Personal Fall Arrest Systems - Calculating Total Fall Distance

The idea of wearing a personal fall arrest system is to stop you before you strike the ground or other object below should you accidentally fall. However, many times workers do not properly consider the total distance they would fall if they were to actually fall. This calculation is important to the worker’s safety. It is called Total Fall Distance.
 
Calculations must begin at the Anchor Point and we must use the total length of the lanyard whether it be 6ft; 8 ft; 10ft, etc. Understanding deceleration distance is also important when calculating total fall distance. Deceleration distance is the maximum extra distance a shock-absorbing lanyard (deceleration lanyard) is designed to stretch or extend in order to decelerate, or slow down, your fall. Deceleration lanyards with stitches must stop within 3.5 ft. Retractable Lanyards must stop within 24 inches.
The D-ring shift also needs considered-this is the distance the body will sink into the harness depending upon the fit of the harness.  This D-ring shift is often assumed to be one foot, but it can vary, depending on the equipment design and the manufacturer, so read those manufacturer’s instructions. Remember that improperly fit harnesses will have slack in them. Lastly, safety factor. This is an additional distance added to the total fall clearance distance to ensure there is enough clearance between the worker and the lower level after a fall is completely arrested. The safety factor is typically figured to be 2ft - 3 ft.

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Shock-Absorbing Lanyard and D-Ring Anchorage Connector
First, add the length of the shock-absorbing lanyard (6 ft.) to the maximum elongation of the shock absorber during deceleration (3-1/2 ft.) to the average height of a worker (6 ft.). Then, add a safety factor of 3 ft. to allow for the possibility of an improperly fit harness, a taller than average worker and/or a miscalculation of distance. The total, 18-1/2 ft. is the suggested safe fall clearance distance for this example. NOTE: Should the shock-absorbing lanyard be used in conjunction with a cross-arm anchorage connector or other, the additional length of the anchorage connector must be taken into consideration.

Shock-Absorbing Lanyard and D-Ring Anchorage Connector<br>First, add the length of the shock-absorbing lanyard (6 ft.) to the maximum elongation of the shock absorber during deceleration (3-1/2 ft.) to the average height of a worker (6 ft.). Then, add a safety factor of 3 ft. to allow for the possibility of an improperly fit harness, a taller than average worker and/or a miscalculation of distance. The total, 18-1/2 ft. is the suggested safe fall clearance distance for this example. NOTE: Should the shock-absorbing lanyard be used in conjunction with a cross-arm anchorage connector or other, the additional length of the anchorage connector must be taken into consideration.

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Retractable Lifeline
First, add the maximum free fall distance (2 ft.) with a retractable lifeline to the maximum deceleration distance (3-1/2 ft.) to the average height of a worker (6 ft.). Then, add a safety factor of 3 ft. to allow for the possibility of an improperly fit harness, a taller than average worker and/or a miscalculation of distance. The total, 14-1/2 ft. is the suggested safe fall clearance distance for this example. NOTE: When using a retractable lifeline, the distance is calculated from the point where the retractable attaches to the back D-ring of the worker’s harness.

Retractable Lifeline<br>First, add the maximum free fall distance (2 ft.) with a retractable lifeline to the maximum deceleration distance (3-1/2 ft.) to the average height of a worker (6 ft.). Then, add a safety factor of 3 ft. to allow for the possibility of an improperly fit harness, a taller than average worker and/or a miscalculation of distance. The total, 14-1/2 ft. is the suggested safe fall clearance distance for this example. NOTE: When using a retractable lifeline, the distance is calculated from the point where the retractable attaches to the back D-ring of the worker&rsquo;s harness.
So, before you use a personal fall arrest system, calculate the Total Fall Distance. If the distance is not safe either change the anchor point, change the length of the lanyard or use some other form of Fall Protection such as handrails/guardrails. If that is not possible, get with your project manager to determine if a self-retracting lanyard, fall restraint system, or another means of fall prevention will be used instead.

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* 1. Retractable lifelines must stop a fall within how far?

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* 2. Safe fall clearance should always begin at the anchor point.

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* 3. When utilizing a shock absorbing lanyard, what is the calculated safe fall clearance?

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* 4. What is your name?