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#290908 - 10/19/18 09:40 PM Re: Arizona Mine Rescue [Re: Tjin]
DaveL Offline
Stranger

Registered: 10/03/18
Posts: 24
Thanks for the link, I was a SAR MRA member for 12 years,late 80’s to 2001. Never saw this data. Great info


Edited by DaveL (10/19/18 10:02 PM)

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#290910 - 10/20/18 03:59 PM Re: Arizona Mine Rescue [Re: DaveL]
hikermor Online   content
Geezer in Chief
Geezer

Registered: 08/26/06
Posts: 7069
Loc: southern Cal
Yet another example of how inherently dangerous rappelling can be. No real physical effort involved and it looks spectacular, but about a gazillion things can go wrong, resulting in very bad outcomes.

I believe just about as many fatalities are due to failed rappels, as result from leader falls (at least in Yosemite Valley). Be very careful and check everything before going over the edge.
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#290922 - 10/23/18 04:13 AM Re: Arizona Mine Rescue [Re: hikermor]
clearwater Offline
Old Hand

Registered: 03/19/05
Posts: 1124
Loc: Channeled Scablands
Two carabiners chained together and then twisted can break. Has happened in lowering a stokes litter.

I have an REI carabiner from 1979 that has a pronounced crack running across the sharpest bend of the d shape. That guy is old enough to own one of those. There were a few Chouinard Biners from that era that were flawed and developed cracks around the gate pins.

MIT study Analysis of Fatigue Failure in D-shaped Carabiners
https://web.mit.edu/sp255/www/reference_vault/Fatigue_Presentation.pdf

Broken carabiner
https://www.osha.gov/doc/engineering/2014_r_05.html

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#290927 - 10/23/18 02:54 PM Re: Arizona Mine Rescue [Re: clearwater]
hikermor Online   content
Geezer in Chief
Geezer

Registered: 08/26/06
Posts: 7069
Loc: southern Cal
1979? - that recent? I have a steel Gerry carabiner that dates to 1959, as well as a classic Bedayn from the same era. Gates on both still function quite well. Both are essentially retired and looking for a good museum.
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#290931 - 10/23/18 05:08 PM Re: Arizona Mine Rescue [Re: clearwater]
Russ Offline
Geezer

Registered: 06/02/06
Posts: 5237
Loc: SOCAL
Thanks, those links were very elucidating. Point being that carabiners can fail and they may not show any indication of an imminent failure during an equipment check — ...”when the carabiner is un-loaded, all surface cracks completely close”... This makes a catastrophic failure of a “perfectly good” carabiner a possible result after enough cycles. They do have a life expectancy.

The Ringling Bros failure in the second link was a demonstration on how to induce a carabiner failure. The ‘biner that failed was stressed in three directions, but not along the major axis.
Quote:
... “The cause of the failure of the carabiner was the manner in which it was loaded, subjecting the carabiner to tri-axial loading in violation of industry practice and the instructions of the manufacturer. The carabiners are designed to be loaded in their major axes along the spine.”...


It totally makes sense now why the “D” shaped carabiner — the stress is shifted closer to the spine, reducing stress on the gate side.

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#290932 - 10/23/18 05:19 PM Re: Arizona Mine Rescue [Re: hikermor]
AKSAR Offline
Old Hand

Registered: 08/31/11
Posts: 1146
Loc: Alaska
Originally Posted By: hikermor
1979? - that recent? I have a steel Gerry carabiner that dates to 1959, as well as a classic Bedayn from the same era. Gates on both still function quite well. Both are essentially retired and looking for a good museum.
I have a couple of Army surplus biners. I'm guessing they are WW2 vintage. Both are retired from life safety critical usage, but I still use them to hang gear in my garage.
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"Toto, I've a feeling we're not in Kansas any more."
-Dorothy, in The Wizard of Oz

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#290933 - 10/23/18 05:53 PM Re: Arizona Mine Rescue [Re: AKSAR]
hikermor Online   content
Geezer in Chief
Geezer

Registered: 08/26/06
Posts: 7069
Loc: southern Cal
"old biners never die, they just fade away...."
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Geezer in Chief

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#290934 - 10/23/18 06:04 PM Re: Arizona Mine Rescue [Re: hikermor]
AKSAR Offline
Old Hand

Registered: 08/31/11
Posts: 1146
Loc: Alaska
Originally Posted By: hikermor
"old biners never die, they just fade away...."
No, actually old biners just hang in there.... smile
_________________________
"Toto, I've a feeling we're not in Kansas any more."
-Dorothy, in The Wizard of Oz

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#290941 - 10/24/18 01:18 AM Re: Arizona Mine Rescue [Re: hikermor]
clearwater Offline
Old Hand

Registered: 03/19/05
Posts: 1124
Loc: Channeled Scablands
Rappel extensions are gaining popularity. Easier to keep your eye on the belay device, keeps it away from clothing, is easier to use a prussic/autoblock backup, avoids twisting of the carabiner/belay plate or eight to a degree.

https://www.mountaineers.org/blog/extended-rappel-and-updated-belay-techniques

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#290943 - 10/24/18 06:39 AM Re: Arizona Mine Rescue [Re: clearwater]
Tjin Offline
Pooh-Bah

Registered: 04/08/02
Posts: 1765
Originally Posted By: clearwater
Rappel extensions are gaining popularity. Easier to keep your eye on the belay device, keeps it away from clothing, is easier to use a prussic/autoblock backup, avoids twisting of the carabiner/belay plate or eight to a degree.

https://www.mountaineers.org/blog/extended-rappel-and-updated-belay-techniques



Haven't know any better the last decade. Tying a backup prusik on you leg look is uncomfortable and if not positioned right will open up the leg loop buckle.

As for old carabiners; I just replace them over time. Aluminum doesn't have a minimum threshold for fatigue (not sure if that is the correct English term). I'm slowly upgrading to lighter, stronger and snag free type of gates (keylock for screws or those fancy things for the clippers).
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