Build My Own FeedQC Lab: Weakness of Nose-hooked Carabiners
I’ve seen and/or heard of only a handful of carabiners that have broken in the field in my time as Director of Global Quality at Black Diamond, and most have broken in the same way: nose hooked. What is “nose hooked”? It’s just how it sounds: the nose of the carabiner gets hung up on a sling, Stopper wire or bolt hanger.
Carabiners are incredibly strong—they meet a minimum test of 20 kN (4496 lbf or 2039 kg) when properly loaded on their major axis with the gate closed. In an open gate scenario, carabiners still test to a minimum of 7 kN (1574 lbf or 714 kg). But when you test a nose-hooked carabiner, it can fail at less than 10% of its rated closed gate strength—that’s less than 2 kN (500 lbf or 227 kg), a load that can be easily generated in even the smallest of climbing falls or even just a light bounce test.
Why?
Why is the carabiner’s breaking strength so low when loaded in this manner? It’s a combination of an open gate scenario coupled with the fact that the carabiner basket is being cantilevered off of the bolt hanger/sling/Stopper wire, meaning the load is not in line with major axis (i.e., the carabiner’s spine). This off-axis loading causes the carabiner to be excessively torqued and break at an extremely low load.
BD Testing
Black Diamond manufactures a lot of carabiners, and therefore Black Diamond tests a lot of carabiners. We not only understand the loads at which carabiners break, but also the modes (i.e., location of breakages), depending on the way it was loaded. So it’s possible to look at where a carabiner is broken and have a good idea of how it was loaded.
The photos below show typical failure locations for one style of carabiner tested in four different configurations. As you can see, a nose-hooked carabiner will most often break at the top of the spine, while open and closed gate failures typically occur at the bottom of the spine, and minor axis failures almost always occur at the gate.
[Disclaimer: All carabiners are different, and detailed analysis of the particular carabiner’s geometry and failure modes is necessary in order to be able to estimate the particular loading scenario with any level of confidence.]
Closed Gate Failure
Open Gate Failure
MInor Axis Failure
Nose Hooked Failure
Bottom Line
When a carabiner is loaded while the nose is hung-up on a bolt hanger, a leveraging open-gate scenario occurs. Carabiners are significantly weaker in this configuration—less than 10% of closed-gate strength.
How to avoid this? Always ensure that the carabiner’s gate is closed and the carabiner is correctly seated.
Climb safe -
KP
Kolin Powick (KP) is a Mechanical Engineer hailing from Calgary, Canada. He has nearly 20 years of experience in the engineering field and has been Black Diamond's Director of Global Quality since 2002. Kolin oversees the testing of all of Black Diamond's gear from the prototype phase through continual final production random sample testing. If you have a technical question for KP, please email him at askkp@bdel.com and he will TRY to respond.
United States / English 
28 Sep 2009, 4:35PM
How about nose hooked with the gate closed? How weak is that and have you heard of it happening? It is possible with a wire gate on a bolt hanger especially if it has a large (gate receiving) notch. There are not many wire gates I will use as a top biner (on a draw) for this reason.
18 Sep 2009, 8:46AM
Minor Axis loading occurs when the carabiner is cross loaded. Say for example the bottom biner of a quickdraw flips around and ends up being horizontal within the draw. Then if the climber were to fall, and the biner doesn’t rotate, then the rope is loaded across the gate… THAT is an example of minor axis loading. And when a biner is loaded like that, the “outward” force across the spine, and opposing “outward force” on the gate, causes the spine to bend outwards, the gate to bend outwards, and therefore the two ends, or baskets of the biners are “pulled” inwards.
Check out this recent post with a video that shows a Livewire being pull-tested for a better understanding:
http://www.blackdiamondequipment.com/en-us/journal/climb/qclab/carabiner-testing-video
16 Sep 2009, 9:29AM
The minor axis failure doesn't make sense to me. What could cause the carabiner to collapse inward like that?
27 Aug 2009, 12:40PM
Thx for the pix. It's nice to see the result of sloppy clipping, be it from inexperience or being tired after a long day. I have accidentally nose hooked a placement, but luckily did not fall or even weight it.