Caisson Drilling Rig Tipping Over 2

[phillyfrank]

I am working on a forensic investigation of a caisson drilling rig that tipped over. I have searched OSHA and google extensively, and can find no similar incidents. Manufacturers supply graphs and charts of limits, but there is always operator error. Any tipping-over incidents would be welcome.

 

[Qshake]

This probably isn't going to be directly helpful for the drill rig, but it does go to the level of experience for operators.

Many years ago, an operator was hired out of the hall (in the midwest, its still union) to run an ordinary cherrypicker - telescoping crane. The project was a river bridge and the crane was sitting on a levee.

The operator got in and started the crane up and, with no one looking/supervising - who would've thought, in the next few minutes the crane wound up in the river on its side! Luckily for the operator the cab door was upward and not mired in the muddy river bottom.

A more recent incident here in the midwest was a large crawler crane overturning in Missouri on a bridge job. The crane operator had made a pick and swung and boomed out beyond the recommended amount.

Two examples of operator error.

 

[jheidt2543]

Just a couple of more thoughts:

1. Try looking at crane tip overs, they happen a little more frequently and are of a similar type of equipement.

2. You might try a search of Engineering News Record, they report on most construction accidents of note. Of particular interest might be the crane tip over on the Milwaukee Brewer Baseball stadium a few years ago, although that was a very big crane, lifting in "high" winds.

 

[austim]

Don't forget that the operator is not the only possible source of error. A crane can still be tipped while being operated entirely within the manufacturer's limits.

Detailed reasons for this sort of event are usually difficult to find, since they tend to be obscured by legal secrecy.

On a freeway construction job not so long ago near Melbourne, a crane tipped over into the adjacent creek. Rumour in the industry was that the crane lift had been carefully engineered, and piles driven at the four planned outrigger positions to provide the necessary foundation capacity. However, as it turned out the crane was not accurately positioned over the piles, and it tipped due to foundation failure.

I recall an occasion many years ago when a sub-contract crane erector was installing the machinery deck for a tower crane on the base of a floating concrete caisson (for final fitting out prior to floating to location some miles off the Queensland coast).

The sub-contractor was quite convinced that he knew the mass of the machinery deck. He also knew that it was at the maximum radius/capacity of the mobile crane that he was using for the lift. He happily directed the crane driver to jib out, with the load about 30 feet above the deck of the caisson.

Fortunately two experienced rigging foremen from the main contractors were monitoring the operation. When the two rear outriggers went slack in their housings (indicating that the mobile crane was right on the point of tipping about the remaining two outriggers), they stepped in and ordered the crane driver to jib in, and replace the load on the wharf from which they were working.

The subcontractor protested loudly (he had been aiming for a bonus for early completion), telling anyone within earshot that the crane would p... it in". He was instructed to weigh the load on the nearest weighbridge. When the foremen went to the weighbridge next morning they observed the water tank being drained, and reels of hoisting cables and other surplus items being removed from the load! (Subsequently the lift was successfully completed, but with the load limited to the items listed in the manufacturer's weights). Had that crane dropped its load onto the caisson, it would almost certainly have sunk it, with a probable cost of $10 million or more.

 

[krd]

As mentioned above there are all too many crane accidents and the causes are well documented. So you don't have a typical a crane accident? I wouldn't think you'd find many instances of drill rigs, crane mounted or otherwise, turning over. First, the equipment selected usually has plenty of spare capacity because sometimes you need brute force in foundation work. And second, the equipment is usually set up adjacent to the hole so there should be no need to boom way out where radius is a problem. The heaviest overload can occur when you're trying to pull something out of the ground and it doesn't want to come. But then foundation contractors that are still in business know to stop pulling before something breaks.

 

[Focht3]

Pay attention to the working surface - was it "firm and unyielding", or potentially suspect?

I participated in an investigation of a 900 ton crane that tipped over and killed a man. (Yes, 900 US tons!) The crane had an out-of-plumb tolerance of only one degree. I can't be more specific about the time, place, parties involved; there is a "secrecy" gag in place. But the final conclusion was that one of the crane's tracks pushed aside a plywood "mat" and dug into the gravel working surface while moving the load, causing the fully loaded crane (about 890 ton load) to tilt and begin swaying. After an agonizing 3 or 4 seconds, the crane fell. One man was crushed by a falling counterweight. This was all captured on 3 synchronized video cameras. We spent a full week looking at the videos and site. Operator error was not to blame. In my personal view, the project manager was at fault for choosing gravel and plywood over concrete.

The crazy thing was that construction cost was not the issue - the site could (and should) have been levelled with lean concrete.

phillyfrank -
Be sure that the site was level and that the crane was properly supported. While I, too, suspect operator error, the setup may have been a contributing factor - or could have initiated the overturning.

 

[phillyfrank]

Focht3 -- Thanks, we are going in the same direction, but only have photos taken by many individuals immediately after the fact, about 15 minutes. We are trying to reconstruct the pre-accident situation as best as we can.

 

[phillyfrank]

I have since stumbled onto this site:

http://www.craneaccidents.com/

for those interested in the subject. Lotsa links.

 

[DRC1]

Crane Works magazine publishes monthly reports of accidents. They could probably point you to a wealth of information. Their website is

http://www.liftlink.com.

Also if you have to get into a detailed analysis of the failure, get "Cranes and Derricks" by Howard Shapiro, et. al. and published by McGraw Hill.
By the way, what type of rig was it?

Good Luck!