Tuesday, January 11, 2011

February 3rd, 2009

Malaysia A luffing Tower Crane suffered a boom collapse while lowering a load. In the report given, no injuries are reported.

The picture leaves the crane a bit distorted, but the lower crane was the Luffer. Apparently taller crane, the Hammer Head swung into the luffer while it (the Luffer) had a load on the hook. The contact caused the boom to collapse. It's not clear if the Hammer Head had a load on the hook and thought that he was clear or thought that just the hook was clear and was swinging past but the hook acted like a wrecking ball on the jib. A solid strike on a loaded boom chord with even an empty block could certainly collapse a boom.

As operators we get into a hurry. There are always pressures. The Hammer Head operator has a to be sure to be clear of the lower crane. He could certainly hoist over the lower crane, trolley out past it, or swing left rather than right. Contacts happen between very good operators. I've made contact with another crane that swung out of my area then back in with out announcing. I got myself in a hurry and I didn't double check. It's like not looking over your shoulder when changing lanes. I was relying on the radio (mirror) and not taking that half second to just look.

Another potential problem goes to job and crane planning. When using Luffers with Hammer Heads, it's important to keep the boom of the lower crane out of the air space of the Hammer Head at the slewing level. It might be difficult to plan around that, but it is a cost of having the two cranes on site. Certainly you can check the clearance on the forward jib, but with counter jib and weights hanging below the jib, there maybe little to not visibility, and even less forgiveness if you were to contact a heavily loaded crane boom.

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