Quick Planning Guide on How to Correctly Position Your Fall Arrest System
What must you be aware of?
The area where there is an acute danger of falling is defined as being 2 meters or less from the edge. The edge may be the edge of the roof but could also be a domed rooflight, a smoke and heat extraction system or strip lighting.
Anchorage points are arranged around the fall danger zone. Cabling systems can be used to get nearer to the edge. This is due to their permanent nature.
The basic rule is that the most dangerous spots are always the outer corners because this is where a fall with a resulting swinging motion is most felt (the length of the diagonal to the corner is greater than the straight stretch to the edge). This means that at the corners the distance from the anchorage point to the edge should never exceed 5 meters. In straight sections the only thing which determines the distance of the anchorage points from the edge is the length of the lanyard. This can be adjusted and shortened to the required length. This means that the anchorage points do not necessarily always have to be at the same distance from the edge of the roof/precipitous edge.
This is why one first has to plan how to secure the dangerous corner areas. Each of these spots is secured using one anchorage point. The remaining stretch is divided into sections of max. 7.5 meters.
Also dangerous are areas where the fall distance is fairly small (3-6 meters) because anyone falling over the edge hits the ground fast.
Example:
A person who is 1.80 meters tall falls over an edge attached to 2 meters of loose or suspended rope. This results in the lanyard fall absorber being stretched 1 meter with the complete fall arrest system being stretched yet another.
As a result the total possible fall distance has already reached 5.80 meters. It is vitally important to take this into account!
This is why fall arrest systems with a fall distance less than 6 meters are always designed as retention systems. Here safety is achieved by setting up the system parallel to the edge so that the lanyard can always be tautened to the shortest distance. This rules out someone falling over the edge right from the word go.
Easiest to plan are round roof surfaces where one central point suffices.
Cabling system or single anchorage points?
The decision whether to go for anchorage points or a cabling system usually depends on the respective usage. The following generally applies:
Anchorage points are arranged around the fall danger zone. Cabling systems can be used to get nearer to the edge. This is due to their permanent nature.
The basic rule is that the most dangerous spots are always the outer corners because this is where a fall with a resulting swinging motion is most felt (the length of the diagonal to the corner is greater than the straight stretch to the edge). This means that at the corners the distance from the anchorage point to the edge should never exceed 5 meters. In straight sections the only thing which determines the distance of the anchorage points from the edge is the length of the lanyard. This can be adjusted and shortened to the required length. This means that the anchorage points do not necessarily always have to be at the same distance from the edge of the roof/precipitous edge.
This is why one first has to plan how to secure the dangerous corner areas. Each of these spots is secured using one anchorage point. The remaining stretch is divided into sections of max. 7.5 meters.
Also dangerous are areas where the fall distance is fairly small (3-6 meters) because anyone falling over the edge hits the ground fast.
Example:
A person who is 1.80 meters tall falls over an edge attached to 2 meters of loose or suspended rope. This results in the lanyard fall absorber being stretched 1 meter with the complete fall arrest system being stretched yet another.
As a result the total possible fall distance has already reached 5.80 meters. It is vitally important to take this into account!
This is why fall arrest systems with a fall distance less than 6 meters are always designed as retention systems. Here safety is achieved by setting up the system parallel to the edge so that the lanyard can always be tautened to the shortest distance. This rules out someone falling over the edge right from the word go.
Easiest to plan are round roof surfaces where one central point suffices.
Cabling system or single anchorage points?
The decision whether to go for anchorage points or a cabling system usually depends on the respective usage. The following generally applies:
- If one rarely goes on the roof surface which needs to be secured then single anchorage points often suffice.
- If one often has to go on the roof surface or if it is slippy (e.g. metal or foil roofs with an inclination of 4-5
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