A crawler crane in NYC fell over. I came across the investigation's report.
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US Government
[Note that the couterweight stacks remained intact even though the house had been flipped 180 degrees.] |
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Since the accident was that a luffer crane fell straight forward, let me first introduce some terminology for a luffer crane.
This photo shows a Manitowoc 2250 crane in its stowed or parked position because the day was too windy to work. The boom attached to the crane is called the main boom, and the boom attached to the main boom is called the luffer jib. Typically, the main boom is called the boom and the luffer jib is called the jib.
This view allows me to see the tip of the jib. Note the tip of the jib is resting on a block to hold some of the weight when it is stowed.
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| Digitally Zoomed |
This Manatowoc MLC 300 is in a normal operating position. During operation, the main boom stays in a fixed vertical position of around 80 degrees and the radius of the load is changed by raising and lowering the jib.
To lay the boom down, first put wheels on the tip and...
...then lower the main boom. Note in Peter's photo that they have left the tip wheels on. If the winds are going to be too high, some cranes are big enough that they need to be stowed with the boom laid down rather than just jack knifed.
If you scroll down in
this page you can find a video of the crane falling over. After the videographer observes that it is falling over, mute the audio because the rest of the sound track is just
continuous expletives.
The Liebherr LR1300 had a 194' main boom with a 371' luffing jib. It was installed on the street to raise generators and cooling towers onto the roof of a 25-story building. There was no load on the crane other than the "headache balls" (hooks) as they were trying to lay the boom down on the street to weather a windy snow storm that was in progress. Evidently the crane was left overnight with its boom up because the first thing the operator tried to do when he arrived was to lower the boom. The report is a little ambiguous, but it sounds like the crane was parked overnight with its boom and jib at 80 and 45 degrees, respectively.
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The tip of the jib hit some buildings as it fell, so the end of the jib got smacked up pretty good. A woman who was getting into her car as the boom fell on it was killed. (A crane should have a big red button mounted near the cab door so that the operator can easily push it as he is bailing out of the cab. This button would activate a continuous, distinctive siren so that people up to 570' away would know to stop what
So strike one was that they did not park it overnight in a Jack Knife position.
The report on page 14 talks about the main boom angle in Figure 12 but doesn't say anything about the luffer angle. If I look at Figure 12, the operator lowered the main boom instead of the luffer boom. Specifically, the main boom went from 80.1 to 69.4 to 34.5 while the luffer was still at 13.9. Lowering the wrong boom would be strike two. Unlike baseball, that is enough strikes to be out.
Furthermore, a storm had been predicted:
At the end of the day on February 4, 2016, the weather forecast for the wind for the night and the next morning were reportedly known to Galasso Trucking & Rigging Inc. but no decision was taken to lay down the crane. That proved to be a grievous error. . [Page 35]
The report could have stopped right after the computer read-out analysis because the two errors that caused the problem have already been identified: 1) it wasn't stowed properly, especially since a storm had been predicted and 2) the jib was not lowered before the main boom was lowered. Instead the report continues with a wind analysis that concludes that it is safe at any wind speed between 20 and 30 mph with an 80-degree boom angle and it is not safe at any wind speed at a 69.4-degree angle. In fact, the manufactures load chart does not even have entries for angles below 75 degrees. Was this wind analysis done because government employees feel that they have to write long reports even if it means inventing some filler? Or is it done to try to distract the reader from the root causes --- operator errors? One tidbit I did learn by scanning the report is that, because of the long jib, it is not safe in the jack knife position for winds above 20mph according to the operators manual. The boom should have been laid down overnight given the prediction of a storm. But when email was sent to
Liebherr for an analysis of this specific case, the jack knife position would have been safe up to 67 mph.
The site plan indicates the crane should be stowed in a jack knife position, pages 36 and 46. The report whines about the plan not indicating which angles it should be stowed with. But if everybody is willing to ignore that the crane was left sticking up in the air rather than jack knifed, they sure aren't going to pay attention to specific angles. Furthermore, as long as the end of the jib is resting on the ground, I don't think the angles matter. So the author's concern about the specific angles indicates a lack of expertise concerning cranes.The operational error of the crane not being properly stowed before the storm is not only the fault of the person sitting in the chair, but his entire line of supervision and all contractor and city employees who are responsible for safety/inspection.. Somebody should have noticed that the site was left with a "ticking time bomb" standing up in the air. If none of the safety and/or inspection personnel for that site in a city that large could recognize a problem that is that obvious, then what kind of personnel competency are the city fees and city taxes paying for?
As for the operator lowering the boom instead instead of the jib, did panic cause such a significant "brain burp?"
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John Hartline commented on Clyde's posting
[Another example of luffer cranes being parked in the jackknife position overnight. This is two Manitowoc 2250's at a Notre Dame job.]
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This view allows me to see the tip of the jib. Note the tip of the jib is resting on a block to hold some of the weight when it is stowed.
