Friday, June 6, 2008

May 30th 2008

New York a 24 year old Kodiak tower crane suffered a turntable failure causing the collapse of the superstructure, killing two and injuring one.

The turntable in question appears to have been removed from service previously. At this time it is unclear if repairs were made and how. To give the benefit of the doubt, let's assume the cracked weld was repaired. Often a cracked weld is only removed to the point at which you can see the crack with the naked eye. The problem is that cracking often continues well past what you can see with the naked eye. If you do not remove and replace the rest of this weld that is cracked, you could end up with a situation just like this where the crack reappears over a short amount of time and fails catastrophically. Due to the location of the weld, it would be hard to detect on a daily inspection by the operator.

Also a crack in the weld could indicate further micro cracking. Cranes that are 24 years old are subject to metallic problems. How many lifting cycles was the crane designed for, and how well is the steel performing? We often ask too much of our cranes when they are 25 years old when we run them at maximum capacity, maximum speed.

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