Wednesday, December 29, 2010

November 26th, 2007

Xi'an China. A Tower Crane suffered a structural failure injuring one worker. The crane broke from it's base and leaned into the scaffolding next to the building. The stop must have been very soft due to the scaffolding bending which may have been critical in keeping the crane as vertical as it was.

Clearly you can see the base of the crane from the screenshots. It would appear that the base was fabricated, set in place for the concrete pour, and the tower was added later. You can see clearly where the red arrow is (photo below) pointing where the welds broke. It's certainly possible that the welds were simply poor quality and that's why they failed. but let me complicate this in order to help prevent this from happening in the future.

You'll notice that the legs are welded to the lower frame. Since you don't only have to hold the crane down, you have to be concerned about the torsional moments induced. The twisting forces. If you've ran a crane before, you know that it's substantial. The welding should include bevels with multiple passes. I would have added gusseting running at least off of the two sides. This will aid in absorbing that torsional force, but it will help reduce any flex in the structure vertically as well due to compression or tension in the over turning. It also adds more weld and who can complain about more glue? The other thing that I would do if it's feasible, is plan to bury this base in concrete to aid in stabilizing it. This would hold that base as stable as is possible and limit any potential cracking due to those movements over the life of the crane, or length of time on that job site.

I couldn't get the video to play on any other source than on the website. YouTube and blogger both reject it. The video loads horribly but the link is here in case you want to see the story or watch the new coverage of the accident.


Monday, December 27, 2010

April 30th, 2009

Chernvtsi, Ukraine A small self erecting tower crane suffered what appears to be a structural failure during the dismantling process killing a man. These old self-erectors often dropped the jib tip of the crane to the ground then maneuvered the mast down and eventually the jib would be stored horizontally. In this one we see what appears to be a fresh structural failure. I don't know if it was the cause of the accident or a result. But what is clear is that some of the best practices aren't being observed in the maintenance of this crane.

You can see the clean gray steel that appears to have ripped and or fractured. The top appears to have a fractured drop forged piece of steel on what I assume is a top chord. 

On this picture it's clear at the red arrow that the dead leg and the live leg are clamped together. This severely weakens the ability of the load line to sustain the load. If you look at the blue arrow, you'll see that it's pointing at a wedge and socket on the opposite side and it appears to be loose. I don't have enough details to see if that's due to a broken line or due to a luffing drum failure. Either way, this isn't the right way to do it. Add a slug of wire to the dead leg. Add enough length to the dead end to clamp it back to itself which would prevent it from being able to run. Or, even better, use a Crosby Terminator which takes most of the work out of the issue. Just maintain the cranes properly. 

If you speak Russian, there is a lengthy News story here that might get more of the story out for you. If you want the original link, here it is

Sunday, December 26, 2010

June 25th, 2010

Cessna, Italy. The jib of a tower crane came down shortly after it had been erected. The boom came down with a father and son team working at a height of 7 or 8 meters. The translation isn't clear about where the two were working. Were they in a suspended platform? arial lift, actually on the jib? Clearly the crane is taller than 7-8 meters, but I don't see any other place where they could have fallen from 7 or 8 meters. The story notes that they are basically the crane erectors and they were finishing up verifying that the crane was working well and certifying it. The father ended up on a Conex roof and the son was badly wounded on the ground. The son was transported to the hospital where he was treated but the father died on the job site. Link

The cause of the accident is listed as a "rupture or leakage" of a pin. I can only assume from the pictures that we are talking about a jib pendant pin and it would appear that it's at the Tower Top connection. Certainly looking for bent keepers on pins is one of the primary things that I get concerned about. They do get missed. People get into a hurry or distracted and simply forget to double check. In this case, a story came out two days later that another party was being investigated for Manslaughter in the matter. That could be due to many different laws, abdication of responsibilities like providing training, or a more serious charge.

It may seem interesting that a father/son team is working on cranes and gets injured together. But it's happened two other times that I know of. Here and Here. In all three cases it was the father that died.

Wednesday, December 22, 2010

November 20th, 2010

Busan, Korea. A luffing tower crane lost it's boom on the Paragon Apartment project. It sounds as if no one was injured in this accident.

