ASME Code Case N-513-4 allows evaluation of flaws in elbows to be treated as straight pipe if the flaw is located within a distance √Rt from the weld centerline, provided the elbow is welded to straight pipe. In addition, N-513-4 provides guidance for evaluation of flaws in elbows when the flaw is remote from the weld, but this approach may be increasingly conservative for flaw locations closer to the weld. For the instance where a flaw evaluation is necessary at a weld adjoining a 90° elbow to another 90° elbow, it is not clear if the stress distribution would be significantly different from a weld connecting a 90° elbow to straight pipe. This paper will employ finite element models to examine the stress distribution near elbow-to-elbow welds under a moment load and compares the results to straight pipe. The results of this paper may be used as a supporting basis to modify the Code Case guidance in a future revision.
Flaw Evaluation at Pipe Weld Connecting Two 90° Elbows
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Dawson, B, Houston, E, & McGill, R. "Flaw Evaluation at Pipe Weld Connecting Two 90° Elbows." Proceedings of the ASME 2016 Pressure Vessels and Piping Conference. Volume 1A: Codes and Standards. Vancouver, British Columbia, Canada. July 17–21, 2016. V01AT01A008. ASME. https://doi.org/10.1115/PVP2016-63946
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