I have a question on the NIOSH Lifting Equation. My boss wants me to make a recommended weight limit for a task of unloading a 4-tiered pallet. When I perform the multi-task, I get a CLI of 3.67. He suggests that I can just take the known load of 20 pounds and divide by the CLI to get a recommended CRWL of 5.45 pounds. I read through the Revised NIOSH Lifting Equation book, and I don’t see any equations to do a “composite recommended weight limit” CRWL.
I tried taking the least RWL for an individual task, and re-running the whole multi-task calculation. The CLI dropped to 2.4.
Can I suggest that the boss be asked, does he/she want to know the result of the equation (the final number?) or does he want the overt physical, musculoskeletal strain significantly reduced or eliminated? My guess is that his/her objective is to reduce or eliminate the need to lift whatever is being lifted which is the essence of the human factor/ergonomics intervention…..I’ve done this several times in the past with EHS Managers quite successfully….just get rid of the problem and forget about the result of the calculation (it’s ancillary)……move-on with the next workplace challenge, put the old one “to bed”.
Thanks for your reply. You are correct in that we want to reduce/eliminate the musculoskeletal stress associated with this task. We want to use the appropriate ergo analysis tools to help us make the case. So getting the numbers right is important. If we get the numbers right, then hopefully we can measure the effectiveness of any suggested solutions.
Part of this problem is how we communicate to our clients. Giving them a LI or CLI is good, but it many do not understand what it means. Recommended weight limits may be easier to understand for non-ergonomists.
You are correct, many non-ergonomists do not understand the equations. I wish you success in your endeavor. It is obvious from your message that you have your priorities in order. BTW, most practitioners struggle with the NIOSH equation; you may want to contact one of the university Human Factors profs. to support your cause.
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