Looking at the video, The only things notable are that the gantry looks to be intact. Without better pictures, the number one suspect is the Luffing rope failing. The only effective way to really get a good look at these is while the crane is being erected. If you have a bellman, or an inspector available, make sure that they are running a towel over the line as it's being pulled out by the crane erectors. There are often six long parts of rope that you'll never get to on the drum after the crane is put into operation. After it's erected, you'll be faced with having to inspect it visually. Effectively if you could see 100% of the outside of the rope, you are really only inspecting 20% of it. A good inspection requires tactile inspection feeling displacements, bird cages, broken wires on the side opposite of where you stand and and potential displacements of the core.

Outside of the rope, be sure to fully load test the crane and visually inspect that luffing winch brake to make sure that it isn't glazed or simply worn out.  

Link to story
부산 한국 타워 크레인 사고

Tuesday, December 21, 2010

April 14th, 2006

Tampere, Finland. A tower crane operator was killed when his tower crane tipped. It didn't hit the ground, but it would appear that in the process the cab was struck by a collapsing jib, or at least deformed in the process.

The crane was on rails and properly counterweighted. There really doesn't appear to be anything wrong with the crane specifically. For some reason, the end of the rails were removed, taking the interlock ramp to shut down the bogie motors down out of the equation. At the same time, this removed the end of rail buffers as well. the crane ran off the rails and down it went.

This has been done at the end of the job before in St Petersburg killing 3 there. No Buffer or stop. I know of others that I just haven't posted as of yet. There are an extra few hours left in the schedule. There really is no excuse for this type of behavior, but we see it all too often.

torninosturin romahtaa

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.

October 28th, 2005

Shenyang, China. It's not often that we get full reports on why accidents happen from anyone that investigated an accident. I ran across one that even though it's a translated article, it does a decent job of telling the story. It comes from the Safety Research Institute of Liaoning Province, Shenyang with the full report being found here.  

A QTZ315 Chinese made tower crane was being climbed down in good weather. It collapsed with 5 workers on the crane. The report doesn't indicate the fate of them all, but given a nearly 100 foot fall and the volume of blood on the site, the prognosis isn't good. The crane was found to have what's listed as an "ash bucket" (concrete?) on the hook and a tower suspended on the armature. The accident investigators found that the "claws" (either resting dogs or climbing dogs) failed structurally due to what is called a scratch and uneven loading. The failure caused the superstructure fall and crash into the tower. At this point the lowest mast section just above the knee brace section collapsed due to the vertical overload. The crossbase stayed in place and the rest of the crane fell over.

Looking at the pictures of the "dogs" it would appear that it simply wasn't in far enough. I think that the report is trying to indicate the same, but it's lost in the translation. There is an armature that is also fractured and that's likely due to the failure and subsequent slamming into towers and lacings as the superstructure came down. In my experience in climbing, it's 3 guys trying not to sleep for 25 minutes between sections while one guy makes sure that the lower dogs are in tight with each stroke and a technician runs the pump. Buy always, you have to make sure that the dogs are in tight. They are only designed to work if they are all of the way in and even if they aren't all of the way in and can take the load, they can slip in with 300,000 lbs of load on them, and that isn't good for any structure.

Thursday, December 16, 2010

February 10th, 2009

Palencia, Spain. Juan Jesus Sanchez Chapels, 58 years old, was killed after being knocked to the ground  by the crane working on his job site. The translation of the story makes me assume that he was hit by the block of the crane as it swung by. You are welcome to see if you gather something else out of it if you speak Spanish. Link

Job sites are constantly transforming as the job goes on. Operators are running at timing and speeds that they have been used to for weeks at a time. You might have been stuck on one floor for a couple of weeks depending on how it's going, it's size and the schedule. So you get lulled into habit operating just as you might fall into habit driving near your home. If something changes, you might not notice it the first time by. Well if floors are being built or scaffolding is going up and a man is standing on it to build it or work from it, and you are used to hoisting up for 17 seconds before you can swing, and are looking ahead for the location of your bellman instead of where your hook is, that man might be higher than you have seen and the next thing you know, you've knocked him off the scaffolding. Of course, I'm just talking this out from the limited details shown.  

Grúa accidente en Palencia

Wednesday, December 15, 2010

October 23rd, 2010

Yibin China. On October 23rd, 2010 there was a boom collapse in Germany. All of the way on the other side of the world, China lost an entire superstructure of a crane killing 3 and injuring 4.

