23.07.2009

How not to move a 1,350 tonner over soft ground

A 1,350 tonne Liebherr LR11350, crawler crane has tipped over as it tried to move across soft ground while fully rigged. The unit, the first of this new crane to be shipped, was originally delivered as the LR11250 to a Chinese company for power station and petrochemical work.

The model designation was changed after the later production models were renamed following conclusion of the full test programme.
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The massive crane before the accident

The crane has been busy since it was delivered back in 2006, most recently working on a nuclear power plant in Guangxi Zhuang, southern China, where it is reported to have carried out a tandem lift with a more recently delivered LR11350-1.
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In the mire big time - note the mats under the tracks

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Amazingly the boom and jib structure prevented the crane going the whole way

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As the track tip reached the edge of its little mat it sunk into the soft ground

Looking at the photos which have been fairly widely circulated, it would appear that the relatively small steel mats were laid end to end and hardly improved the cranes floatation, rather than laying then laterally. Additionally the almost horizontal luffing jib would have helped transfer weight forward and it appears that the superstructure has been slewed slightly placing more of the load on the front of one of the tracks.
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The jib tip sunk into the soil and helped support the crane

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The ground conditions were far from ideal

All would have helped cause the front of the machine to sink, as it went over some of the counterweight sections have fallen off, making the crane even more front heavy. The jib tip buried itself in the ground and the crane was prevented from tipping all the way.
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The superstructure was slightly off centre