Each steel block is built from smaller ‘sections’ that are welded together, and made up of a combination of steel plate, structural steel bars (‘stiffeners’) and ‘bulkheads’ — upright walls within the hull.
Australian Antarctic Division Icebreaker Project Manager, Nick Browne, said a number of high tensile grades of steel are being used to ensure the ship can cope with freezing Antarctic temperatures.
“The grade refers to the strength and toughness of the steel to withstand the cold, before it becomes brittle and loses its ability to withstand impact,” he said.
“Above the water line the steel can withstand temperatures down to −40°C, but it’s optimised for −30°C, while the steel below the water line can withstand −10°C.”
Before any steel plate is cut, computer software is used to arrange the shapes of the parts that need cutting, to minimise wastage. A combination of laser and plasma technology and high pressure water is use to cut the plate, some of which is 130mm thick. Any leftover steel is melted down and reused in new plates.
After the parts are cut they are welded to big panels of deck plate. Then the steel bars or stiffeners are added to create a skeleton, and the outside of the hull, called the shell plate, is welded over the top.
Once a block is complete, it is painted and moved from the construction warehouse to the dry dock, where it is craned into place. It can then be welded to other blocks in a process known as consolidation.
“The keel consists of three blocks and was the first part of ship to be consolidated in August 2017,” Mr Browne said.
The block construction method allows the shipyard to build different parts of the ship at the same time, to make best use of the resources (labour and yard space) available. At Damen Shipyards in Romania the block sizes are limited to 300 tonnes, which is the lifting capacity of the cranes.
“The building strategy broadly reflects the cranes’ lift capacity,” Mr Browne said.
“It will take 58 building steps to produce 229 sections that will be consolidated into 57 blocks. There are so many sections because the steel is thick and heavy, due to the structural requirements of icebreaking.”
Because of its weight, only about half the ship will be constructed in the dry dock, before it is floated out to a wet dock for completion.
“The ship will have a displacement of 25 500 tonnes when complete and a draught — the distance between the waterline and bottom of the hull — of 9.3 metres,” Mr Brown said.
“In the dry dock there’s a gate with a draft restriction of 4.5 metres, so if we tried to build the whole ship there it would get stuck.”
Once the superstructure of the ship (area above the main deck) is consolidated, the fun begins, with the interior fit-out of laboratories, cabins, offices and other spaces. Some interior sections, such as moulded bathroom cubicles, will be prefabricated and simply dropped into place. To save arguments amongst future users of the vessel, the interior decoration is being left to the “professionals” — the ship builders and a Norwegian outfitter.
One thing the Australian Antarctic community can agree on though, is that Nuyina will be painted in an iconic International Orange, reminiscent of the nation’s current icebreaker, the much-loved Aurora Australis.
Australian Antarctic Division