What is the impact force of a rope? - Petzl USA
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What is the impact force of a rope?

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The impact force of a rope is the force transmitted by the rope to a mass in the standard test. The measurement is made at the falling mass, climber side. This impact force is not representative of actual forces encountered in a climbing fall. The dynamic test of the standard is an extreme test, as it simulates a factor 1.77 fall with a metal mass, with the rope attached to a fixed point.

In practice, numerous factors can limit these forces: energy absorption by the climber's and belayer's bodies, rope slippage in the belay device, belayer displacement, deformation of the harness...

Rope type Test mass Max. impact force Number of falls
Single rope Single rope 80 kg 12 kN 5
Twin rope (on 2 strands) Twin rope (on 2 strands) 80 kg 12 kN 12
Half rope (on 1 strand) Half rope (on 1 strand) 55 kg 8 kN 5
Rope type Test mass Max. impact force Number of falls
Single rope Single rope 80 kg 12 kN 5
Twin rope (on 2 strands) Twin rope (on 2 strands) 80 kg 12 kN 12
Half rope (on 1 strand) Half rope (on 1 strand) 55 kg 8 kN 5

Explanation of table

The single rope on a single strand must withstand 5 successive falls. The impact force in the first fall cannot exceed 12 kN.