Ascender Safety 101

       Ascending Rappel Ropes 101

       Autoblock Misuse (ATC-Guide)

       Avalanche Safety

       Belay School - Why Dynamic Matters

       Can A Hot Belay Device Melt My Slings?

       Carabiner Off-Axis and Tri/Quad-Axial Loading

       Choosing the Right Carabiner

       Common Belay Screw-ups

       Connecting Two Slings Together

       Daisy Chain Dangers

       Dangers of Rope Worn Carabiners

       Dangers of Worn Lowering Anchors

       Do Ropes Need to Rest Between Falls

       Draws in a Gym

       Extending a Cam Sling

       Fall Factors Explained

       Full Strength Haul Loops

       Gear Doesn't Last Forever—Crampons

       Gear Doesn't Last Forever—Ice Tool Picks

       Gear Doesn't Last Forever—Slings & Draws

       Girth Hitching a Stopper

       How Sketchy Is a Sharp-Edged Carabiner?

       How Strong are Himalayan Fixed Lines?

       How Strong is the Spinner Leash?

       How To Belay, Part 1

       How To Extend a Rappel Device

       Knot Passing 101

       Rappelling - Climbing's Diciest Business

       Re-Slinging Cams

       Rethinking the Double-Loop Bowline

       Retiring Old Ropes

       Sharpie for Marking the Middle of a Rope?

       Sling Strength In Three Anchor Configurations

       Spectra versus Nylon

       Spotting for Bouldering

       Surviving Bad Weather on El Cap

       The Dangers of Modifying Your Gear

       The Dangers of Short Static Falls

       The Electric Harness Acid Test

       The Skinny on Super Light Ropes

       Top Roping is Not So Safe

       To Screamer Or Not To Screamer

       Via Ferrata

       Weakness of Nose-hooked Carabiners

       What is the Safest Rappel Knot?

       Worn Belay Loops and Retiring a Harness

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Climb Safe: How Strong Are Himalayan Fixed Lines?

By Kolin Powick

The following article is courtesy of Black Diamond Equipment.

Ama Dablam. Photo: Kolin Powick. I just got back from a month of volunteering at the Khumbu Climbing Center in Nepal. It was quite an experience to say the least. Crushing, however, was looking at all the amazing Himalayan peaks all day and not being able to climb any of them—I guess I'll just have to go back. 

The stunner of course was Ama Dablam—just have a look—enough said. One of the Nepali instructors had guided Ama Dablam 18 times, so naturally I was grilling him for beta: not too high (6,812 meters / 22,349 ft), not too cold, climb it in the fall, kinda crowded, interesting and varied climbing, some fixed lines. Fixed lines? I immediately wondered what they used, what diameter, how heavy it was, how long it stayed in-situ, how it was fixed on the mountain, etc.

Ironically, as I arrive jet-lagged back in the office last week, one of the other engineers here here in the lab had a section of some sketchy looking rope on his desk. It turns out that his buddy guided Ama Dablam last fall and took some of the fixed line off the mountain and sent it over so we could have a look and do some impromptu testing. Thanks to Peter Anderson for thinking of us, for the photos and congratulations on a great summit.

One of our crack QA engineers dreamt up a quick batch of tests based on how Peter saw this rope being used on Ama Dablam, including: single strand strength, testing with an ascender, testing with knots, testing on a picket, etc. Here is the quick run-down:


  • From fixed lines on Ama Dablam
  • 3 strand "Korean" fixed line, looks to be about 8mm (maybe 3/8")
  • Guessing that it's polypropylene


    Assorted fixed tat on Ama Dablam. Photo: Peter Anderson.All tests were simple slow-pull tests to failure in our trusty tensile testers. Values shown are ultimate strength in that particular configuration and where the failure occured. Just for point of reference, a sewn sling must meet 4946 lbf to be CE certified.

    • Single Strand: The strength of one single piece from the sample, pulled between two rope clamping fixtures (1 sample): broke at 2,022 lbf. Location: rope at fixture.
    • Figure 8 Knots: Exactly how it sounds - a Figure 8 knot on each end of a sample, non-dynamically loaded to failure: 1,401 lbf, rope at knot.
    • Tied into a loop with a Fisherman's: self explanatory - and how this cord was seen used a lot on the mountain: 2,016 lbf, rope at pin.
    • Ascender on single strand: one end of the rope with a figure 8 using a pin to attach to the tensile tester, while an ascender is clamped to the rope and also connected to the tensile tester. Slow pull to failure. This is a typical CE test configuration for ascenders: 735 lbf (less than the CE Ascender proof by 165 lbf), rope at ascender.
    • Clove hitch on RockLock carabiner: a RockLock is a carabiner with a large rope bearing surface and round cross section. A clove hitch is a knot commonly used for connecting fixed line to carabiners which are in-turn connected to anchors on the route up the mountain: 1,270 lbf, rope at knot (minimal slip).
    • Clove hitch on VaporLock carabiner: A VaporLock has a smaller rope bearing surface and more of an I-beam cross section: 1,087 lbf, rope at knot (minimal slip).
    • Rope loop through picket eye: Some of the fixed line was connected directly to pickets buried in the snow so we tested a sample in this configuration: 1,879 lbf, rope at picket.


    Jugging fixed lines on Ama Dablam. Photo: Peter Anderson.
    • I don't think I've heard of fixed lines snapping too often in the Himalaya or anywhere for that matter
    • Obviously it's a fine balance between weight and strength—someone has to carry these spools of fixed line at high altitude in order to prepare the route for clients or others, but it's got to be strong enough to be able to withstand the rigors of many people jugging, weather, UV, etc.
    • My guess is plummeting down a fixed line and slamming into the next anchor could generate loads in excess of some of the values seen above - though the amount of stretch and give, if any, in the anchors will help reduce this.
    • It would be conceivable to shock-load an ascender to values greater than that seen above.



    We haven't really done enough testing or know enough about the actual usage in order to draw any firm conclusions but what I can say is:

    • Don't fall on fixed lines—you just shouldn't.
    • The Himalayas are incredible.
    • The Himalayas are cold in January - who knew?

    There you have it. Be safe out there.



    Kolin Powick (KP) is a mechanical engineer hailing from Calgary, Canada. He has over 20 years of experience in the engineering field and served as Black Diamond’s Director of Quality for over 11 years. He is currently their Climbing Category Director. If you have a technical question for KP, please email him at and he will TRY to respond.

    To help make more climbers safer climbers, Rock and Ice has teamed up with Black Diamond Equipment to present the information here.

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