Looking at the picture of the crane, Three things strike me as things that I really want to see in person.

  1. Why does the tower go from nasty old tower with no corrosion protection (paint) on it to a new looking tower? 
  2. Why is just that one tower fractured and do we not see any other damage? 
  3. Was this crane being climbed or did the mast bolts snap without even damaging the one side of the structure?
Besides the obvious point that any self-respecting contractor would not be pleased with the obvious state of disrepair of the paint on the crane, The different color makes me wonder if the mast was a knock off by a manufacturer other than the original manufacturer. You can buy Korean Liebherr Mast sections. You can buy You can buy Chinese Comedils. Chinese Tadano's. What I'm getting at is that there are tons of knock off's out there. Do they do engineering or do they just mock up what they see? Do they use the same materials in terms of grade and quality of production? A mast section that fits and looks right, may not be right. (I'm not adding pictures or naming names for obvious reasons.)

I assume that the one tower is damaged because it was of poor quality. I can't imagine another reason that enough welds failed to leave the one side standing perfectly vertical but the other three sides look like toothpicks. We are talking about welds with incomplete fusion from the factory.

I have to go with the idea that this crane was being climbed at the point of the accident, and here's why. Mast bolts do break as a cause and during accidents. But again, we have a side perfectly vertical still. By contrast, In the first New York accident, the point that struck the building next door on the mast ripped the steel column off on one of the sides instead of breaking the bolts. The clamping forces on these bolts are designed to be so strong that there is no way you could fold the tower on three sides and have the bolts simply break on the one side left without buckling it severely.

China continues to make poor decisions on their cranes, but more importantly we see structural failures time and again. Not all of these cranes are that old either. They are just so poorly designed and the materials are subpar. My only regret is that I don't know the models and manufacturers to start tracking which ones are failing how and why so that they can be avoided. Until that's revealed, I would just recommend not going near a Chinese crane at all.

Original Link


Tuesday, December 14, 2010

December 9th, 2009

Liaoning, China In the process of being climbed, a tower crane counter jib lost support at the top pendant connection. It immediately fell crashing into the climber killing at least one and injuring two others. The dead man and the two other workers had to be rescued by the fire department. The accident is similar to another accident that I reported on just last week. Notice the pendants hanging straight down on next to the red arrows and the tower on the jib still on the where the yellow arrow is.

It's important to note the accidents on the counter jibs because you don't generally see them failing as often as the jib of the crane. I don't think of them taking the same level of stress, but clearly the can fail just the same. On this particular one, I'm not sure if it's a weld failure at the Tower Top of if it was a pin failure as if possibly it didn't have the keeper, or a proper keeper retaining the pin. I think of some of the older 390 and 550 Liebherrs that had pendants that had to be removed in order to be shipped on a truck. They had a single pin that was a pain to install due to lining up two pendants at once, but worse was trying to drive it out later. It could tie up an assist crane for 20 minutes on the seemingly simplest of project that just never seemed to work out well.

Look over the structure of the tower top, the keeper installation, the pin itself, and pendants including the welds. The vibrations sometimes induced by a bouncing climber on a pin that doesn't have the right keeper in place could cause that pin to walk all of the way out just like this accident's potential cause.

Monday, December 13, 2010

March 6th, 2009

Mesero, Italy. A load on a tower crane dislodged while being flown on a job site. The load weighed approximately 300 pounds and appears to be have been on a set of flying forks. The load came off and struck a 33 year old worker in the chest whom was airlifted to the hospital to no avail. He died of his injuries.

The video shows the emotions of the workers involved. It's certainly not surprising but an emotion that we should think of when we are rigging up a load that is iffy. If you have a load on a set of flying forks using a ratchet strap to secure it to the forks would be a good idea. Another idea is simply engineering out the problem. We get used to the run of the mill solutions to rigging and throw up our hands when we run a new solution is required. It might be that you take the pallet and put it in a bin with a four point pick. Or it might be getting a manufactured solution that addresses the problem like this.

