Tech skills: Retiring textile equipment

Posted by Dan Middleton on 04/11/2006
Is your harness still up to the job?

In a rush to buy the latest sexy, metallic equipment climbers often overlook the less glamorous side to their arsenal – the textile equipment such as slings and harnesses.

Some climbers even parade their fluffy slings and 20-year-old harnesses as battle-worn badges of honour. But the most advanced and lightweight karabiner in the world won’t do you any good if the tape it’s attached to is dangerously weak. So when is it time to bin it?

What is textile equipment?
Textile equipment means ropes, slings, harnesses. But here we’ll leave ropes aside – although they are textiles, the technologies involved are somewhat different, and their strength giving fibres are protected by an outer sheath. What we’re looking at here is tape in all its uses; from simple slings, to sewn-in slings on cams, to belay loops on harnesses.

How is tape made?
The first slings used by climbers were no more than knotted loops of hawser-laid rope or cord, but like ropes, the introduction of nylon caused a revolution. This provided the much needed advance in technology, being stronger and lighter, and the first factory stitched slings began to appear. Modern stitched slings now fall into two camps, nylon and spectra (Dyneema). Nylon slings are manufactured of “flat” woven tape (cheap, light, flexible), or have a tubular construction (stronger, more durable, more expensive, bulky). Dyneema slings combine the best of both types of nylon tapes, being very light and strong, and in addition are less susceptible to UV damage. However the melting point of Dyneema is lower than nylon (which is low anyway), and being less elastic it doesn’t absorb as much energy under a shock load.

How does tape fail?
No incidents of direct tape failure have yet been reported to the BMC Equipment Investigation Panel, since another component of the safety chain normally fails first, and seriously compromised slings are usually easily identified and discarded by the user. However many, many incidents of sling failure have been observed worldwide, with the majority involving failure of badly weathered (abraded, frozen, thawed, UV damaged) in-situ slings. The other common mode of failure involves the melting of a sling from friction generated by pulling a rope through, or lowering off directly. Hand tied slings are also open to failure if the tape knot loosens.

How to prevent failure in use
Don’t become the first instance of reported sling failure in the UK. Remember the following:
Never lower off a sling directly. Always use a karabiner. The friction generated can easily be enough to melt a sling in as little as 3 metres. When abseiling you’re OK as the rope does not move under load, but take care when pulling it – heat glazing could damage your rope if you whip it through.
Don’t use hand tied slings. Modern sewn slings are cheap, and they eliminate the very real risk of the knot slipping.
Treat in-situ slings with extreme caution. Never rely on them totally, and always use a backup. In-situ rope or cord can be more reliable, since the core is protected from UV damage.

Care and maintenance
All items of textile equipment need the same care. Avoid contamination with any substances apart from water and chalk – be especially wary of oils, cleaners and corrosives lurking in the kitchen, garage, or car. Store the gear in a cool, dark, dry place to avoid unnecessary exposure to UV light. And if exposed to sea water, give them a rinse in fresh water.

When to bin slings
Frequently inspect your webbing gear for signs of damage to the tape or stitching. Nicks are generally very easy to spot. Due to the way slings are constructed, a small nick may not affect their failure load dramatically, but there’s no denying that not only are the number of yarns taking the stress reduced, but that stress concentrations are set up on the damaged section of tape – so bin it. Also pay particular attention to your quickdraw set up. Bolt scarred karabiners could rip through a sling under load – so keep that rack organised. Slings should also be discarded following a severe fall, even if there is no visible damage. Shock loading can cause elongation, and if over stretching has occurred it causes the individual fibres to break, forming small lumps within the weave and weakening the sling. You’ll be able to pick up this damage with both the fingertips and visually. Don’t forget that we’re not just talking about long slings here - this advice equally applies to the tape sewn on to gear. In general you can be fairly rigorous when retiring webbing items as they’re inexpensive to replace – so why chance it?

