Tuesday, November 30, 2010
Portland, Oregon A Liebherr 100 struck power lines which electrified the crane but did not electrocute the operator. After the power was shutdown he climbed down the crane with the Firefighters. Source
The pull on the loadline looks as though the operator was swinging the crane with an empty hook at a radius that was too far out and with the hook too low. A lapse of thinking while operating?
The crane was clearly grounded well since he isn't dead. Potentially there could be quite a bit of damage done to the crane even with proper grounding. The motors could end up burned out due to the immediate surge. The issue that stands out to me is the condition of the slewing bearing. Cross arcing between the balls is a known problem on cranes that have received multiple lightning strikes and it leads to premature deterioration of the bearings themselves. The Loadline is destroyed on this crane. While you might be able to pick up a small line like this for a few thousand dollars, you'll have to have it installed, potentially wait for it and what does shutting the job down really cost? All of these consequences assume that there is not a load on the hook and that no one is touching the crane itself.
This is where I speak of the virtues of modern cranes over even a 10-15 year old crane like the one in this case. Most modern cranes have the option of what Liebherr calls a ABB system. What it does is allows the crane to block out areas of operation. In a case like this, you would trolley out to the tip and swing out to the limit of operation (10 feet away from 50kV and add .4 inches of clearance for every kV above that), mark that spot then travel to the opposite point, mark it, and the crane will prevent the operator from swinging into that area. It knows the virtual location as a straight line, or you could set it up for multiple direction changes. Almost every crane manufactured since 2005 has this option, so if you are going to work with a tower crane near power, I cannot recommend this feature enough. I've had older operators balk at the idea, but I frankly don't understand it. It's like being against a seat belt or Anti-lock brakes. Unless you are in a race car, why is that again? If it's my insurance on the line, the system will be turned on when I'm there.
Posted by Gaytor Rasmussen at 9:49 AM
Monday, November 29, 2010
Downpatrick Ireland. Getting back after a long US Holiday weekend and I find that Vertikal.net is reporting a Self-Erecting Tower crane having suffered a jib collapse. It's one of those stories that never made the news and is only known because of a reader. Likely the accident caused no injuries, but what could have caused it?
Vertikal notes that winds can cause this. It's true. When you have the jib only partially folded out or stacked, the torsion on the jib is higher than when it's profile is lessened and the entire jib is folded out. But this isn't what sticks out to me. The jib being partially folded in or out is relevant, but what really sticks out to me is the trolley position.
If this were an overload, the hook would not be at the jib. If it were winds at night and the crane were simply weather-vaned, the trolley should be back next to the mast. But the position of the trolley and hook height leads me to think that the crane was being folded up to be removed from the site. The position is where many popular models require the trolley to be placed during erection or dismantling. If a person were to become complacent, and not put that trolley in the right place and span both the eventual horizontal and vertical jibs and continue to fold up the crane, you could easily bend that small jib section.
An odd potential is the Queen's Post suffering a structural failure due to binding during or an undetected detected defect. The big picture is that Self-Erectors need to be treated with care as well. Often contractors and users view them as a toy, but the reality is that they can be dangerous if not handled with care. You have to carry out maintenance and inspection. You need qualified operators and technicians. Follow the manuals and make sure to go back and read it periodically. We get used to doing things one way and a refresher from time to time may expose that you are making a mistake that could be avoided.
Vertikal notes that open discussion is critical to crane safety. I couldn't agree more and that's why I do this blog. It's not to cause fear or hesitation but to insight thought in the process of handling cranes. To cause the operators, and those responsible, to realize that laziness and complacency leads to death. Take that extra moment to do things right. In the end everyone wins. First and foremost, everyone goes home. The equipment lasts for decades. Insurance rates are kept to a minimum which means more money available for tools and wages. And finally, no one's reputation is damaged which can be a really large and unseen expense.
Posted by Gaytor Rasmussen at 7:25 AM
Monday, November 22, 2010
Bejing China A tower crane being climbed, apparently down, collapsed killing three workers and injuring two including the operator. The Operator was asked some questions in the hospital and seems to be indicating in this blog that the hydraulic pump may have had an issue.
