Bushwalking gear and paraphernalia. Electronic gadget topics (inc. GPS, PLB, chargers) belong in the 'Techno Babble' sub-forum.
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Fri 10 Aug, 2012 2:40 pm
I thought this topic might be of interest to any canyoners, climbers or other users of carabiners on here.
One of my canyoning mates has done some research and pulled together a post on what a range of experiments and experts from around the world have to say on the impact of falls on the strength of carabiners.
(You can read it here: http://fatcanyoners.org/bush-guide/dropped-carabiners/
Most manufacturers seem to advise that you dump them after any significant fall, and given they are such an essential piece of safety gear most people would comply. But interestingly there seems to be very little if any evidence to back that up. Even in some extreme examples -- a guy in the Blue Mountains has dropped them 255m onto a steel plate then tested them -- they seem to retain their rated strength.
Obviously people will always make their own mind up on when it is time, but it does seem to throw into doubt the concept of these 'micro cracks' that are invisible to the eye but weaken the structure of the 'biners. That said, if anyone has any evidence to the contrary I'd love to hear about it!
Fri 10 Aug, 2012 4:07 pm
I don't intend to offer specific advice but just a comment. The issue of not using the biners after a fall is NOT that the fall directly weakens them, it won't unless there is detectable physical damage. What is the issue, as you allude to is that shock loading may introduce stress concentrators such as invisible cracks which, over time, perhaps a very long time, will open up and grow every time a load is exerted on the device. For this reason, the ultra-conservative approach of manufacturers and climbers is to say discard them, as wasteful as this may seem.
A fairer way to test this idea, rather than testing their strength after a drop, is to drop them or subject them to a shock load and then cycle them through a series of loads for thousands or tens of thousands of cycles and then test their ultimate strength. If cracks were introduced from the first shock load the regular loads should open them up and the cracks wil grow and eventually weaken the device. Note that there is a difference in this fatigue crack growth between aluminium and steel. In steel there is a critical crack size below which crack growth will NOT occur. In aluminiun there is no critical crack size, any crack introduced will EVENTUALLY grow large enough for failure to occur.
If biners were aircraft components they would be regularly crack tested and I expect could be used indefinitely if no cracks or other damage was found but such testing on biners might not be practical or cost effective.
Fri 10 Aug, 2012 6:06 pm
I was always told if they 'ping' on a drop retire them until you can have them x-rayed for cracks.
Fri 10 Aug, 2012 10:16 pm
i have some that are over twenty years old (only reason i dont use them is they are *&%$#! heavy compared to modern ones). Incidently my old man told me dropping them did nothing back when they were still new. Glad he knew what he was on about!
Sat 11 Aug, 2012 2:28 am
David, I've actually had a couple interesting email response that covered the cracking issue. The first, from a guy who worked for Black Diamond for over a decade, is below:
The "micro-cracking" phenomena is found in high-tech ceramics, a very brittle material, and in the over-eager minds of engineering students who are introduced to the concept in a sophomore engineering class. Fully hardened aluminum is not at all like high-tech ceramics, and micro-cracking has never been observed.
The second guy is someone who has a friend in aviation who for fun scanned some old 'biners with a mass spectrometer. He also failed to find any with any signs of hidden cracks.
I've always heard the same from people, but it is interesting that I am yet to see any reports that provide evidence for it. If you've seen something I'd love to have a read!
Re the cycled shock loading, I think that sounds a great idea and I'm going to pass it on.
Sat 11 Aug, 2012 9:08 am
I'm still using 40 YO Chouinard crabs, I scrap them only if heavily scarred.
Lucky for me mine are the first generation of lightweight crabs ( mix of 2200kg and 2000kpa ) so not too heavy, not that I climb anymore but I always have my belay crab and a length of tape with me "Just in case" as well as the Spectra line.
