Why do I need a via ferrata set?
A brief excursion into the background of safety theory makes it clear why a good via ferrata set can save your life in the event of a fall. When you are climbing, there is usually quite a lot of rope between the person falling and the companion who is able to gently break the fall, in a similar way to bungee jumping. In specialist jargon: a small fall factor means a low impact force. In contrast, in a via ferrata tour, only the short length of rope in the via ferrata set is available to brake you and the braking distance is almost too short as if you were traveling into a wall. Only the dynamic function of the via ferrata set is able to reduce the generated energy to an acceptable level.
Mountaineering ropes stretch slightly when subject to load and therefore absorb energy. The shorter the available rope length and the greater the height of the fall (= the more energy is involved), the more difficult this task becomes. The severity of a fall is measured in terms of the fall factor: the height of the fall divided by the length of the rope section that absorbs the fall. For example, if a rock climbing enthusiast suffers a fall of 5 meters after a climbing distance of 20 meters then the fall factor is 5/20 = 0.25 – nothing to worry about. Falls of a factor of 1 or more are referred to as "hard". A via ferrata se( possesses only a 1-meter long brake rope: Considering the same 5-meter fall, the fall factor is now 5/1 = 5 – and the stress on the carabiner and the body is twenty times as great as for the rock climber.
The impact force is the maximum force to which the body and fixing points are subjected during a fall. It corresponds to the jerk which you feel on braking. It grows with larger fall factors and can be reduced by dynamic braking. To avoid injuries to the spinal column and discs and the the fracturing of the carabiners, the standard for via ferrata sets limits the maximum impact force to 6 kN. This corresponds approximately to the drag force that a weight of 600 kilograms would impose on the body. Therefore, even using a via ferrata set that complies with standards, forces may occur which make falls somewhat unattractive – quite apart from the danger of colliding with the rock face.
On a via ferrata tour, you can still see occasional individuals who secure themselves with a simple climbing rope, cable or even ordinary rope sling. If they were aware of the dangers of this type of static fixing then they would happily invest in a dynamic via ferrata set.
Static braking effect
If you fall with a fixed rope then the rope has to stretch to absorb the entire energy. Because of the shortness of the rope section during via ferrata tours and the potentially large fall heights (high fall factor), enormous force peaks may occur (impact force) – as if you were braking through a concrete floor. Braking becomes even harder if ordinary rope or cable material is used statically since these materials do not stretch and generate even greater impact forces. This is a fatal hazard!
Dynamic braking effect
In the case of a dynamic via ferrata brake, it does not matter whether you use rope or cable material. This is because, in this case, the energy is absorbed by friction as the safety rope is pulled through the brake. If the shape of the brake and the employed rope material are optimally harmonized then the fall is braked gently as if through a trampoline or air cushion. The correct sizing of these components is tested by the standard and the measured impact force may not exceed the value of 6 kN.