Dismantling Concrete Crane Devonport Editorial Image

A major engineering project to remove what is believed to be the largest crane in Western Europe has been completed at Babcock Marine`s Devonport Royal Dockyard in Plymouth.The 1,450-tonne Stothert & Pitt hammerhead cantilever crane, built in the 1970s and used by the Royal Navy to refuel submarines, had come to the end of its design life. The crane had a 120m-long steel jib structure supported on a slew ring, mounted on a concrete plinth built on four 2[m.sup.2] reinforced concrete legs extending down into the bedrock.Various methods of removal were considered, with Dutch heavy lifting specialist Mammoet eventually chosen to carry out a `one piece` removal. Four bespoke jacking brackets were attached to the crane, through which the jib was jacked up and raised clear of the slew ring, using specialised jacking and skidding equipment.The jib was then hydraulically slid on to supporting beams. It was then lowered, inch by inch, on multi-strand cable jacking units, on to a barge. Once secured, the barge and crane jib were towed away and offloaded at a ground-level location in another part of the dockyard.