The Myth of the 5000 lb. Anchor Point
Anchor point selection can be difficult. For many safety professionals, it is a black and white area that offers no gray option in between. The rule says the anchor point must have the ability to support 5000 lbs. per person attached or it’s no good, right?
Maybe not.
Perhaps the reason that this belief is so widespread is that it’s the simplest way to enforce the rule. 5000 lbs., yes or no? Most people relying on safety personnel to interpret the OSHA standards will think it sounds plausible enough and find ways to be compliant. The catch is, though, that this is not exactly what the standard says. In fact, by following this cut-and-dried rule, you may be eliminating perfectly good anchor points in a situation where it’s already difficult to achieve proper fall protection. The OSHA standard actually states:
“Anchorages used for attachment of personal fall arrest equipment shall be…capable of supporting at least 5,000 pounds (22.2 kN) per employee attached, or shall be designed, installed, and used as follows: as part of a complete personal fall arrest system which maintains a safety factor of at least two,” [29 CFR 1926.502(d)(15) and (d)(15)(i)]
There seem to be various theories as to why OSHA settled on 5000 lbs. (from it being twice the forces incurred in the freefall of an average worker to the weight determined in testing on dropped dogs years ago), nevertheless, that’s what the regulations have set forth for decades. In fact, when testing systems, you are required to use a weight of 220 lbs. (plus or minus 3 lbs.) at a freefall of 6’ [29 CFR 1926 Subpart M Appendix C]. The system would fail the force test if it recorded greater than 2520 lbs. of force during this test. If the system passes, a safety factor of two applied to 2520 lbs. would be approximately 5000 lbs. However, 5000 lbs. is where many people stop reading. The “or” clause in the above standard often gets missed (or ignored). But why does it matter?
It matters because the forces incurred during a fall of a 220 lb. worker who is utilizing a fall arrest system could be approximately 900 lbs., not 2500 lbs. (remember that fall arrest systems would have some type of deceleration device that engages after freefall and reduces the force). If we look at the “or” clause in the standard and apply the safety factor of two, it means that in this scenario our anchor point only has to support 1800 lbs. of force. That’s a huge difference from 5000 lbs. In reality, there may be a number of fixtures in your work area that don’t meet the 5000 lb. requirement but satisfy the 1800 lb. requirement - a roof truss, for example. By eliminating all potential anchorage points that do not meet 5000 lbs., we may be making a difficult situation unnecessarily more difficult.
There is a flip-side, though. Consider the example: approximately 2500 lbs. of force is incurred when a worker weighing 220 lbs. freefalls 6’. In this day and age, many workers, with or without tools, weigh more than 220 lbs. What force do they exert on the system in a fall? Regardless of what it may be, we can assume it’s MORE than 2500 lbs. Therefore, the 5000 lb. rule would seem to NOT support anybody over 220 lbs. OSHA addresses this in a note that states that your system will be deemed to be in compliance if the worker’s combined tool and body weight is less than 310 lbs. Any combined weight 310 lbs. or more would require a modification to the system to ensure it accommodated the extra weight.
Now, this doesn’t mean we can go tying-off to things all haphazardly. Whether reducing the capability requirement of an anchor point for use with a fall arrest system or increasing it due to a heavy worker, it is vital that you don’t guess at capacities and imposed forces. Documentation is the key. Rather than make assumptions, check the manufacturer’s paperwork to see what the numbers actually are. If that doesn’t give you the answers you need, have a PE perform the necessary calculations to determine if what you plan on doing is sufficient (note the words “plan on” – this should always be done before beginning the work).
Keep in mind, you can always choose to keep it simple and stick with the 5000 lb. requirement for your personnel and subcontractors (though you would still need to make adjustments for any combined weights 310 lbs. and above). Anybody can choose to go above and beyond what OSHA requires. In this case, going above and beyond could reduce the chance that something is done incorrectly, but you don’t need to. Following the regulation as written, though potentially more complex, could open up new, perfectly safe solutions that were never before an option.
