Estimated Fall Distance for SRLs vs. Lanyards
Posted by PK Safety Team on Jun 23rd 2011
Fall protection is one of those things you can never be too careful with so I am constantly getting questions about it. Here is an example:
I am going to be doing some work on a platform that is only 1.8 meters off of the ground. My self-retracting lifeline (SRL) will therefore be hung about 3.8 meters off the ground. I know that I am going to need fall protection, but will that be enough clearance to arrest a fall? I don’t want to hit the ground. Is 1.8 meters enough distance for the SRL to both decelerate and arrest my fall? Do SRL’s have shock absorbers?
I double-checked with the engineers at DBI-SALA to get a precise response to your question. The recommended clearance below a person connected to an SRL is 6ft (1.8M). Someone standing on a platform 1.8m tall, connected to an SRL directly overhead, who falls, will stop within 1.8m or less. We mention ‘directly overhead’ because any offset will add to the free fall distance, as well as introducing a ‘swing fall’ element.
This distance is for the worst case scenario, that is, a person weighing 310 lbs.. This calculated fall distance also includes a safety factor. That being said, it is never recommended to have less clearance than this, even if the person connected weighs less than 310 lbs.
Here are the numbers that go into that calculation. The free fall distance will be less than 2 ft. The deceleration distance (for shock absorption) will be 3.5 ft. These two distances, plus the safety factor, make up the 6 ft., or 1.8m.
SRLs have built in energy absorption (or shock absorption). Some models have a disc brake system and others have an external shock pack that extends during a fall to absorb energy. In all cases, the brake is activated by inertia. This means that you can move around easily, but sudden moves, like in the case of a fall, will activate the brakes, and arrest your fall.
As I have said before, fall protection is not something to mess around with, so if you have questions about your specific application, don’t hesitate to contact us and ask.