Monday, November 1, 2010

March 29th, 2009

Miass, Chelyabinsk Region Russia As a tower crane was being disassembled the jib collapsed. fortunately no one was injured in the accident and it sounds as if only the crane was lost. 

The collapse happened after the counterweights  and what sounds like the base ballast were removed. The contractor is asserting that a unforeseen Gale Force wind came up causing the crane to fail. They are being forced to assert this as the insurer is questioning the collapse. Article about the insurer's concerns. Then there is a second article a few days later that asserts that the winds never occurred. (The picture is from the second article and I'm not clear if that's the crane that went down or just a stock photo because it doesn't match the story exactly.) 

What strikes me as relevant is I don't know of a manufacturer that would, or does, suggest to remove the ballast prior to removing the horizontal superstructure. I mean really, we are talking about the the greatest overturning stresses on the crane being induced during this process and you want to remove the ballast that is designed to prevent that? Shy of removing the knee braces (if so equipped) and the final tower section, the ballast is the next to last thing to remove. Remove all but the final tower, pull the ballast, braces, tower then the cross base. This is the normal process for the four different manufacturers I've seen with cross bases. So if you remove the ballast, you certainly won't need a gale force wind to cause the tipping of the crane. 

More importantly, I have a question about what is going on in Russia. They seem to be acting as if wind is always an excuse for losing a crane. Here we have two downed in a legitimate wind storm. Here we have another just a few days later downed in what may have been a wind storm. Wind will occasionally happen and down a crane. There are weather events that you cannot prepare for. In this case, it sounds as if it's a easy reach for a crutch rather than simply fessing up to the reality, that you removed the ballast out of sequence.  

 крах башенный кран,   аварии башенного крана 

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