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Re: WELDING: NDT Methods for PJP Weld

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Bill,

I think I know what you meant but be aware that there is no such thing as a "butt weld" although the term is commonly used.  Per AWS D1.1 there are "butt joints" and "square welds".  I am no expert in NDE but AWS D1.1 Section 6.13.3 indicates that there are no standard acceptance criteria for UT of tubular connections however they do seem to provide some guidance for which you need to make part of your contract documents.  Section 6.27.1 appears to require that a special written UT NDE procedure be written if this is a tubular T-, Y- or K- connection.

In general the usefulness of UT is that it can determine issues deep within the metal whereas MT will only show you surface cracks.  Since UT is based on reflecting sound waves through the material I can see that this would be very difficult in a tubular connection (i.e. UT is sometimes considered a bunch of hocus pocus even with flat plates).

Thomas Hunt, S.E.
Fluor



"bill(--nospam--at)polhemus.cc" <bill
06/28/2010 09:13 AM
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WELDING: NDT Methods for PJP Weld





Greetings, friends.
 
We originally required on our drawings/specs using radiography (RT) for acceptance of a 1/2" effective throat PJP tubular girth butt weld. Subsquently the contractor requested that we accept ultrasonic (UT) testing. We accepted.
 
Still later, they asked again if magnetic particle (MT) would be good. That's where we drew the line in the sand. Personally I've never seen MT used except for non-butt welds (e.g. fillet), but beyond that we just don't see the purpose.
 
The contractor insisted their "Level III NDT tech" claims that UT for PJP is "not allowed" by AWS D1.1:2008. I could find no such prohibition, and in fact Part F talks about UT of groove welds, and does not distinguish between PJP and CJP, only that the minimum weld thickness must be 5/16".
 
They have backed off on that claim, but now insist that WE must provide an acceptability criterion for the UT. To me, it ought to say "we've got at least 1/2" of sound weld metal in there," and that's that, but I recognize there might be other issues that need addressing, such as imperfections not related to inclusion like a cold-crack or some such.
 
Has anyone got any experience with UT of butt welds, and did you deal with acceptability?
 
Thanks.
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