This accident happened on October 17th of 2003 at the Harculo Power Plant Netherlands. The Harculo Power Plant is a natural gas plant in Zwolle, Netherlands. It has an output of 349MW. It is important to know that the plant was mothballed in 2001 and then brought back into production in 2002. This is a good indicator as to the condition of the cranes during this overhaul that was taking place at the time of the failure.
I have read several different blogs on this accident. Many say that it was a wire rope failure. Some say operator error, or even the crane manufacturer. The more I look at this though the less I think it was a wire rope failure. It looks more like a load brake failure to me. If it was a wire rope I think it would have dropped quicker than it did, and you would have seen the frayed ends on top of the rotor when it fell to the ground. This crane was hoisting and moving a 70 ton gas turbine rotor that was worth 8.5 million dollars. The failure almost killed two workers. They were so close to the drop that it must have been pretty traumatic for them. This is a great video for training purposes to show why you should not be standing under a load during operation.
It you get anything out of this video, I hope you get how important load brake inspections are. Load brakes cannot be inspected during a routine quarterly or annual inspection. This is an inspection in and of itself. Especially on larger cranes like this one it will take a couple guys and will take the entire day to go through the dis assembly and inspection process. Check with your hoist manual to see when the frequency of gear box inspections should take place on your equipment. Now.. check out this video and tell me what you think....
I'm a little late coming to this, but my guess would be a motor coupling failure. There was a shot of a destroyed coupling at the end of the video. Without knowing more about the make and design of the hoist, I'm assuming that the motor was Vector Loop controlled. The VFD using the motor as an eddy brake (load brake). If the motor coupling breaks, there is nothing to hold the load but gearing (if the holding brake is on the back of the motor).
ReplyDeleteI noticed that the rope didn't spool off the drum (inertia of the spinning drum). I would guess that they probably had a holding brake independent of the motor and coupling. The holding brake wouldn't be able to control an over speeding load if the operator didn't remove the input command from the drive for a half a second (typical reaction time). Although it may eventually slow it to a stop, or stop the rope from spooling off the drum.
Hope that helps.
I had another thought on this while driving to a customer's site to give a consult. If it was using closed loop vector control, they may have programmed a load float into the VFD. If the operator didn't hit the emergency stop when the load fell then the brake wouldn't set until the programmed time expired. Also explaining why the rope didn't spool off the drum.
ReplyDeleteAgain... that's if the holding brake was independent of the motor.
Sorry for the delay with getting back to you on this. It could be the motor coupling. However I feel that because of the noise it made the motor coupling breaking is the not the root cause. Something failed prior to the motor coupling failing. I don't know if ithad a closed loop vector control on it, however I would have to think that it did not. I think the noise you hear prior to the failure is something happening internally in the gearbox. It also appears to happen when the load started going down. I think the gearbox had an internal failure causing the motor to try to push through it and snapped the motor coupling.
ReplyDeleteYou are correct however about the VFD. That is exactly what would happen if that was the case. I just don't know the probability of them doing that. This accident makes me wish they would make crane accident records public information so we could study this more. I have been looking into this accident for a long time but could never find much information regarding it. Thanks again for posting your comments. They are greatly appreciated.
Hi i am a piping foreman/supervisor in the oil industrie, and worked whit small 25T crane's up to the 7000T Saipem 7000, and even placed two flare tips whit a helicopter.
ReplyDeleteWorked all over the world, started in Holland, and Europe, and ended up ware the money was in shit holes like Azerbaijan Nigeria and all over the middle east, and work now in the Norwegian offshore as a maintains supervisor on one of the oldest platforms Gullfaks A, a old stile platform ware there is always a lot of work.
I looked at the video and it looks like the coupling between the motor and the gearbox, or between gearbox and cable drum had catastrophic failure.
This i don't know for sure, but i think the crane operator tried to lift the load backup in a reaction of what was happening in front of his eyes.
And in doing so he released the brake, if he would had released the controls, properly the load would have stopped, as a crane like that almost always has breaks on if there is no input from the operator.
My view on this incident, to put it blunt, shit happens.
You say this is a good example why we need better inspections, i think the the inspections we have good enough, as better inspection you will have diminished returns, and it may sound crud, but how mouths is 100% preventing accidents like this worth.
You cant put a value on a life is the saying, but thats not really true is it, ask a health insurance company, and they can tell you precise whats it worth.
I started working in the 80s, before the safety change that was set in in the 90s, and don't get me wrong i am all for most of the safety improvements, but i also think we went to far in it.
As in the 50s till 90s, we got a hell of a lot more done in a day, and we also had lots more fun at work, and you did not have to be on the look out for backstabbers.
So my conclusion from what i can see from the movie, is that the coupling of all cranes of the same design have to be inspected, and preferably replaced by a stronger type, if it was not a manufacture fault or broke by external influences like corrosion or ware because of misalignment.
But there are no general lessons to be learned from this accident, as the only way i see to preventing something like this happening again is by over design the cranes by using a higher safety factor, and way more inspections that would run companies with small margins in to the ground because if inspection cost.
I am a retired millwright who had 40 years of service in the manufacturing sector. The last 20 years of work involved using and also servicing cranes of that style.
DeleteWhat I see in this accident is: the load dropped and pulled the hook with it. The title indicated the weight of the rotor was 70 to 75 tons. ( Different videos) Is that US tons or metric tonnes? What was the weight of the rigging including the spreader beam? The shot of the equipment tag indicates an load rating of 60,000 Kg. for the hoist. The coupling between the motor and cable drum gear reducer appears to be catastrophically damaged and the material appears to be some type of ductile iron or cast iron. There are too many unknowns to make an educated guess about what the cause of the failure was except for the weight discrepancy. My opinion based on available information: This was an over capacity pick which caused the crane to fail, dropping the load, almost killing at least 2 workers and damaging at least 2 pieces of expensive equipment, the turbine and the crane.
Who is the turbine OEM?
ReplyDeleteTower cranes, conversely, do not generally have a moveable base. These are often the tallest cranes, and have to be assembled piece by piece. The base looks like a long ladder, and the boom is perpendicular to the base. Tower cranes are used to construct tall buildings, and in the case of skyscrapers, the tower crane is often assembled and affixed inside the building itself during construction. Find out more: workboathire.com
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