3. Fall arrest
The fall arrest system is a belay system that is
independent of the progression or work
positioning system, connected to the A (fall arrest)
attachment point of the harness.
The fall arrest system doesn't prevent a free fall.
Its role is to arrest it while limiting the impact force
experienced by the user. It must therefore be used
with enough clearance to allow for a free fall.
• Limiting the impact force: absorption of the energy
Example for 80 kg
of a fall:
JANE or PROGRESS lanyard without energy absorber
A fall arrest system usually has an energy absorber.
It is designed to limit the impact force for a predefined
maximum fall length, under the conditions specified in its
Instructions for Use.
Fall factor
0.5
Fall factor
1
Fall factor
2
Lanyard with
ABSORBICA
energy absorber
A dynamic rope lanyard has a low capacity for energy
absorption. Its use requires great caution: reducing the
length of a potential fall and staying in a work position
below the anchor.
A sling lanyard or cable, with no capacity for energy
absorption, can not be used to arrest a fall.
Fc < 6 kN
Fc > 6 kN
Fc > 6 kN
Fc < 6 kN
• Distance for fall arrest and clearance:
Clearance is the minimum amount of clear space below
a fall arrest system that prevents the user from
contacting any obstacle in case of a fall.
The required height varies with the system employed
(energy-absorbing lanyard, mobile fall arrester...),
with the user's weight, and with his initial position in
relation to the anchor.
Clearance takes into account:
- The stopping distance of the mobile devices or the
length of the lanyard (A)
- The tearing length of the energy absorber (B)
- The average height of the user (C)
- A safety margin (D)
- The potential elongation of the support
(rope stretch) (E)
A clearance estimate is proposed in the Instructions for
Use for each device.
A
B
Clearance
C
D
? E
A
A+B
Clearance
B
C
C
D
D
VERTICALITY
Information is non-exhaustive. Refer to the other pages as well as to the Instructions for Use and technical manuals. Technical training is essential.
A fall arrest system must ensure that the impact force
experienced by the user is no more than 6 kN.