Abstract
Pipeline integrity programs require validation techniques such as in-line inspection (ILI), pressure testing (PT), or direct assessment (DA). Many unpiggable pipelines present operational restrictions for the use of ILI tools. DA is applied through four steps: data gathering; indirect examination (IDi); detailed examination (DEx); and post-assessment. The flow and corrosion models used for the IDi are physics-based and do not quantify the uncertainties in the variables, the models, nor the corrosion process. The selection of verification sites for the DEx from the IDi, is not risk based. The post-assessment does not include a formal risk evaluation. The purpose of this paper is to present a framework for the integrity assessment of unpiggable pipelines, which are subject to internal corrosion. This integrity assessment is done by combining probabilistic flow and corrosion models with risk assessment. The flow model calculates variables that affect the corrosion process, thereby enhancing the predictability of the corrosion model. A risk analysis combines the information from the corrosion model with a consequence model to define the verification sites, and field verification is used to update the corrosion model. Risk evaluation uses the output of the risk analysis to recommend optimal inspection, maintenance, and risk mitigation strategies.