When to bin harnesses
Most problems to harnesses affect either the buckle or the belay loop area. Check the buckle for bending or corrosion that could affect its operation. Be aware that gradual buckle slippage can occur in some harnesses. In general this is too slow to be of concern in general climbing but any slippage could be accelerated by loading and unloading - for example when jumaring. Also keep an eye on your belay loop area. The belay loop itself is phenomenally strong - in normal circumstances the rope (and certainly your body) would snap before this gave way. However, as the recent Todd Skinner accident illustrates, in very unusual circumstances a loop could be damaged to the point of failure - the combination of an old harness, and sustained, heavy rock abrasion could do it. Abrasion damage to the tie-in loop could also occur by continued rubbing of the rope against the harness during repeated falls, or direct abrasion against the rock. This situation has been observed in the UK, but only in extreme cases. It generally happens when long periods of hanging in the harness are combined with a dirty or gritty environment - for example when cleaning routes. But it’s certainly something to be aware off, especially if you repeatedly work routes. So, if an examination of your harness reveals cuts, tears, or serious abrasions in the tape webbing, or buckles or adjusting devices appear damaged then it’s time to go shopping.
 
Is furry to be feared?

Possibly. Like a new car, slings and harnesses start to depreciate as soon as they leave the shop. Their strength is provided by fibres, and damage to these fibres will reduce their breaking strain. There is, however, a difference between abrasion (fibres have been cut) and fluffing (fibre loops have just been pulled). Fluffing has little impact on the breaking strain, but the effects of abrasion were visibly demonstrated at the recent BMC “Know Your Stuff!” Conference. Two identical new tape slings were taken; one was nicked with a knife part way through, the other abraded quickly against a brick wall. The sling with the knife cut looked the most damaged, but in fact failed at over its stated load. However the abraded sling had lost up to 30% of its strength almost immediately. Most people left the demonstration vowing to retire their ten-year-old quickdraws.

In conclusion
Retiring climbing gear isn’t rocket science. If you are starting to wonder if it’s time to replace something then it probably is!
 

EXPERT Q&A

This issue’s equipment guru is Pete Robertson. Pete currently works for Lyon Equipment as a rep and trainer. He is also a member (and Equipment Officer) of the Llanberis Mountain Rescue Team.

Q. I’ve heard that Dyneema slings can cause problems with certain karabiners - is that true?
A. Yes and no. In recent tests at Lyon Equipment we found that wide (25mm) slings were actually more likely to have problems as they can be more prone to cross loading karabiners. But with some of the new super thin Dyneema slings (6mm) it is possible for the sling to hook onto the nose of the karabiner, and cause gate open failure.

Q. Can I hand tie slings?
A. Yes, although since factory stitched slings are so cheap these days there’s usually no need, unless in an emergency. If you must, remember to only use a tape knot, to leave long tails, and to check it’s always tight. Dyneema must not be tied as it slips too much.

Q. Can I re-use slings after a big fall?
A. All climbing equipment is designed and tested to arrest one major fall, impact or load. If you continue to use equipment after a fall you may have altered the characteristics of the item and may have caused hidden damage and weakening.

Q. Help. I’m about to ab off some old tape – any advice?
A. Just don’t do it. You have no idea of how old the tape is. Is it faded? Was it safe in the first place? Has it been damaged, cut or burnt by someone pulling a rope through? Surely your life is worth the price of a sling.

Q. When should I retire my harness?
A. Start with the manufacturer’s recommendations, usually about five years. But remember these are guidelines for “maximum life”, or “potential life”. The actual duration will be affected by the intensity, frequency and environment of use. Always retire a harness if it has visible wear, has sustained a major fall, or has been contaminated or cut. Some people pride themselves on using old kit, but is it worth the risk?

Q. Are harnesses susceptible to UV damage?
A. Perhaps. However recent tests are beginning to question the impact of UV on harnesses. Abrasion and wear and tear seem to play a far greater role in loss of strength.

Q. How do I clean my harness?
A. Follow the manufacturer’s instructions - check their website if in doubt. Warm water and a mild soap is normally the recommendation for getting rid of dirt and chalk. If it’s contaminated with anything else (oil, petrol etc), then you should just replace it.



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