The crane is lifting entire sections of the new ships from their transport supports onto specially designed cradles where they are pieced together. This "blocking build" method not only requires high capacity, but also finite precision as each block must be positioned in exactly the right place, as Kelvin Kent, general manager for Manitowoc in Australia, explains.
One recent lift at the project involved a 200 t block that was lifted, rotated and aligned within an accuracy of 2mm – an impressive feat considering the section measured 18m by 12m by 7 m. The entire operation took an hour and a half to complete.
Each Air Warfare Destroyer is 146 m long, 18 m tall and weighs more than 6,500 t. So the right crane for the job had to offer both reach and strength. The 21000 has 109 m of main boom in its standard configuration, but with the MAX-ER attachment, it can be fitted with up to 146 m of main boom. The crane is also working with a specially configured sling that ensures the over-sized loads remain level when in the air.
Although a very large crane, the 21000 has a relatively small footprint of just 14.5 m x 14 m with a tail swing of 18 m including the MAX-ER attachment. This makes it ideal for working at the busy and confined shipyard.