Crossloading Carabiners

[PeteHall]

Moderator comment: posts moved from thread https://ukcaving.com/board/index.php?threads/kong-ovalone-dna-twistlock-carabiner.32773/ to this new topic

These can be somewhat helpful with rappel racks too, as the 90* twist can re-orient the rack from a "straight" to "sideways" orientation just by swapping a regular carabiner, for this one.

I would never use s carabiner witha rack, even a steel screw-gate. Cross-load it (after taking your weight off to pass a constriction, for example) and it will pop straight off.
Much safer to use a maillon.

 

[JAshley73]

I would never use s carabiner witha rack, even a steel screw-gate. Cross-load it (after taking your weight off to pass a constriction, for example) and it will pop straight off.
Much safer to use a maillon.

Really? Lots of us do... Personally, I use a captive, anti-cross-load carabiner - A DMM Ceros to be exact.

I don't think cross-loading that big steel twist carabiner is going to be too much of a risk...?

 

[alanw]

I posted in this thread 6 months ago:

Doing titan soon any thoughts on my SRT kit

It looks as if your main harness krab, that your simple, cowstails and chest ascender are attached to, is an ordinary screwgate. They are only intended to be loaded along their length, not across their width. You should have a D shape one such as a Petzl Omni or a D maillon that's designed to...

ukcaving.com

Mark Wright said:
There is a video that I'm sure someone will be able to link to, showing how easy it is to break a mis-loaded carabiner gate with just your body weight.

Me:
I don't have a link to a video, but I was present decades ago at the BMC offices in Manchester when Neville McMillan demonstrated this effect. He didn't even have to simulate a fall, he just put his foot in the loop of a sling and stood in it.

I do have a link, however to his paper. Well worth a read, quite a detective story: "Abseiler found dead below bridge" - how?

https://www.c2safety.com/wp-content/uploads/2020/05/karabiner_breakings_with_figure8.pdf

The problem is not with the body of the karabiner, it's the way the twistlock sleeve can fracture allowing the gate to open.

 

[PeteHall]

The problem is not with the body of the karabiner, it's the way the twistlock sleeve can fracture allowing the gate to open.

Exactly. And the problem can occur with any device that has a large attachment ring; typically rack, or figure-of-eight descender.

It's most likely to occur when you have taken your weight off the descender in a confined space, eg on a very tight pitch, and you can't see that it's happened. It is also possible on a free abseil, as indicated by the example above, however this is easier to mitigate by checking your set-up before loading it and removing other pounts of attachment. Part way down a tight pitch, you don't always have that luxury, and you're also unlikely to have any backup still attached at that point.

 

[hannahb]

Exactly. And the problem can occur with any device that has a large attachment ring; typically rack, or figure-of-eight descender.

It's most likely to occur when you have taken your weight off the descender in a confined space, eg on a very tight pitch, and you can't see that it's happened. It is also possible on a free abseil, as indicated by the example above, however this is easier to mitigate by checking your set-up before loading it and removing other pounts of attachment. Part way down a tight pitch, you don't always have that luxury, and you're also unlikely to have any backup still attached at that point.

I can't visualise how it happens - is it also likely/possible with a Stop or Simple? Or is the attachment "hole" too small?

 

[mikem]

Try the c2safety link posted by alan

 

[Mark Wright]

This is the video I was referring to.

 

[alanw]

Here's a copy of Neville McMillan's report "Karabiner Breakings when Using a Figure-of-Eight"

 

[rm128]

This is the video I was referring to.

Scary stuff! Thanks for posting.

 

[PeteHall]

I can't visualise how it happens - is it also likely/possible with a Stop or Simple? Or is the attachment "hole" too small?

It's impossible with a Stop or Simple

 

[PeteHall]

This is the video I was referring to.

In the demonstration, his rack remains "attached" to the carabiner gate, which would potentially give him time to realise the problem and attach a jammer.

Depending on how it is cross-loaded, it can also pop straight off, giving absolutely no chance to attach anything else.

Once you've seen this demonstrated, or tried it yourself, you can't unsee it. For the miniscule extra weight and few seconds faff kitting up, there's really no excuse not to use a maillon if you're using a rack (or fig-8).

 

[PeteHall]

Depending on how it is cross-loaded, it can also pop straight off, giving absolutely no chance to attach anything else.

Having just had a play in the shed, it's basically if you have the gate up, not gate down that it will pop straight off.

Demonstrated here with a snap-gate as I didn't want to break a perfectly good carabiner, but the principle is the same.

 

[JAshley73]

Alright, in the name of science, you all have given me motivation to try and see if I can break a couple things...

 

[JAshley73]

Ok folks, I did some playing tonight with various carabiners connecting my rappel rack to my harness' D-ring. One thing that I learned, is that it's almost impossible to "break" the carabiner when the rack is in a 'normal' orientation.

I keep the 'open' side of my rack facing the right, and with the brake strand of the rope running to my right side. As shown, with a Petal Sm'd screw-lock carabiner. (Not my regular BTW)

Keeping the rack oriented this way, it's almost impossible to get a carabiner to cross-load. I'm fact, I tried several different carabiners, and this Petzl Sam's might have been the worst. If I was careful, I could get the rack's eye to 'snag' against the screw-lock, and with *just* the right pressure, I could get it to stay cross-loaded as I pulled up on the rack. (Simulating sitting down in the harness, and loading the rack.) However, cross-loaded like this, it still is holding the gate "closed" and is still within the rated cross-loaded configuration of the carabiner. As shown.