I started doing this when my kids were little and just got into the habit. been useful more than once
Sat 11 Aug, 2012 9:09 am
I think a new crab is cheaper than an X-ray
Sat 11 Aug, 2012 9:28 am
FatCanyoner wrote:The second guy is someone who has a friend in aviation who for fun scanned some old 'biners with a mass spectrometer. He also failed to find any with any signs of hidden cracks.
Doesn't a mass spec measure molecular composition? I do know it requires the sample to be vaporised - would make finding cracks a bit difficult?
Sat 11 Aug, 2012 10:32 am
Moondog55 wrote:I think a new crab is cheaper than an X-ray
Yeah - and it appears from this discussion that the advice i was given is now bunkum
Mon 13 Aug, 2012 1:20 pm
Strider, I think you're right. I'm trying to chase the guy down who did the tests to get the exact info. I presume it was probably an x-ray or similar.
nq, I think a lot of the info around on this topic is bunkum, hence my interest in this post. It is amazing that the common wisdom seems to have no evidence to back it up!
Moondog, your 40 year old crabs are probably better quality than half the cheap stuff around these days. I've been talking to some canyoners in the states re this, where sand abrasion is huge, and they have the same view re heavily scarred biners. They say they wait until it is about 1/3 cut through before they retire!
Mon 13 Aug, 2012 6:34 pm
FatCanyoner wrote:It is amazing that the common wisdom seems to have no evidence to back it up!
So very true on so many topics.
At least with climbing gear I will tend to stick with the most conservative half-sane approach until really good evidence to the contrary!
Mon 13 Aug, 2012 8:23 pm
Perhaps the people were confusing the ideal situation on ropes, I am very cautious with ropes, 10 years or two falls usually
Tue 14 Aug, 2012 11:06 am
This is a question that has come up repeatedly over the years and continues to be asked.
If you look around a bit on the web it isn't too hard to find out where the truth lies. In a nutshell, microfracturing isn't an issue with carabiners and it is a pretty good bet that a carabiner that looks okay with a close visual inspection and has a smooth gate action is safe.
Here is an excerpt from an article written by Clyde Soles in a rock climbing magazine from the late 1990s:
Unlike nylon products, carabiners do not lose
strength with age -- they will pretty much last
indefinitely. Which is not to say that carabiners
don't wear out... or that you don't have to take
care of them.
The primary reasons you will need to retire a
carabiner are grooves worn by abrasive ropes,
gouges caused by steel pitons and bolt hangers,
and corrosion (white powdery substance) caused
by salt water or even the sweat from your hands.
Inspect your biners carefully for these signs, as
well as any evidence of tiny cracks -- particularly
around gate pins and hinge pins.
Some climbers are concerned about the poten-
tial for strength-robbing micro-cracks that are not
visible to the naked eye. Indeed, conventional
wisdom says that a carabiner which has been
dropped must be retired, even when there are no
signs of damage. Perhaps not.
In a recent test by Steve Nagode, an engineer
at the REI quality assurance laboratory, 30 cara-
biner bodies (half ovals, half D's) were each
dropped six times onto a concrete floor from a
height of 33 feet. Following the drops, their open-
gate strength was measured and compared to 30
control samples from the same production batch
and that had not been dropped. The statistical
result was no loss of strength.
According the Chris Harmston, the quality
assurance manager at Black Diamond, "I have
broken hundreds of used, abused and dropped
biners (even some that fell 3,000 feet from the top
of the Salathe). 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.
Dropping them, even from great heights, may not
harm them unless they are in any way deformed
(because metal doesn't fatigue by impact but by
bending or stretching -- which can happen when
loaded almost to failure or over an edge).
Immediately retire any carabiner that is crooked,
has deep indentations or has a gate that doesn't
operate smoothly -- three problems more liely
to occur in ultralight carabiners.
If a carabiner gate is sticky because it's
tweaked rather than oxidized or gritty, you
should retire the biner. If you use your biners
near saltwater, be sure to rinse them thoroughly
in fresh water, allow to dry in a warm place and
then lubricate them before storage. Remember,
it's the water inside the biner, where you can't see
it, that is of greatest concern. WD-40 is a good
water dispersant and penetrating lubricant.
