Carabiners are the metal snap links that connect the parts of the climbing system. Climbing carabiners are made of aluminum and come in two gate shapes: straight and bent.
Straight-gate carabiners are the most versatile. They can be used for any application.
Bent-gate carabiners have a dogleg in the gate that facilitates clipping the rope. For this function, they work very well. Bent-gate carabiners are to be used only on the rope-end of a sling or quickdraw. The bend in these carabiners that makes them easy to clip also makes it easy for them to unclip themselves.
Bent-gates can unclip themselves if clipped directly to a fixed, immobile point like a bolt or piton. Be careful where they are used.
Wire-gate carabiners are also available. Using wire instead of aluminum stock for the gate creates a carabiner with a huge gate opening, high strength, and great performance in freezing conditions (regular carabiners can freeze shut). Wire-gate carabiners also minimize the phenomenon of gate flutter.
Laboratory tests have shown that during a high-force leader fall, the climbing rope moves rapidly through the protection-point carabiner. That action creates a harmonic vibration in the carabiner that can make the gate of the carabiner begin to open and shut very rapidly.
This is called gate flutter and is amplified by the mass of the regular, aluminum-stock gate. It is possible, therefore, that the gate of the carabiner could be open when the load of the fall is caught by the carabiner. Carabiners are only about one-third as strong with the gate open as when it is shut.
Carabiners do break; gate flutter, combined with a worn-out rope that is not absorbing enough energy, are two contributing factors. Another way to avoid this situation, besides using wire-gate carabiners, is using lots of protection and locking carabiners on potential high-force protection points.
Carabiners also are made in a variety of body styles. The most versatile is the D or modified D shape. They are strong and easy to use. Oval-shaped carabiners are good for racking, but not as strong, and sometimes it is hard to figure out where the gate opening is in a pinch.
There are some important numbers embossed on the spine of carabiners. They are the UIAA strength ratings. Carabiners are rated for failure strength with the gate closed in both the major (end-to-end) and minor (side-to-side) axes. High numbers are a good sign of a secure and durable carabiner, but sometimes at a premium price. Carabiners are rated in kilonewtons (kN), a measure of force, which is mass times acceleration.
Remember, a falling climber is accelerating. For conversion purposes, 1 kN is approximately equal to the force of 220 pounds.
Locking carabiners are important, too. Besides the pear-shaped locking carabiner used on the harness as described in the previous section, it is wise to have a couple more locking carabiners on the rack (the climber’s collection of protection, slings, and other hardware) for other purposes. When in doubt, use a locking carabiner.
Carabiner Safety Dynamics
- Construction: Carabiners are made of aluminum and come in many shapes and styles. The basic shapes are oval, D, and bent-gate. The two basic styles of carabiner are non-locking and locking. Non-locking carabiners are used in most parts of the system between belays: They connect quickdraws and slings to pieces of protection and are used to link parts of the belay anchor. Locking carabiners have a mechanism that locks their gates in the closed position. There are many variations that incorporate a screw gate or some kind of twisting lock mechanism. They are used when maximum security is needed: belaying, rappelling, clipping into an anchor, or creating a top-rope anchor.
- Strength Characteristics: Carabiners are capable of holding far more than they will ever need to. However, they are only strong enough when they are loaded along their major axis and with the gate closed. Cross-loading them (along the minor axis) or loading them with their gate open greatly increases the risk of failure. When climbing, ensure that no carabiner will be cross-loaded, bent over an edge, or positioned in such a way that it could accidentally open.
- Care: carabiners need no special care. Keep them clean and check them periodically for excess wear (grooves worn from rappelling or lowering, weakened gate springs, cracks, et cetera). A carabiner that has been dropped a few feet but has no visible cracks can be put back into service.
Locking Carabiners
A locking carabiner is an essential part of your personal climbing gear. It attaches a belay/rappel device to the harness, and is often used to attach the climber’s rope to a belay anchor. A good choice for the primary locking carabiner is one that is large, easy to handle, and pear-shaped (called HMS). These carabiners do everything well, including operating a Munter hitch, a special belaying hitch.
These carabiners all have locking mechanisms that help keep the gate closed and provide a much greater margin of safety over non-locking carabiners. The lock on these carabiners consists of either a sleeve that screws over the gate or some type of spring-loaded autolocking mechanism. Either type works well, although screw-gate lockers can offer more security.