What I did learn after watching several YouTube videos, is that it seems only possible to break, or "lever" the carabiners to failure, if the rack is unweighed, and then rotated 180* from it's "normal" orientation. That means in my case, the rack would be rotated so that the 'open' end is facing the left, with the brake-strand of the rope facing the left too. See screenshot from YouTube video. It's hard to see, but his rack is rotated 180* from normal - open end facing his left...

(Ironically, this is the same creator of the "Swaygo" packs that I was discussing only a few days ago in another thread.)






And me duplicating this "failure" with the rack rotated 180* - open end facing my left. I could probably load the rack with my weight, and brake that carabiner - but only after rotating the rack 180* from normal...

Now, my regular linking carabiner is a DMM Ceros. It's anti-criss-loading feature seems to prevent even this from occuring. It's possible to rotate the rack, but pressure is kept off the gate. See below.

I legitimately tried to "break" this one by contorting and twisting the rack and carabiner every which way. But either the carabiner would self-correct, or bind/pinch in such a way, this no critical component was stressed.

Shown in the normal & correct orientation...

I'm summary, I'm quite happy to understand the why & how that carabiners can be broken with racks. It seems that it takes quite a bit more cocking-about with the rack, to create this type of leveraged, broken-gate failure. And knowing that, I'm quite happy to continue using the DMM Ceros. It's very secure, and quick to remove, without needing a wrench or pliers that a Mallion needs.

 

[PeteHall]

it's only possible to break the carabiner when the rack has been rotated 180* from normal.

Agreed, however this situation can (and does sometimes) occur when you are passing a constriction on a pitch.
For example, there are many caves where a constricted pitch-head forces you to get onto the rope, feed some slack through your descender and wriggle/crawl backwards over the edge. There are other pitches where a constriction part way down, likewise forces you to feed a bit of slack through while you wriggle/squeeze down.
In both these types of situations, your descender can become twisted and cross-load the gate.
This has happened to me once, though I did manage to correct it before the gate broke, as I was continuing down in a tight rift, but once was enough to swap to a maillon.

The DMM Ceros looks a good alternative, but I'd speculate that a maillon is much cheaper 😁

 

[JAshley73]

This post was missed when the moderator pulled the posts about cross-loading carabiners from the original thread. Copied/Pasted here...

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A screenshot from the previously shared video. His rack is setup so that in it's normal orientation, the open end is facing away from the caver. But in this screenshot, his rack has been rotated 180* from normal, so that the open end is now facing his stomach. Just like the scenarios posted above, it's only possible to break the carabiner when the rack has been rotated 180* from normal.

 

[JAshley73]

This has happened to me once, though I did manage to correct it before the gate broke, as I was continuing down in a tight rift, but once was enough to swap to a maillon.

The DMM Ceros looks a good alternative, but I'd speculate that a maillon is much cheaper 😁

So, I have the Ceros, because the sales person at the caving shop recommended it to me as we were buying our SRT kits, as he said, "You need this to go with that..." 😅 At the time I was vaguely well-read on the subject and gear, but still didn't know anything. So I took his advise, and I'm glad I did, regarding that DMM Ceros anyway. (Plus, I have this weird appreciation for "nice things," and just about anything DMM is really satisfying in that regard, as their craftsmanship is just outstanding...)

If I were outfitting several more cavers, I might skip that bit for cost's sake, as you mentioned. Then again, maybe not? 🤷‍♂️ The rack itself is quite pricey anyway, and this is a great quick attach/detach option, that's pretty secure, robust, and doesn't require a wrench for the final tightening. So in that aspect, I don't need to worry about carrying & losing a wrench as well... (Or it getting snagged on a rock, and then it's shock-cord sending the wrench towards my face...)

In fact, if I were going to outfit a caver for SRT on a budget, I'd probably skip the rack altogether, and go with Petzl Simple + oval auto-locker + cheap braking-krab. That would be considerably cheaper than the cost of a rack, and would suffice all but the longest of drops.

 

[Cantclimbtom]

The caving shop person is right. Ceros will mitigate the risk because when attached the way round you pictured (small/captive end for rack) if the rack gets twisted it'll be against the body of the carabiner not the gate. Although a quick link/maillon is cheaper. Not tried it with a Simple, but you might be able to use it to tighten/loosen a quick link?

 

[JAshley73]

Not tried it with a Simple, but you might be able to use it to tighten/loosen a quick link?

I'm not sure what you're speaking of. My understanding was that you're NOT supposed to use a mallion with a Simple/Stop, as this same roll-out situation can cause the latch, and then the frame to open.

I guess if you used a BIG mallion, it would be OK...?

 

[PeteHall]

I'm not sure what you're speaking of. My understanding was that...

I think he's talking about using the end of the simple as a spanner (wrench in American speak ), to undo a large maillon. I know a Stop works in this way, so assume a Simple would too, but I've never tried.

Personally, I've never used a spanner of any sort on the maillon on my rack, I just do it finger tight, so I can quickly remove it between use. I do sometimes use a spanner on my central D-ring, but only ɓecause it has a habit of getting a bit stiff and can be awkward to get a good grip on if your harness is tight.