Monday, October 25, 2010

October 23rd, 2010

Cologne Germany What appears to be a Speirings 599-AT5 has suffered a jib failure causing about half of the jib to fall into a tree and dangle from the pendant. No injuries were reported in the accident. The building was struck which will require some repairs.

The Speirings Cranes are mounted to an All Terrain Mobile crane frame. They are very convenient for jobs that don't need a crane full time. If you have a wood frame building maybe you only need a crane a couple days a week. The Speirings Self-Erecting Tower Cranes can drive in, set up in about 30 minutes, make your picks for a few days then be off the payroll while the carpenters frame the floor.

The downfalls to using a crane in this manner come in the form of wear and tear on the cranes. In particular, if you have jibs being folded over and over, what kind of wear are you putting on the connecting pins on these lower chords and through the pendants? Are you looking at them every year or so to be sure that you aren't getting wear that wouldn't be visible without dismantling the connection?

At the end of boxed jib chords you'll find that the male and female pin connections are welded into place. often these welds are ground smooth so it's hard to notice that it's a weld, but it's a weld nonetheless. Cracking can certainly occur there and since it's not an obvious place to look, it can be overlooked in a normal inspection. You have to also be cognizant that you have layers of steel moving at these joints. they can bind on one another or drag also causing undue stress that you may be unlikely to see during the normal crane erection process.

I prefer to walk the jibs of self erecting cranes after they are folded out. Trust me, I don't like it because the jibs are tiny, not designed to walked on so foot placement is akward, and the bouncing at the tip is interesting at times. But I've found trolley ropes out of their sheaves and other problems that are likely to only be found after folding out. The picture is low resolution, but I'd like to see a close up of the but of the jib section that broke. I really wonder if there might have been pin walk. It's something that I look for. Pins in holes have a tendency to walk in or out during "action". Tie in collars pins are really bad for this. Sometimes tower pins do this as well. Even with a keeper in place, you'll want to see if the keeper is deforming or marring showing that it's under stress during the folding process. Since no obvious structural damage is evident on the lower chords, from the poor picture quality, is it possible that one of the pins simply sheared it's keeper than walked out? Just a final concern and something to watch for.

The likely crane that failed.

Turmdrehkran Unfall

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