13.05.2013
Another tree another crane
A boom truck went over yesterday in the town of Spotswood, New Jersey as it lifted tree limbs from the back yard of a home.
The crane, a Terex boom truck, was operating with a full boom and extension and lifting a tree limb when the load-side front outrigger sank into the ground – the operator had set it up on the grass near to the house. We believe that the crane is owned by the tree company.
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The crane was working at full stick
As the leg sank into the ground the crane overturned and its boom came down on a wall, damaging the front of a garage building was it went. A lady inside the house was taken to hospital suffering from shock. The crane operator was also taken to hospital, but was not reported to have been seriously injured.
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The crane was set up on grass
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A closer look shows the sunken outrigger
Vertikal Comment
Trees are a minefield for cranes, but in this case it seems that main cause was not the usual overloading due to underestimating the weight of a tree limb, but more related to setting the outriggers up on what was obviously going to be soft ground – lush green grass!
The operator does at least seem to have made an effort with some wood mats, but clearly not sufficient for the job.
Sherm
Miscalculations: 1. insufficent outrigger support...needed poly mats, 2. a counterweight outboard on driver's would have helped offset the weight of the extended boom, 3. limbs might have been pulled closer to the house to reduce the boom extension distance.
This incident reminds me of a new Liebherr crane that was parked on the second level of a concrete parking garage intending to lift a large A/C unit with fully extended boom. Before the load was even hooked on the weight of the boom caused the front outriggers to break through the concrete, then the rear outriggers and the entire crane sank as though in quicksand. It was totalled before it earned one dime.
oops! Sorry guys Not + pressure on one outrigger but: TOTAL WEIGHT OF CRANE(don't forget the extra counterweigt) + WEIGHT OF CHARGE : 4 x 2,5 = PRESSURE ON ONE OUTRIGGER
Know the weight of the charge before you begin to lift. Know the weight of the charge certainly when it hangs in the air or by dismanteling. Because you know guys...it will always come down...
The outriggers on soft ground or grass? Use bigger mats!You can always calculate the pressure on the outriggers. The pressure/cm² under one outigger must be always lower than the resistance of the ground. How to calculate the dynamic pressure? : TOTAL WEIGHT OF CRANE(don't forget the extra counterweigt) + WEIGHT OF CHARGE : 4 x 2,5 + PRESSURE ON ONE OUTRIGGER
Keep it safe guys!
Tmayes
NO COMMENT!!! Lol