Deep groove in carabiner?

[nkanarik]

I recently rappelled a ~150' rappel (1st one of that day) on single strand using a fairly new Black Diamond Rocklock aluminum carabiner attached to my ATC. I weigh ~220 lbs., and the rappel was fairly slow and controlled. When I completed the rappel, I noticed the fairly deep groove in my carabiner, which made be a little bit worried about using an aluminum carabiner as my main carabiner for rappel. I usually do a double strand rappel, and never had anything close to this.
1. Is this normal???
2. I'm considering switching for a steel carabiner for my main ATC carabiner (~x3 weight DMM Steel BOA HMS)...any opinion?

[Scott P]

1. Is this normal???

If your carabiner is aluminum they can groove rather quickly, but this is especially true if the rope is wet and sandy.

Was your rope wet and/or sandy?

[skunkteeth]

I've been using the carabiner in the link below for about the last 10 canyons and there is very little wear. But my usual canyons are nowhere near as abrasive as those in the Plateau. The weight is about 1.7x your rock lock. I have not noticed much of a rappel smoothness difference between it and the Attache.

http://www.scarpa.com/edelrid/hms-bruce-steel-fg

[deagol]

that seems to be a lot of grooving for one rappel to me. I use an aluminum biner with my rap device and have done several rappels on it and the grooving is much less than that picture.

I try as hard as possible to keep the sand out of my rope for this reason.... but it is, at times, a losing battle..

YMMV

[harness man]

X2 to Deagol
It is CRAZY :eek2:what a sandy rope will do to biners and devices...

[qedcook]

The thicker canyon ropes that Tom makes, like the Imlay Canyonero 9.2mm Rope, cause really deep grooves really quickly.

[spinesnaper]

The thicker canyon ropes that Tom makes, like the Imlay Canyonero 9.2mm Rope, cause really deep grooves really quickly.

Don't know about that.

What I do know is that wet sand embedded into rope makes a very efficient grinding tool when you rappel on it. I now have retired many biners and rap devices with notches like this. Once I hit about 1/3 of the way through, even though it is body weight, I feel it's a good time to replace the gear. All gear in the field is an expendable. I personally can't bring myself to use a steel biner but these hold up much better than soft aluminum, or so I am told. I guess you could also buy a steel rappel device but that all seem like a whole lot of weight. So I just keep an eye on the gear and remove and replace it when it makes the hair on the back of my neck stand up.

Ken

[Felicia]

The thicker canyon ropes that Tom makes, like the Imlay Canyonero 9.2mm Rope, cause really deep grooves really quickly.

In theory, a smaller diameter should cut more efficiently due to higher pressure (pressure = force/area). The smaller the diameter, the higher the pressure. It's why dental floss is banned in some prisons because of its utility as an escape tool.

In reality, dunno. Maybe larger diameter = more sand per foot = more cutting power? Would be interesting to test some extremes and see what happens. Super stiff old ICG 8mm vs. a soft 9 mm rope such as Sterling C-IV or even a 10 mm dynamic, both coated in wet sand.

hank (posing as Felicia)

[kiwi_outdoors]

Don't know about that.
Once I hit about 1/3 of the way through, even though it is body weight, I feel it's a good time to replace the gear.


1/3 !!! From an engineer's viewpoint, that's not a good idea. Your life should be worth more than that.

[qedcook]

In theory, a smaller diameter should cut more efficiently due to higher pressure (pressure = force/area). The smaller the diameter, the higher the pressure. It's why dental floss is banned in some prisons because of its utility as an escape tool.

In reality, dunno. Maybe larger diameter = more sand per foot = more cutting power? Would be interesting to test some extremes and see what happens. Super stiff old ICG 8mm vs. a soft 9 mm rope such as Sterling C-IV or even a 10 mm dynamic, both coated in wet sand.

hank (posing as Felicia)

In use, Tom's thicker canyoneering ropes have FAR more friction and resistance than his skinnier ropes. All I know is I did Checkerboard Canyon with two fairly new carabiners and the thicker 9.2 mm rope of Tom's, and both carabiners were destroyed by the end, but I've been using the skinnier 8 mm rope of Tom's for over a year and haven't seen nearly as much grooving.

