What’s the Buzz? Force factors and G Forces
By Mark Damon Damon Inc
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In the quest to further confuse the use of fall protection, ANSI has introduced new issues in the world of fall protection.
First came the change in Force Factor. In the late 1970’s, Rose Manufacturing Company sought an equivalency factor in order to use a steel weight to test the performance of their DynaBrake shock absorbing lanyards. The engineers determined a force factor of 1.4:1. The concept was a steel weight would impart 40% more force on the shock absorber than the equal weight of a human being.
Since the maximum allowable weight of a worker was 310 pounds, a 220-steel weight was used to test the effectiveness of the shock absorber for the heavier worker. OSHA later adopted this force factor when they published 1926.500 Subpart M, January 1, 1996.
Recently ANSI changed the force factor from 1.4 to 1.1. This changes the test weight to 282 pounds. This has led to a variety of issues. First, the manufacturers were forced to increase the length of the shock absorbers from 42” to 48”. Second, all the shock absorbers sold by manufacturers are out of tolerance with the OSHA requirement of 42”.
Was this all necessary? I don’t think so. My own testing indicates the force factor may need to be adjusted, but probably not to 1.1:1. I am also not aware of a preponderance of information about the 310-pound worker injured due to full deployment of a 42” shock absorber. In fact, shock absorbers already exist for heavier workers that have a 60” shock absorber.
More testing is needed. In the 1950’s, Colonel Stapp conducted some ground-breaking testing on the effects of G forces on the human body. This was done in conjunction with sled testing to prepare pilots for the greater G forces, and G forces applied by seat belts in automobiles. One of his conclusions was 10Gs of force for an extended time could cause injury.
ANSI applied this body of information to fall protection. The difference of course, is that impact forces in a fall are applied over a much shorter period of time. In addition, I question their assertion the lighter weight worker will be exposed to excessive G forces. My own testing disputed this claim.
As with the change in Force Factors, this has resulted in unnecessary confusion in the fall protection market. If you notice, most harnesses purchased now have a warning label stating the minimum weight of the worker must be 130 pounds. If a lighter weight worker uses the harness, they are in violation of the manufacturer’s instructions, which could mean an OSHA citation.
I believe we should be focused on the real issue in fall protection. The failure of the worker to use or use properly the fall protection equipment. Greater emphasis should be made to produce light weight and comfortable equipment to encourage more usage of the equipment
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