Failure assessment on offshore girth welded pipelines due to corrosion defects

摘要

Corrosion is an electrochemical process in offshore pipelines where the material strength begins to decrease as corrosion advances. Numerous studies have been performed to determine the remaining strengths (failure pressure) of corroded pipelines. Currently the axial corrosions of the girth welded pipelines still leave much to be understood. This study attempted to simulate girth welded pipeline with various corroded depths and lengths in order to compare with offshore pipeline design manuals. Based on the numerical results, the influence of corrosion defects parameters on remaining strengths were investigated for girth welded pipelines. The investigation on the effect of strength mismatch revealed that in the cases of under-matched, higher failure pressures are obtained. Comparisons of current results with B31G-2012 and DNV-RP-F101 demonstrated that both codes may produce somewhat conservative predictions on the failure pressure. Furthermore, an equation was proposed to evaluate the corrosion progress across girth welded pipelines.