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Re: Chain Link loads

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>Could somebody direct me to a glossary or provide information on and 
>differences between "working load", "breaking strength", "proof load", and 
>"ultimate load".
If you're talking about rigging elements (slings, cables, hooks, 
what-have-you)--
--Working load is the maximum expected load in ordinary service. Abuse is 
not considered part of the working load.
--Breaking strength isn't well-defined, but it's used for ropes and 
cables. It's synonomous with ultimate load.It's not a good idea to use it 
where specifications are concerned, since a rigging element can yield and 
lose its strength before is actually ruptures.
--Proof load is the load which can be withstood without permanent 
deformation. It is usually something like 90% of the yield load and is 
actually the lower bound limit load.
--Ultimate load is the maximum load which can be withstood--the upper 
bound limit load.

Both proof load and untimate load are measured quantities, found by 
pulling new equipment. Working loads are typically, but not always, the 
lower of 1/2 the proof load or 1/5 of the ultimate load. You can get a 
pretty good handle on this from the Rigging Handbook (not the exact name 
but good enough for a Google search). Reputable rigging element 
manufacturers like Crosby publish this kind of information is their 
catalogs which are available on line. OSHA Regs also specify this kind of 
information including special additional requirements for particular 
service.

I find contract specifications (even for nuke plant systems) throw terms 
around pretty loosely. Make sure your specification is 
self-consistent--that is, that specified working loads throughout the 
system are pretty much the same and that any specified ultimate loads are 
about 5 times the working load. It's also common for design requirements 
to be phrased as 1/5 of the ultimate tensile stress, when in fact the 
proper requirement should be 1/5  of the ultimate load. Elements in shear 
or compression or bending all have different ultimate failure modes for 
which the material UTS may be irrelevant. 

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw



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