Difference between grades of chain

[mjw56]

Feel free to move this question to a more appropriate forum, i just couldn't think of where else to put it as there is no rigging forum.

So im looking at chain to replace the steel cable which currently supports the raceways and battens on our electrics (5 of them). i think im gonna use 3/8 grade 80 chain(7100# WWL) (way stronger than the 1/8 the aircraft cable(1700# break strength) that's up there now and was installed by a local company, without thimbles in the swages mind u).
But i was wondering, what is the primary reason that only grade 80 and above is rated for overhead lifting and hanging. for the sake of argument why couldn't i use a 1/2" grade 43 (9,200# WWL).

Id also like your opinion on not having thimbles in the steel cables. frankly i don't like it.

Thanks

[derekleffew]

The Facility Forum seems as good a place as any, as we are dealing with the physical plant.

This thread is treading on thin ice, see

The users of ControlBooth, in a effort to police themselves, have evolved the following: No discussion of "how-to" of rigging, pyrotechnics, human flight, stunt falls, weapons and electrical will be permitted. Our stock answer to these questions is always "Consult a qualified professional."

but we'll leave it open as long as no one says "Use X for application Y."

Originally Posted by mjw56

...But i was wondering, what is the primary reason that only grade 80 and above is rated for overhead lifting and hanging. ...

Short answer: because ANSI / ASTM / ASSE says that's what is to be used. The same reason that only Grade 8 and above bolts are used in overhead lifting/suspension.

You are correct in thinking that thimbles should be used in all terminations of wire rope, with very few exceptions.

[sk8rsdad]

The difference between Gr.80 and Gr.43 is documented in the NACM Welded Steel Chain Specification. Grade 80 is designed to resist catastrophic failure better than Gr.43 will, due in large part to it's elongation coefficient which means it will stretch more before it breaks. It requires almost twice as much force to proof test 1/2" Gr.80 (107kN vs 61.3kN).

[Footer]

As Derek said... because it is. If you are going to put something over someones head, might as well be the best possible thing. This is one place you don't want to cut corners. Grade 80 chain is expensive, but it is the only way to go. It also comes in black if your into that sort of thing.

By not using a thimble on the line your are cutting the working strength of that wire rope by at least half, if not more depending on how tight the bend is. Its a good thing you are looking at changing it out. I don't think it would survive a quake or something along those lines. For my money, if you are going to dead hang anything chain is the way to go. Its makes life easier if you need to raise or lower a pipe and it makes install faster.

[mjw56]

ok to reiterate. I AM TELLING THE SCHOOL TO PURCHASE GRADE 80 CHAIN and i will not install anything less. there was a rant with a bunch of calcs written out but that probably would have looked like "Use X for application Y." so i refrained.

the school was not happy about the price though. i told the music dept. chairperson nothing less is approved for overhead applications. he said he would talk to the principal.

as for the lack of thimbles. that installation was done by a local company that handles everything from rentals to home theater installs and we haven't modified it in any way. so if it falls, that's on them....i think...i hope. the part where the cable should have a thimble is connected to a 3/8 " quick-link so its a pretty tight bend.

thanks for the straight answer sk8rsdad. telling a bunch of suits/musicians "because ANSI/Astm/ASSE/I said so doesn't usually work

the comment about the bolts is good to know also as there is a lot of old hardware (probably original to the school so almost 50 yrs old) using god knows what and it should be cheap enough to replace

thanks for the info

[Footer]

Originally Posted by mjw56

so if it falls, that's on them....i think...i hope.

Unless it falls on you. Then its on you.

Because ASSE says so is a completely valid argument. These are the people that are responsible for making sure bridges stay up and buildings don't fall. I don't think your principal or music dept. head has the knowledge to question these groups.

If you want to have things overhead, its expensive. Rigging is expensive because it had to be done right. Every grade 8 bolt and grade 80 chain is tested and marked. Huge amounts of time and money go into making sure that the load rating printed on the box is true.

[mjw56]

sorry i didn't mean to sound like they have no value. but we all know (i hope) that those institutions do have value and why what they say is doctrine. 99% of the people i deal with just don't have a clue. if u want to know how to play jazz sax, or write a speech though they would be able to help you out

[cdub260]

Originally Posted by mjw56

as for the lack of thimbles. that installation was done by a local company that handles everything from rentals to home theater installs and we haven't modified it in any way. so if it falls, that's on them....i think...i hope. the part where the cable should have a thimble is connected to a 3/8 " quick-link so its a pretty tight bend.

Now I could be a little off base on this, but I believe that once you (the facility) are made aware of a safety issue, if you do not address it and something happens that results in injury or death, the liability falls squarely on your shoulders. The school district should consult their attorneys and insurance company on this subject.

And I don't believe quick links are rated for overhead lifting.

[Footer]

Originally Posted by cdub260

And I don't believe quick links are rated for overhead lifting.

They are not.... they are just not rated... at all. Tie up your dog with a quick link, use a shackle for anything real.

This is one of the reasons that I feel ANY hardware entering into a theatre should be grade 8 or rated. If it walks through the doors it could be used for overhead lifting at some point. Might not be for this production, but who knows what will be going on in the future after you leave. I have thrown away more hardware then I can count for this exact reason. I knew I know better, but who knows what the next guy will do. Its a bit extreme, but it does keep things a bit safer.

[mjw56]

hhmmmm. quick links aren't rated for overhead?? im never letting the school work with this company again. that's just ridiculous.

this might be pushing the TOS but how about screw pin shackles, are they rated for overhead? if this is outside the tos just dont answer it.

a better question might be what standard governs whether or not something, like shackles or quick-links, is rated for overhead use? this way ill be able to know if the materials im ordering are up to snuff.