Aker Arctic says although less costly, Aurora Slim has a number of advantages compared with the Aurora Borealis design (shown here)
Consortium (Ericon) had planned to build a highly sophisticated Polar class research icebreaker, Aurora Borealis. The design would have integrated three different vessel types: an icebreaker, a drillship and a research vessel, but fell foul of the financial crisis in Europe. It would have cost around €800 million had it been built. The European Commission may have dropped the idea for now, but as Mr Niini said, a lot of good work and results were achieved in the project, and in 2011 Ericon asked Aker Arctic to study a more cost-efficient version of the design. Mr Niini explained that one particularly
important step towards helping to make the vessel smaller was ABB’s commitment in 2011 to develop a new range of Azipod propulsion products, including a 15MW Azipod that would meet Polar class ice-class requirements. The new, smaller vessel has been dubbed
‘Aurora Slim.’ Whereas Aurora Borealis had two separate moonpools, the somewhat smaller
Aurora Slim would have one; purpose-built, fixed drilling equipment has been eliminated; and the dynamic positioning requirements of the design simplified.
The vessel’s shaft power has been reduced from a total of 81MW to 45MW, with four engines rather than eight, and the shaft lines replaced with azimuthing thrusters. All six retractable thrusters in the original design have been replaced with two tunnel thrusters in the bow; two large deck cranes have been installed, rather than three; fast trimming system will not be required in the new design; and fin stabilisers are not installed. Mr Niini said Aker Arctic estimates that
changes such as these would reduce overall project cost by a third, whilst offering the same level of accommodation on board, along with the same research capability and at least as much space (although the purpose-built drilling rig has been eliminated). The new design would have increased performance in ice and better
container-handling; station-keeping in ice would be possible thanks to the adoption of the azimuthing thruster concept. The revised design has reduced fuel consumption and emissions, a larger tank capacity than Aurora Borealis and reduced draught compared with the original vessel, enabling it to operate in a wider range of areas. Interestingly, in keeping with the growing emphasis on environmentally friendly operations, the vessel could also be configured to burn liquefied natural gas (LNG) rather than fuel oil. “Although
the main dimensions of
the vessel and propulsive power have been reduced”, Mr Ninni concluded, “operational and scientific capabilities have not been compromised. In fact, the smaller vessel has several advantages compared to the original design, such as improved manoeuvrability in heavy ice conditions. The building costs are also considerably lower, and consumption of fuel oil during scientific missions has also been considerably reduced.” OSJ
Lloyd’s Register develops rules for stern-first ships
Classification society Lloyd’s Register has drawn on industry experience to issue new rules for stern-first ice-class vessels. The company says the rules are the first of their type, and answer growing demand for technical support as industry continues to explore the potential of polar transportation routes and new energy reserves in the far north.
The release of the rules comes as more and more ships are being ordered with options such as podded propulsion systems and azimuthing thrusters – products that can improve icebreaking capability and reduce resistance – allowing them to navigate stern first through ice.
www.osjonline.com
“These practical rules are answering a growing demand in the market and include the use of standard operational scenarios to provide designers with a basis for prescriptive rule applications that have been validated with designers and operators of these specialist ships,” said Robert Tustin, Lloyd’s Register’s technical manager for new construction in Asia.
The class society said the interpretation of regulatory and other rule requirements – and validation of strength levels for the hull and propulsion units – were confirmed by a review of the current fleet of double-acting ships, ensuring that practical experience
supported the development of the rules. They offer the following key interpretations:
• the ship is considered as a bow-first and stern-first vessel for application of ice-class rule requirements for hull and machinery • it is also considered as a stern-first ship for the application of navigation-related rules and regulations • in other cases, the rule applies to bow- first ships only.
The rules also include a framework for alternative-load scenarios when unusual operations are envisaged, as well as interpretations of international regulations and classification rules based upon industry precedents, said Mr Tustin.
Offshore Support Journal I June 2012 I 69
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