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Re: Investigating Welds

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>What is the standard I should follow to evaluate the welded connections that
>support the 50-kip counterweights? What percentage of welds should be
>checked? Should they be X-rayed, magnafluxed.....?
Bill's right--the standard is AWS 1.1, but there's more to it. You need 
to start with the AISC spec for structural welds for sizing and basic 
design issues. You'll also need to set up a means to insure you have 
qualified welders and weld procedures. Most of the QA problems I've run 
into started with welds specified and supervised by people who know 
nothing about welding and weld quality. 

Sticking my neck out a little, you'll probably be dealing with fillet 
welds performed in the field. If it were me I'd restrict testing to 
either liquid penetrant or magneting particle testing of a representative 
sample (5-10%)of critical welds. Tests like these are practical, and my 
experience has been that NDT has a hidden benefit--welders really don't 
like repairing welds and they tend to work more carefully if they think 
subsequent examination means grinding out defects and reworking a weld. 

Your service sounds very much like critical lifting: highly cyclic and 
service load dominated. Weld defects, especially cracks that grow 
quickly. kill people in such circumstances, so quality is very important. 
You probably won't be doing any impact testing, but you should be using 
weld metal with minimum impact test properties. The work goes a little 
slower, but I doubt if it'll make any real difference in this case. Your 
clients will be laity who work under pressure on a budget and don't care 
jack about engineering so be very careful about someone's brother-in-law 
who works cheap. 

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

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