Lifting Cranes
Created | Updated Aug 5, 2015
Just hope there are no casualties1.
A pet dog was not retrieved alive.
One taken to hospital, rescued from 'under' the debris, hurt his hip.
It seems the hip was already bad before entering the shop2.
None missing.
Accident on the Rhine3
Two cranes each on their own pontoon tried to lift a bridge part. This leaf of a bascule bridge4 had to be replaced. The leaf had arrived on its own pontoon and was resting on a support structure keeping it near vertical. Two essentially mobile cranes6 with their outriggers fully extended just fitting between the boards each hooked to a side. As soon as they took the weight of the leaf one started to turn away dragging the leaf into a swing. The rotating crane fell on the houses lining the shore. The leaf followed as well as the second crane. Three shops and four apartments above were completely collapsed. The cranes also hit the first floor of an apartment across the street.
Mail online reports external news site as long as the external site lasts.
How to Hoist a Heavy Load on a Pontoon Crane
Make sure the crane is fixed secure to the pontoon and can not slide. Any motion you make should be compensated with ballast in the pontoon. You cannot just swing a load from one side to the other.
When using two cranes, each on its own pontoon, move even more slowly then with one crane. Not only the pontoon on which the crane is moving has to refit the ballast, also the other pontoon has to refit ballast.
Using Ballast in a Pontoon
_____
/| |
/ | |
/ | |
____________/___| Load
|1|2|3|4|5|6|7|8|
|_|_|_|_|_|_|_|_|
For simplicity lets assume the pontoon is 12 metres wide 4 metres high and 32 metres long. Over the length we have 8 compartiments inside over the beam we have 4. Each compartiment will have a volume of 4*4*4=64 cubic metre, filled half7 32 tonnes of ballast. For stability we start off with all compartiments filled with 1 metre of water. A total of (1*4*4)*8*4 = 5632 tonnes just to sit in place. The crane we assume is 32 tonnes, to compensate we reduce some ballast in row 7 and 8 and add some in 1 and 2. The level in 7 and 8 would be about 87 centimetres. The level in 1 and 2 about 112 centimetres.
Now we start to lift with the crane. For each tonne we lift we have to pump some 1000 litres of water out of the pontoon. Lets assume the load is 32 tonnes, we now have to reduce the levels in 7 and 8 by another 12 cm. As we work together with two other pontoons we do want to keep levelled, instead of adding water in rows 1 to 4 we reduce rows 5 and 6 also by some 12 cm. Nobody has ever told it was an easy job, nobody would assume lifting half a bridge is a piece of cake and can be done in an hour. Pumping the water around in the pontoon goes rather slow, checking the assumed volume in each compartiment and checking the overall balance takes hours.
Observations
After some study of the video I have to conclude there is no use of ballast whatsoever. As well as the cranes are using outriggers and panels to level them and spread the forces over the deck of the pontoons. No significant fixation of the cranes to the pontoon is used.
Both cranes have their individual ballast stacked behind the rig. During the actual hoist, the taking over of the weight from the third pontoon, the ballast in the crane pontoons was not adjusted.
Data Research
The pontoons of the 'Lastdrager' series should be capable of holding ballast. The ballast tanks are all in other arrangement then suggested; two or three tanks over the beam and five to eleven rows over the length, all in range 50m3 to 100m3. As we only need the exact arrangement to calculate the actual required ballast the used model is adequate.
Preliminary Conclusion
One of the cranes got stuck in a rotating motion. Either the controls failed, the hydrolics failed or the brake failed.
