Posted by MCox on November 01, 2001 at 11:11:17:
In Reply to: Re: welding failure of the feed nipple entering the drum posted by lou christou on October 14, 2001 at 23:39:05:
: Sounds like thermal stresses are the problem.
: Is your feedwater temperature too low?
: You might consider using a thermal sleeve for this nozzle.
:From my point of view as a certified x-ray welder, I beleive Mr. Connor has identified the first possible cause. Secondly dissimilar metals and improper weld materials would also be another indicator. If for example this is a chrome moly base metal and someone used an A-106 E70 gtaw wire or a 7018 smaw wire this would be the most likely cause of weld failure at the weld itself. In the case of a high pressure/ high temp weld such as this one, an ASME sec.IX procedure should have been designated by the A.I. in the district and he would have designated the proper weld materials to be used for this repair. The contractor in turn would be responsible for obtaining and using the correct weld metals and procedure. Short of failure to pull back the socket fitting 1/16" after bottoming out and using an 8018 smaw or higher or an ER/80-90 gtaw welding wire with pre-heat this joint shouold not fail unless excess temps are reached and pressure exceeds the ratings for the weld placed on previous attempts. MCox
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