Calculation: the Minimum Free Fall Distance

Before installing a horizontal lifeline, if this is certified to European standards EN-795:C and TS 14.615, the following calculation must first be made.

The aim of this prior calculation is to determine:

• The fall clearance required to arrest the fall.
• The maximum load generated on the line components. This seeks to ensure that the line to be installed meets the requirements of the case under study.

Free fall distance

The fall clearance required to arrest the fall will be determined by:

• The fall factor, so that the greater the FF the greater the free fall distance.
• The deployment of the actual PPE used, so that the greater the free fall the greater the opening.
• The number of users anchored to the lifeline, so that the higher the number of users, the greater the clearance.

The force

The fall arrest forces for which the lifeline has been calculated mean that the fastenings of its various components are critical.

This is due to the fact that, in addition to the cable deflection generated by the fall, the cable itself tends to have a force multiplying effect on the curves and end points. This is known as the cable multiplying effect.

Therefore, the force applied to the lifeline ends and curves will not be the maximum force of 6kN required by the standards governing the PPE for the point at which the fall occurs, instead this force may be several times multiplied up to the ends.