Rothoblaas Catalogue 2019

ARRESTING FORCES THROUGH ENERGY ABSORBER

ARRESTING FORCES THROUGH ENERGY ABSORBER Regarding the design action, quoting EN 795:2012 point 7.b: “The user shall be equipped with a means of limiting the maximum dy namic forces exerted on the user during the arrest of a fall to a maximum of 6 kN”. This requirement is also reported in all product manuals, there fore we consider this value as the design load for the calculation. Observing real life situations has confirmed that, with the use of ener gy absorbers, retractable devices or guided-type fall protection, devices show an arresting force between approximately 4 and 4,5 kN. ITALIAN STANDARDS UNI EN 355:2003 UNI EN 355:2003 establishes that in experimental tests, the braking force Fmcs necessary to stop a 100kg bodyweight mass in free fall from a heigh equal to 4m (hcl) must not exceed 6 kN, and the arresting distance must be: arresting distance < (2L t + 1,75 m)

[kN]

4

3

2

1

0

[s]

1 2 3 4 5 6 7 8 9 10 Test 100/F/1m progress of F (kN) relative to time t (s)

[kN]

4

3

2

where: L t = total length of the energy absorber (including rope) h 1 = attachment point distance - ground before the fall h 2 = attachment point distance - ground after the fall h cf = h 1 - h 2 = braking length

1

0

[s]

1 2 3 4 5 6 7 8 9 10 Test 100/F/2m progress of F (kN) relative to time t (s)

[kN]

4

3

2

1

0

[s]

1 2 3 4 5 6 7 8 9 10

Test 100/F/3m progress of F (kN) relative to time t (s)

[kN]

h cl

h cl

4

h cf

3

2

h 1

h 2

1

0

[s]

1 2 3 4 5 6 7 8 9 10

Test 100/F/4m progress of F (kN) relative to time t (s)

8 | ARRESTING FORCES THROUGH ENERGY ABSORBER | FALL PROTECTION SYSTEMS