An interesting discussion recently came up on the ANSI/ASSE SH&E Standards Information Center group on LinkedIn. With the group leader’s permission, I’m sharing it here to get the information out to more people.
The Issue: OSHA says that a fall arrest system should be designed so that maximum extension in case of a fall should not exceed 42 inches. Similarly, ANSI Z359 says that max extension on a fall arrest energy absorber should not exceed 42 inches during testing (220-pound test weight, 6-foot fall). How does this relate to the total potential maximum extension in the force absorbing lanyard? In other words, if the max extension of the energy absorber is consistently less than 42 inches when tested as specified, is it okay for the force absorber to contain enough force absorbing material to allow extension beyond 42 inches in case of a greater force?
The Answer: The science used at the time OSHA published its last regulation on this subject is now vastly outdated. OSHA stated in one of its compliance letters, that as long as you limit the maximum arresting force (MAF) to less than 1,800 pounds and make sure the worker does not strike the lower level, you will be fine in that your free fall exceeds the requirements. Even though the original OSHA 1926 document states that maximum deceleration distance should be 3.5 feet, they are clearly more interested in MAF, assuming the person does not strike the lower level.
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