Wednesday, December 15, 2010

October 23rd, 2010

Yibin China. On October 23rd, 2010 there was a boom collapse in Germany. All of the way on the other side of the world, China lost an entire superstructure of a crane killing 3 and injuring 4.

Looking at the picture of the crane, Three things strike me as things that I really want to see in person.

  1. Why does the tower go from nasty old tower with no corrosion protection (paint) on it to a new looking tower? 
  2. Why is just that one tower fractured and do we not see any other damage? 
  3. Was this crane being climbed or did the mast bolts snap without even damaging the one side of the structure?
Besides the obvious point that any self-respecting contractor would not be pleased with the obvious state of disrepair of the paint on the crane, The different color makes me wonder if the mast was a knock off by a manufacturer other than the original manufacturer. You can buy Korean Liebherr Mast sections. You can buy You can buy Chinese Comedils. Chinese Tadano's. What I'm getting at is that there are tons of knock off's out there. Do they do engineering or do they just mock up what they see? Do they use the same materials in terms of grade and quality of production? A mast section that fits and looks right, may not be right. (I'm not adding pictures or naming names for obvious reasons.)

I assume that the one tower is damaged because it was of poor quality. I can't imagine another reason that enough welds failed to leave the one side standing perfectly vertical but the other three sides look like toothpicks. We are talking about welds with incomplete fusion from the factory.

I have to go with the idea that this crane was being climbed at the point of the accident, and here's why. Mast bolts do break as a cause and during accidents. But again, we have a side perfectly vertical still. By contrast, In the first New York accident, the point that struck the building next door on the mast ripped the steel column off on one of the sides instead of breaking the bolts. The clamping forces on these bolts are designed to be so strong that there is no way you could fold the tower on three sides and have the bolts simply break on the one side left without buckling it severely.

China continues to make poor decisions on their cranes, but more importantly we see structural failures time and again. Not all of these cranes are that old either. They are just so poorly designed and the materials are subpar. My only regret is that I don't know the models and manufacturers to start tracking which ones are failing how and why so that they can be avoided. Until that's revealed, I would just recommend not going near a Chinese crane at all.

Original Link


No comments: