UKC

I was climbing at a local crag in Finland yesterday when there was a serious accident lowering off a sports route. The person climbing was unable to finish the route and lowered off an in-situ maillon. He had removed several of the draws below when the maillon failed, dropping him to the ground from about 10m. Luckily, he didn't receive any head injuries, however he broke three ribs and his wrist.

I'm not a sports climber and haven't used maillons, and so am not sure of which sort are suitable for which use. This was a maillon rapide. It was made in France and carries a CE stamp. There is also other information on the maillon, but it is hard to make out. The maillon looks smaller than others that I have seen. There is a picture of it, with a scale bar on http://desert-climbing.blogspot.com

On the route in question the anchor is two Petzl expansion bolts which you can't thread a rope through. There is no lower off chain. There is also a similar maillon attached to one of these bolts which would suggest that at least someone else has lowered off a single maillon of this type.

I don't know if this was a result of a rare occasion of gear failure or if the maillon in question was unsuitable for the task. If it is the latter, I would like to draw other crag users attention to this and replace all the old maillons. Of course I can provide more detailed measurements if required.

In reply to TonyB: Looks like he hasn't screwed it up.

In reply to TonyB:

Was the maillon done up?

The thread appears (as far as I can tell from the picture) to be surprisingly intact, which would imply the maillon was not done up as the thread would presumably have to have stripped to cause this failure had it been.

Can you measure the diameter of the metal used? 7mm I believe is the standard used which should be good to 25kn when done up and loaded correctly...

In reply to quadmyre: This looks like about 6mm I would say but thata still should be fine.

The chap hasn't screwed it up thats all.

In reply to TonyB:

My bet is that wasn't done up at the time it failed, the threads look unharmed (and would be plenty strong enough anyway). Either it was never done up (sloppy but it happens). Or the rope unscrewwed the collar as it ran through.

What's perhaps surprising is that there's not enough residual strength in the hooked wire body to hold a couple of hundred kilos without being screwwed closed.

jk

In reply to Richard Hall:

That was my first thought, if it had been screwed up I don't see how it could have failed in that way without visable damage to the threads.

Also, I've just measured one of my caving ones (standard size common in climbling use)and it's a couple of cm longer than that one.

In reply to Richard Sutton: you can get long options, possibly 7mm or 6mm long from the look of it,

and as others have said, either it wasnt screwed up, or it undid with vibration, which is unlikely, i would go for not done up in the first place

http://www.peguet.fr/gb/peguet-produits.html

p.s. i have used 5mm long for quite a few abseils and never worried

In reply to gear boy: Good point, I always get the long option as the wider gate is easier to use with mud encrusted caving ropes. The one in the picture looks like a 6mm to me which should be more than adequate. I'm surpried it failed even if the gate wasn't done up.

In reply to Richard Sutton:


Me too but I guess there's twice the load on it when lowering (as opposed to abseiling) and there was no mention of what the unfortunate chap was doing, he could have been swinging wildly to get the draws out. Still... surprising!

jk

I'm surprised too, that's quite a burly one.

Did a longish ab off one of the smallest maillons once. Shat myself then gave myself a slap on the wrist and said not to be so cheap in future.

In reply to TonyB: probably about 250 kg undone and 2500 done up, so entirely possible

In reply to gear boy: I'm quite interested by this now (nothing better to do). 10 mins of googling doesn't reveal the gate open strength of maillons. Does anyone have access to a tensile test machine?

In reply to Richard Sutton: http://www.peguet.fr/gb/produits/grande_ouverture.html

In reply to Richard Sutton:

I used to work in the test lab for Lyon, the UK importer. Maillons don't have a gate open strength marked - as is already mentioned, they must be done up. Cavers, who use maillons a lot, know that just bodyweight can deform them if not screwed fully closed. In fact, the threads and barrel are lined up by hand during manufacture, by bending the frame.

I can't remember off the top of my head the load figures for the different size maillons, but suffice to say, if you had a 6mm maillon, and taking into account the pulley effect nearly doubling the load on it, you'd be close to the ball park for doing this to it if not done up.

The maillon barrel may have been unscrewed by the action of the rope - its a good idea to check the barrel position before lowering. For in-situ maillons some loctite is a really good idea.

Hope the guy makes a full recovery, sounds painful.

In reply to gear boy: That's major & minor axis but not gate open unless I'm mistaken.

In reply to Richard Sutton: not sure as if you go via ppe you get Kn not Kg
http://www.peguet.fr/gb/produits/EPI_industrie-EPI_montagne_grande_ouvertur...

and a 7mm does 500 and 2500 or 25Kn and 10Kn

In reply to gear boy: That's all well and good but they assume you're not an idiot and have fastened it up properly.

In reply to TonyB:

I don't have a pair of calipers to measure the diameter accurately but I am fairly sure it is a 6 mm maillon. I don't know if the person was swinging or lowering carefully. It is alarming to hear that the gate open strengths are so low. I too would suspect that the gate was open at the time of failure as the threads are perfectly intact.

I also hope that the person involved makes a quick recovery.

In reply to danm: Ta for that but I want numbers! Want Want Want!

As you say the lesson to be learnt from this is always double check that the gate is done up and that the orientation isn't going to unscrew it. And don't be a cheapskate an exta few pence for 7mm over 6mm could save your life if the worst does happen

In reply to Richard Sutton:

Its all major axis in that table - WLL is 'Working Load Limit' and BL is 'Breaking Load'. WLL is just BL divided by 5, to give a 5:1 safety factor (which is standard for rigging bits & bobs). WLL is mostly used these days where it used to say SWL (safe working load), the terminology has changed a bit.

I'm not sure what CR stands for in the other table though.

In reply to deepsoup:


If you go to the French version of the site the CR column is also labeled "petit axe" which, not speaking any French, I'm translating as minor axis.

In reply to TonyB: Well if the photo (and the measuring tape in it) is accurate, then the width of the bar stock is bang on 5mm - and there's a significant difference in 1mm when the photo is viewed at full resolution.

Harry.

I've done a more accurate measurement and agree that the maillon is 5mm.

Things are looking well (under the circumstances) with the climber involved and he should be on his feet in a few days.

In reply to TonyB:

The maillon was loosely tightened. I think some of you might be interested in the discussion we had on another forum:


JAB wrote: Does finger tight count as properly tightened?

According to the manufacturer a 5mm maillon should be tightened to 0,80 N m. In practical terms this would translate to 408 grams hanging in the end of a weightless 20cm wrench. I made some test (well, I'm an engineer after all) and I think finger tight would be around 0,20 N m. In other words, finger tight is not properly tightened.

If there is something to be learnt from this accident, I would suggest thinking twice before lowering off a single improperly tightened maillon. I think many people will trash their lower off maillons once they hear about this accident.

In reply to adnix:

Finger tight should be fine if the rope was arranged to tighten the collar should it accidentally catch AND the collar was arranged so that it tightens downward so as not to vibrate open. What's the chances of getting it right every time though!?

I can't see how torquing it up adds any extra strength, just added security against coming undone.

Use 6mm or 7mm mallions seems to be the best advice I'll be taking from this which is a surprise. I wouldn't have expected a 5mm one to fail under lowering loads even with the collar open, you learn something new every day.

Hope you're recovering ok, sounds like you were lucky.
jk

In reply to jkarran: The more you tighten it, the further it goes up the thread, so the larger the surface area, the smaller the pressure on a particular bit of the thread, so the less metal.

In reply to jkarran:

I would say the chances are close to zero. It is impossible to know which direction maillons are tightened without trying. Good rule of thumb for using maillons would be.

1) Lower off is ok if the maillon is properly tightened (ie. it can't be undone by hand)
2) If it's not properly tightened, abseil down.

In reply to jkarran:

7mm is the smallest one that is approved for mountaineering use (EN 12275). It's good to remember that the thickness is really hard to examine on the field, too. For example, Toby first thought this was s 6mm maillon but it turned to be a 5mm maillon after further examination.

EN 12275 Approved maillons:
http://www.peguet.fr/gb/produits/EPI_industrie-EPI_montagne_grande_ouvertur...

In reply to adnix:
Eh? No its not, they're tightened clockwise. They don't make them with a left handed thread do they?

Afaik 7mm long pattern is also the smallest one that opens wide enough to put a 11mm rope in without having to thread it through, so thats the one to carry if you're using it to bail out/lower off and placing your own imo.

Sean
x

In reply to TonyB:

Are mallions generally weaker than screw gate krabs? I always understood that the gate played little if any contibution to the strength.

In reply to Trangia:

Done up correctly and loaded correctly on paper there's little difference in strength between an average screwgate and a 7mm maillon.

The gate does make a significant contribution to the strength of a krab. That's why the gate open strength is also given and normally in the region 7-10kn. When lightly loaded the gate has little effect - the gate doesn't even properly contact the nose - but when loaded above a certain amount (5knish?) the krab bends a little and the gate comes into full contact and becomes a significant part of the structure.

This incident makes it apparent that the gate open strenth of a maillon is much, much lower and this situation should be avoided at all costs.

In reply to deepsoup:


If we have ten climbers threading the rope through a maillon, what do you think, how many will have it the right way?

In reply to TonyB:

I have no doubt that the gate was undone at the time of failure.

It may have vibrated open with gravity assisting it, because the Mallion was orientated wrongly. Although the chances of vibration are slim, because the rope should have been running smooth.

In my opinion it more than likely opened as the rope run through it, and the friction of the rope against the gate undid it.

Also, I agree that the one pictured is a 5mm (short) type.

Irrespective of all of the above it highlights the fact that:
1. You should use a minimum 7mm long Mallion
2. You should orientate it correctly
3. Ensure that the rope, as it runs, has a tightening (screwing up) effect on the gate
4. Always consider ab’ing from that point rather than lowering off

Would anyone out there like to offer another cheap means of leaving a route mid-point using a lower off?

In reply to adnix:
Dunno, as low as about 50% if they're just threading at random I guess, or as high as 100% if they're all being careful to thread it the "right" way.

It isn't something I've ever really thought about before, but I think I'll be making an effort to thread maillons the right way from now on. (Not that its something I do much of, but y'know.)