It seems that few climbers are fast and smooth. Often I've been on climbers that caused the jibs to bounce. Overtime the bounce becomes a rhythm which is hard on the jibs and pendants. Sometimes the technician needs stop and let the bounce settle then get going again in hopes that he can get the fluid flowing smoothly. The only other thing that strikes me as likely to be within the hoist mechanism is in the ram. If a person were to not have a positive acting check valve, a failure of the pump to create pressure or a hose bursting could quickly drop the entire superstructure which can certainly be a serious problem as it endangers the integrity of the crane itself.
There is more information in this article as well, but the translation is terrible and so I cannot make heads or tails of it.
Posted by Gaytor Rasmussen at 10:29 PM
Dandong China A tower crane being climbed suffered a failure killing 6 people and injuring one man on the ground. The crane was up at 50 meters reported to be on the 25th floor (does China count from below ground floors?) and Vertikal reports that one report they found has the crane as being dismantled but it's not confirmed. They also have the injured person on the ground listed as a woman, but two stories that I have found have the victim listed as a man. Either way, it's a innocent by stander being struck by falling parts.
Chinese news often doesn't come out with pictures, but I find them later. I'll keep an eye out for them and add them as soon as I can. Story links Here and Here
Chinese news often doesn't come out with pictures, but I find them later. I'll keep an eye out for them and add them as soon as I can. Story links Here and Here
Thursday, November 18, 2010
Studen, Switzerland. A 45 Meter Tall Wolff Tower crane on a cross base fell injuring two people on the ground and the operator of the crane. Also a building that was occupied has been virtually demolished and surprisingly no one was reported as injured. Two cars were struck by the jib of the crane and were certainly a total loss. They were virtually pancaked.
The crane fell backwards onto it's counter jib which had punched into the building. It stayed partially airborne because of this but the quick stop dislodged the cab from the crane tossing the operator in it on to the other side of the building. The operator is listed as seriously injured but I'm not finding any listing of the extent of those injuries.
In one of the pictures it's pretty clear that the cross base was sitting on soil that was under water. The concern with that is any under mining and is the soil staying compacted while it drains? I have had one crane that had a base below the water table during the winter. I showed up and the base was completely under water and the water was moving. The soils engineer had used sand and gravel to achieve his desired compaction in my case and I can only hope that they did the same on this site. Even with the soils engineering being done, I spent that entire winter thinking about that crane. As I look at the base though, one side of that cross base does appear to be lower than the rest which makes me really want to see if the soil has eroded over there. Clearly ballast was on the cross base and hopefully that was the correct weight.
Potentially everything was intended to have been done right but water is simply not something you want moving around the base of your crane because it's unpredictable in nature.
You can see more pictures Here
Turmdrehkran Zusammenbruch, Grue à tour l'effondrement
Posted by Gaytor Rasmussen at 8:16 PM
Lasi Romania, A small Self Erecting tower crane tipped and fell during the dismantling process. I managed to strike four cars but did not injure anyone. The jib and likely the mast, are a loss but possibly the base is salvageable.
With the crane coming down, I'm reminded of an accident in Hawaii where the crew dismantling the crane got a step ahead of themselves and removed the weights prior to getting the crane adequately folded down. Without more information, I can't understand why a crane that was used to work on a job for months would fall over during the dismantling process. The ground certainly would be compacted. But if you remove the weights without the crane being adequately folded down, this may happen. Some of the small Potains have weights bolted to the frame to prevent this sort of thing. Mistakes always seem to have a way of happening anyways.
macarale turn accident
Posted by Gaytor Rasmussen at 8:01 AM
Wednesday, November 17, 2010
Ming Pao China A luffing tower crane boom was blown over backwards in a typhoon. Fortunately, the area where the boom fell was a no-work area due to safety and the cab was no struck by the boom so no one was injured.
The translation makes it sound as if the crane was no able to be weather vaned for one reason or another. I think that we've all been caught in winds that were above our chart, but don't you have full warning that typhoon is coming in? I know that in Hawaii I was always aware. Maybe it was a long pick and they were supposed to have been missed?