[Felicia]

In use, Tom's thicker canyoneering ropes have FAR more friction and resistance than his skinnier ropes. All I know is I did Checkerboard Canyon with two fairly new carabiners and the thicker 9.2 mm rope of Tom's, and both carabiners were destroyed by the end, but I've been using the skinnier 8 mm rope of Tom's for over a year and haven't seen nearly as much grooving.

I hear ya. what kind of rap device?

hank the poser

[hank moon]

Qedcook have you noticed faster device wear, or just on the carabiners? Wondering if 9mm stiffness helps concentrate pressure on the 'biner...

[spinesnaper]

1/3 !!! From an engineer's viewpoint, that's not a good idea. Your life should be worth more than that.

I guess I am more extreme than I thought.:cool2:

[qedcook]

Qedcook have you noticed faster device wear, or just on the carabiners? Wondering if 9mm stiffness helps concentrate pressure on the 'biner...

Faster device wear in general. Both the carabiners and the ATC were deeply grooved. Only one side of the ATC was badly grooved though, the brake side. I can post a pic if you guys want.

I got the 9.2 mm rope because I wanted more friction, but the 8 mm canyoneering rope feels like it provides as much friction, for me, as a 10 mm climbing rope.

This isn't a negative review on Tom's canyoneering ropes in general, just on the 9.2 mm version. I LOVE the 8 mm version!

[Slot Machine]

I've done that much damage several times in one rap. Sure gets your attention the first time.


1/3 !!! From an engineer's viewpoint, that's not a good idea. Your life should be worth more than that.

Meh. Biners are tough. I go 1/2 through before replacing. I seem to remember somebody weight testing a grooved biner a while back and it held something like 90% of the original kN's.

Don't bother with a steel biner. They are too heavy and just one more thing to worry about. I my groups we shuffle our biners around so much that I probably use a different biner for every rappel. Just try to groove your friend's biners when you can. :haha: :twisted:

[hank moon]

If your carabiner is aluminum they can groove rather quickly, but this is especially true if the rope is wet and sandy.

Was your rope wet and/or sandy?

X2 on that question.

Note that device wear in sandstone canyons is mostly a function of how the rope is handled. Most canyons that have water have pools of water. Use a rope bag and feed the rope straight out of the water and into the bag. This keeps sandiness to a minimum. Some canyons are mostly just "damp" (Spry comes to mind) and these are the worst for chewing up gear. When water is lacking, squeegee the rope through (leather) gloved hands before the rope goes into the bag.

[rick t]

Trying to keep the rope out of the sand, especially when wet really helps, but sometimes its unavoidable. Some devices will wear biners more than others, I used an SBG for a couple of years and went through a biner each year, with the metal on metal. Finally switched to a Rock Exotica Assault Stainless carabiner for my rappel device, heavier and pricey, but maybe the ultimate bomber biner.

[spinesnaper]

Trying to keep the rope out of the sand, especially when wet really helps, but sometimes its unavoidable. Some devices will wear biners more than others, I used an SBG for a couple of years and went through a biner each year, with the metal on metal. Finally switched to a Rock Exotica Assault Stainless carabiner for my rappel device, heavier and pricey, but maybe the ultimate bomber biner.

That sound about 4 times as expensive as my soft petzl biners. You probably still win because it probably last more than 4 of my biners. I personally have not figured out how to keep the sand off my rope in the plateau. In fact, I am fairly sure that is basically impossible.

Ken

[Skeeter]

I've done that much damage several times in one rap. Sure gets your attention the first time.



Meh. Biners are tough. I go 1/2 through before replacing. I seem to remember somebody weight testing a grooved biner a while back and it held something like 90% of the original kN's.

Don't bother with a steel biner. They are too heavy and just one more thing to worry about. I my groups we shuffle our biners around so much that I probably use a different biner for every rappel. Just try to groove your friend's biners when you can. :haha: :twisted:


Why do you shuffle carabiners around on your rappel device?

[ratagonia]

1/3 !!! From an engineer's viewpoint, that's not a good idea. Your life should be worth more than that.

