Doug Schumann
Safety Advisor
Safety Management Group
Fall protection devices such as shock-absorbing lanyards prevent an untold number of injuries and deaths on jobsites each year. However, a worker who doesn’t use the devices correctly will perform tasks with a false sense of security.
Lanyards must be connected to anchorage points that provide enough height to accommodate the distance a worker may fall. If the anchorage point is too low, the worker may hit the floor or other surface before the lanyard has the opportunity to do its job – and even a short fall can cause significant injury and lost time.
Before identifying an anchorage point, the worker needs to calculate the potential fall distance. While the physics involved may get complicated, the math is actually very simple.
For example, let’s assume that the worker is using a six-foot shock-absorbing lanyard attached to a full-body harness. According to the lanyard’s specifications, the maximum elongation of the shock absorber as the worker decelerates is three and one-half feet. If we assume that the worker is six feet tall, we simply add his height to the length of the lanyard, and then add in the maximum elongation. That gives us a total of 15 1/2 feet, so you might assume that would be the potential fall distance.
But things in the real world rarely follow theory perfectly. Suppose the harness isn’t fitted properly. Maybe the leg straps are uncomfortable, so he loosens them a little. Perhaps the worker is really 6’3” tall. Or he may have eyeballed the height of his work area as 25 feet, when it’s really 21 feet. To account for unknowns like these, you should add in a safety factor of three feet.
That brings the total safe fall clearance distance in this example to 18 1/2 feet. The worker must attach his fall protection device to an anchorage at least 18 1/2 feet above the floor or the equipment that’s below the place where he’ll be working. If there’s less clearance than that, the worker should use other safety equipment, such as a fall limiter.
Generally speaking, it’s important to tie-off as high above the worker’s head as possible. Not only does that reduce the chances of striking the ground or other objects below him, it also limits the potential fall distance and the forces his body will experience in a fall. A high tie-off may even keep him close enough to his work area to allow for self-rescue if he falls.
Pay attention to the lateral distance from the tie-off, too. It’s not unusual to see a worker using a retractable lanyard who has moved 15 or 20 feet away from the anchorage point. Should he fall, all of that extra cable will factor into the distance, and may even create a pendulum effect in which he swings back and forth. That’s not necessarily a problem if he’s in an open area, but if machinery or structural components are nearby, he could expose himself to serious harm.
When choosing that tie-off location, consider what’s below. If there is energized equipment, moving machinery such as exposed drive shafts, or other potentially hazardous objects, calculating the correct fall distance will ensure that the worker does not come into contact with them. Be sure that anchorage point for the tie-off is adequate. Normally, it should be able to support 5,000 pounds for each person that is attached.
Finally, have a rescue plan in place before work begins. When a fall occurs, it’s important to rescue the worker as quickly as possible. That’s not the time to decide exactly how you’re going to do it. In addition, some harnesses put so much pressure on a wearer who is suspended that they can reduce blood circulation in important arteries. Releasing that pressure too quickly can cause a rush of blood to their heart. Developing a thorough rescue plan will ensure that an averted tragedy doesn’t turn into a real one.
Computing Fall Protection Distance Resource Guide