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JeffreyR

Carabiner Failure...?

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Gene,

 

Maximum stress is what breaks stuff. There is no time component. If the force divided by the area across which that force is distributed is higher than the maximum tensile stress of the material, even for a nanosecond...snap.

 

Force itself has a time component, of course. F=MA and all that rot.

 

Human error (not locking the gate) is pretty common. In addition, some locking biners, my big Omegas included, can get stuck in an 'almost locked' position sometimes. Usually a little hand filing will fix things.

 

Biner gates sometimes momentarily open when the biner, particularly its spine, is slammed against something. The biner stops suddenly, the gate keeps moving (and opens) due to inertia. If the biner's under a huge load, it might deform enough during that brief time such that the biner can no longer close. This is one reason why wire gates are inherently a tad bit safer in general: lighter gates = less gate inertia, and wires allow for more room for a stronger gate spring in the biner itself.

 

The twang of a slackline could also vibrate a biner fast enough to open the gate momentarily, I'd wager. Don't know.

 

I suppose that if you've got a mix of biners on your draws, its best to use the wire gates for the rope end...they're the most likely to be slammed hardest against the rock during a fall.

Edited by tvashtarkatena

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OK. another theory if you will.

 

Flexing of metal will cause it to fail at some point. How about the tolerance between gate and biner body? If the gap between the gate pin and body notch is larger enough, then the flexing of the body before the gate prevents further movement could with time, weaken the body. (I think this biner is a keylock but I don't know what to call the respective parts in a keylock, key bulb and lock notch?)

 

The bouncing around on a slackline would give repeated heavy stresses to the locker biner. Suppose it comes down to ductility and the flexing ability of certain metals which aluminum should do well with.

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That's not impossible. Unlike steel, aluminum can't be designed for infinite life under fatigue loading. It would probably take a lot of cycles, however. Plus, the gate doesn't have much play, so maximum stress caused by fatigue loading would be limited.

 

I'll need to perform a virtual finite element analysis on the biner in question based on the photo before fabricating a conclusive cause of failure.

 

I just think that the the slackline was too tight and the force on the anchor headed for infinity...when the gate momentarily opened for some reason...the group was forced to break out the hacky sack.

 

For you slackers out there, keeping your loaded slackline angle below 172 degrees should prevent similar failures. Steel locking biners are an even better idea...double up on that webbing, though.

Edited by tvashtarkatena

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Actually there Tvash, even steel does NOT have infinite fatigue life. That said, civil engineering projects that use steel are (often, not always) typically not driven by fatigue design, unlike (often, not always) aircraft designs that typically use aluminum. Plus civil projects have (typically) far higher (static) margins of safety (what is it - 5, 10?), which provides for better fatigue life. Aircraft typically have far smaller static margins of safety - 1.5 is the regulation. This plays directly into fatigue life.

 

But, what's germane to this particular question: One thing as it relates to fatigue - applying a load cycle close to ultimate (breaking) load does incredibly more fatigue damage than does applying a load cycle at a small fraction of limit load. Only a few cycles of near ultimate load can initiate fatigue cracking where hundreds or thousands of 1% of ultimate load cycles will do negligible fatigue damage.

 

http://en.wikipedia.org/wiki/Fatigue_%28material%29

 

See the S-N plot - note the logarithmic scale - as the load increases toward the (static) breaking strength, the number of cycles drops on a logarithmic scale. One doesn't need to think about it too many times to understand the nature of the problem as it relates to slack lining. Each time someone hops on the slack line, they're imposing a stress cycle on the attaching hardware. Each time they do a jump or trick where the line is un-loaded then loaded again, it's a cycle. Even bouncing up and down applies cycling loads - each one does fatigue damage. It doesn't take too many of those cycles at 1/2 to 2/3 of the ultimate strength to fatigue out the hardware.

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This doesn't really have much to do with anything, but this past summer while commercial fishing we had a steel biner bend open (the long side without the gate bent in half). It was holding two long, heavy gill nets together and we think that maybe it got slapped by another boat's prop or maybe the gate was pinned open when the nets got an extra forceful tug on them. Everything has it's limits.

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Drop the % UTS below the endurance limit and your steel part will give you infinite fatigue life. S-N diagram from Strength of Materials 101 and all the rot. Practical factors like surface damage, etc notwithstanding.

Edited by tvashtarkatena

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A newton is about the weight of an apple. It probably took more than 50,000 of em to break that fishing biner. You'd see that if you were trying to pull up an orca.

 

Attention on deck, bitches.

Edited by tvashtarkatena

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I think you'd more likely catch a Beluga or some seals where I was. Apparently these things happen. I'm pretty sure we just caught a boat. Everyone was pretty surprised about the broken biner though (or clips, as they're called in boat speak). Lots of forces at work there.