Are you an engineer?

THIS engineer (mechanical engineering, B.S., 1982) thinks engineering is about UNDERSTANDING systems. I have the advantage of having seen 1000's of broken biners in my time at Black Diamond, and having seen the FEA of carabiners under development. There are critical locations on carabiners that you should have concern about compromising, but the basket, where the rope runs, is not one of them. I don't have too much concern about rope grooves from rappelling, and also use the "1/3 rule".

However, I have also seen a carabiner cut half way through on a 100' rappel, when conditions were perfectly bad. Matter of fact, that was two carabiners under an ATC, and both carabiners were chewed pretty good. If I had only one biner, would it have cut all the way through?

A good reason to use FAT carabiners like the Petzl Attache carabiner. And check it after every rappel.

Tom

[harness man]

X2!
1/3 rule, fat biners are best.
Also we have found that rappel devices with more surface area seem to help the 'biner by taking some of the heat (so to speak) from a sandy rope.
We have found, in sandy conditions that the devices that last longest with the 'biner, from worst to best are:
ATC
ATS
Pirana
CRITR
(A TOTEM user will have to tell us how they wear!)
We also presume, because of it's surface area, that the SQWURL will perform well in this regard.

[deagol]

X2!
1/3 rule, fat biners are best.
Also we have found that rappel devices with more surface area seem to help the 'biner by taking some of the heat (so to speak) from a sandy rope.
We have found, in sandy conditions that the devices that last longest with the 'biner, from worst to best are:
ATC
ATS
Pirana
CRITR
(A TOTEM user will have to tell us how they wear!)
We also presume, because of it's surface area, that the SQWURL will perform well in this regard.
Hmm, I was a Totem user until I got the CRITR. I think the CRITR might wear just a tad faster than the Totem?? but probably because the Totem has various rigging options that spread out the wear a bit more (but after time, I decided I would rather just rig the "easy way" instead of having several inferior options for rigging that the Totem provides). However, I have a hypothesis about the CRITR vs Totem in that . It is basically that the CRITR spreads some of the wear to the carabiner, where the Totem takes all of the wear itself (the way I rigged the Totem). Time will tell...

[hank moon]

Why do you shuffle carabiners around on your rappel device?

I have the same question. My rap device biner stays put, attached to the rap device. Also I generally use an auto-locker on my rap device (screwgates for all else) so don't want to share that around.

[spinesnaper]

I have the same question. My rap device biner stays put, attached to the rap device. Also I generally use an auto-locker on my rap device (screwgates for all else) so don't want to share that around.

X2 Except: I sure as hell don't want to share my rap device. (emergencies excepted)

Ken

[Slot Machine]

Why do you shuffle carabiners around on your rappel device?

Rap 2 biners with an atc one rappel, then one biner with an atc on the next rappel, then two...

Then remove the ATC while I meat anchor, place it on a side biner.

No sense in trying to keep it all straight. A waste of energy.

They all get very mixed up in the group, then mostly sorted out at the end of the day.

[spinesnaper]

I have dug up some biners and rap devices that I have retired. Notice that I have not melted them down and they are still in my gear box but no longer on my harness.

When I look at these now, these notches do not look so deep.

Here are my questions: Would you have retired these? Would you feel safe rapping on these? How compromised do you think these devices are as a percentage?

If any one is interested in testing the breaking strength of these, please let me know, they are available for research.

Ken

768237682476825

[kiwi_outdoors]

Are you an engineer?

THIS engineer (mechanical engineering, B.S., 1982) thinks engineering is about UNDERSTANDING systems. I have the advantage of having seen 1000's of broken biners in my time at Black Diamond, and having seen the FEA of carabiners under development. There are critical locations on carabiners that you should have concern about compromising, but the basket, where the rope runs, is not one of them. I don't have too much concern about rope grooves from rappelling, and also use the "1/3 rule".

However, I have also seen a carabiner cut half way through on a 100' rappel, when conditions were perfectly bad. Matter of fact, that was two carabiners under an ATC, and both carabiners were chewed pretty good. If I had only one biner, would it have cut all the way through?

