End of an era

Demolition contractor Liberty Industrial, based in Sydney, Australia was awarded a contract to dismantle a historic 61 metre high, 250 tonne capacity hammerhead crane at the Garden Island Naval Base on Sydney Harbour, Australia.

Todd Solomon, Liberty Industrial project manager, said, “We were able to engineer an efficient alternative design solution for the Department of Defence, reducing the proposed number of lifts from the planned 250 lifts to 70. Safety was paramount; our design reduced the number of lifts required, greatly reduced our personnel’s exposure to working at heights and significantly minimising the safety risks involved with carrying out the works.”

Favelle Favco M2480D and M120RX luffing jib tower cranes were wet hired from Marr’s Contracting for the project. Its capacity of 330 tonnes out to a 15 metre radius makes the diesel hydraulic M2480D one of the world’s largest tower cranes. It lifts 100 tonnes out to 45 m and can achieve a freestanding hook height of 130 m. The M120RX is an 18 tonne crane (out to 12.5 m radius) and it lifts 2 tonnes at 50 m radius on the maximum 51.7 m boom.

To allow the cranes to free stand, a steel support structure off the wharf was constructed. The lower third of the M120RX was erected using a 55 tonne capacity wheeled mobile crane and a 300 tonne wheeled mobile. The base for the M2480D was provided by Brookfield Johnson Controls. A 230 tonne lattice boom truck crane in conjunction with the 300 tonne mobile crane, were used to lift the boom into position. The tower self-climbed the last 12 m.

Solomon said, “We carried out spray painting and paint stripping works to prepare the crane for disassembly, encapsulating the crane’s existing paint coating with a high build flexible water borne acrylic paint to stabilise any flaky paint on the structure, to prevent the release of lead chromate paint. The acrylic was applied by airless spray to avoid disturbing the crane’s hazardous coating.”

The hammerhead crane was dismantled in large sections, which were rigged to the M2480D and separated from the remaining structure by oxy cutting. The cutting was carried out from a work box rigged to the M120RX tower crane, a spokesperson said. Once separated, the sections were lowered to the ground for dismantling. The largest lift was 65 tonnes.

Solomon added, “We deployed a 33 tonne Volvo EC330LC hydraulic excavator with a shear attachment to carry out the heavy duty downsizing. Oxy cutters assisted to further downscale and process scrap materials, removing paint from the cut locations prior to cutting. The processed components were transported to an offsite recycling facility. An approximate 1,700 tonnes of steel was recycled.”

The project also involved the salvage and restoration of heritage items. Components of the crane including the main hook assembly, hook platform and trollies and driver’s cabin were removed and transported to an offsite facility. A few machine house plant items and some of the slew motor room equipment did not require refinishing and was stored in its original condition.

Solomon explained, “Because of their significance to the community it was imperative these items were not damaged or structurally altered during the removal and refinishing works so we developed a detailed methodology for the removal, relocation, refinishing and storage of the heritage components to ensure their condition was maintained. We even fabricated a specialised frame for the crane’s enormous 25.7 tonne hook assembly so it could hang in its original position. The 25 tonne hook platform and trolley is the largest heritage item to be salvaged. At 7 m wide and 8 m long it was transported under police escort to the storage location.”

Challenges on site included working on a working naval base, restricted working areas and difficult weather conditions. “We were severely restricted for landing loads and the materials processing workspace is limited,” Solomon explained. “Logistics can also be challenging at times. It can be difficult getting trucks with oversize loads in and out of the site. But these factors had been taken into account at the planning stage of the project, and considerate solutions were adopted to minimise disruption and ensure that the works continued unhampered.”