Sharp Edges while ascending on a rope?

Sharp objects and edges in the course of the rope are one of the main risks in all activities on ropes, regardless of whether in commercial rope access or in alpine use. The national associations for rope access have developed and published a hierarchical series of measures to protect the rope, for example here.

These measures and recommendations must be followed in order to prevent damage to the rope from the outside.

In practice, however, situations can always arise in which a rope comes into contact with a critical structure despite all precautionary measures. As long as the rope is statically loaded and not moving, this does not generally pose a risk at first. However, when climbing on the rope in particular, movements of the rope on the edge occur due to rope elongation and these movements can quickly damage the rope.

In this publication, we have looked at the question of how quickly a rope can be damaged on an edge by ascent movements and which parameters have what effect.

The parameters we analysed were:

Ascent system

The ascent on the rope was carried out once using a hand ascender with a foot sling and a descender in the ventral eyelet of the harness. The outgoing hauling rope was deflected in the hand ascender.

In the second setup, a hand ascender with foot sling, a chest ascender and a foot ascender were used for the ascent.

Technique

In one test series, work was very dynamic with powerful lifting movements; in a second series, the ascent was even and homogeneous.

Rope length between anchor point and edge

In the first setup there was 20 metres of rope between the anchor point and the edge and in the second only 3.5 metres.

Rope diameter and type

Some tests were carried out with ropes of different diameters and types.

In all tests, the rope was placed on a 90° granite edge with a deflection of 30°, i.e. a wrap angle of 150°, and ascended a distance of 5m below the edge. The condition of the rope on the edge was then assessed.

As a result of the tests, we have sorted the influencing factors according to efficiency:

1. Techique

In all scenarios, the method of locomotion made the biggest difference in terms of rope damage. While the ropes suffered almost no visible damage with a constant, gentle method of locomotion, the rope sheath was usually completely severed before the 5 meter mark was reached with the powerful, sweeping method. With a 9.5 mm rope, the rope was completely severed after 20 metres.

2. Rope length between anchor point and edge

The more rope there is between the anchor point and the edge, the greater the effect of even small movements on the rope due to the increasing elongation. With 20 metres of rope between the anchor point and the edge, the rope sheath was completely severed after just 3 metres with poor technique, whereas with 3.5 metres of rope between the anchor point and the edge, 20 metres of ascent were required to sever the rope sheath with poor technique.

3. Rope diameter and type

With 20 m of rope in the system and poor technique, a 9.5 mm rope was completely severed after a 20 m ascent. An identical rope with a diameter of 11 mm was severely damaged over the same distance (complete sheath breakage and breakage of 25 % of the core), but not completely severed. These two ropes were the Enduro Static 9.5 mm and 11 mm respectively, a semi-static rope in accordance with EN 1891 with an undamped PA6 core and a twisted, single-braid polyester sheath.

The 11 mm Interstatic Protect was roughened up considerably with poor technique, 20 metres of rope in the system and 20 metres of ascent, but the sheath did not break. The construction of the rope sheath therefore has a significant influence on abrasion resistance and safety. With identical ropes of different diameters, thicker ropes offer greater safety reserves. The construction of the rope sheath has a greater influence than the diameter.

4. Ascent system

The choice of ascent system has the least influence on the effects of the rope on the edge. In the tests, a gentle ascent with the abseiling device produced only slightly more abrasion on the rope than a gentle ascent with a hand and chest ascender.

Conclusion

Under no circumstances should ropes come into contact with sharp objects or edges. Suitable measures to avoid this problem are trained and publicised by the alpine and rope access technician associations.

If a rope still has to be used despite contact with an edge, it must be clear that a gentle, constant movement provides the greatest safety reserves.