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broken%252520carabener.jpg

 

One of my friends was slack-lining and had a carabiner snap. It was a fairly short line (no more than 30') and shouldn't have been under a huge load. Any thoughts...?

 

looks like a nose hook failure to me ... an open gate failure looks a bit different as per the BD examples

 

The photos below show typical failure locations for one style of carabiner tested in four different configurations. As you can see, a nose-hooked carabiner will most often break at the top of the spine, while open and closed gate failures typically occur at the bottom of the spine, and minor axis failures almost always occur at the gate.

 

Nose Hooked Failure

 

 

DSCN2622.jpg

 

Open Gate Failure

 

DSCN2623.jpg

 

Bottom Line

When a carabiner is loaded while the nose is hung-up on a bolt hanger, a leveraging open-gate scenario occurs. Carabiners are significantly weaker in this configuration—less than 10% of closed-gate strength.

 

How to avoid this? Always ensure that the carabiner’s gate is closed and the carabiner is correctly seated.

 

http://www.blackdiamondequipment.com/en-us/journal/climb-qclab/qclab/qc-lab-weakness-of-nosehooked-carabiners/

 

 

Edited by bearbreeder

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Hard to imagine a hooked nose scenario on a line someone is walking. I'm going with Tvash's scenario for the gate opening or it just being a shit biner and the gate popping out of lock.

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Interesting. Thanks for the post.

 

Apparently the force that caused the open gate failure in the 2nd photo straightened the biner's spine. Damn.

 

 

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I think you'd more likely catch a Beluga or some seals where I was. Apparently these things happen. I'm pretty sure we just caught a boat. Everyone was pretty surprised about the broken biner though (or clips, as they're called in boat speak). Lots of forces at work there.

 

Take a 50 tonne boat and slow it down from walking speed (1 m/s) to a stop in one second and you've got 50,000 kN and a broken clip. Doesn't take much of a nudge with something that massive.

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Hard to imagine a hooked nose scenario on a line someone is walking. I'm going with Tvash's scenario for the gate opening or it just being a shit biner and the gate popping out of lock.

 

wed have to see a drawing of the setup ...

 

ive seen a nose hook on webbing and other such ...

 

 

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are you sure it wasnt hooked to begin with ... or something didnt shift?

 

neither i or you were there so theres no way to tell ... were just arguing in circle about who has the bigger diick ...

 

the only evidence would be a photo/drawing of the setup and the failed biner ... which according to our BD friends, OG failures usually break at the bottom of the biner ... perhaps you have test data which shows otherwise?

 

my suggestion would be for the OP to send the biner in with a description and drawing of the setup to a manufacturer ... and let them analyze it

 

i assume that the OP used 2 opposed in the setup since its a non locking biner?

 

 

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No use arguing who has the bigger dick here.

 

I do.

 

Looking at the original photo again...and comparing to the BD site pics...it does look like a hook failure, given the break in the upper location and lots of deformation of the hook end. Each of the four main biner failure modes leave a pretty distinctive signature. Thanks again for the link.

 

Hope I never have to refer to it practice....

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are you sure it wasnt hooked to begin with ... or something didnt shift?

Only an idiot would get on one without checking the rig so nose hooked on setup is incredibly unlikely. And after they are set up and tensioned they don't "shift" in the way you are thinking.

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I'm going with Tvash's scenario for the gate opening or it just being a shit biner and the gate popping out of lock.

 

 

It does looks like the gate and nose were not in contact in any meaningful way before the carabiner broke. Look at all that blue anodizing on the nose. No apparent gouges.

 

 

Chad

Edited by Lodestone

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I'm going with it's a total piece of shit biner which failed for exactly that reason. Buy their shoes if you must, but hardware? From those guys? Never...

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It actually looks like a really good biner design to me. 24 kN instead of 22. Nice geometry. Light.

 

I think it just got overloaded with Higgs bosons.

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Only an idiot would get on one without checking the rig so nose hooked on setup is incredibly unlikely. And after they are set up and tensioned they don't "shift" in the way you are thinking.

 

there are idiots climbing ... no offense to the OP ...

 

you werent there and you dont know

 

however we do know that everyone loves comparing their diick size on the intrawebs ...

 

the people best suited to figuring what happened are the people on the scene .... or professionals ... in this case likely the people who make biners

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you werent there and you dont know

I don't need to have been there to know that no one got on a slackline with a hooked nose - you can't tension a slackline with it in a hooked nose configuration.

 

And if the biner was sold by those guys then I don't care what shape it is or what's stamped on it - I wouldn't trust it as a key chain.

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