Most often in the tower industry, there are anchorage points in convenient places. When you’re on a tower, you have steel surrounding you that your rebar hooks easily attach to. But occasionally you might find yourself with no overhead anchorage available. When this happens, you’ll need specially designed equipment for foot level tie-off. This is also known as 12 foot free fall or extended free fall.
Normally in a personal fall arrest setup, the anchorage is above you. The maximum distance that you can legally travel before your lanyard arrests your fall is 6 feet. Because of this short distance the lanyard doesn’t have a hard time reducing the arresting forces to an acceptable level. It still won’t be comfortable; you’re going to experience upwards of 800-900 pounds of force on your body. But that’s much better than the potentially fatal force that you would feel without a shock absorbing lanyard.
During a foot level tie-off scenario, your anchorage is, obviously, below your dorsal D-ring. This means that if you fall you’re going to travel up to 12 feet before the lanyard even begins to stop you. In terms of speed, you’ll fall 6 feet in 0.61 seconds. And a 12 foot fall only takes 0.25 seconds longer, so you’re obviously travelling much faster.
A standard shock absorbing lanyard is not designed to safely stop you while travelling at that rate. If and it’s a big IF, it even stops you at all, you’ll be subjected to more force that is legally allowed. Luckily, fall protection companies like DBI Sala, FallTech, Skylotec, and WestFall Pro have specially designed equipment to make sure you’re safe in foot lev el tie-off situations.
An important thing to keep in mind when tying off at foot level is fall clearance. Fall clearance is the distance below your anchorage that you’ll be able to safely fall without hitting the surface or structure below you. What good is fall protection if you’re going to splat into the floor or an I-beam before your gear can stop you? In 12 foot free fall, you’ll fall 6 feet before your lanyard starts to catch you. Add the length of the lanyard, which is 6 feet. Then allow 60 inches, or 5 feet for your lanyard to expand, also known as arresting distance. Also, your overall height, let’s say another 6 feet. So far we’re at 23 feet of fall clearance. Finally you always need a safety factor; we’ll call it 1.5 feet. So for this scenario, you would need almost 25 feet before the nearest obstruction to safely work.
Have some extended free fall work in your future? Click here to see all of our 12 foot free fall rated lanyards. Some are designed only for this type of application, others, like the BlackMax from WestFall Pro, can be used in either standard fall arrest or extended free fall situations.