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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.

 

KARABINERS

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.


Photo 1


 

This is a standard major axis tensile test using 12mm pins and simulates the forces generated with correct use of the karabiner.

 

Photo 2


Failure of the karabiner in this mode – the gate has broken.


Photo 3

 

 

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.


Photo 4


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.



Photo 5



Failure of the karabiner in cross-loading mode where the gate has pulled through the keylock nose.

Rating?
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 DAISY CHAINS

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.

 Photo 6 Photo 7

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.

 
Photo 8Photo 9

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.

 

Conclusion

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.
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HARNESS GEAR LOOP

With gear loop failure the most common mistake is to attach the belaying device in the gear loop or to attach the rope directly or with a screwgate karabiner in the gear loop. The minimum strength for the belay loop required by European standard EN12277 is 15kN. If you check your harness you will usually find the maximum load of the gear loop ranges from 0-5kg. But what is the real strength of gear loops?

 

Plastic gear loop (Photo 10)

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).


6mm tape gear loop (Photo 11)


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.

 

Conclusion

This is a big gap between the strength indicated in the information notice on your harness and the real breaking strength. Manufacturers want climbers to understand immediately that the gear loop should only be used to carry runners and protection. If manufacturers indicated a 100kg maximum load some climbers might think it’s OK to use it to abseil which is, of course, completely wrong. To make gear loops that would be strong enough to take falls on they would have to reach 15kN, which no harnesses on the market currently do.

 

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.

 


ROPES

One of the less obvious dangers associated with ropes breaking is when they have been contaminated by chemicals such as acid – a risk if ropes are stored in garages or car boots. A recent incident examined by the BMC’s Technical Committee highlights just how much ropes can be weakened by chemicals without any obvious physical signs on the rope itself.

 

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.

 
Photo 13

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.

 

Conclusion

The owner and user of the rope should check that locations where the rope may have been stored or transported are not contaminated. The BMC has advice on looking after your equipment and technical booklets, while the BMC’s Technical Committee investigates incidents of equipment failure that are reported. Go to www.thebmc.co.uk for more info.

 



What do the kN ratings mean?

The kN (kiloNewton) rating on your climbing gear is a measure of force. In mathematical terms it is equal to the amount of force required to accelerate a mass of 1kg at a rate of 1m per second – a rough guide is that 1kN equals about 100kg. The maximum force climbing gear can withstand varies with big pieces of equipment such as a number 10 hex rated 22kN, a wire-gate karabiner 23kN but a number 1 nut 4-6kN. But these ratings don’t factor in wear and deterioration or cross-loading – for example that 23kN wire-gate karabiner’s maximum rating can go down to just 7kN if it’s cross-loaded. Other things such as fall factor, rope stretch, anchors can also have an impact on the force generated.
 



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