Boscaro makes a pallet bin that goes over the pallet. Then you place the tines through the pallet and all of the items are secured. If you have a pallet of bolt kegs for a structural steel building, the bolt kegs are secured inside the mesh. Even if a keg falls over, no one is in any danger. The bin is hoisted on a four point pick, so you couldn't unbalance the load enough to ever endanger anyone. These are the types of solutions that you should be looking for. In the US we are required to engineer out all potential hazards and I think that's a good way to go. If this solution is one that you need, you can contact

Link to story
gru incidente + milano + 6 Marzo 2009

June 15th, 2008

I had originally posted this video back on June 15th, 2008 but the link is now dead. So I've uploaded it to YouTube so that it won't go dead on us again. It's clearly a tower crane on a travelling cross base going over. I can't tell if it's intentional or not. You would think not, but was it just happenstance that someone was videoing? Why does the guy at the end start sprinting towards the crane? It seems that the two action are contrary to each other in making assumptions.

Clearly the crane hit something. It should have been the end stops on the rails. Many Russian cranes have gone down due to the rails not having stops at all and so the trucks just run off the rails and sink into the soils. It's possible that this crane was being operated at the time, but I can't imagine an operator being quite so unaware of where the end of the tracks are. Could it have been blown that way? Were the traveler brakes not working well and the rail clamps not added for safety? I don't have anything but the video to go off of.

Sunday, December 12, 2010

February 28th, 2006

Malnate, Italy. The load line on a tower crane ruptured which induced a shock load strong enough to separate the turntable. One worker was struck by the line and injured, but by in large, the crane came down in and area that did not have many workers in it.

The jib went over the top of the building and ended up leaving the turntable suspended on the side of the building. The building itself suffered minimal damage and so with the replacement of the crane, only one minor injury, the only real loss was the crane and the confidence of the workers.

Respect for load lines and regular inspections are necessary. I'm a fan of going for a ride in the trolley basket to see the rope on the jib. not only do you get to see all of the line, but you get to hear the sheaves and rollers for their bearing conditions. I'd suggest that you need to inspect the ropes not only visually as many people do, but I would suggest that the right way to do it is tactilely as well. I do this by wrapping an old towel around the line in a safe spot and have the operator hoist it through your hands slowly. Any broken wires grab the old towels immediately and I can't tell you how many times that I've found broken wires on the opposite side of the side I was looking on. The notion that an operator has inspected a line by sitting in the cab and watching it go by is not an accurate or informed position. Certainly it's the most practical as a lone operator up there, but it's not the best that we can do. Get a bag of old used cotton towels that will tear easily. Wrap it around the line so that if it does hang up it won't immediately get dragged into a sheave. Hold on to it in a manner so that if it hangs up it won't tangle in your hand. And position yourself in a manner to be able to communicate clearly with the operator at all times, including by radio if need be. Don't let your load line develop a problem that you never see simply because the breaks are on the opposite side of the line that goes by your line of site.

Link to Original Story
Crollo della gru a torre a Malnate

Saturday, December 11, 2010

September 16th, 2010

Rosrath, Germany. A Self-Erecting Tower Crane Collapsed damaging multiple cars and the roof of at least one house. No injuries were reported. The report does note some wind and that's what the police suspected that wind was the cause. I'm skeptical of that claim in favor of looking at two other potential causes. 

The ballast on the crane seems to be lacking in mass from what I'm used to seeing. Frankly, I've seen the smallest of cranes have more ballast than this. To be fair, I've never worked with this model of crane. It just strikes me as not enough ballast, but I have no real evidence that this is the case.

The other issue that stands out for me is the quality of the wood used. From the picture of the base of the crane it would seem that some of the wood is showing signs of rot. To make matters worse, the wood is spanning over some concrete blocking so there is no under laying support in the middle. This really shouldn't be done with suspect materials.

Both of the conditions that I have listed would affect the crane more than your standard wind. The crane was still in operation and anyone that has spent any time on a self-erecting crane knows that running them in the wind is anything but fun or easy, so you even shut them down earlier than a top slewing crane. I reject the claim of the officers and present the pictures as my reasoning.

Friday, December 10, 2010

Mobile Crane Unknown Date

It's not a tower crane, but it's compelling. It's a mobile crane going over due to poor soils. It would appear that everything was intended to have been done right (matting layers are perpendicular), but the big picture is that you can't be so close to the edge on non-native soils without reinforcement of some sort. It would be best to use a soils engineer.

