BillConnerFASTC
Well-Known Member
I'm pretty clear on what constitutes overhead lifting, and that the application in question is not. What is wacky about the current E1.4 (and especially this annex entry) is that it seems to want to require, or at least suggest as an acceptable example, the characteristics of overhead lifting rated chain for purposes other than overhead lifting. So, the term "overhead lifting" gets used a lot where it is not truly in play and better language might be something like "alloy" or whatever communicates the material properties and strength characteristics of chain rated for overhead lifting. The design requirements need to be de-linked from the definition of the overhead lifting application.
Plus, to me the origin of the confusion about what is and isn't overhead lifting is the term itself. It is easy for someone approaching the issue for the first time to look at a counterweight set, read the words "overhead" and "lifting", and think that those words must describe trim chains on a moving (lifting) batten. A little more digging clears it up, but it seems like it would be more clear to alter the term to acknowledge the key concept of "freely suspended" right off. Then in the definition of terms, a little more about the definition of "freely suspended". But that's the NACM writing that definition, right?
Right now the best plain language explanation I know of comes from JR Clancy and even they use iffy language like "we think Grade 30 Proof Coil Chain is acceptable [as trim chain] from an engineering perspective." Some people are going to be twitchy about it until someone changes "think" to "know" and adds clarity to the standard. Glad we have some CB members who are involved in the process. What a task...
I'm not clear on what you are saying but I strongly believe that a trim chain is an example of overhead lifting as used by the NACM, who write the standard for chain and who coined the term overhead lifting, and thy and their members individually say trim chains are an overhead lifting application and that grade 30 is not approved by the chain manufacturers for trim chains when used for overhead lifting.
I think what you are referring to was written by someone trying to rationalize what they had been doing, and interpreting the NACM standard without contacting NACM. I contacted them and spoke with the executive director as well as the members of the committee that writes the standard, mostly tech people from the manufacturers, and that is what I base my opinion on. I've expounded many times on the 'freely suspended" term and what you reference ignores what the NACM says it mean, and it's their term.
This can become very personal. I have been libeled in public meetings by some who disagree, claiming I said things I did not say and which I could prove by recordings. Simply a lot of people don't want to admit that what they have done should not be done. If the prohibition is justified or not, I'm not commenting, but technically you cannot use grade 30 chain for a trim chain application when it used to lift (raise and lower) loads over (peoples') heads.
You're darn right they use iffy language. I hope you don't feel that way about what I say. And just to be sure, do not use grade 30 chain as trim chain material for loads over head on a stage which are lifted by manual or motorized rigging.
It is like $50 per lineset to use a chain that is so $50 for manual at $7000-8000 per set or motorized for $18,000-50,000 or more per set. Why bother trying to defend it for that puny amount of money?