Articles - How strong is your gear?
Andy McCue - Posted on 05 May 2010
Modern climbing equipment is a million miles from the home-made engineering nuts, chockstones, bits of wood and anything else that could be fashioned into a runner by climbers of yesteryear. Not only is gear a lot lighter it is also a lot stronger. It also gives us a sense of invincibility, that gear never fails. In truth, if used correctly, it is exceptionally rare for a piece of kit to fail. But, used incorrectly – whether accidentally or through a lack of knowledge – gear can fail under significantly lower forces than the maximum stated kN rating you’ll find on the label.
It’s impossible to go through all the scenarios for the wide range of gear used by climbers today but Climber got access to the testing labs of DMM and CAMP to illustrate just a few of the examples of the situations when misuse of gear can have serious consequences.
DMM is the only remaining UK climbing manufacturer and makes its range of karabiners, protection and other equipment at its factory at the heart of the climbing world in Llanberis, North Wales, using its signature hot forging process to create very light, but very strong products. Testing is a key part of the manufacturing process and DMM let Climber into its testing lab to see how different loading can significantly affect the strength of karabiners.
This is a standard major axis tensile test using 12mm pins and simulates the forces generated with correct use of the karabiner.
Failure of the karabiner in this mode – the gate has broken.
Digital readout of the test in photo 1, with load measured in kN. In this test it was able to withstand just over 26kN of force before breaking.
Minor axis test using 10mm pins, which replicates the cross-loading scenario. It is actually difficult to locate the karabiner in this orientation as DMM’s designs try to avoid this.
Failure of the karabiner in cross-loading mode where the gate has pulled through the keylock nose.
Daisy Chains are used by many of us as a convenient way of clipping into belay anchors and for aid climbing. But the strength of daisy chains varies greatly depending on how they are used. CAMP ran some tests for Climber in its factory in Italy to illustrate the dangers of incorrectly loading a daisy chain.
When using a daisy chain as a loop (Photo 6), the stated strength is 22kN. When using as a daisy chain (Photo 7), the strength falls to 3kN (although when tested by CAMP using a pulling machine the real strength is higher at 5.36kN). You cannot reach the 5.36kN by just loading the daisy chain with your weight but if you fall on it, can you exceed that maximum load? CAMP carried out a dynamic test to find out what the risk is.
To simulate this configuration the CAMP laboratory used a CAMP Dyneema daisy chain and a CAMP Cream Ale harness with a free fall tower and 80kg dummy (Photo 8). The goal was to test a fall factor two at a height of 70cm above the anchor. The theoretical drop height is 70 + 70 = 140cm. But because all pockets on the daisy chain break, the real drop height is 190cm (Photo 9). The maximum registered strength is 4.73 kN. When clipped to an anchor with a daisy, you must never climb above the anchor.
When your harness attachment point is above the daisy chain anchor, if you fall, you break the pocket with two possible outcomes:
1. The karabiner is clipped as shown in Photo 7; all pockets break and you are terrified but still alive and in one piece.
2. The karabiner is clipped into more than one pocket at a time as shown in Photo 8. The bar-tacks between the pockets fail under load and you go to the ground a bit faster than you envisaged! This scenario could occur when any two pockets are connected to a single karabiner.
Do not rely on only one anchor or connect to your anchors with only one piece of gear such as one daisy chain or one karabiner. Use multiple anchors and redundant connection equipment whenever possible.
HARNESS GEAR LOOP
Plastic gear loop (Photo 10)
CAMP used a pulling machine at its lab to test the plastic gear loop on its Cassin Cream Aleharness. In the test the maximum load was 55.3daN (decanewtons).
In a similar test on a 6mm tape gear loop on the CAMP Jasper CR harness the maximum load was 108.4daN.
10mm tape gear loop (Photo 12)
On a 10mm tape gear loop on the CAMP Air CR harness the maximum load was 161.1daN.
So why don’t manufacturers make gear loops whose real strength is actually only 5kg to avoid any confusion? One reason is that if the gear racked on your gear loop got caught and locked itself into the rock and the climber pulled then the loop would break and you’d lose all your gear.
In the incident examined by the BMC the rope was being used at a climbing wall and while being lowered off, the rope broke, causing the climber to fall to the ground. Fortunately no injuries were sustained. The climbers had noticed some white staining when uncoiling the rope but assumed it was chalk dust. Apart from the staining and odd texture, the rope appeared to be in good condition, with very little evidence of abrasion or scoring to the sheath.
Inspection of the area where the rope had snapped found that the sheath was badly stained in this area. The break itself had occurred over a fairly localised area. The ruptured core strands appeared to be stained a yellow colour. Around the break, some of the exposed core strands could be pulled apart easily by hand (Photo 13).
Further inspection of the rope by the BMC’s Technical Committee found it had been contaminated with an unknown chemical, most likely a strong acid. Climbing ropes are made from polyamide (nylon), and it is well known that polyamide can be severely degraded upon exposure to strong acids. Possible sources of the acid are a car battery or certain household products such as drain, toilet or oven cleaners.