On and off I keep on bumping into discussion about rigging with karabiners, images or videos of choked lanyards and other more outlandish uses of karabiners. This is nothing new, it is a discussion that has been rolling along for many years. Well, maybe the social media-based iteration has some more aggressive, assertive overtones (I think it is fine to do this, so it is safe to do so – talk about a self-fulfilling prophesy!), yet the facts remain the same as when we first started looking into the matter, and the discussion was not new then!
Manufacturers are absolutely unambiguous about how karabiners are designed to be used and what constitutes safe and correct use, unless otherwise specified, this will be loading along the major axis, avoiding torsional or sideways loading over the spine or pressure against the locking mechanism due to contact with structure.
As you can see from the images above from Petzl’s Carabiner Basics on correct use of connectors, the doc warns very specifically about jamming karabiners against structure, three-way loading or cross loading the frame. DMM make similar statements in their user manual, shown above on the right.
And here is what puzzles me: in face of such clear statements, how is is non the less possible for individuals to declare that they know better than the manufacturer (who designed, tested and builds the device) how to use it correctly? This just really has me stumped.
To be completely clear: Choked karabiners, unless otherwise specified by the manufacturer, are a misconfiguration.
Back in 2006 we did a series of tests on choked configurations on a range of karabiners. We performed a 15kN static pull for 3 minutes on three diameters, 82, 127 and 245mm, representing a small and a sizeable limb and a stem. As you can see from the images below, all karabiners struggled with the smallest diameter, there was some serious deformation and even a failure on the 82mm “limb”. Even the large 245mm diameter posed an issue for a number of the krabs we tested. This does not highlight a quality issue, but rather the fact that the connectors are not intended to be loaded in this fashion.
Phooey, 15 kN, you say, like really? That is never going to happen!
Well, if part of this discussion is indeed about rigging, these kind of loads are well within the range of what a connector will encounter, also in a climbing situation in case of dynamic fall or a rescue scenario, 15kN cannot be excluded – always bearing in mind that the Petzl Carabiner Basics document specifies that a 1kN (≈ 100kg) sleeve strength of the locking mechanism on the gate is all that the standard requires, this kind of load is obviously easily reached in the field should pressure be applied to the gate. The ANSI 359.12 standard demands 16kN gate strength when loaded from the outside for certain applications, this is an interesting development, yet will not be the solution for all situations as it makes for quite bulky locking mechanisms.
This discussion is by no means limited to tree care, it seems to be a feature wherever connectors are used to protect people from falls. I winced when I saw the way in which a karabiner is used in the images below in a fire fighter evacuation kit. O-kaaaay, I get it, the kit is used in life or death situations, the fire fighter needs to get out of the building in a serious hurry – but actually you would have though especially in a situation like that, the last thing you would want to be worrying about is failing connectors?!
As I said above, none of this is new, by any stretch of the imagination, yet some things obviously bear repeating and facts need pointing out. So, let’s go configure, work on our connector issues and make sure we are putting them to correct use!