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?
Bill, I trust nobody's view on this more than yours. But then we have a large portion of our industry, including leading rigging companies like JR
Clancy and Sapsis, seeming to say something different, so I'm just trying to get to the bottom of that
disconnect because until we do it is going to be darn near impossible for a lot of end users to push your recommendations through their bureaucracies. It shouldn't take finding you on a forum to get this right, but that's about all there is right now. I'm concerned with the real-world consequences of this as an end user who has neither your intimate knowledge of the standard-making process, nor your direct contact with the NACM. Does everyone really need to interview the NACM executive and committee in order to understand the standard? Aren't standards written in order to eliminate that need? Clearly it isn't working that way, and whether it is because people are willfully ignorant, stupid or something else, something should be done to reduce the possibility of erroneous interpretations becoming so pervasive. While it may not be the NACM's top priority or responsibility to intervene with an unsolicited public clarification of their definition of
overhead lifting, it sure would be helpful. Bill, are you aware of anything to that
effect?
JR
Clancy has put their (wrong, I guess) interpretation in writing. To be fair, I haven't heard it explicitly from Sapsis, but Bill Sapsis himself did my last inspection and was fine with our grade 30
trim chains, and some that aren't even stamped. The argument that you are at odds with, which like I said before is too tenuous for my comfort, but which seems to be in
line with every
counterweight system installation I come across, is that a chain is only considered to be in a lifting application if it is being lengthened or shortened by mechanical means, as in a
hoist. The other part of the argument is that 'freely suspended' involves a possibility of torsional stress as in a single
point from a crane for instance.
So using that argument, the
counterweight system designer tells the end user that their grade 30
trim chains don't fall under the
overhead lifting definition, and one of the most respected
ETCP riggers out there doesn't say peep about them during inspection. Meanwhile, from what you say it sounds like nobody is backing any of this up by actually asking the NACM. That part I didn't know until now.
It would be really nice if all the experts would get together on standards and definitions that provide absolute clarity for our industry's common applications, because otherwise end users like me and the OP just don't have enough to back up (or refute) our less-expert interpretations.
Save for running into generous experts like you, Bill, people are naturally likely to trust what the
system designer says. It may be some comfort liability-wise to have
Clancy standing behind their proof coil
trim chains, but if the NACM says they're no good then there is at very least a moral dilemma for the hundreds? thousands? of facility managers who currently have proof coil
trim chains in the air.
What if a TD wants to secure funds to follow your recommendation to
switch to
overhead lifting rated
trim chains (with my regular budget $50 per set is actually prohibitive without a multi-year plan)? If I need to go ask for more money and my president, provost or trustees want me to prove the necessity (they will) then it is the written word of the company that designed the
system versus the NACM who are not specifically theater rigging experts. It is indeed infuriating that the NACM is not being asked about their own definition, but try convincing the average academic bureaucracy that the company they already picked to do the original
system and that devotes all its time to specifying theatrical rigging is wrong, and some other body they've also never heard of is right...
