The current ASME Boiler Pressure Vessel Code doesn’t provide the primary stress indices (B2) and primary plus secondary stress indices (C2) for a pipe cross connection. In this study, two types of Finite Element Analysis (FEA) models were created to calculate the stress indices for such a configuration: the first was a 3D solid model to calculate the stress intensities and the second a simplified pipe model to calculate the bending moments to obtain the pipe nominal stresses. For both types of FEA models, loads were applied in one direction at either run pipe or branch pipe to ensure in-plane or out-of-plane bending moments were produced in the model. This analysis includes 28 cases for multiple combinations of loads and boundary conditions. As defined in NB-3682, stress indices are determined by B, C = σ/S where σ is elastic stress in the component and S is the nominal stress in the component. The B2 indices were calculated by two methods: method one which is the default solution in FEA program, all six stress components were applied to calculate the membrane plus bending stress; method two, axial and hoop normal stress components and torsional shear stress components were used to get the membrane plus bending stress. The results show that the method two for B2 indices are more reasonable and realistic. For C2 indices method one was determined to be more appropriate. This paper presents the results of the analysis, the basis for stress indices development and the resulting stress indices.
Development of the Primary Stress Indices and Primary Plus Secondary Stress Indices for Pipe Cross Connection
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Adams, TM, & Wen, J. "Development of the Primary Stress Indices and Primary Plus Secondary Stress Indices for Pipe Cross Connection." Proceedings of the ASME 2015 Pressure Vessels and Piping Conference. Volume 3: Design and Analysis. Boston, Massachusetts, USA. July 19–23, 2015. V003T03A023. ASME. https://doi.org/10.1115/PVP2015-45610
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