AGEING OF DYNAMIC ROPES IN USE
Due to different influences on use and specialities of use it is impossible to give an exact numerical value, only a roughly estimated time value can be specified. Depending on frequency and intensity of use, external effects as abrasion, contamination, mechanical loading (static), rope work (lowering and/or abseiling), loading by falls (dynamic), intensive action of UV radiation, aggressive climatic conditions etc. lead to reduction of safety reserve of the dynamic rope.
■ The consequences of abseiling and lowering are reduction of dynamic performance and reduction of safety reserve of the rope.
■ Abrasion leads to gradual weakening of consistency of the sheath. Heavier abrasion makes the sheath “hairier” and reduces the loadability of the sheath and its protective effect on the rope core.
■ Particles of impurities and rocks inside the rope, especially in combination with heavy performance of the rope, result in abrasion of fine fibres of the core and the sheath. The particles act as abrasive sand and lead to reduction of the load-bearing cross section of the fibres, especially during frequent abseiling/lowering.
■ Dynamic load results in loss of rope performance – the ability of arresting dynamic (impact) energy decreases. This depends on the hardness of the fall considerably (hardness of the fall is given by the belay method and the fall factor; falls with a fall factor of > 1 are classified as hard falls according to the general state of the art).
Safety investigations performed by mountaineering associations reveal that if the rope sheath is not excessively damaged and shows no signs of heavy abrasion, a loading by falls with a fall factor of < 0.5 and correct dynamic belaying does not represent a safety risk provided that the rope is not resting on sharp edges.
If all general instructions for safe use of dynamic ropes are observed, the following tentative life span data can be recommended:
</=1 year – Intensive use (everyday use) with high intensity of use, mechanical loading and falls (active sport climbers, mountaineering schools, mountain guides, …)
1 - 2 years – Intensive use with normal intensity of use (several times a week, all year round), without considerable mechanical loading, minimum loading by falls (active climbers)
2 - 3 years – Frequent use (weekends, all year round) with low intensity of use, without considerable mechanical loading or fall arrest (active weekend climbers)
3 - 5 years – Frequent use (several times a month during the season) with low intensity of use, without considerable mechanical loading (suspension, occasional lowering or rappelling) or fall arrest (seasonal weekend climbers)
5 - 7 years – Occasional use (several times a year) with an intensity which is not worth mentioning, without considerable mechanical loading or fall arrest, without recognizable wear or contamination.
Max. 10 years – Unused rope