I guess I should start this with my credentials. I have been a
theatrical rigger for 20 years and presently make my living designing
and installing rigging systems in theaters and other entertainment venues.
Both of the above descriptions of 'proof coil' are correct. Home Depot
and Lowe's both carry it. So does Ace and many other local hardware
stores. The only other thing that I would mention is that any chain made
in the US or other 'industrialized' nation (UK, Denmark, Oz, etc.) will
or should have a load rating attached. That load rating is the end
result of a design factor (5:1) that basically takes the breaking point
or deformation point (depends on the manufacturer) and divides by five
for a load rating. Simply put, the working load rating is one fifth of
the load that will break the chain (or other device). If the chain
breaks at 5,000 lbs., then they give it a working load rating of 1,000
lbs. Basic rule is, if you don't know that the maker is of good repute,
then take the stated working load and divide by five and that's what it
will safely hold. Sure, I've bought Chinese equipment, but I always
derate it by a factor of five. You can't sue China.
The other very important thing to remember is that the chain is only as
strong as its weakest link. If you've got the best chain in the world
and you're attaching it to something with an old bolt that you pulled
out of your bin, then the load rating on the chain means absolutely
nothing. A lifting system is as integrated as an electrical system. They
put fuses in electrical systems in order to protect the system by
being the weakest link. Lifting systems generally don't have fuses
unless they're motorized. They just have a weakest link. Make sure *ALL*
of the connections in your lift are equal to the job. New, grade 3 or
better bolts are always recommended when doing any overhead lifting.
Be safe,
Glenn
> Subject: Re: [Mgs] watch your chains
> To: mgs@autox.team.net
> Message-ID: <885450.91745.qm@web112113.mail.gq1.yahoo.com>
> Content-Type: text/plain; charset=us-ascii
>
> --- On Wed, 6/2/10, Max Heim <max_heim@sbcglobal.net> wrote:
>
>> > OK, I'll bite -- what is "proof coil
>> > chain"?
>
> Chain that is certified for "overhead lifting" and is
> rated by lift capacity. Any decent hardware store
> should have it.
--
Nil desperandum
Glenn Schnittke
-----------------------
g.schnittke@comcast.net
Home - 615-837-5883
Cell - 615-319-5534
_______________________________________________
Mgs@autox.team.net
Donate: http://www.team.net/donate.html
Suggested annual donation $12.75
Archive: http://www.team.net/archive
Forums: http://www.team.net/forums
|