21/08/2012 - 13:51 pm

Crawlers work in tandem to lift ring gear for crane vessel


Engineering service provider Penglai Jutal recently lifted a 330-tonne ring gear for a crane vessel onto a cargo ship on behalf of Cosco Shipyard. A pair of Terex crawler cranes—a model CC 6800 and a CC 2500-1—worked in tandem.

The load, with dimensions of approximately 15.3m x 18.6m x 15.6m, had an awkward centre of gravity, making it necessary to balance the ring gear with perfect precision in order to perform a safe lift.

“This is where the precise and easy-to-use IC-1 touchscreen control system in both cranes proved to be absolutely invaluable, as it enabled us to perform a perfectly synchronised tandem lift,” says Mr. Chen, the Penglai Jutal director responsible for the project. Load moment indicators showed the crane operators how much weight was on their hooks at every moment during operation.

The CC 6800 was set up with an SSL configuration, a 90m-long main boom, a 40.5m-long Superlift mast, a working radius of 24m, a superstructure counterweight of 250 tonnes, and a central ballast of 80 tonnes. The CC 2500 was also set up with an SSL configuration but with a 72m-long main boom, a 30m-long Superlift mast, a superstructure counterweight of 160 tonnes, a central ballast of 40 tonnes, and a working radius of 15m. In order to pick up the load safely and with stability, the two crawler cranes worked with spreader beams.

The two cranes lifted the load to a height of approximately 4m, and then travelled under load in the direction of the cargo ship. While the CC 6800 stopped and slowly lowered its main boom, the CC 2500-1 kept moving forward until the load was at a working radius of 24m relative to the CC 6800. The two cranes then continued travelling forward together until they finally brought the ring gear to the desired position above the ship. The cranes lowered the ring gear onto the deck and secured it to the cargo ship.

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