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RE: proper weld metal notes

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Title: RE: proper weld metal notes

>It was an eye opener when a big steel  fabricator stated that the main
>reason that fillet welds were cheaper than groove welds was that there was
>no NDT of fillet welds.

As another thread already explored, NDT requirements for all welds vary and are essentially at the discretion of the engineer. UT can't be used to inspect fillet welds, but there are other NDT processes that can be used if inspection is required. Bob Shaw's previous comments were right on the money: in-process visual inspection (i.e., inspection of the joint before welding, during welding, and after welding) is most important for any type of weld.

As far as cost goes, inspection requirements definitely drive cost, but so do other factors in the labor, like preheat requirements, volume of weld metal required, base metal preparation required, post weld treatments (postheat requirements, backing bar removal, etc.). With all things considered, a fillet weld probably costs on the order of $30 per pound of weld metal; a CJP groove weld on the order of $60 per pound of weld metal.

>With groove welds you can use UT to find weld defects
>which then have to be repaired.  You probably have many of the same
>defects in a multi-pass fillet weld that you would find in a multi-pass
>groove weld but because you don't test them you don't repair them.

The direct comparison of fillets and groove welds isn't always valid, since the two weld types aren't always applicable to a given joint. When a fillet weld is appropriate, most fillet welds are (or can be) the single-pass variety. The typical applications, like connection angles and plates, hardly ever can't be sized to get the fillet leg size down to a single-pass weld (usually 5/16 or 1/4, depending upon process and position). This is a hallmark of an economical job. When you get into vary large fillet welds, I suggest that it's time to rethink the joint to get the weld size down.

>Thus it appears that when you use a fillet weld instead of a groove weld to
>save money you are also accepting a lower level of reliability.

I think the reliability that results for all welds that meet the requirements in AWS D1.1 is acceptable.