In this research paper, the failure pressure predictions were obtained for a pipeline section by analyzing a combined corrosion defects, which joins together a general corrosion and a pitting corrosion defects. Well-known conventional mathematical methods were used in this study to predict the failure pressure of corroded steel pipelines, such as: B31G, RSTRENG-1, Shell-92, DNV, PCORR, and Fitnet FFS. The equations reported for corrosion defects with more complex characteristics developed by Choi et al., and Cronin et al. were also used. Furthermore, Finite Element (FEM) is one of the most employed nonlinear methods because of its good response of pipeline failure prediction under the corrosion mechanism. So, FEM methodology results the least conservative in comparison with the others mathematical models, according to the literature, for this reason it was used to compare the standard deviation  of the methods. Failure pressure predictions determined that the most conservative methods were: Shell-92, Fitnet FFS, Choi's method, B31G, RSTRENG-1, Cronin´s method, PCORR and DNV, in that order.

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Abstract:The mechanical behavior of API 5L X52 steel with planar type laminations was studied in the present work. Planar laminations were proposed in the base metal (BM), heat affected zone (HAZ) and welding bead (WB). Three-dimensional finite element (FE) models, kinematic hardening and mechanical properties for BM, HAZ, and WB were activated in the finite element program. The results showed that crack propagation corresponds to the direction of the main stress. For a crack length (2a) of 10.01 mm, crack propagation may occur at the right crack tip towards the outer wall of the BM. For 2a of 15.12 mm, crack propagation was located on the right crack tip and propagates to the inner wall. For 2a of 17.12 mm, crack propagation was observed at the left crack tip and propagates to the outer wall in the BM. The results achieved by FEM agree when compared with real laminations in API 5L pipelines.