Forums: Climbing Information: Accident and Incident Analysis: Re: [bill413] Rope severed by worn carabiner at RRG, climber decks: Edit Log




Partner rrrADAM


Sep 28, 2010, 12:25 PM

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Registered: Dec 19, 1999
Posts: 17543

Re: [bill413] Rope severed by worn carabiner at RRG, climber decks
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bill413 wrote:
rrrADAM wrote:
iron106 wrote:
Worn biners are usually stronger than new ones.
Huh?????

What leads you to believe this? Seriously, what? Do you have any data, or anything to support this?

In all my years (22, the last 16 at nukes) of performing inspections of materials, and doing failure analysis, I have never, ever heard this... Worn = Less material = Less strength.

At least one basis for the statement that worn biners are stronger is here, based on unofficial testing. However, here is unofficial testing that is specific to this type of accident.
That is misleading, as the groove serves to keep the rope at the biner's/shut's strongest point, even though it has been weakened.

The biner/shut is NOT stronger, as less metal equals less strength for two pieces of identical design. Period.


Example:

Would you rap off of a bush/tree that was 1" in diameter, strongly rooted, with a small groove worn into it at the base that was opposite the direction of force, if the load (rope) was just a few inches above the base/groove? Hell no!

BUT, if the rope was in the groove, keeping it at the base, it would likely still be hella strong.


Point... The base of the tree/bush is akin to the strongest point in the biner, and even though there is a groove, it is still string enough (if the load is applied in the right place), BUT NOT AS STRONG as if there were no groove IF the load were applied outside that groove, it would be WEAKER. And where would the biner fail? At the weakest point, where significant metal loss has weakened it (I.e., the groove)


(This post was edited by rrrADAM on Sep 28, 2010, 12:35 PM)



Edit Log:
Post edited by rrrADAM () on Sep 28, 2010, 12:31 PM
Post edited by rrrADAM () on Sep 28, 2010, 12:35 PM


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