This has been posted on Summitpost as well.

This is really weird and I can't seem to find a logical explanation. Today I rapped four pitches and used the following gear:

ATC Guide
Petzl Drangonfly 8.2 doubles
Klemheist autoblock made of nylon 6.5 mm

I was the first climber to rap on every pitch. Once I reached the ground, I removed the klemheist and disconnected the ATC. The last rap was 180 ft. long. After my partner reached me on the ground I noticed that there was a core shot in my yellow Dragonfly. I knew the core shot was not there before climbing today as I inspect my gear after every outing. The part I couldn't explain is that the core shot was at the 20 ft. mark off the end of the rope and that one side of the tear was melted. The damage was pretty much at the same height of where I was standing when I came off the rope (200ft. rope - 180ft rappel).

Knowing that the my ropes have never been close or in touch with anything hot, I simply couldn't find an explanation. Until I started suspecting if the belay device could have caused that.

I usually rap down pretty fast but not super fast, just a steady speed. The device does get hot, but I never thought that it could get so hot to melt through the rope. Could have the ATC Guide melted the rope as I was standing while I was removing the Klemheist?

Have you ever seen or heard anything like it? Or do you have any other idea on what could have caused it? I am really curious to find out because I have never heard of such a thing.

I found this video on the internet that only partially explain my dilemma:

http://allclimbing.f5sports.com/node/27210


http://www.summitpost.org/images/original/571202.jpg

http://www.summitpost.org/images/original/571204.jpg

Cool video at allclimbing. A couple of points need to be added to the lab tests that may help you figure out what happened.

People glaze rope sheaths all the time while rappelling. Sport rappellers and military units are constantly doing "speed rappels" and sheath glazing is common.

Here's a good way to check gear temp. Spit will sizzle in a pan at a surface temp of about 250° F. Nylon melts at 460°F. I've done the spit test on some pretty hot rappel devices and never, ever had them sizzle so I can't imagine that under a climbers rappelling scenario that you'd melt the rope.

Pressure and Temp are like white and rice. A physicist may need to jump in here to help out. I suspect that a surface temp of, say 200°F combined with the pressures occurring in the rap rig might result in a combination of Temp/Pressure that would glaze the rope.

Can't imagine it being enough to blow through the sheath, though.

Climb safe,
Mal

I've got an ATC-guide and a set of dragonflys...and I decided after my last rappel on those that I was getting a reversino because 8.2mm is TOO SMALL for an ATC-Guide. I know the specs say otherwise, just my opinion.

(Good idea with the autoblock)

Anyways, is it possible that the mismatch of rope diameter and ATC size increases the friction and thus temperature in this example?

PS- I assume you were using the high friction side of the ATC?

Belay devices can definetly get hot enough to melt nylon. Usually, it will only be superficial. It is extreme that it melted through to the core. It is really difficult to tell if this is where the core shot came from, but it is plausible. Do you recall stopping during the rap about where the damage is?

I find it especially surprising with a guide, since that has a lot of metal mass to disperse heat compared to say an ATC. On the other hand, I can see the thinner ropes being a factor due to more localized pressure and in turn, more heat.

A few good tips to avoid this happening are go at a moderate pace, don't stop mid-rap if possible, and immediately feed slack through your deivce and unclip it from the rope once you are on the ground/anchored.

Evan

No, it cant.
plus look at the rope, if it was melted while stationary it would not look like that.

I melted through my backup (6mm) just a few weeks ago, but I use a Prusik.

Sergio,
What kind of belay biner were you using? Is it grooved from wear? It seems to me that the rope bending around a hot biner with some force could produce the type of damage youre talking about.

Sergio,

I think trying to reproduce the wear on your rope in the oven is a good idea, but it might not be that accurate.

In order to get the oven up to 200 degrees the heating element gets much hotter, but because temperature that registers is the air temp. So the metal parts would get much hotter too. So I'll bet the metal where the rope was touching and melting was closer to that 400 degree mark that nylon is rated at.

Also did you let the rope cool all the way down before upping the oven temp?

In the 2008 American Alpine Journal, Dave Turner describes his experience with the belay device melting through the sheath of his rope and partway though the core.

the prusik stuff is qualitatively different from the ATC situation at hand: for a prusik, the heat from the friction is split between the rope (moving away from the hitch) and the hitch (staying in place). The hitch is an insulator, and the heat builds up there, especially where the friction is the highest, leading to melting of the nylon. In the case of the ATC-rope situation, the metal ATC still has to deal with part of the heat from friction, but it's a conductor so the friction heats up the whole device, not just the part in contact with the rope.

Whatever was that melted my rope, yesterday's experience was an eye opening for me, as I have become aware of another potential problem in climbing. I am wondering if anyone else has ever experienced anything like this, and if so I would love to compare the scenarios.

I also wonder if this issue was known to rope and gear manufacturers, and if it was, how many people are really aware of it? I certainly wasn't and probably it is an area that should be further tested to see if there is some truth to it. The guys in the video did a great job with their test but it's still leaving me with some doubts.

I've never experienced any rope damage from a belay device, but I have been burned by one. After a long (200') double-rope rappel at the Gunks, I'd removed my ropes from the device and leaned over to pick up something. The belay device (still on my belay loop) came in contact with my arm and burned a big blister. Don't know if that translates to being hot enough to damage a rope, but it was good reinforcement for my practice of always getting the rope out of the device as soon as I hit the ground.

JL

Here are a few heat guidelines:
Nylon Melts to liquid at around 460°F
Nylon will start or "move" or ooze at around 420°F
A hot skillet will sizzle a drop of water at 250°F
Skin will blister at between 135°F and 175°F

If you do a really fast rap and you think your device is hot enough to melt the rope, try the spit test. If it doesn't sizzle, there is no way it can melt the nylon. Regardless, fast rappels on fig 8s have been known to glaze rope sheaths.

Pressure definitely affects this. Very probably, a 350°F temp combined with the pressure between the device and the rope create a combination which can glaze the nylon.

Can't imagine a situation where the combo would be enough to actually melt through the nylon, however.
Climb safe,
Mal

I wonder if you are over looking something here:
Fast or simi Fast rap
8.2 mm rope = more concentration of the heating
Klemheist auto block 6.5 mm

I might suggest the culprit was the combination of everything above fast rappel ButI think the 6.5 rope did the damage not the rap device...