The crane is clearly a loss from the boom and gantry stand point. Much of the rest of the crane may be salvageable. Link
Posted by Gaytor Rasmussen at 12:26 PM
Tuesday, November 16, 2010
I ran across a forum at Skyscraper City that has a number of old accident pictures in it. For the most part I don't have dates or much information. The pictures are interesting nonetheless. So I thought that I would throw them up all in one post and note that it comes from that forum so you could dig in to the forum if you like and see how the Aussie Crane Operators love their Favco's. They almost reminisce about each crane by serial #. I'll put up a link to the source for the photos and you will be able to see a larger format at the source than on my blog.
Listed as St Kilda Road, this accident is with a crane that is well before my time. It appears to be a early Luffer that could date back to the 50's. It seems to have lost stability at the base. It may have the record for the most cars gotten in one accident! Link
If you haven't seen a GCI before, you should check them out. They set up in 20 minutes, come self contained with motors instead of needing 480v 3 phase power, and have capacities up to 60,000 lbs! They also had fixed jibs available or lattice conversions for greater capacities. Manitowoc still has a spec sheet available here. The claim in the forum was that they crane was swinging too fast with to large of a load. I'm not sure if that means that it was torsionally overloaded or the stopping of the load caused the load to swing so far out of line with the counterweights that they were ineffective. Large picture Link
More Accidents after the Jump
Posted by Gaytor Rasmussen at 8:47 AM
Monday, November 15, 2010
Turkey, A Self Erecting Tower Crane was dumped over in an apparent overload. The only source I have is the video itself which lists the upload date of the January the 26th 2009, and the language of the type is Turkish. I don't know any other details.
Looking at the accident I notice that the person taking the video is standing off to the side in a smart location behind another building. Why would he be standing there, videoing at random, unless they knew that they were about to overload the crane? You would need someone to back off the Over Turning Moment limits, intentionally. Then you might have someone scale out the load and assume that you are within the limits. The difficult part is that when you ride the theoretical limits on a Self-Erector, you aren't likely to account for shock loading. Most self-erectors are anything but smooth operationally. I've watched the outriggers get light during a limit test at the tip. The crane was cutting out and the operator kept trying to hoist up and the perfect frequency of the hoist up and cut out began leading to a bounce that made my hair stand up. Fortunately the technician with him told him to stop it because he was abusing the crane. Even then, make an effort to be smooth about it.
Rely on the limits at 100% of the rated load only.
kule vinci kaza, kule vinç çöküşü
Posted by Gaytor Rasmussen at 9:00 AM
Wednesday, November 10, 2010
Koksijde Brussells A counter jib for a tower crane snapped while being handled killing one man and breaking the hip of a second. The accident was immediately blamed on metal fatigue by the Office of Verune.
The crane appears to be going up. The pick points used look to be substantial and the counter jib is being lifted off of the truck apparently to have it fully unloaded while all of the horizontal structure is prepared to be erected. Often when you have counter jibs consisting of one piece the pick points end up being a wide spread. It would seem that the only things to take away from this in the field is to not choose the widest pick points for stability purposes, and when you ship the piece, be certain that the center of gravity is well supported. If you send a counter jib down the road over bumps, speed bumps and more with no support under the Machine Package, over time it will be weakened. Inspectors should be sure to look at the beams for cracking and stress as well. Sight down the beams to make sure that they aren't twisting or developing creasing as a tell-tale that the stress has weakened the structure. There doesn't seem to be much else to beware of other than to be clear enough of the piece in the event of failure.
Sometimes the accident doesn't have anyone to blame, just ways to be sure that you are protecting yourself. Link to story
Monday, November 8, 2010
Magnitogorsk Russsia A self erecting tower crane was being dismantled when the truck crane being used to assist was apparently overloaded and tipped. No one was reported as being injured in the accident.
The crane appears to have been climbed down at which point many of the older style self-erectors would lower the jib tip on to the ground. From here the pendants would have been disconnected, the truck crane connected to the top chord of the jib, and when sufficient load is pulled off by the truck crane, the lower chord pins at the mast would be pulled and the jib lowered to the ground.
Looking at the picture of the truck crane, it doesn't appear that there is a soils issue as the ground is quite rocky. The outriggers swing out and lock into place so it wasn't as if the outriggers were only at the mid extend point. My suspicion would be that the crane was scaled out to be able to pick the load of the jib, but someone forgot that either the truck crane would have to boom down to clear the tower, or boom up to to clear the tower. In reality, sitting farther away and booming up would be the way to go if you think that you are close to a stability or structural limit. By being farther away, you can have the truck crane hoist up to about the proper load and read the pins (see if the pin is sitting down hard in the hole or riding up) and even pull one pin to see how the jib hangs and the truck crane is performing. At this point, if you have a problem you can re-make the pin and get a bigger crane. By doing this, when you cut the jib free, it would be booming up towards yourself which would eliminate the stability problem. If you are going to boom down and away, you better be sure that you have the right weight and radius figured out.
