Monday, December 20, 2010

December 11th, 2010

Singapore. Vertikal is reporting that a luffing tower crane in Singapore lost it's boom in the backwards direction over the top of the crane. I have been unable to find any other stories on this and I've been searching since Friday. But at least they have someone confirming the story in the comments.

The crane appears to be a Potain MR 295. They have a up to 60 meters (197') of boom and with the largest hoist package and in 4 part operation they are capable of hoisting 50,000 lbs. I love luffing cranes in terms of operation but they are such a pain in the ass to erect due to so many things going up on a small space. But back to the story. I don't see anything obviously wrong with the crane. The crane is PLC (computer) controlled so I don't imagine that the limits on the boom weren't working. Setting up the upper and lower boom limits are critical and many PLC systems won't let the crane run properly until the limits are set.  So there are three other thoughts that I have.

In Malaysia, we are talking about an island. So winds are always a concern. An unloaded boom up to 80 degrees or more with the crane pointed into the wind could be pushing it. I personally hate looking up at booms when my inclinator is reading more than 80 degrees. They look like they are ready to come over at any time. The booms get into reverse camber and it's just unnatural. I guess it's a Seattle thing where we don't see Luffers up too often. But each crane has wind limits and luffing crane operators really need to be aware of the winds on unloaded booms and the direction they are facing.

Wind is also a problem in making sure that you store the boom at night at the proper angle. In Seattle a few years ago we had a Kroll that was caught in the wind due to too low of a boom angle and the corridor effect in cities where the winds are channeled down the streets in between the buildings. The effect is that the crane cannot properly weather vane and point down wind. I suggest that you do go to the link to see the video to see how fast the crane was spinning. The core point of the boom angle is that at night if the crane does not weather vane and the winds hit the boom while it is up too high, they can be blown over.

The only other thing that occurs to me is the load line or rigging failing and inducing a shock load on the crane. The balance of the luffing booms that have failed seem to be from heavy winds. They find a way to get blown over backwards whether it's brakes dragging, high boom angles, or simply gusting winds. The issues seem to all be avoidable short of hurricanes, but the guys in the field want to get home and the job wants to get the crane up and running. Neither pressures are conducive to making certain that everything is done as well as possible.

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