22.10.2010
A tree or an outrigger accident
A 70 ton truck crane tipped over and sliced through a house in North Carolina yesterday evening while helping remove a large tree from its back yard.
The accident occurred in the historic district of Gastonia, to the west of Charlotte, while working for Denton Tree Services. The crane, a Grove truck crane owned by AME of Charlotte was set up with the outriggers on the side of the load only partially extended in order to get closer into the building.
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The crane was working with partially extended outriggers
The outrigger beams on the other side - under the counterweight - were fully extended.
The crane had apparently taken the weight of a large trunk section of the tree of that had just been cut, when according to an eye witnesses the “tree started swinging around” causing the crane to ‘teeter’ and then tip. As it tipped its boom sliced through the house, fortunately the only resident present was watching from the other side of the street.
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The fallen crane
An employee of Denton Tree Service was actually in the tree when it went over and jumped clear but suffered non-life threatening injuries and was taken to hospital and held overnight. The crane operator was badly shaken, but not injured.
The 35 metre high tree was being removed as its branches were resting on the house and it was considered to be a safety hazard.
Vertikal Comment
Whether extending the outriggers fully and working at a longer radius would have made a difference, only the operator and crane owners know. Tree removal is a hazardous job, full of unknown and variable factors that make precise planning difficult.
AME prides itself on the training that it puts its operators through and given that the rear outrigger beams were full extended, one has to assume that the operator was working from a partially extended load chart. If so this was a tree accident and not an outrigger accident.
If a larger crane had been used this may also have helped, given the number of crane accidents while doing this sort of work, grossly over specifying the crane will provide a comfort factor.
Mark Krajci
Although it may appear that the crane was set up on short outriggers & it may have been, remember that the outrigger beams will push in as the crane is "stood up" by an overload condition.
This could result in the appearance of the outriggers not being fully extended.
THis is a good example of why the outrigger beams need to be pinned/bolted when this is provided by the manufacturer. All new cranes need the beams pinned at any time the crane is set up!!