Do you need to retire carabiners that have been dropped

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bjorniam
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Do you need to retire carabiners that have been dropped

Post by bjorniam » 27 May 2018, 20:42

This is shared from https://fatcanyoners.org/2012/05/05/dropped-carabiners/

This is a controversial topic that comes up every so often and which, due to the often singular importance of carabiners, is worth some further research.

If you want the one word executive summary, it would read; “No” (as in no, you don’t need to immediately discard dropped carabiners). If however you want to know when you should and shouldn’t, and why, then read on…

Firstly, lets look at some of the specific testing that has been done on the topic. Basically they all boil down to dropping some ‘biners from a great height, setting up an industrial tension rig and testing said ‘biners to failure. A summary of a few such reports follows.

According to Chris Harmston, the quality assurance manager at Black Diamond: “I have test-broken hundreds of used, abused, and dropped ‘biners (even some that fell 3000 ft. (1000 m) from the top of the Salathe Wall on El Capitan). Never have I noticed any problem with these unless there is obvious visual damage to the ‘biner. While somewhat reassuring, this does not give you carte blanche to use carabiners that have been dropped a significant distance. Immediately retire any carabiner that is crooked, has deep indentations, or has a gate that doesn’t operate smoothly.” (If you dont know what the Salathe Wall is check out Mayan Smith-Gobat climbing it!)

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Impact point on Wild Country ‘biner dropped 255m onto hard surface (photo Richard Delaney)

Closer to home we have a new test rig set up in Katoomba that is churning out some very interesting results (and is always looking for some damaged ‘biners to test).

Richard has started a facebook group that includes lots more discussion and videos of ‘biners being loaded until failure. He has for instance tested 6 locking gate carabiners (3 x aluminium, 3 x steel) that were dropped 255m onto a steel plate (a fairly extreme scenario).

Post drop observations:
  • 3 steel ‘biners all obviously broken and unusable
  • 3 aluminium biners some observable impact marks but appear normal
Post drop destructive pull tests:
  • 2 recovered steel biners: gate open strength as expected (normal)
  • 3 aluminium biners: 1 landed on crotch and impact resulted in complete gate separation. Destructive pull-test performed (gate open). Failed at 19.20kN (rated gate-open strength 20kN). Another survived with gate intact and failed at 23.79kN (rated to 24kN). A video of the later is here.
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Gate blown off ‘biner that was dropped 255m onto a steel plate sitting on concrete (photo Richard Delaney)

From these tests we can conclude:
  • Steel carabiners, for many reasons, appear to suffer obvious physical damage from large drops
  • Aluminium carabiners may not have any obvious physical sign of damage from large drops
  • 3 aluminium carabiners suffered no loss of strength from large drops
  • This was a very small sample size. However even with a sample size of 1000 one cannot be assured that number 1001 may not land in a particular orientation and suffer some undetectable damage resulting in a significant loss of strength.
So what would be a good legal recommendation for a website to make? (legal disclaimer; no one in any way associated with this post is qualified or generally recommendable for legal advice) Follow the manufacturers’ instructions with regard to use, inspection, and maintenance for all your equipment. If they say destroy after a significant fall then send it to “Rope Test Labs, PO box 193, Katoomba, NSW 2780” and Richard will gladly destroy it for you. This is a way for them to increase their sample size and thus validity of the results (so we can follow their recommendations with greater trust).

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Presumed impact point on aluminium ‘biner dropped 255m onto hard surface (photo Richard Delaney)

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Same ‘biner post pull test. Peak force was 23.97kN, just short of rated strength or 24kN (photo Richard Delaney)

And lastly 2 more experiments;
  1. In a test conducted by REI, thirty carabiner bodies (half ovals, half Ds) were each dropped six times onto a concrete floor from a height of 33 ft. (10 m). Following the drops, their open-gate strength was measured and compared to thirty control samples from the same production batch that had not been dropped. The statistical result was no loss of strength.
  2. At the International Technical Rescue Symposium, 2000, Garin Wallace and Kevin Slotterbeck of SMC presented data on the strength of carabiners that had been dropped 27’ or 54’ onto concrete or asphalt. One by one, they dropped 115 new, SMC locking D aluminum carabiners. Then they broke the carabiners, measuring the breaking strengths. What do Garin and Kevin say about using climbing hardware that has been dropped? Retire your hardware if you drop it (they do work for a manufacturer, after all). What do their numbers say? The carabiners that were dropped were no weaker than the un-dropped carabiners. In fact, the average strength of the dropped carabiners was slightly stronger than the un-dropped carabiners, but the difference was not statistically significant (during the presentation a certain engineer from an unnamed airplane manufacturer in the Seattle area was heard muttering something about forge hardening).
All in all the data from these diverse range of experiments using a mix of different ‘biners seems to be confirming the same thing, that unless there is clear visual damage it is unlikely the ‘biner has been weakened. That said, when it comes to essential safety gear that is used in life and death situations, it is probably best to err on the side of caution.

Finally, if you want to inform yourself about some more rope work related concerns / myths you can check out ‘On Rope’ by Smith and Padgett, onrope1 (not related to the book) and geir hundal. Some of these are climbing specific but most are life and death issues for every canyoneer.



Neo
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Re: Do you need to retire carabiners that have been dropped

Post by Neo » 27 May 2018, 21:26

Noice

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marilyn_scott1950
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Re: Do you need to retire carabiners that have been dropped

Post by marilyn_scott1950 » 28 May 2018, 09:33

Excellent post, thanks Bjorn!

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Re: Do you need to retire carabiners that have been dropped

Post by Flynny » 28 May 2018, 16:24

I always thought the issue with dropped Aluminium compounants was not with static strength but with the effects heating and cooling have on possible mirco fractures.

This is more relevant to descenders that heat up a lot when descending then cool rapidly when they get plunged into cold water at the bottom but also relevant to carabiners that are used for for z lines, belay situations and stuff.

The Linear Temperature Expansion Coefficient of Al is about twice that of steel. It's also work hardens. All that expanding and contracting on something that is already stress fractured can't be good.

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Re: Do you need to retire carabiners that have been dropped

Post by tom_brennan » 30 May 2018, 15:21

Flynny wrote:
28 May 2018, 16:24
I always thought the issue with dropped Aluminium compounants was not with static strength but with the effects heating and cooling have on possible mirco fractures.
The "micro fracture" theory was what I heard when I first started canyoning. And that was why you were supposed to retire any piece of gear you dropped, even if it was only a metre or so.

But as far as I can tell, that was a myth, and there's no evidence of micro fractures.

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Re: Do you need to retire carabiners that have been dropped

Post by Flynny » 03 Jun 2018, 10:52

It would be good to see the test done thou with the heating and cooling rather than just drop it and put it straight on test machine.

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Re: Do you need to retire carabiners that have been dropped

Post by T2 » 04 Jun 2018, 13:35

Flynny wrote:
03 Jun 2018, 10:52
It would be good to see the test done thou with the heating and cooling rather than just drop it and put it straight on test machine.
You should pass that onto Richard Delaney from RopeLab.

That said, given the temperatures that 7075 aluminium (the find used in most climbing / abseiling applications) can operate at, the temperature changes we impart on them are quite minimal. I'd be surprised if a 'biner varied more than about 40C between being hot while descending and being cooled in the canyon water.

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