If you are close on weight, it would also be better to be closer to the butt of the jib near the mast. It's marginal, but you want to keep as much weight on the jib tip as possible.
The tower crane may have only received minimal damage to a few lacings or potentially dents in the box chords. Easy repairs. The truck crane would really need to be torn town and fully inspected, even to the bearing. I don't know if that's worthwhile in a crane that old, so it may be a loss. Looking at this accident and thinking about how it likely happened, I'm reminded of a saying that my first iron working boss used to repeat often, "Know your escape route." You have to plan for the worst in this business and by doing so, you'll likely avoid it. Link to story
Posted by Gaytor Rasmussen at 8:31 AM
Sunday, November 7, 2010
Penang Malaysia. A tower crane operator had to be rescued due to running across a hornet. Apparently a single hornet incapacitated the man from being able to climb down. The story doesn't note if he's allergic and went into Anaphylaxis Shock. News being news, either he's allergic and had a severe reaction, or he actually found a full on hornets nest which can take down even an adult and this wouldn't be a first on a tower crane.
The rescue of the man did not go well. The incident was originally reported at 2:30 PM. When the Fire Department arrived the initial thought was to use a "Super Gyro Skylift". I believe this is a aerial work platform mounted on a truck from. However this wasn't quite tall enough. So a crane was brought in and a dumping bin was used to remove the worker. The rescue was finished at 4:30 PM, 2 hours later.
Serious incidents do happen on tower cranes. Operators have medical emergencies. Here in Seattle we had a brand new technician get sloppy with a wrench and drop it in a live electrical panel which then blew up in his face and all over his hands. He was able to climb down. In LA, the story as I know it, was that a crane erector was dereeving a Liebherr 630 and rolling up the trolley line when it went over the side. As it ran his leg was in the bite and running and eventual snap of the trolley line severed his leg. You don't have 2 hours to get that man down. Heart Attacks, Strokes, trauma, etc are all cases where 2 hours is not an acceptable time frame. Especially in a city of 1.7 million people. The Fire Department should be prepared for this and be able to rope that man down.
It just illustrates the need for planning ahead. I really do believe that you should have rescue kits on the crane, training in how to use them available for enough workers on the site. It's really not that difficult. There are times when it will make the difference between life and death.
Link to story
Posted by Gaytor Rasmussen at 7:00 AM
Friday, November 5, 2010
Chaohu China A QTZ63 tower crane collapsed on a job site killing the operator in the cab. The Report on the accident simply notes the Manufactuer, crane used, and the job known as Country Garden Pheonix Hotel. In addition to that it does note that China is requiring that cranes be inspected and everyone on the crane through out the job must be "trained". Hopefully this will be taken seriously over time and China will improve.
The crane itself is a modern PLC controlled crane. It's a small crane with a maximum capacity of 13,200 lbs. and a maximum jib of 148 feet if I'm understanding their data. Considering the limited pictures and the depth of the video found, it would appear that no fault occurred in the structure that is visible. However, we can't see the base. The PLC controlled cranes from France and Germany are difficult to fool even if you wanted to. In order to properly run, they must be put through a load test, or at least I don't know a short cut. I can only assume that Chinese manufacturers set up the same parameters for the own protection if not keeping up with the European manufacturers. Combine this with the fact that the accident happened at 7:20 AM and I would wonder if there were a soils problem and rain and or wind in the cranes recent past. That's my wild speculation anyways.
Video found on the crane. If you speak Chinese, maybe you'll understand more from the story.
Posted by Gaytor Rasmussen at 9:24 AM
Thursday, November 4, 2010
Molfetta, Italy A tower crane collapsed injuring no one. The cause is listed a mechanical, but given computer translations, that could mean anything. The crane appears to be a small crane sitting on a modern cross base complete with ballast, knee braces and even a climber down at the base. The counterweights sitting on the tower appear to be an older design, shaped like an inverted T. These older weights were often found on Older PECCO or Peiners on the 170's and some 180's (US Designation). The rest of the counter jib and the Tower top don't match that model or anything else that I would recognize.
