Preparing for a fall arrest situation
Nobody likes to think that they are going to suffer a fall and the thought of a fall from height is even more daunting. This is why we use fall protection. Fall arrest systems such as anchor points, static lines and rigid rails combined with fall arrest harnesses and lanyards are all
Fall arrest devices do not stop a fall, rather they arrest the fall once it has occurred. This means that the operator has to travel several metres before the device deploys into action and stops their fall.
When choosing to design, install or use fall arrest systems it is vital that you have calculated the correct fall clearance distance that a person will travel until their fall is completely arrested, to ensure they do not suffer any injuries by contacting lower level hazards.
What is fall clearance distance?
Fall clearance distance is the measurement which is calculated by totaling the length that a person travels from their working position to the position that they will end up at when their fall has been arrested. It also factors in a clearance measurement.
The importance of getting this calculation is imperative. Correct calculation ensures that should their fall arrest system be activated they do not get injured by coming into contact with any structures or obstacles below them.
The fall distance clearance required is dependent on the following factors:
- Elevation of anchorage
- Anchor deflection (the distance from the anchor/static line to the fall arrest device)
- Lanyard length
- Lanyard elongation on deceleration pull out (personal energy absorber)
- Operator height
- Fall distance residual clearance ( ie. distance from nearest object/hazard below)
How to calculate fall distance clearance?
The below diagram is to be used as a guide only to calculate the fall distance required to calculate fall distance clearance.
In the example shown, a 1.8 metre tall worker with a line deflection* of 500mm, a 2.0 metre lanyard and a 1700mm energy absorber extension would experience a total fall distance of 6.0 metres. Into this equation you must add in the additional 1.0 metre clearance necessary to ensure they do not impact any objects underneath them. This therefore makes the fall distance clearance that you must allow 7.0 metres.
If your fall clearance is 7.0 metres or more, then you’ve selected the appropriate length lanyard. If your fall distance is less than 7.0 metres then you may need to select a shorter lanyard or use a different device like a self-retracting lanyard.
*Line deflection is not always added.
Fall distance calculation made easy!
So, that's the technical side, but how do you quickly and easily do these calculations?
Use the SAYFA Fall Distance Calculator to ensure you have correctly assessed what is required. Feel free to share it with your team so that they always have accurate measurements at easy reach.