FALL FACTOR & FALL DISTANCE

When setting up a fall arrest system, fall factors and fall distances are critical factors to be considered. The principle behind fall factors is the basic physics of gravity and energy. Energy is Mass multiplied by velocity.

By minimising the height of the fall, the speed will be reduced (velocity) at the point when the arrest event starts. Check there is sufficient distance between the work surface and any surface below to enable the system, including the action of any shock absorber, to deploy fully without the worker hitting the below surface.

 

 

What is Fall Factor?

The fall factor is a measure of the severity of a fall, calculated as the ratio of the potential fall distance to the length of the lanyard or rope used to arrest the fall.

Fall Factor Formula:

 

• Fall Factor 0: Anchor point is above the worker, minimising the fall distance.
• Fall Factor 1: Anchor point is at shoulder or waist height, leading to a fall distance equal to the length of the lanyard or rope.
• Fall Factor 2: Anchor point is below the worker's feet, causing a fall distance twice the length of the lanyard or rope.

Why it Matters:
Higher fall factors result in greater forces on the worker and equipment. To ensure safety, always aim to minimise the fall factor by anchoring above the worker and using energy-absorbing lanyards.

 

What is fall distance?

The fall distance is the total vertical distance a worker could fall before being stopped by a fall arrest system. Calculating this distance is essential to prevent injuries caused by ground impact or collisions with structures.

Factors to Consider in Fall Distance:

1. Free Fall Distance: How far the worker falls before the fall arrest system engages.
2. Deceleration Distance: The additional distance required for the fall arrest system, such as an energy absorber, to arrest the fall safely.
3. Rope or Lanyard Stretch: Dynamic elongation under force.
4. Safety Clearance: The minimum distance below the worker to prevent contact with the ground or obstacles.

Example Calculation:

• Free fall distance: 2m lanyard, anchor at foot level → 4m free fall.
• Deceleration distance: 1m (energy absorber elongation).
• Safety clearance: 1m (to avoid contact with the ground).
• Total Fall Distance: 4m + 1m + 1m = 6m

 

Reducing Fall Risks

To ensure maximum safety:

• Always position the anchor point above the worker to reduce the fall factor.
• Use energy-absorbing lanyards to minimise the force during fall arrest.
• Calculate and ensure adequate fall clearance to prevent ground impact.
• Regularly inspect all fall protection equipment for wear or damage.