Using Ascenders in a Rescue System, Is it safe?

[Vickster]

Is setting up a Z pulley rescue system like the one displayed here http://www.highpeaksclimbing.com/Training/ZPulley.htm safe?

 

I have read in a few instructional books that all clearly state mechanical ascenders are ALL designed to be "used under body weight only" and should not be used in any rescue system.

 

The combination of the facts that: 1) I often end up in the middle of a rope team on a glacier 2) I am 6'6" 250 with huge feet 3) my hands chill easy so I don't want to mess with prussik knots bare handed 4)I don't mind ballast because I often travel faster than anyone I am roped to. All led to my decision to bring mechanical ascenders on climbs for my own self rescue.

 

I figured that using the ascenders in a Z pulley rescue system looked like a pretty trick idea since I already have them on me. That is if the system displayed is a reliable and safe way of hauling someone out of a crevasse.

 

Anyhow, I would like to hear what some of the experienced guys have to say. In the meantime I was going to rig up something similar to what is in that diagram and fool around with it. I do not want to endanger someone by using some microwave ready crevasse rescue I found on the internet. However, if something can be done that is faster and better, why the hell not do it?

 

Jim

[JosephH]

Self-Rescue by David Fasulo

 

Climbing Self Rescue: Improvising Solutions for Serious Situations by Andy Tyson and Molly Loomis

[genepires]

for a regular z or zc system, there are either 2 or 3 places to put a ascender onto to replace a prussik. The prussik near the anchor point and pulley will not take more than body weight, ever, due to rope drag. It holds the victim minus the rope drag. The other prussiks are attached to the pulling ends and it depends on how much friction is in the system, you may or may not exceed a body weight in force. If you do exceed a couple hundred pounds of force, you probably still won't exceed the breaking strength needed to cut the rope. And even of you did cut it (as far as I know, has never happened in a crevasse rescue situation), the main prussik or ascender would hold the victim anyway.

 

using the ascenders in a z/c pulley system is not a unsafe idea. what is very unsafe is to have the ascenders attached to the rope while climbing on the glacier. A shock load onto the rope (fall into crevasse) will cut the rope. Leave the ascenders on the harness or better yet, leave them at home. The amount of time falling into crevasses is so small as to not justify the weight. Get faster partners. I am not faster so don't ask me.

 

why does reason #2 have anything to do with your decision to use ascenders?

[spotly]

I found the drawings in the David Fasulo book to be pretty useless - it's difficult to see what the ropes are doing unless you already know what they're doing. The other book looks interesting - I'll check that one out.

 

I attach my ascender (previously a prussik but now a Ropeman) to the rope while climbing but it's set back near the tie in knot and won't take the load in a fall.

 

 

[sobo]

I'll weigh in from the Mountain Rescue community. You think I'm gonna say it's crazy, right? Wrong!

 

In a full-blown technical rescue situation, I say it's crazy. There is no safety factor. In full-blown technical rescue situations, we strive for a static system safety factor of 10:1 (or better) in every component of the system, which means the strength of the weakest link is 10 times the load. This constraint precludes the use of mechanical ascenders from the get-go.

 

That being said, I have no problem using mechanical devices for a glacier crossing team (which is the scenario you're talking about), but I would not use the "Jumar-style" ascenders shown in the link (nor Clogs, Frogs, etc.). I would use a Tibloc-style ascender in this application. Why?

 

First off, it would be quite easy for the rope to twist itself out of the jaw of the ascender under a shock load at an angle to the direction of the rope path through the jaw. Mountaineering books from the days of yore are chock full of stories of people falling off ropes to their deaths because their Jumar took a load at an angle to the rope path through the ascender jaw. ANAM has an incident of this same type every few years or so. The Tibloc-style ascenders minimize this flaw by the very nature of their design.

 

Secondly, the Tibloc weighs next to nothing, and takes up no room at all on your harness. And that goes back to what gene said: whatever you decide to use, leave it off the rope until after you've fallen in the hole. Unless it's a prussik cord.

 

My $0.02

[Vickster]

why does reason #2 have anything to do with your decision to use ascenders?

 

The load put on the foot prussik is significant making the knot difficult to free. Bottom line, I want to be as self sufficient as possible and get the hell out, not spend an hour or longer trying to free knot and then warm up my hands. I have always been about 60lbs heavier then any other climber I have climbed with and assume I will fall farther into a crevasse before I am stopped than say someone of equal weight of the other party memebers. Essentially I am trying to prepare for worst case scenarios where I take the typical short 5-10ft fall then start to drag people... or pendulum in and have to climb out 40 ft or more.

 

There is also the case to be made that if I am someplace remote I would have better chances climbing with with ascenders with an injured arm etc. I guess it comes down to preference and I am still trying to figure out what works for me.

 

I would of course not climb with the ascenders on the rope... they would be on my harness, backed up, and ready to get out when needed. I am going to pick up that mountaineers self rescue book, it looks cool.

 

I also pinged the guy who wrote that page... I will post his response when I get it.

Edited March 27, 2008 by Vickster

[Vickster]

I sent an email that contained the same question I asked here. This is the response I received:

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Hi Jim,

 

Your comments are all good. There is always an open debate on the use of mechanical devices in certain uses such as a Z-Pulley. One disadvantage is that they destroy a rope faster, often after just a few uses.

 

One of my trips to Rainier, we jumped into a crevasse near Camp Muir for practice. We went down about 75 feet and tried to climb our way out. The wall of the crevasse was to poor to use ice tools and ultimately we had to get out using the self-rescue method with ascenders or prusik knots, which ever your choice was. Although we setup the Z-Pulley system above the

crevasse, we chose to practice self-rescue. It is rather difficult to setup a prusik knot when hanging, especially if you have only one hand available. If it was very cold, that would make it even more difficult.

 

The advantage of the ascender was one hand operation and the ease by which it could be moved up the rope. If you are setting up the Z-Pulley system with two people, one acting as an anchor while the other builds the Z-Pulley system the saving in time is often an important factor. In 2005 I took a group of 12 fellow climbers up Rainier and one day we took a private course with RMI. Brent Okita was our instructor (

http://www.rmiguides.com/about/guides/brent_okita.html ) which was especially satisfying based on his experience. We practiced the system a few times and there we used mixed prusik and ascender setups. There appeared to be no preference by our instructor on this issue.

 

Now on the technical side, you can find good information on the

manufacturers site at:

 

http://en.petzl.com/ProduitsServices/B17_ASCENSBAS_B17504-H.pdf

 

The manufacturers reference a international standard called "Personal fall protection - Rope access systems - Rope adjustment devices" which has a document number EN 12841: 2006. I have never been able to get my hands on one as it is only available to purchase, around $135.

 

Within this standard it does call for a backup system to be in place which is another type of mechanical device. However, in practice this is never done with prusik or mechanical setups.

 

A single ascender is rated between 900 - 1450 pounds dead weight on a rope(depending on rope diameter/condition). That seams pretty good to me.

 

Good Luck,

Ed

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In response to Sobo, I have a pair of Tiblocs but have a hard time fitting my big hands in a standard beaner to climb with them. I guess I could use them with a couple big ass HMS beaners.

[Layback]

I've used the Tibloc system before myself. I've recently converted over to the simple prussik system because ultimately the prussiks are more "multi-use" l for the weight.