On Aug 1, 6:46 am, Jim Wilkins wrote:
On Jul 30, 6:08 pm, wrote:
...

If you know what you're doing you can fabricate one yourself. Use
your best judgement and simply test it with a load 5X as heavy as the
intended load rating of the hook. Check for cracks, and if all is OK
you're good to go. ...
Wolfgang

From what I've read, test samples are generally checked at 4X or 5X,
then working parts proofed at 2X. I tested my overbuilt, overweight
scaffold section to 1000 Lbs vertically and 500 on all diagonals,
which the 3/4" EMT braces initially failed.

What is normal practice for testing a single piece without damaging it?


This is from memory, but: Industrial material hoists / cranes are
designed with a factor of safety (FOS) of 5 on the structure.
(Hoisting ropes have a minimum FOS of 6, often more). Companies
designing & supplying underhook appliances (lift beams, spreader
beams, etc.) often also use this factor of safety, although I have
seen FOS as low as 2 or 3 on these appliances.

Engineering designed hoisting equipment is often tested after
installation, with a load of 1.25X the load rating to ensure what??
Absence of gross errors, I suppose, and functioning of load brake and
overload protective devices.

For the Do-It-Yourselfer the easiest approach is to load test his
creation at 5X the rated load. If this is a commercial application
then the witnessing of this load test (at 5X rated load) by a P.Eng.
would be, in most cases, sufficient for him to sign off on the
design. At least I would be prepared to do this provided reasonable
workmanship was apparent.

As an aside, people hoists require a factor of safety of 10.

I am not too familiar with (temporary) scaffolding, but I seem to
recall that a factor of safety of 2 is required. I forget whether
this applies to the tensile strength or the yield strength of the
material, but when I design access platforms, walkways, etc. I always
base the FOS on the published yield strength of the material.

I use the rules as laid out in the Canadian Handbook of Steel
Construction, the Ontario Health and Safety Act, and the Ontario
Building Code as applicable.

In case of a scaffold I suppose you could test individual pieces at,
say, 3X or 4X the working load, but this is not normal practice.
Normal practice is to use the published strength of the material in
the design, with the working stresses, at full load, in compliance
with the laws and regulations.

Just a word of caution on compression members (posts, bracing, etc.).
These are subject to catastrophic buckling failure with very little or
no warning of the onset of this mode of failure. The best way for a
Do-it-Yourselfer to deal with this is to copy a good existing design.
Fortunately the strength of the material affects the buckling failure
only minimally, but do not substitute say aluminum for steel when
copying the design of a compression member.

Experimental design could be used, also: Make 2 and test load one to
destruction. This is sometimes used in the case of pipe fittings or
small complex machine components. Also in airplanes :-)).

Wolfgang