Operationally, guys noticed the soil giving way while the load was able to be landed back on the pilings. There really isn't a good reason why they didn't do that. Always take a moment to stop for safety. Even if there was no other injury, this is a 2.5 to 3 million dollar accident. How much would have it cost to set the load back down?

Thursday, December 9, 2010

December 12th, 2008

Lindenthal, Germany (suburb of Cologne). Two Tower crane erectors suffered leg injuries that were described as severe and were taken to the hospital. Looking at the pictures, I can almost promise that it's broken legs, and lets get to why.

In the picture we have a crane boom that has been set down on the ground. The journalist isn't sure if this crane was going up, down or was dropped. I would suggest that this boom was set on the ground that was uneven. Even at this point, it still looks like it's not all of the way down on the ground on the sidewalk.

The lower chord pin at the Red Arrow appears to have been removed while the jib was partially airborne with the jib touching at each end. The jib is under tremendous stress at this point. Either the jib should remain suspended by crane while only the lower chord pins beyond the rigging points are removed, or the jib should be set down on dunnage (wood) to support the jib at either side of each splice. If you have wood under each sectional connection, you can safely remove the pins. But even then, there are two measures the erector should do to protect themselves, and I don't think that they did either.

First, when you are removing these lower chord pins, stand on the lower chord. If you have your feet planted on the ground and the jib shifts violently, you become the target. If you are standing on the lower chords, you go for a bit of a ride and might end up smirking due to surprise only. The second thing is the hammers used. Yes, hammers, plural. Don't just use a sledge alone. When the pin gets close being ready to be driven out, if there is any tension on it, you should use a B&O (backing out) Hammer. With one hand hold the snout on the pin. With the second hand you swing the larger sledge on to the face of the B&O. The long snout protects the hole from being marred by strikes. Additionally, when the pin frees, the snout will follow through. This will prevent the radical shift of the piece. When you are dismantling, this tool is incredibly useful, especially in the air.

A quick story, a rookie Iron Worker was with myself and another journeyman. We set a jib down on uneven ground. We had a second (assist) crane so we were going to pull the pins after we had the jib supported by the second crane. I'm off disconnecting the fall protection. Keith is bending keepers so that we can move quickly when we start to work with the crane. The Apprentice starts to drive the pins at a point where there is significant clearance between the ground and the lower chord. I walk by and say, "Hey, get up on that jib. Your feet are in the bite." He gets in the right spot and I walk away. He's swinging away at this pin and it isn't moving well. He puts his feet back on the ground and Keith see's it. "Hey, didn't Gaytor just tell you to stand on the lower chord?" He gets back to where we told him to be. He swings a couple of times and again puts his feet on the ground. The pin comes free, the jib shifts down and breaks one of his feet. Sigh... In the US we have a saying, "You can lead a horse to water, but you can't make him drink" He's a nice guy, but he was one of those young Iron Workers who is the son of an Iron Worker so somehow he knew best through his genes.

Stand on that lower chord, support the jib, use a B&O and you'll never have broken bones in your legs and feet from a loaded jib.

Turmdrehkran Demontage Unfall

Wednesday, December 8, 2010

January 16th, 2009

Monteprandone, Itlay. A Tower Crane fell over after being contacted by a second crane on a neighboring job site. It would appear that neither crane have operators cabs on the top of the superstructure. So neither operator is reported as inured. However, there was a Grandmother and her Grandson whom were lucky in their escape of injury.

Even when you have two jobs that are not related to one another, but they have the cranes have potential of making contact, you need to give the operators a specific radio to inform one another what you are up to. When you'll be in the other guys airspace. I have substitute operated quite a bit. I recall one job where I showed up in the morning on a Saturday. The neighboring crane was idle and I was clear of it. It was a luffing crane I was in a saddle jib. I got rid of a load and due to the clearance while hoisting up (It was a tall crane) I start my swing going around the long way. I'm paying attention to my clearance so that I can reach top speed on the swing. I was working with Iron Workers and no one likes speed in their cranes more than Iron Workers. As I get clear with the hook and have reached top speed in my swing I look out horizontally and notice the neighboring crane is not only now working, he's in my airspace! Fortunately I was on an old PECCO 400 Tower Crane that had three swing motors to get me stopped quickly with counter swing. No note from the regular operator, no note from a bellman, no second radio. I nearly swung into another crane because there was no crane to crane contact and I had no idea that he could even reach into my airspace, let alone that they were going to be working. I had no normal reason to look up. When you are 300 feet up, what is going to get in your way?

