Robert Boesch
 

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Special safety advice

Even the best equipment does not last for ever. Wet conditions, chemicals, falling rocks and most importantly friction burns can prematurely age or destroy slings. Note the potential risk factors and inspect your slings regularly for damage!

Pay particular care to the risks described on the following pages and avoid them at all costs.

Knots

In particular in webbing, but also in cords and ropes, bending, compressive and shear stress occur in knots in addition to the normal tensile load.
The breaking/tear strength in knots is therefore always lower than that in the individual strands. Since the bending and shear strength in webbing is particularly high, we recommend that you do not knot this material.

Friction burns

Friction heat rapidly damages man-made materials. You must therefore never allow rope and/or sling materials to move on top of each other. For abseiling slings, there is a risk of friction burns if the rope is let out too fast or too strongly. Check abseiling slings and replace them if in doubt.
Even worse is releasing directly through a sling. This creates around ten times more force than when a rope is let out. This significantly higher load creates considerable frictional heat at the anchor point. The sling would melt through on the first release. Particular care is required if several rope teams are released or abseil at the same anchor point. If the rope runs over a sling, it may burn through the sling when it is let out.

Mechanical damage

Cliff edges: In addition to the pure tensile load, bending, compressive and shear stresses reduce the tear resistance of slings. The tear resistance of textile fibres on edges depends on the shape of the edge. The sharper the edge, the lower the edge tear resistance. Since in practice there are an infinite number of edge shapes, it is almost impossible to specify the edge tear resistance for each edge load.
Webbing has a significantly higher edge tear resistance compared with cord of the same width, since the webbing cross section can adapt better to the edge, placing a less harmful load on the individual fibres. In situations where slings could be subject to higher stress on cliff edges, we recommend using webbing rather than cord. The sling material also plays a role in edge loads. Dyneema offers an advantage in comparison with polyamide. Dyneema has extremely high tear resistance. Dyneema slings should therefore be used in preference to polyamide slings for edge loads.

Abrasion

Slings are harmed by friction in the carabiner and on the rock, particularly on sharp edges. This friction tears small fibres and the sling becomes frayed. This can make handling more difficult, as well as increasing the water absorption of the sling and considerably reducing the breaking strength. Make sure you replace your sling in good time.

Chemical damage

Nowadays, apart from falls involving sharp edges, the few tears in ropes and slings are the result of chemical damage from acids. In particular, sulphuric acid from car batteries attacks and can dissolve the man-made fibres of ropes and slings. Unfortunately, this kind of hidden damage produces no external signs. You should therefore never store ropes and slings near chemicals. It is difficult to estimate the potential damage that can be caused by solvents. Never use a marker pen or similar item on slings.

Wet

A wet sling is heavier and more difficult to handle. If it then freezes, its performance is reduced as well. Frozen slings can lose around half of their strength. There is a risk of dangerous freezing/wet situations on glaciers melting in the sun, during sudden falls in temperature and in water-covered areas in ice falls.

UV exposure

UV exposure ages the material, making it brittle and fragile. Dyneema reacts a little faster than polyamide. To prevent this, chemical substances are used to stabilise the fabric against the effects of UV light. The chemical is designed to bond with the free radicals created by the UV light. When this treatment wears off, UV light has a harmful effect on the exposed fabric. However, the penetration depth of UV light is low and in general only the sheath is affected. This explains the low loss of strength of core sheath material subjected to high UV exposure over a long period of time. For webbing, which has no protective sheath, the effect of UV exposure should therefore be assessed rather more critically.

 
 
 
 
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