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?

[hank moon]

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?

If one rope fails, the dissimilar diameters problem arises.

[verticalAndy]

ek wrote:
Does anybody know the reason for this prohibition, by the way ... But what's wrong with having a shunt on two separately anchored ropes?

I was practicing in a gym last weekend, and I spent some time experimenting with the Petzl Shunt so that I would understand it a little better. It was my experience that the Shunt slides in unpredictable ways when it is used on two ropes that are separately anchored. The sliding was much more of a problem as the anchor points were placed further apart. I found it exceptionally challenging to safely climb two separately anchored ropes using a Shunt. I'm glad I had the chance to experiment with this in a safe setting (like a gym, where I had options if I became stuck). I agree with Petzl that the use of a Shunt with two separately anchored ropes should be discouraged (or, could be dangerous) in a cave or on a rock face.

[snoboy]

Just to add to this discussion:

The Shunt is indeed used on a second rope at all times.

When rappelling, the 2mm (or thereabouts) cord is held by trapping it under the pad of your thumb and the side of your index finger. Alternately, it can be pinched between you index and middle finger, or between middle and ring. Some sources recommend leaving off the knot at the end. Since autostop rappel devices are probably most common in rope access, the left hand is also required for squeezing the Stop or pulling down on the control handle of the i'D/Rig. The between fingers grip allows this quite well.

On the way up, the Shunt is generally moved after two cycles of the ascending system. It is grabbed by the carabiner to move it up the rope. It is not considered acceptable to grab the body of the Shunt at any time.

If descending in a rescue situation with two people, then it is necessary to keep it as high as possible in order to reduce the possible slippage if it should be called into use... The descender also requires extra friction (braking biner)... Now you use the left hand on the stop/i'D control, and use the right hand to brake through the biner, holding the Shunt string in the same grip, and as high above you as possible.

A few more details here: http://www.ropeworks.com/s.nl/it.I/id.79/.f

[hank moon]

Some sources recommend leaving off the knot at the end.

i support leaving off the knot at the end. Why compromise your backup system?

[Tim White]

I'm with Hank, I don't use / teach the knot method in the end of the Shunt pull cord.

@ Hank- glad to see you are still alive, miss your postings, buddy. Jump in more often.

@ snoboy- You seen will versed in SPRAT/IRATA techniques. Drop me a pm and let me know a bit more.

[sherppa]

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).

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?

In the industrial rope access, the belay device is attached to a separate rope while rappeling or for work positioning. The device is attached to the same rope (there are devices for cable) while climbing (up or down) a ladder. However many people prefer the ASAP instead the shunt.

- -

[NZcaver]

I'm with Hank, I don't use / teach the knot method in the end of the Shunt pull cord.

For what it's worth, I learned this technique from Ken Laidlaw. It was he who promoted the use of the small stopper knot in the end of the cord, so it seats comfortably between the fingers but will safely pop out if you start descending a little too quickly.

I don't do the industrial rope access thing, so I submit to your wisdom on this one.