A good reason to use FAT carabiners like the Petzl Attache carabiner. And check it after every rappel.

Tom

Masters in structural engineering, and licensed structural engineer in California. Mostly practiced in steel design. I own only aluminum carabiners, and retire them with shallow grooves. If I ever get back into canyoneering, it will be with steel carabiners. I value my life a lot.

Tom, real world experience always trumps theory, but 1/3 depth groove is something that I would never accept on a critical link in my life support system.

[harness man]

:popcorn:
Black Diamond (where Tom worked) is famous for break testing every type of climbing gear under the sun: there is certainly some test results in their archives on carabiner wear....
I think Tom's point is that 1/3 wear thru in this particular area of the carabiner does not compromise the strength much, as long as the carabiner gate is closed and locked. Also, 1/3 wear thru is when to RETIRE the biner (not keep using it).
1/3 wear thru on a Petzl Attache is different than 1/3 thru on a micro-biner (which should not be used for rappelling in the first place).
If you compare the mass of aluminum left on a FAT biner after 1/3 wear it will still be substantial compared to some micros.
Spinesnaper, lets break some worn biners!
Our ship to address is at http://canyonwerks.com if you want to send one.
We have a couple worn biners of our own and will pull them out and pop 'em:mrgreen:
the test rig
76826

[skunkteeth]

I have dug up some biners and rap devices that I have retired. Notice that I have not melted them down and they are still in my gear box but no longer on my harness.

When I look at these now, these notches do not look so deep.

Here are my questions: Would you have retired these? Would you feel safe rapping on these? How compromised do you think these devices are as a percentage?

If any one is interested in testing the breaking strength of these, please let me know, they are available for research.

Ken



I wouldn't have a problem using those. Looks like some of the reflections in the pictures makes them look deeper than they actually are.

[spinesnaper]

I wouldn't have a problem using those. Looks like some of the reflections in the pictures makes them look deeper than they actually are.

When I first discovered the grooving, I was freaked. However, I don't feel trouble in the slightest that they are off my harness. Probably reasonable to replace them but yeah, looking at them now, they do look meaty.

Harnessman

I am packing up the gear and shipping it to you. Please let us know what you learn.

Ken

[nkanarik]

Just wanted to comment that the groove in the picture I uploaded when posted this thread was from a single 150' rappel on a fairly new carabiner.

[harness man]

Thanks Spinesnaper!
we are in breaking mode (check out the SLING thread) and will post
Best
Todd and Desi

[harness man]

Thank you Spinesnaper for sending your gooved biner samples:haha:
Now we have a nice little collection to try to get a handle on the burning question: how strong are grooved/worn biners?

76901

We have utilized our very best grade-school math and a set of calipers to estimate the amount of missing material on each biner.
Close up of the last two 30% biners:

76902

Next step- the set up on the test rig.....

[ratagonia]

Thank you Spinesnaper for sending your gooved biner samples:haha:
Now we have a nice little collection to try to get a handle on the burning question: how strong are grooved/worn biners?

We have utilized our very best grade-school math and a set of calipers to estimate the amount of missing material on each biner.
Close up of the last two 30% biners:

Next step- the set up on the test rig.....

Could you be more specific on what your number means? Did you make several measurements and do some geometry to estimate the total amount of (cross sectional) material missing? or does " -30%" mean that the narrowest measurement was down 30% from the original.

From a mechanical engineering perspective, the part that is grooved out is primarily stressed in bending, and therefore the stiffness is not proportional to the amount of material, but to it's "beam stiffness" ~ w * h^^2. Therefore removing the material as shown would make it a LOT weaker. A more recent ME grad could probably spin those calculations off pretty quick (but not me).

My hypothesis, however, is that even with a 30% cutting, this is still not the critical point on the carabiner, so they should still go to full strength. I hope you are using the appropriate 9mm steel pins when you pull these, or something similar, such as a shackle. On these carabiners, the pin used probably does not make much difference. On D-shaped carabiners where the pin sits against the spine, it can.