However, such a petroleum product will work
well at first but can attract grit, possibly causing
worse problems than what you tried to solve. A
better solution for sticking gates is a dry silicone
lubricant, such as Finish Line or Pedro's, both
used for bike chains.
(Clyde Soles, Rock & Ice #81, September/October 1997, pp 117-118)
And here is the latest advice from Black Diamond Equipment:
Q. Is it okay to use carabiners that have been dropped?
A. Unfortunately, the only way to know if “dropped” carabiners are fit for use is to test them to their breaking point. This doesn’t do you much good, now does it? It's best to inspect dropped gear for dings and significant trauma. If only light scratching is visible and gate action is still good, there is a good chance it is fit for usage. Remember, only you know what your gear has been through and if there is any doubt, it's best to retire the gear rather than take a risk.
Q. When should I retire my carabiners?
A. Here are our suggestions on what to look for when retiring aluminum carabiners:
1) Check for good gate action: The open-gate strength of carabiners is roughly 1/3 of the closed-gate strength. If a biner has a gate that rubs or sticks open, it should be cleaned and lubed. If this does not improve gate action, the biner should be retired. The same holds true for any gate locking mechanism.
2) Check for excessive wear: If you can feel that the rope-bearing surfaces of the biner are significantly worn (wearing off the anodization is normal after a few uses) the biner should be retired.
3) Check for deformation: If a biner has been loaded such that the body or nose has deformed—or the carabiner gate rivets have been bent (this usually results in poor gate action)—the biner should be retired.
4) Check for nicks or deep scratches: If a biner has nicks or deep gouges beyond the normal light scratching that occurs in use, it should be retired. Carabiners are more susceptible to surface damage near the nose hook or within an inch of the bending radii of the body.
5) Has the carabiner been exposed to extreme heat? If a biner has been exposed to "extreme heat" (i.e. a fire) it should be retired and destroyed due to possible negative affects to the heat treatment the carabiner underwent when it was made.
6) Has the carabiner been exposed to harsh chemicals or excessive corrosion? If your carabiner has been exposed to aggressive chemicals (like battery acid, petroleum-based fuel, ect.) its a good idea to retire the biner. Likewise, any corrosion beyond the normal thin gray/white oxidation layer that forms on exposed aluminum should be grounds for retirement, especially if it starts to affect gate action (see #1).
In closing: Keep in mind that only YOU know what your gear has been through. If your instincts tell you that the gear is dubious, retiring it is a good idea. Confidence in your equipment is not only key to climbing at your limit but helps you stay relaxed and having fun.
(Black Diamond Equipment FAQ -- http://www.blackdiamondequipment.com/en ... rvice/faqs
Some research into the failure modes of carabiners, including cyclic load testing:http://stuff.mit.edu/afs/athena/course/ ... ne_622.pdf
or if you prefer, here is the slideshow presentation for this research:http://web.mit.edu/sp255/www/reference_ ... tation.pdf
Carabiners are cheap, almost disposible.
Wed 22 Aug, 2012 1:56 pm
Thanks for all that added info. I think at the end of the day you are right about the price factor though. While you don't want to be throwing out perfectly good gear based on a myth about micro cracks, if there is any doubt, it isn't worth risking your life to save $20!
Moondog, I agree re that. Ropes are actually much more of an issue, with age, UV exposure, exposure to solvents etc all leading to reduced strength. In those cases the loss of strength often isn't visible. One positive for active canyoners is that your rope will be worth through by abrasion long before the other impacts on strength take hold. That said, there was a tragic accident around Christmas caused by a relatively new rope cutting...
Tue 28 Aug, 2012 6:54 am
I replaced my Chouinard / Black Diamond krabs when l found cracks on the gates of some of them.
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