Since mechanical failure is listed, it could run from a run away trolley that overloaded the crane to a broken weld in the cross base. From what is shown, I don't see a way to tell, I'm just glad that no one got hurt in the accident.
Edit: I found that I didn't look at all of my info that I had found before I posted this. As I was closing it out, I realized that it isn't Balice Poland as I had originally noted but it was in Molfetta Italy in a area known as Balice. I also noticed that I have a video about the accident as well that may lend some clarity. At one point it sounds as if the reporter is talking about a computer and then I hear quatro. If anyone speaks Italian, and can clear it up, have at it. But was the crane overloaded due to a computer or computer set up issue?
Posted by Gaytor Rasmussen at 10:54 AM
Tuesday, November 2, 2010
Klagenfurt, Austria. Most Self-Erecting tower cranes have a derricking crane off the mast that allows for counter weight removal. In most cases it's slow and clumsy and requires that the weights be double handled. So in every case but one, (we were 19 stories up on a building) we have always used an assist crane or fork lift to add or remove weights. In this case, they were using a articulating crane with a fixed hook to remove the weights. During the operation the weights were caused to topple injuring one worker and destroying the cab of the crane.
The crane appears to be a Potain HDT 80 (U.S. Designation). Each of the weights weighs 6300 lbs or roughly 2860 kg and there are 13 of them. On the side they have ladder rungs that form a ladder that becomes quite tall and those rungs lead to the top where you'll find two picking eyes. The picking eyes are embedded into the concrete on top of a raised section that mates to a recessed area on the bottom of the next weight. This eliminates the needs for tie downs and aligns the weights automatically.
The difficulty in removing these weights is that when you use a fixed hook on the end of a boom, you must be cognizant of the boom angle and keeping the picking eyes from binding on the recessed area. The higher up the weights, the steeper the boom angle is. So as you boom up to lift the weights, you decrease the radius quicker than you gain clearance. The solution is to extend the boom in order to gain clearance. The same is true with Tele-Handler Forklifts. In this case it would seem that someone wasn't paying enough attention to the boom angle on the load an pulled the remainder of the load on to the truck crane itself. The concept is basic, but if it's your first time, it's better to ask questions, give up a modicum of appearance of expertise, and have everyone go home healthy and alive. Link to story.
Posted by Gaytor Rasmussen at 11:21 PM
Monday, November 1, 2010
Miass, Chelyabinsk Region Russia As a tower crane was being disassembled the jib collapsed. fortunately no one was injured in the accident and it sounds as if only the crane was lost.
The collapse happened after the counterweights and what sounds like the base ballast were removed. The contractor is asserting that a unforeseen Gale Force wind came up causing the crane to fail. They are being forced to assert this as the insurer is questioning the collapse. Article about the insurer's concerns. Then there is a second article a few days later that asserts that the winds never occurred. (The picture is from the second article and I'm not clear if that's the crane that went down or just a stock photo because it doesn't match the story exactly.)
What strikes me as relevant is I don't know of a manufacturer that would, or does, suggest to remove the ballast prior to removing the horizontal superstructure. I mean really, we are talking about the the greatest overturning stresses on the crane being induced during this process and you want to remove the ballast that is designed to prevent that? Shy of removing the knee braces (if so equipped) and the final tower section, the ballast is the next to last thing to remove. Remove all but the final tower, pull the ballast, braces, tower then the cross base. This is the normal process for the four different manufacturers I've seen with cross bases. So if you remove the ballast, you certainly won't need a gale force wind to cause the tipping of the crane.
More importantly, I have a question about what is going on in Russia. They seem to be acting as if wind is always an excuse for losing a crane. Here we have two downed in a legitimate wind storm. Here we have another just a few days later downed in what may have been a wind storm. Wind will occasionally happen and down a crane. There are weather events that you cannot prepare for. In this case, it sounds as if it's a easy reach for a crutch rather than simply fessing up to the reality, that you removed the ballast out of sequence.
крах башенный кран, аварии башенного крана
Posted by Gaytor Rasmussen at 12:29 PM