Especially on NPS 6 and above, heat input becomes problematic. One issue could be that your welders are using cosmetic 'wash' passes with GTAW on the cover pass of the weld. These welds should be performed with a maximum of 2 passes.
Also, re-work in localized areas of welds (RT or PT failure for example) may neccesitate the cut-out of entire welds, piping sections and fittings in order to meet code requirements, material specifications or end user requirements in the finished weld.
ASME B31.3 limits "internal protrusions".
The piping and fitting specifications will limit the acceptable ID of the components which can be extrapolated from measuring the OD.
The end user may have service conditions which require minimal turbulence.
Finally, when measuring and determining the extent of the distortion, be cautious to differentiate between misalignment and 'cave-in' type distortion.
Best regards,
Darcy Morin
API 570 Refinery Piping Inspector
On 2009-12-11, at 20:16, "Rajak, Sanjib (Bantrel Constructors)" <RajakS@BantrelConstructors.com> wrote:
Hi Guys,Can anybody through a light on how to control distortion in thin wall Stainless Sch10s piping welding. Fit up looks absolutely good but after welding we see cave in on weld upto 5/32".what is the acceptable limit or is there any acceptance critiria for cave in condition.Thanks,SanjibThis e-mail and any attachments may contain confidential and
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