Wärtsilä 32DF engines operate on the lean-burn principle, which implies that the mixture of air and gas in the cylinder contains more air than is needed for complete combustion. Since lean combus- tion reduces peak temperatures, the formation of NO X is greatly reduced. Furthermore, sulphur oxide (SO X) emis- sions could be completely eliminated as gas contains no sulphur, and since natural gas contains less carbon per unit of energy than liquid fuels, emissions of CO 2 are also lowered. Natural gas has no residuals, so the production of particulates is practically non-existent.