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Tensioning Karabiners
I recently ran a one day skillls drill session for a local mine rescue company.
One of the drills was to set up a highline and transport a rescuer across a void.
Whilst setting it up, I was alarmed (maybe too strong a word) to see the way they set the tension on the highline.
They anchored it at one end and then ran the other end through an Petzl ID20. They then set up a 3:1 Z Rig and began tensioning up the highline, with the ID20 keeping the tension as they reset the Z Rig.
What concerned me was that the karabiner between the anchor sling and the ID20 is left undone and the person there continuously opens/closes the gate on the karabiner until it begins to catch. (Hope that makes sense???). In the diagram below, the operator opens/closes the gate until point A and Point B catch each other, then lock the gate.
When it catches, they do the screw gate up- that's how they know the highline is tensioned correctly.
I was really concerned with this- first issue is that the highline is under immense strain, placing a mammoth loading on the anchor points. the other issue is that the karabienr is being pulled apart/stretched beyond what it's designed for.
Anyone else seen this or aware of this method????
Replies to This Discussion
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Permalink Reply by Robert Barbarini on
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That would be a NO never seen or heard of it before . . . where are they from and did they say where they learned this ?
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Permalink Reply by Ben Waller on
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First, is the ID20 the large one? If not, then it's not rated for general rope rescue use and shouldn't be used in anything more stressful than a single-person personal use situation.
More importantly, you should NEVER tension a carabiner with the gate open.
That puts all of the tension on the spine, which isn't rated as strongly as the entire 'biner with the gate closed and locked.
When tensioning an open carabiner, it is possible to pull the ends apart enough so that the carabiner gate can no longer be closed or locked.
This situation sets up the system for failure, and I'd want no part of it anywhere I worked. -
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Permalink Reply by lutan1 on
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I'm with ya' on all accounts Ben. I raised it as a concern. No one could tell me where it came from- "we've always done it this way".
It was only used in a single person system, but.....
This method and system had bad stuff written all over it I felt. -
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Luke, the problem with using this on a highline system isn't that it's a single-person system.
The problem is that this system is tensioned while anchored at both ends.
Go back to the basics of Critical Angles with these guys and point out that the 180-degree highline angle is the most stressful possible rope angle, and that just applying tensioning force can fail the carabiner without ANY other load on the system.
I actually put my tandem prussic belay on a carabiner seperate from the base pulley on our 3:1 systems. We either put the TPB on a carabiner anchored to an adjacent hole in a rigging plate or if I'm in a wilderness or swiftwater situation and don't have an anchor plate, I hard link the TPB to the pulley carabiner on the spine side with an extra carabiner.
I know, I know, I've seen all the opinion about not hard-linking carabiners, but we hard-link stuff all the time - swivels, pulleys, rigging plates, 540 belay devices, descenders... -
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