B2 stress index for elbow analysis Original Research Article

The purpose of this study is to evaluate the effect of end constraint, geometric dimension and internal pressure on the B2 stress indices, and thus to determine the conservativeness of the code equation for B2 stress indices. For a series of stainless steel elbow-straight pipe connections of different sizes and schedules, with flanges attached at different locations and with different levels of applied internal pressure, nonlinear finite element analyses were performed considering both material and geometrical nonlinearities. Load-deflection curves were obtained, and from these curves, collapse limit loads were determined. B2 stress indices were computed using the equation B2=Sy/(Mcl/Z). The B2 stress indices of elbows with flanges attached at different locations were compared. Also compared were B2 stress indices of elbows with different levels of internal pressure. Finally the B2 stress indices from the finite element analysis are compared with the B2 stress indices computed from code equation. Regression analysis is used to determine revised numerical values for the code equation for B2. A new, less conservative equation is proposed to be used to compute B2 stress indices for elbow component.