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Posted By Dave Clinton
I have recently come across some chain blocks with a 2mm cut through one of the links in the hand chain, apparently for safety purposes? Has anyone come across this before?
Question: If this is added as a safety feature to enable the chain to separate under excessive load; 'as I have been told' then could this lead to a failure of lifting equipment and so be reportable?
The amount of pressure and force it would take to bend and release this link would be phenomenal and I would imagine anyone who could apply this much force when pulling would hit the floor very quickly after the link had separated, potentially causing an accident!
I have quarantined the blocks for now and I am awaiting clarification from the hire company, has anyone got any thoughts on these issues?
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Posted By Andrew Joule Land
Dave - You say it is the hand chain that has the link with the cut in it?
This chain would not be used for lifting but only to turn the lifting ratchet and so not subject to any load?
I have not come across this or maybe just haven't noticed. there again it is load bearing chain and hooks that I look at.
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Posted By Dave Clinton
Andrew, thanks for the reply.
Would the hand chain not be under load from the operator during the lifting operation for this link to potentially separate?
The chance of this happening is "I hope" remote, however because the link has been cut then it must be expected to separate under excessive load as a fail safe? I'm not to sure where this is going but I want to cover all the angles.
If it is an engineered fail safe trigger then it should be added to the risk assessment as an existing control measure for lifting operations, with the additional controls possibly being information and instruction to the operator?
Anyone who has lifting equipment; chain blocks etc might want to have a look and see if they have the same issue?
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Posted By Merv Newman
This is weird. I have never heard of nor would ever condone such a practice. The "handling" chain is just that, a light chain which acts through gears to activate the lifting chain.
The lifting chain will have it's own load limiters and end stops.
I can just imagine a handling chain failing because of a weakened link and lashing someone about the head.
Merv
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Posted By Dave Clinton
Thanks for the comments Merv,
I haven't seen this before on any other chains? but I have just received a note from the company who want to use the chain blocks stating;
"The hand chain is equipped with a safety link. When the safety link opens or deforms, stop at once and inspect for the cause."
This apparently has come from the hire company. On further inspection it has been identified that three other chain blocks have had a tack welded to the inside of the link across the cut? Something isn't quite right here, so I think the chain blocks can be sent back and changed out.
I haven't heard of anyone being struck by a chain because of this cut link failing, but until I'm totally sure that this is a recognised fail safe trigger we not going to use them.
Thanks for your comments.
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Posted By Jeepster
You will find this pretty common if you look.
It is the way you cut and adjust the length of the endless hand chain.
obviously, if you have to put so much effort on the chain that the link deforms and opens then you are probably exceeding the capacity of the chainblock and remember the hand chain goes through a gearbox to give the mechanical advantage.
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Posted By Robert K Lewis
This one has the alarm bells ringing. Yes such as chain saw chains have their own safety link. I personally have only ever found one of these on chain blocks as a result of non-manufacturer repaired chains.
I think you need more than just a piece of paper from the hire company - you need chapter and verse from the manufacturer. Endless fall chains are manufactured to pre-set sizes and can be mounted by the manufacturer/authorised engineer as a continuous loop, you do not need to shorten them or join them.
Any cut in the surface of a link is liable to create zones of high stress and thus sudden failure. I rather think these chains were damaged and have been repaired/shortened by the hire company internally to ensure continued life at "reduced cost". Look carefully at the last test certificate, see who undertook the examination and test, and compare what you have with the certificate.
Bob
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Posted By Jeepster
The important thing to remember here is that the hand chain is not a component that is in the load path. Therefore it is often not given the same consideration as a load path item.
The hand chain is a fail safe item, if it were to part and come off the block, there should be no reason for the load to drop etc. It would be inconvienient though to complete any lifting operation and require a replacement block to be rigged and the load transferred. A task not beyond any competent rigger.
Certainly hire companies / manufacturers could improve the practice by rewelding the link but I suggest that this is rare.
What is more concerning is when you buy wire rope slings with a load test certificate and by the loose shape of the eyes it is eveident that they have never been load tested in their lives.
I am not sure how they can generate a load test certificate for a serial numbered item based upon statistical sample testing to prove the effective swaging of the rope ferrules.
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Posted By William
This is something i have not came across and i am a rigger and work offshore, just wondering if the pull lifts have a chunk taken out of the lever so that they don't have too much force exerted on them. Quarantining them sounds a very good idea as something does not sound right, if anyone is worried about too much force being exerted on them then simply ensure all operators are trained in their safe use, the last thing you want is the link goes when you have a ton suspended off the deck!
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Posted By Dave Clinton
Thanks Will, The contract company involved has had the chain blocks backloaded for inspection by a third party lifting gear inspection company.
The issue was initially raised by a competent rigger carrying out the pre use inspections prior to our shutdown, so this was in my opinion" a great spot by him, he was rightly concerned as he had never come across this before and therefore raised it as a safety concern.
We are now waiting for the inspection findings, so I will update for any interested parties when we get the results.
Thanks to all who responded.
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