industrial self-belay with Shunt

[ek]

I recall that in a previous thread, a technique used in industrial rope access was mentioned but not elaborated on, where a Petzl Shunt is held open by a tiny piece of cord between two fingers, the idea being that if you get out of control while rappelling, you'll let go of the tiny piece of cord and the shunt will engage. The shunt is therefore necessarily above you--you're reaching up to the cord. I'm wondering if anyone can detail this technique. In particular, I am interested in whether the shunt is placed on the same rope, or on a separate rope (as I know that, in industry, a separate belay rope is generally required by safety standards).

NZcaver, was it you who mentioned this technique?

[YuccaPatrol]

I saw someone with this setup at Bridge Day and asked him to explain it to me. He had it set up so that he held the small cord with his teeth to keep the shunt from engaging and joked that all it took to stop was to scream. I thought it seemed odd and awkward, especially when I considered having to keep my jaw clenched for 10 or more minutes during a long rappel.

f

[NZcaver]

I recall that in a previous thread, a technique used in industrial rope access was mentioned but not elaborated on, where a Petzl Shunt is held open by a tiny piece of cord between two fingers, the idea being that if you get out of control while rappelling, you'll let go of the tiny piece of cord and the shunt will engage. The shunt is therefore necessarily above you--you're reaching up to the cord. I'm wondering if anyone can detail this technique. In particular, I am interested in whether the shunt is placed on the same rope, or on a separate rope (as I know that, in industry, a separate belay rope is generally required by safety standards).

NZcaver, was it you who mentioned this technique?

Yes, it was me and Hank Moon who both mentioned it. See this post and the ones Hank posted before it.

I don't have my Petzl Shunt on me right now (it's in storage - not used much). I recall it has about a 6-inch piece of thin cord tied to it with a barrel stopper knot in the end. This gets clenched between your fingers when you make a fist, but pops out and locks the Shunt when you start going too fast or unclench your fist. Good question about ropes. I'm not sure if rope access techs usually attach the Shunt to the same rope they are rappelling on, or to a separate self-belay rope. Either should work, but maybe industry standard require it to be on the belay rope? Or since the Shunt can be a single or double rope device, maybe both?

I can't imagine any sane person wanting to operate the Shunt with their teeth. Ouch!

[ron_miller]

In the SPRAT (Society of Professional Rope Access Technicians, thankfully they chose not to be the Society of Professional Line Access Technicians!) industrial rope-access "sandbox", the Petzl Shunt "self-belay" device is indeed attached to a separate rope.

Most industrial rope access work in the SPRAT sandbox is undertaken using two-rope systems, one for work positioning, and the second for fall-arrest.

Ron Miller
Level 1 Rope Access Technician, SPRAT

[ek]

Yes, it was me and Hank Moon who both mentioned it. See this post and the ones Hank posted before it.

Thanks for the valuable info!

I'm not sure if rope access techs usually attach the Shunt to the same rope they are rappelling on, or to a separate self-belay rope. Either should work, but maybe industry standard require it to be on the belay rope? Or since the Shunt can be a single or double rope device, maybe both?

Probably not both. Petzl specifically prohibits using the Shunt on two ropes that can be under different tensions, that is, separately anchored ropes (and also prohibits use on ropes under the same tension but of different diameters, as when tying together two ropes of different diameters for a rappel).

Does anybody know the reason for this prohibition, by the way? I can see what the diagram is indicating with regard to ropes of different diameters--the thicker rope prevents the Shunt from engaging sufficiently to grab the thinner rope, and you could fall as though the thinner rope weren't even there. But what's wrong with having a shunt on two separately anchored ropes?