With an inertia reel connected to dorsal attachment point
Fall arrest systems
If there is a risk of a fall of more than 0.5m, the worker must use a fall arrest system.
Fall arrest is a technique that uses elements of PPE (personal protective equipment).
In practice, this means that when a worker at height is in such a positionthat, in the case of loss of control, a fall cannot be avoided, then PPE comes into play to reduce the height and the severity of the fall.
If a fall occurs, a fall arrest system is designed to minimize the effect of the fall on the human body (reduce the impact force, avoid or slow down any impact against obstacles). In spite of this, the consequences of a fall are often serious.
Inert suspension in a harness, whatever the model, can have a serious physiological consequences. These problems do not occur in the case of prolonged suspension of a conscious person, since the points of contact with the harness are constantly changing.
Conclusion: work teams must be informed, trained and capable of independently coming to the aid of a fellow worker who is unconscious or incapable of self-rescue.
With a mobile fall arrester connected to sternal attachment point
In this example where the worker is working with a 1.15m Absorbica-I energy absorber (connectors included) the fall taken will be 3m (2 x lanyard length + energy absorber extention) and the minimum required clearance distance is 4.35m.
Limitation of impact force
If a fall occurs, the worker must never be subjected to a force greater than 6 kN (threshold of injury).
Two methods are possible:
to ensure that lanyards remain attached to points above the level of the head, so as to minimize the length of the fall and the impact forces generated by the fall
if it is not possible to limit the possible length of the fall, then an energy energy absorber must be used. The most frequently used items of PPE which can be used to absorb energy are the following: energy absorbers and dynamic rope systems.
Clearance: unobstructed space
This is the free space necessary below the user so as not to encounter any obstacle during a fall: see diagram.
Notes:
Lanyards or energy absorbers must not exceed 2 meters in length.
The height of the fall must always be reduced as much as possible.
The calculation of the clearance varies according to the system employed: lanyard, energy absorber, portable fall arrest device, inertia rell, etc.
Fall factors
Fall factors express the proportional seriousness of a fall, it is a relationship between the length of the fall and rope available to absorb the impact force of the fall, this is expressed as equation:
Fall factors = Length of fall / Length of rope or webbing in system
