The existence of corrosion features in energy pipelines can adversely affect the stress/strain state of the pipe body leading to potential integrity concerns. These concerns can be intensified when a corrosion feature is suspected to be interacting with deformations in the pipe geometry such as dents. While explicit models are available for the individual analysis of corrosion and dent features there is significant room for research and development in the assessment of these features when they interact. Additionally the uncertainties associated with the input variables (such as in-line inspection measurements pipe attributes operating conditions etc.) are often neglected or considered within a limited scope in the analysis methods typically being implemented in the pipeline industry today. This paper presents a methodology for the assessment of corrosion features interacting with dents in pipelines through the use of Finite Element Analysis (FEA) and reliability analysis. FEA is a numerical analysis method which can be used to account for geometric and material non-linearities in order to accurately predict the mechanical behaviour of a system. FEA is used to model the 3D geometry of the corrosion and the dent features (with geometries reported by in-line inspection tools) and calculate the stress/strain state of the pipe resulting from their interaction. Reliability analysis is performed to account for the uncertainties associated with the input variables to determine the potential severity of the features. FEA and reliability analysis can be integrated through reliability-based stochastic finite element methodologies; however these methods are typically computationally demanding and not feasible for frequent integrity analysis. In order to improve the feasibility of detailed analysis of interacting features this study demonstrates the application of Reliability-Based Surrogate Models (RBSM) as a means of integrating FEA and reliability analysis. The application of RBSM significantly reduces the computational demand without compromising the accuracy of the reliability analysis. First Order Reliability Method (FORM) and/or Monte Carlo simulations are used with the RBSM to assess the structural limit state and resulting reliability of the pipe section modelled. The proposed approach was applied to example cases of corrosion features interacting with dent features (as measured during in-line inspection) to evaluate the probability of failure of the pipe section modelled. This method provides an additional assessment technique for interacting features which can be a valuable tool for managing pipeline integrity.

Key words: Pipeline Dent, Pipeline Corrosion, Finite Element Analysis, Reliability Analysis, Response Surface Method, Reliability Based Surrogate Model