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????