Tom

[harness man]

Note: the majority of our biners are Petzl Attaches rated at 23 kN.
Also in the mix: a Petzl William (marked B2) at 25 kN.
And a Rock Exotica Pirate (marked B6) at 26 kN.
I our test set up we connected all biners with the basket (wide part) on the bottom and placed the shackle IN the biggest groove in the biner.

76903

then we pulled until failure (BOOM!)
Here are results in lbs:

76904

Notice something STRANGE about the breaking strengths?
The biners are arranged by how much wear (grooving) from least to worst.......but the breaking strengths DO NOT match up!
In fact, the BRAND NEW biner broke at the lowest value, 3,700 lbs.
Can you figure out (from the photos) why?
Hint: I marked the position of the lower shackle on the basket in blue pen...

[spinesnaper]

Presumably this means that the grooved spot closer to the spine of the biners is stonger than the more lateral spot that the shackle sat it for the unused biner. This makes sense since the shackle sitting away from the spine of the unused biner will have some addition torsional forces applied into the spine of the biner.

I am not an engineer but I did stay at a Holiday Inn Express last night.

Ken

[harness man]

It turns out, at least in this group of test samples, that the amount of 'grooving' (up to 30%) does NOT significantly affect the breaking strength.
What DOES effect the breaking strength is how far the rope or connection point at the bottom is from the spine of the biner.
HMS biners have a big "basket" at the bottom to allow for smooth flow of double ropes for rappelling.
If the groove we were pulling from at the bottom was close to the spine (less leverage on the spine) then the carabiner was STRONGER.
If the groove was further from the spine (more leverage on the spine) then it was weaker.
The amount of grooving seemed to have no effect!
Here are the same carabiners arranged by how close the groove (or shackle placement) was to the spine, from closest to farthest:

76905

In order to prove the point we set the shackle on the New biner furthest from the spine, and it broke the lowest at 3,700lbs.
Conclusion: Ratagonia :moses: is Right!!!!

(up to 30% grooving does not lower the breaking strength in this test)

[ratagonia]

In order to prove the point we set the shackle on the New biner furthest from the spine, and it broke the lowest at 3,700lbs.


Good to clarify this point - that the new carabiner did not "break below its rating"... it broke below its rating because the loading point was constrained to an un-natural position.

Thanks for your work on this Todd. Let me go take pics of these slings I have for you and get them shipped off.

Tom

[spinesnaper]

So the logical question would be at what point should these biners be retired? Obviously one can tolerate more and 20% grooving and more than 30% grooving.

[harness man]

Thanks for the clarification, Tom.
Sample B3 is a lightly used Petzl Attache and the groove in this sample was in a position close to the spine similar to how the carabiner would normally be tested. B3 broke at 5,820 lbs, well above it's rated strength of 5,170 lbs(23 kN). This, in spite of the 20% groove. So the petzl Attache seems to perform well (it is my favorite CRITR/rap biner combo).

By contrast, here is the position that we broke the new Attache in (sample B1), with the bottom shackle the furthest from the spine, in the LEAST favorable position, yielding a lower breaking strength of 3,700 lbs.

76906

Spinesnapper: when to retire a worn biner?
The testing we have done is "theoretical" in the sense that it is a simple tensile test in the main axis pulling end to end,, but there could be other weird, unanticipated forces in real world use.
So we are retiring our biners at 30%! :haha:
Best
Todd and Desi

[harness man]

Tom- to your earlier post:
our calculation for the grooving was for the total loss of material at the narrowest cross section of the groove.
To calculate we measured the thickness of the cross section at different angles, made a scaled drawing and compared to the original round cross section then used some basic math (and eye-ballin) to approximate the difference.
the calculations were conservative: the worst biners were probably a full third grooved...

[ratagonia]

Tom- to your earlier post:
our calculation for the grooving was for the total loss of material at the narrowest cross section of the groove.
To calculate we measured the thickness of the cross section at different angles, made a scaled drawing and compared to the original round cross section then used some basic math (and eye-ballin) to approximate the difference.
the calculations were conservative: the worst biners were probably a full third grooved...

Thanks for the clarification, and for putting in the effort to do a thorough job.

