Pipe bends (e.g. 90° and 45°) are trimmed at pipe fabricator shop to suit the required angle per design. However, B31.3 Code requires all pipe bends that are trimmed more than 3° from its original configuration to be treated as an unlisted component. In addition, the stress formulas provided in the ASME B31.3 Code are only intended for 90° elbows without considering the effect of bend angle. The objective of this study is to evaluate stresses in elbows of various bend angles and to provide a design justification for the field disposition. To serve this purpose, elbows with outer-diameter sizing from 4 to 60 inches and angle ranging from 25 to 75 degrees have been studied and compared with 90° bends under the same loading conditions. The results reveal that the stresses are reduced in the trimmed elbow. And the reduction trend in the stresses due to trimming can be predicted by the bend angle and the flexibility characteristic.
Bend Angle Effect on Stresses of Trimmed Elbow
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Liu, Y, Shen, L, Diwakar, P, Jaouhari, M, & Patel, P. "Bend Angle Effect on Stresses of Trimmed Elbow." Proceedings of the ASME 2017 Pressure Vessels and Piping Conference. Volume 3A: Design and Analysis. Waikoloa, Hawaii, USA. July 16–20, 2017. V03AT03A037. ASME. https://doi.org/10.1115/PVP2017-65026
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