Risk-based inspection and maintenance planning to manage the integrity of corroded pipelines

Many pipeline operators use risk-based methods to manage the integrity of their pipeline networks. The objective is to provide an overview of state-of-the-art pipeline risk and lifecycle assessment including probabilistic modeling of inspections and corrosion growth processes. After initial construction, the total lifecycle costs of a pipeline are primarily governed by inspection and maintenance costs as well as the risk of failure. To quantify these costs, the future corrosion process needs to be modeled probabilistically and updated based on expected inspection results and repairs of the system. While corrosion rate models are preferred in practice, they do not adequately capture the temporal uncertainties of corrosion growth and should be avoided in any reliability and risk assessment. Stochastic processes better suited for uncertain corrosion growth modeling. They are inferred from pipeline inspection results where sizing errors, detection errors, and false identifications need to be considered for an accurate assessment of the uncertain state of corrosion. Using a lifecycle approach, optimal inspection and maintenance strategies are identified by minimizing the total costs under risk constraints. Examples are provided to illustrate the risk-based planning including a discussion on some current challenges.