Thank you all for the replies. It appears that the failure was due to wear, I suspect it was the brake mechanism was what failed, but there was also excessive
play in the shaft that is driven by the
winch handle which may have contributed. The handle spun rapidly as the
electric descended. The
electric was likely loaded near, but below, the rated capacity of the
winch. I asked Jeamar (through their website) if they had any winches designed for theatrical use, and received no reply. It appears the Thern
winch is the ONLY
hand winch of this style that would be appropriate for
stage use/
overhead lifting, and I have forwarded the info to the responsible parties.
As for finding the applicable standards (which was what I was looking for initially) what I found was:
OSHA Simplifies Documentation on Overhead Lifting
http://www.plsn.com/news/21-news/8021-osha-simplifies-documentation-on-overhead-lifting.html
And the relevant
OSHA regulation:
https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9830
Key paragraphs from the regulation:
1910.179(f)(1)(i)
Each independent hoisting
unit of a crane shall be equipped with at least one self-setting brake, hereafter referred to as a holding brake, applied directly to the motor shaft or some part of the gear train.
1910.179(f)(1)(ii)
Each independent hoisting
unit of a crane, except worm-geared hoists, the angle of whose worm is such as to prevent the load from accelerating in the lowering direction shall, in addition to a holding brake, be equipped with control braking means to prevent overspeeding.
So, you need both a control brake and a holding brake, without that it's not going to be
OSHA compliant. The Thern
winch has both, the ones currently in use don't. This is pretty close to what I was looking for, as it's a regulation that would disallow the use of (most)
hand winches. Unfortunately they were very common to use in the 1970's and 1980's, and convincing the school
system to replace all of them is going to be a tough sell. But at least now we have the combination of a failure, the regulations, and a reasonable replacement to push the issue. If your
stage has a similar setup, learn from this and act now!
-Fred