Lockers in Crevasse Rescue
In my opinion, it is acceptable to build the entire 3-to-1 crevasse rescue system with non-locking carabiners. Of course, there are variations to everything, there's always more than one right way of doing things. In my experience, most people in the Seattle branch of the Mountaineers do this like I do, and build the entire system with non-locking carabiners. That said, let's talk about some appropriate uses for lockers in crevasse rescue, from most important to least:
So that's it, my opinions on the lockers vs non-locking carabiners in crevasse rescue.
- Even though I just said you can build the system with all non-lockers, the one place you should always use a locking carabiner, in any variation, is when connecting your PA to the anchor.
- Where your anchor-slings attach to the anchors themselves (the actual pickets or ice axe,) we traditionally girth-hitch the sling to the picket. I think that's great as long as the thing you're girth-hitching around has at least the diameter of a carabiner and no sharp edges. If, for some reason, you wanted to use a carabiner there rather than a girth hitch, it would be wise to use a locking carabiner. When you bury a deadman anchor in the snow, the gate of a non-locking carabiner is likely to be pushed open a little as it's buried and snow is packed in around it. It probably won't unclip, but it's strength will be reduced from 20kN to 7kN or so, and you don't want that.
- A few instructors teach (possibly even require) you to use a locking carabiner to attach the prusik-minding pulley to the two anchor carabiners. (In my picture, that yellow wire-gate biner would be replaced with a locker.) If you do this, I'd strongly recommend NOT clipping the backup figure-8 to that locking carabiner. I would introduce an additional non-locking carabiner who's only job is to be the clip-in point for that figure-8 backup, since you're constantly putting it in and taking it out. It would be a waste of time to have to unlock and re-lock a locking carabiner each time you do that, and you need to perform the rescue quickly.
- The traveling pulley (the one you set up closer to the crevasse edge) is traditionally a non-locker. It's not a big deal if that fails, because the stationary prusik that's attached to the anchors should catch the rope. However, if you wanted to make this a locker anyway and had a locker to spare, go for it. Once upon a time I had a misadventure because a wiregate dragged on snow enough to open its gate and become unclipped, but that was during a very different scenario then crevasse rescue.
- I have occasionally seen someone build the whole freakin' system with nothing but locking carabiners. While that's definitely overkill, if you want to do that, fine. I won't fault you for using a locking carabiner where you could have used a non-locker. However: you had better not be out of lockers later on when you do really need one, like when connecting your PA to the anchor. Also, you had better not be the slow hiker in the group if you made your pack heavier by carrying heavier gear you really didn't need.
So that's it, my opinions on the lockers vs non-locking carabiners in crevasse rescue.
Top picture: practicing the z-pulley setup on my living room floor, a long time ago.