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sed
May 8, 2005, 3:16 AM
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I have some old biners, some stuff I've fallen repeatedly on. Common sense would suggest that repeated falls would weaken them but is this true? And if so then how? Is this the classic microcrack answer, sort of like gremlins or is there a better and more complicated answer someone can offer. I'm not looking for opinions so much as cold hard facts (why am i looking here? i know) And have studies been done to look at the load limit reductions for a biner after each succesive fall?
S
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tattooed_climber
May 8, 2005, 3:20 AM
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one rule of thumb on this topic is if there is any doubt: retire and replace
the other is common sense
i'm no engineer so maybe someone can give you some tech advice
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skymeat
May 8, 2005, 3:29 AM
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This is something that has always disturbed me. Many times I've seen aluminium crack and break, like bike frames...I'm not a metalurgist, but I've never seen a peice of aluminum that I could bend more than once (albeit extremely) without it showing some cracks. Now this is what I think about when I see my biners distort under load (the pin seating in the nose). Anybody here a metalurgist, or do destructive testing of climbing equiptment?
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maxuda
May 8, 2005, 3:35 AM
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I was told by guide that if gate works and no visible signs of damage then they are ok but wy take chance if uncertain.
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curt
May 8, 2005, 3:40 AM
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In reply to: This is something that has always disturbed me. Many times I've seen aluminium crack and break, like bike frames...I'm not a metalurgist, but I've never seen a peice of aluminum that I could bend more than once (albeit extremely) without it showing some cracks. Now this is what I think about when I see my biners distort under load (the pin seating in the nose). Anybody here a metalurgist, or do destructive testing of climbing equiptment?
This topic has pretty much been beaten to death. Aluminum does weaken from flexing, but small displacements require tens of thousands of cycles before there is any meaningful loss of strength. This is something the airline industry is keenly aware of.
Curt
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poedoe
May 8, 2005, 5:35 AM
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Adding just a bit more on to this. The thing about alluminum is that it doesn't have whats known as a fatigue limit. Steel has one, which pretty much means that steel is can take stress (force if you'd like) up untill a certain point, then its starts to become weaker; cracks develop ect. So for example a piece of steel might be fine if its only holding repeated cycles of 1000 pounds, however if it were reapeated cycles of 2000 pounds, well that might be beyond steels fatigue limit so you'll have problems (note that that are truly made up numbers, it was just a ficticious example).
So back to alluminum, which doesn't have a fatigue limit. Repeated cycles of stress, regardless of how high or low, will eventual become a bad thing. However somone has allready pointed out that typically the number of cycles is extremely high, so it's really nothing to worry about; unless your doing reapeated cycles of extreme weight on your equiptment. Well all this is from an engineering / physics perspective, which I think someone was looking for.
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skymeat
May 8, 2005, 5:47 AM
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I never thought of the airline industry. Many of those parts are taking 10,000 plus cycles/flight. Rationally I know that the industry chooses appropriate alloys...Thanks for the info.
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scuclimber
May 8, 2005, 8:30 AM
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In reply to: unless your doing reapeated cycles of extreme weight on your equiptment.
Like slacklining... :wink:
Colin
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adnix
May 8, 2005, 8:50 AM
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In reply to: This topic has pretty much been beaten to death. Aluminum does weaken from flexing, but small displacements require tens of thousands of cycles before there is any meaningful loss of strength. This is something the airline industry is keenly aware of.
On the other hand I have friends who run indoor walls. Some of their carabiners are very old but not one of them has broke. Carabiners brake mainly due to bad position or gate being open. Once the gate stops working and you can't lubricate it to work again, the carabiner is done.
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adnix
May 8, 2005, 8:53 AM
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In reply to: In reply to: unless your doing reapeated cycles of extreme weight on your equiptment. Like slacklining... :wink: |
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mr-pink
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May 8, 2005, 12:30 PM
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that's like crashing a car, if you're not dead you can start using it.
I don't think it works like that.
It's only 10 £/€/$ just replace them, your life is worth more!
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ctardi
May 8, 2005, 3:44 PM
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The slight bending of aluminum will make it stronger while it is in it's elastic range. Up to a point.
If the gate works, it's fine. If it doesn't, time for a new one!
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curt
May 8, 2005, 4:46 PM
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That was exactly what I meant by the "airline industry" reference in my earlier post. That particular aircraft had gone through 89,090 flight cycles--involving the airframe's expansion and contraction each time.
Curt
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adnix
May 8, 2005, 4:48 PM
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In reply to: that's like crashing a car, if you're not dead you can start using it. |
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chriss
May 8, 2005, 7:46 PM
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In reply to: If you do regular paragliding and have climbing carabiner as your master point, it will most likely brake under body weight in two years. Cyclic loading with body weight is a major problem.
I would like to know where you heard something like this?
