Linear misalignment of welded elbow longitudinal seam (as per B16.9)

[QCJT]

Dear experts,

I didn't get a complete answer on a similar question asked about this on ASME forum, so I hope you may explain me what is the tolerance as per B16.9 for the misalignment of the fabricated elbows? We had measured 2.5mm internal misalignment on the 36" 90Deg. elbow. Client insists this should have been tapered smooth to a 30-degree profile as required by ASME B31.3 fig. 328.4 3a. However PO for fabrication of elbows only specified B16.9 and in B16.9 I can't find any clear specification on misalignments. Further, they claim that "collapsed arc" has caused this issue which is just an uneven surface of the weld capping on same areas where internal misalignment is evident. This "collapsed arc" was perhaps caused due to misalignment and not vise versa as they claim.

Hoping to get some help on this

Best regards
JT

 

[DekDee]

QCJT,
Have no idea about the "collapsed arc" you mentioned but just because the elbow complies with the tolerances of B16.9 does not mean it automatically complies with B31.3 requirements for a welded connection.
B16.9 will not list misalignments as it is not a construction code - the construction code (in this case B31.3)states the allowed misalignment between two items (eg. an elbow that complies with B16.9 may be mated to a pipe that complies with A106 Gr B yet you have misalignment that doesn't comply with the construction code).
Is it 100% misalignment (different inside diameters) or is it isolated misalignment (ovality / out of round) ?

Rereading your title you have mentioned misalignment and longitudinal seam - not sure I understand.
Regards,
Shane