A second radio is a critical reminder to pay attention. There may be information that the operators can share that will allow for effective use of the cranes together. Maybe it's that I'm going to be swinging in and out of your airspace for a while so swing in the long way. The second radio may look costly on paper, but you'll make it back up in speed, if not in avoiding wrinkled cranes.

Link to story.

Monteprandone, Italia crollo della gru a torre

Unknown Date

China. A worker was pinned and appears to have been killed during a climbing operation in China. The story only comes from a video that I found, but the scenario appears to be quite unique. The counter-jib appears to have structurally collapsed in the middle and come down simply to crush the man. Warning: This video may be beyond the normal tastes of North American's.

The crane is short with a climber on it. Since I don't see any tall buildings nearby, I'm presuming that the crane has just been erected and was going to be climbed to it's operating position. From the low height, I would even assume that the crane had not even gotten one tower section in yet. The excavator used to get the fire fighters into position seems to easily reach the lower climber platforms.

While climbers do get an ugly and uncomfortable bounce from time to time, could it really cause this? I suppose that you can't rule it out, but a more likely scenario is that the climber wasn't set properly and it slipped or structurally failed causing the crane to crash down hard on the tower. Let me draw it out a bit.

Normally the crane's counter jib has stresses that run down the pendants on the black arrows. From there, the pendants prevent the weight from dropping in the back which translates to force pushing in against the turntable or tower top depending on the design. If you drop the entire crane on to the tower itself during a climb operation, somewhere between the red arrow and the yellow arrow you are going to see significant downward deflection. At the same time the stresses on the pendants are going to increase multi-fold which also increases those inward stresses on the beams, but now on a structure that has deflected. In this case yield was found and the whole counter jib came down like a battering ram killing the man. 

This isn't unique in the sense that we've seen structural failure in the middle of counter jibs. It's happened here, and here. You need to be looking there too for cracks in splicing plate welds and in the horizontal diagonal lacings. I've found cracks in those lacings before.  

Again, the Video shows a body and the man trapped. 


Tuesday, December 7, 2010

November 25th, 2010

Bolzano, Italy. In the north of Italy a Self-Erecting Tower Crane came down striking three cars and injuring none.

In the pictures of the crane, it would appear that structurally speaking, there is no failure that is notable. Certainly damage is present, but it appears to have been caused by the accident rather than before the incident. Looking at the base we see that weights fell off, so we can't get a count. I've never heard of the wrong number of weights being put on. In this case, it would appear that the crane simply tipped, so that possibility can't be ignored. But it isn't likely. The ground looks good. There are matts there that could be a bit better but they do look like they took some time in trying to get the crane level as well.

Looking at the jib of the crane just behind the first car visible, you can see that the location of the trolley  shows that it's likely that the crane was carrying a "bunk" of plywood. Was the moment limit set on this crane? Was the crane load tested to 100% and the limit verified? Does the crane have a scale on it for an accurate reference? Certainly a good operator should be able to guestimate this weight with some accuracy if you are going to be closing in on the limit of the crane. 1/2" Plywood = 1.42 lbs per square foot. 45.5 lbs per sheet, etc. You can have these references in a book, in your smart phone, maybe on a card in your hard hat... I know that I have some buried around the office somewhere that I would put in the hard hat given I were a bellman again.

Load test your cranes. It's really not that difficult, expensive, or time consuming. All of these factors compared to the cost of replacing the crane.. not even close to being on par. The beauty of a tower crane is that if you've load tested it, you can have some confidence that the limits will work and keep everyone safe.

Original Link

consigli gru a torre in Bolzano

Monday, December 6, 2010

July 31st, 2008

Original link

Milan Italy A tower crane was blown over during the night due to an apparent tornado. I don't have any report of any injuries, but clearly the crane and at least one vehicle was destroyed. Did the Volkswagen get spared? I'm not sure but it's close!

The same old story is true, that you need to make sure that your crane weather vanes and does so well. Sometime Technicians are OK with the idea of letting the brakes drag a bit even when they are open. I don't agree with this position. When you get into winds like tornado's, the wind can change direction very quickly and the best chance of survival is to have a crane that points downwind without hesitation. An example of hesitation and the eventual results...

