The energy absorber is clipped at one end to the front loop of the harness, while the rope that forms the two lanyards, no longer than 1 metre, is passed through the rings of the absorber itself.
A via ferrata set is by now a type of mountaineering equipment of which various complete models are on sale.
A via ferrata set consists of an energy absorber and two lanyards of rope or tape, at the ends of which two locking karabiners are firmly tied. The energy absorber is clipped at one end to the front loop of the harness, while the rope that forms the two lanyards, no longer than 1 metre, is passed through the rings of the absorber itself. The rope the lanyards are made of may have a diameter, depending on your needs, of 8 to 10 mm.
The question that comes naturally is: what exactly is a via ferrata set for?
First of all, the via ferrata set allows the person wearing it, together with a good harness, never to unclip from the steel cables permanently fixed in the rock. In fact, whenever along the route you come close to a peg, it is enough to unclip one karabiner at a time, taking it past the peg and then carrying on sliding the two karabiners along the steel cable. Naturally, should you accidentally lose your grip or slip, the purpose of the via ferrata set is to stop you falling into the void.
But how exactly does a via ferrata set work?
It can be shown that, in a fall from a height of 5 metres, an individual of average weight produces a force of over 2000 kg (20 kN), that is a force capable of breaking the karabiners or the weakest parts of the rope (ends or knots).
In a fall the energy absorber transforms the kinetic energy of the fall into heat. In fact the rope, sliding inside the rings of the absorber, produces a great deal of heat through friction. That is how those 20 kN of force are turned into no more than 5-6 kN.
In a fall the equipment is not excessively stressed and/or damaged; we can, if we want, carry on with the outing.
If you don't want to buy a via ferrata set but would like to make one yourself, particular attention must also be paid to choosing the two karabiners at the ends of the rope lanyards. There are two possibilities.
The first possibility is to use two types of locking karabiner: the "Attack" model is a self-locking karabiner which can only be opened at the moment you grip it; the other model of karabiner has a spring-loaded sleeve, which opens by pressing downwards on the sleeve itself with your index finger. They must be used in two different ways: the first model can be clipped into the via ferrata cable directly by pressing the gate against the cable itself, while the second model must be carefully clipped into the via ferrata cable with the opening facing upwards. This is to prevent the spring-loaded sleeve from opening if the hiker falls. It is a safer model, since it prevents the karabiner from opening accidentally, but also less convenient, as it makes clipping into the via ferrata more complicated.
The second possibility, recommended only to the most experienced hikers and mountaineers, is to use ordinary non-locking karabiners, which are quicker to use but certainly less safe than locking ones.
To keep the rope fixed at the narrower end of the karabiner, stopping it from sliding about along the karabiner, it is useful, though not compulsory, to use a rubber accessory that holds the rope always in the correct position.
Further reading:
Frequently asked questions
What is the energy absorber in a via ferrata set for?
In a fall the energy absorber turns kinetic energy into heat, thanks to the friction of the rope sliding through its rings. So the force of over 20 kN produced by a 5-metre fall is reduced to no more than 5-6 kN.
How do you get past a peg along a via ferrata?
You unclip just one karabiner at a time and clip it back onto the cable beyond the peg, then you do the same with the second one. This way you always stay attached to the steel cable and carry on sliding the karabiners along.