For if it was even remotely true, every manufacturer would be warning of this. And carabiner failures would be an everyday occurrence.
chris
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sed
May 8, 2005, 8:34 PM
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thanks noshoesnoshirt and golgiapp(arratus). Good info, interesting reads.
my take from this is that if you rotate your biners occasionally in use type you should be alright with frequent use for a number of years, despite falls. however they won't last forever and should probably be retired after maybe 15 years of solid service.
S
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robdotcalm
May 8, 2005, 8:39 PM
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In reply to: my take from this is that if you rotate your biners occasionally in use type you should be alright with frequent use for a number of years, despite falls. however they won't last forever and should probably be retired after maybe 15 years of solid service. S
Does this apply to climbers as well?
Cheers,
Rob.calm
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adnix
May 9, 2005, 11:05 AM
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In reply to: I would like to know where you heard something like this?
This is one of the sources:
http://www.dhv.de/...oteslist.php?lang=EN
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rightarmbad
May 9, 2005, 12:21 PM
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There have been many biner failures in paragliding. Up until recently the forces applied to this crucial biner were not well understood. There are special biners made for this application and a climbing biner should never be used.
Aluminium does have an elastic zone. It is just that the transition in to the plastic zone is lower than steel and is not as well defined. If graphed, steel has quite a sharp bend where it enters the elastic zone, aluminium in it's various guises has a much broader curve. Any metal will last a long long time if operated in it's elastic zone.
If there are no obvious problems, or a known history that may lead you to suspect a problem, use em.
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waynew
May 9, 2005, 4:09 PM
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Thought this was a decent test - wonder why its just now surfacing ?
Is anyone else concerned about using pins to apply the load or am I just being a bit critical? I realize that this is kind of a standard fixturing but in this application it doesn't smell quite right to me...
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paulraphael
May 9, 2005, 5:46 PM
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In reply to: Aluminium does have an elastic zone. It is just that the transition in to the plastic zone is lower than steel and is not as well defined. If graphed, steel has quite a sharp bend where it enters the elastic zone, aluminium in it's various guises has a much broader curve. Any metal will last a long long time if operated in it's elastic zone. If there are no obvious problems, or a known history that may lead you to suspect a problem, use em.
This is exactly right. Plain english translation: If you don't see visible damage to the biner, then the load was elastic and can be thought of as a single (though pretty large) stress cycle.
Aluminum does suffer fatigue failure from repeated stress cycles, but we're typically talking about a number in the millions (for cycles of low stress, like bodyweight) to the thousands (for cycles of high stress, like cimbing falls). consider the airplaine example: an airplane wing undergoes tens of thousands of stress cycles per flight. The service life of an airplane is decades. You create more stress cycles on a biner with frequent bodyweight loading than you do with falling (how many falls does a single biner actually take in its lifetime)?
Even a biner that you repeatedly load with bodyweight, like your belay/rap biner is pretty safe. You'll saw it in half with rope abrasion long before you get to the point where fatigue would become an issue.
Which leads to a pretty good generalization: the kinds of damage that a biner is really subject to are going to be visible. severe wear, gouges, etc..
you don't have to worry about fatigue or microscopic cracking.* Under the kinds of use that climbers put biners, the failure mode will be ductile, not brittle. This was supported by an interesting (but not exactly scientific) test done by Chris Harmston years ago. He and a partner collected dozens of biners that had been dropped off of El Cap. Some appeared to be many years old and well used. They tested them to failure at the QC lab at black diamond, and found that all of them failed within specification (within whatever number of standard deviations from their rated strength). Not one failed at a scary low load.
* I'm not counting corrosive damage from marine environments. this can be bad news, and knowledge of how to deal with it seems to be evolving. just be careful.
I'm also not talking about biners that have been used for something besides climbing. If a biner was used for something that could have subjected it to tens of thousands of stress cycles, then you have no way of judging how safe it is.
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gunked
May 9, 2005, 6:37 PM
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After spending some time sifting through the Carabiner Testing report, I came across this on Page 22:
7.1 Cyclic Testing
Results of the fatigue tests for the carabiners showed that even at very high loads, carabiners are designed to last a long time. The shortest lifetime observed was 194 cycles at a 20kN cyclic load range, or at 83% of the maximum load the carabiner can carry. These results should be very encouraging to climbers because 20kN falls are the worstcase conditions, and therefore rare in the field. In other words, it is very unlikely for a climber to take two hundred 20kN falls in his or her lifetime.
-Jason :D
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adnix
May 9, 2005, 7:15 PM
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If you take the typical load of falling (about 10kN), a carabiner will last about 5000 cycles. Now if you add normal safety margin of 50%, you got 2500 falls left. If you take 5 whippers every day on the same biner and climb 100 days per year, the biner will last 5 years.
Since I do only trad climbing and fall perhaps once during 10 days of climbing, my biners will last longer than I will.
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