Crollo della gru a torre a Milano

Sunday, December 5, 2010

April 12th, 2009

Donetsk Ukraine. A Tower crane collapsed while installed the "intermediate" section. It sounds as if the female crane operator was injured seriously and was taken to the hospital. Also, a nearby building was struck during the collapse.

The crane is clearly an older model. The jib is made of I beam construction and in my experience, you have to go back to the 70's to find this type of structure. But let's assume that it wasn't a structural failure. What are some of the other problems with cranes this old?

Do you have manufacturer support. The Kodiak Crane that went down in New York had no factory support and the weld repair was done poorly by someone unqualified. If you have an old Pecco crane whom do you call to find out the allowable deformation in a jib lacing on a 170? There are people whom know these things, but it's not like everyone can just pick up the phone and call the right person immediately like you would with a Potain. So problems get brushed over or ignored for years.

How about having a skilled and factory trained technician in charge of the crane erection? Is the technician 65 years old? How many of them are there? Is the technician on site working with the crane with second, third, or fourth hand training? How easily are mistakes made? It just doesn't seem like a good idea to be using cranes that could have structural problems hidden below 9 layers of paint. With a technician that may not have even been trained by someone with a factory background and does the manual even exist? How many old cranes have you been on where there isn't even a manual?

Link to Original story

баштовий кран аварії в Донецьку

Saturday, December 4, 2010

2 Years Ago

Zibo China, A tower crane was filmed as it was down after either moving gravel or concrete using a concrete bucket. The crane appears to be new in condition and design, but it also appears to be Chinese or Korean. What's interesting is that the link lists the video as the "kindergarten" accident from October 10th, 2008. Clearly it isn't the same crane, so I'm not sure where it's from. I couldn't get the video to load into Blogger or YouTube, so here is a link to the original. 

What strikes me about the video is that the crane has the climber left at the top. Often crane manufacturers only allow this if the crane is at least two tower sections below its maximum free standing height either from ground or tie in. The added mass can overload the crane as well as the added surface subject the crane to more wind load. From an operational standpoint, I simply wouldn't want a climber in my line of sight. This is especially true if I were on a crane of significant height because it would block my view. Sometimes due to the tie-in schedule it's the way to go, but for most jobs, it would just be easier to send it down and grab it on the way up next time. What are we talking about, 30 minutes of work for it to be better for the crane and the operator?


Wednesday, December 1, 2010

August 1st, 2010

Harbin, China. A Tower Crane being climbed in Harbin China collapsed after being erected. I don't have any details on the number of people injured or dead as the video is the only source that I have found on this. The link to the original video doesn't have an exact date on it and only lists it as about 4 months ago. So that date listed is just an approximate.

The tower sections are short, and so is the climber. Clearly the climber is broken, but likely that's from the side loading once the collapse began. What strikes me when I look at the tower sections that were bent is that even though they are short, only two are broken. Does this climber only reach down 12 feet or so? Does that allow the spread of the load across enough surface of the tower sections? Does that allow for enough ductility in the structure of the climber itself? Is this a design problem? The quality of Chinese steel is under question to begin with.

In terms of practice, the crane appears to have gone over to the side. So was the tower properly plumbed to 1:500? Was there wind at the time of the accident? It's noticeably calm during the report so that doesn't strike me as likely. Given that there is little twist in the tower, I wouldn't expect that the crane wasn't slewed off kilter. The only other thing that strikes me as a potential is the human error of running the climber over the top of the tower. Often there isn't a terrible amount of play given here, and if you went past the mid rollers, this would be a likely result. Original Link 

中國哈爾濱, 塔式起重機倒塌, 塔式起重機事故

Tuesday, November 30, 2010

June 26th, 2008

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.

Monday, November 29, 2010

November 24th, 2010

Downpatrick Ireland. Getting back after a long US Holiday weekend and I find that 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.

Monday, November 22, 2010

November 13th, 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.

November 20th, 2010

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


Thursday, November 18, 2010

November 16th, 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

November 12th, 2008

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

Wednesday, November 17, 2010

October 22nd, 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


Tuesday, November 16, 2010

1980 and Earlier Australia

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