:2thumbs:

Tom

[harness man]

Thanks for your helpful comments :nod:
and thanks to nkanarik for starting this thread!
Best
Todd

[spinesnaper]

Todd

OMG! I am a 20 percenter. I am a 30% pretender.

Awesome to get real data. Thanks for the investigation.

I guess I will just keep retiring stuff when it looks funky.

Ken

[nkanarik]

Thanks everyone. I'm amazed what a deep discussion my simple question generated :)

[harness man]

nkanarik
While it may be a "simple" question you asked it is an IMPORTANT one we ALL have to ask: when is our safety equipment no longer safe?
spinesnapper
thanks for encouraging and contributing to the test- it helped a lot to have your samples.
Having a 20% or 30% 'notch' carved in a carabiner just LOOKS bad!
None of us would tolerate a 30% cut in a rope or sling- but carabiners seem to be a different animal...
More testing fun to come, surely...
How strong are those worn rappel devices?
How strong are old canyoneering ropes?
How strong are old harnesses (check your belay- loop lately?)
Best
Todd

[mcweyen]

Can we get a list of which carabiners are which in that list of tested biners?

[harness man]

Sure:
all the gold biners (B1, B3, B4, B5, B7) are Petzl Attaches.
The grey color (B2) is a Petzl William
The orange color (B6) is a Rock Exotica Pirate.
Please note that the breaking results we got do NOT necessarily demonstrate which carabiners are "stronger"- only that
loading this type of HMS carabiner further from the spine seems to lower the strength.
Note that the Rock Exotica Pirate has a higher listed strength (26 kN) than the others and it did well in this test.
Funny thing is we found that it seemed to wear out (develop grooves) faster than the Petzls.....go figure?!!
Best
Todd

[ratagonia]

Sure:
all the gold biners (B1, B3, B4, B5, B7) are Petzl Attaches.
The grey color (B2) is a Petzl William
The orange color (B6) is a Rock Exotica Pirate.
Please note that the breaking results we got do NOT necessarily demonstrate which carabiners are "stronger"- only that
loading this type of HMS carabiner further from the spine seems to lower the strength.
Note that the Rock Exotica Pirate has a higher listed strength (26 kN) than the others and it did well in this test.
Funny thing is we found that it seemed to wear out (develop grooves) faster than the Petzls.....go figure?!!
Best
Todd

"Funny thing is we found that it seemed to wear out (develop grooves) faster than the Petzls.....go figure?!!"

a good example of the saying: "the plural of anecdote is not data".

The Petzl Attache biners are made from the same stock on the same machines in the same factory at the Rock Exotica Pirate. There may be some variation in the batches of material (unlikely) and in the heat treatment (unlikely). More likely is that how they were used in the field was different.

Tom

[moab mark]

Excellent thread. Be interesting to see how many feet of rope wearing in the groove for one of the 30%ers to fail. Need some load on rope.

[Rob L]

I'm sorry, did I miss the part where someone said that none of the breaks were at the rope wear groove?

Rob

[spinesnaper]

I'm sorry, did I miss the part where someone said that none of the breaks were at the rope wear groove?

Rob

The engineers can jump in here. But yes, even the grooves leaving only 70% of the biner did not weaken the biner. So we are retiring this gear with still a vast safety margin. For me, that's ok. I like buying new gear. A nice shiny biner on the harness is just one less thing to worry about. On the other hand, if you are out there in the field and seeing some daylight in your biner, no reason to fret, it is going to support your body weight. I suspect that the engineers would also remind us that this was a small sample, your milage may very, and things are closer than they appear in the mirror.:haha:

Ken

[harness man]

Hey Ya'll
Rob, you can see on the group photo on page 2 all the broken carabiners have the groove/pull point at the bottom marked- and you can see the breaks were mostly low on the spine.
Agree completely with Tom about anecdote making POOR evidence!
Thing is, Desiree (115 lbs) on a new Pirate, and Todd (145 lbs) on a new Attache, both using CRITRs in all the same canyons, swapping first person down/ LAPAR and she saws thru her Pirate first....but why?
I had also assumed that the raw aluminum stock is IDENTICAL for the two biners since they are both made at the same
Rock Exotica factory.
Have to as Rock (the owner) about this one.