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Posted By Peter Haughey
One of the sites I look after has just had an accident (nobody hurt, thank goodness), where a bundle of rebar (7 m long, 47 lengths) slipped out of the chain slings and fell about 15 metres.
Some of the bars have a distinct bend as opposed to being straight, probably due to their length, as they are originally from coils.
I am speculating that some of these curved bars twisted within the bundle as it was being moved, thus reducing the diameter of the bundle, and slackening the grip of the chain slings.
Have any forum members had any similar incidents, or any evidence that might support (or otherwise) my theory?
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Posted By alex mccreadie
Peter
This is a difficult one to answer as you will probably not be given the full facts.
Was the slinger qualified? were the chains connected properly? was the load plumbed before lifting commenced?Did the load hit something whilst being raised/
Sadly you will be left with speculation theory unless you can answer the above and probably a lot more I have not added.
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Posted By alex mccreadie
Sorry Peter the computer posted my last before I had finished!
Your theory could be the answer but is purely speculation.
I have not seen this happen before if the load is properly slung, but we learn something everyday.
Ta Alex
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Posted By safety medic
Peter,
It seems you have identified the cause.
My suggestion is to check training records as previously mentioned, refresher training where initial training took place some time ago.
Remember that lifts should be planned and (LOLER) irrespective of the simplicity and written if repetative or complex. Repetative lifting operations such as rebar should be planned and written in my view.
However back to the incident, it is considered best practice that where steel (chains) on steel (rebar) exists then the chains should be double wrapped around the rebar, this provides a choke/bite on the steel whereas a single wrap doesn't due to the hook back onto chain creating a triangular gap underneath, allowing the steel rebar to move if unbalanced.
Whilst you wont find anything in ACoP or LOLER I insist that all steel on steel lifts (rebar) are double wrapped. You can of course use a choke hitch with a webbed sling but it is more likely they will get damaged on the rebar but slings must be used for smooth steel such as scaffold tubes.
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Posted By Peter Haughey
Hi Guys, thanks for your very prompt responses (don't you ever SLEEP?!).
I have studied site security CCTV, which shows it happen, but it is not clear enough to see exactly what started the chain to slip. I understand the bundle WAS only single hitched, though good practice says it should be double.
The crane tracked about 20 yards, before slewing as he lifted, and there may have been some vibration due to rough ground. But this is exactly how he has lifted about 200 other bundles, with no incident.
I will obviously be pointing the finger at the competence of the slinger, but I am still curious about what contribution the curvature of the bars may have made. When laid out, some of the bars are VERY curved, which you don't notice in shorter lengths (these are 7 metres long).
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Posted By Robert K Lewis
Single hitching is always risky and with what was effectively a multiple loose load it had a fair probability of occurrence.
You certainly need to look at the slinger competency but the crane driver also bears a responsibility as this is one of the instances when he had the responsibility to override the signaller, who is the other link if he is not the same person as the slinger. The issue may also be cultural thinking that as nobody, especially a supervisor, has stopped them previously then the system is OK to follow. Look at your supervision - are they stopping poor practice or conniving at its use?
Bob
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Posted By The toecap
If possible i would have choked the load with a man made sling and not chains however it would appear the mass was too great and therefore the load split down into portions.
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Posted By Ali
Ever tried to place the curved bars on the outside to test your hypothesis ? Might even allow tighter bracing.
Ali
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Posted By William
I would never use chains myself as they don't bite as well as wire slings or nylons, but best to avoid using nylons as they tend to be damaged easily. Its always good practice to use a double wrap when lifting anything that needs slung and it would not be easy to do this using chains, I would say make your lifting policy one of using wires and double wraps when slinging, also look at the competency of the slinger and identify if they need further training.
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Posted By Gerry Marchant
Peter
Suggest before you start looking for blame look at the lifting plan..what did that say in relation to slinging of bundles and the lift procedure, i.e. checking for plumb before to far of ground etc
Gerry
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Posted By alex mccreadie
Peter
I was just looking through the previous responses which all give sensible help and ideas as to the incident.
I picked up on one of your comments "the crane tracked" does this mean it was a crawler crane?
If so I would suggest your lifts as mentioned previously are carried out by Wire Rope Slings choked.
If you are Tracking with the load and not slewing yes there would be a lot of vibration.
This would in some cases cause the load to slip (you have the proof). Not definitive but I feel close to the mark although some would say still a hint of speculation.
Ta Alex
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