Structural Integrity of Energy Pipelines: Assessment, Reliability and Optimization

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Pressurized steel pipelines are widely recognized as the most economical means to transport large quantities of hydrocarbon products The Canadian energy pipeline industry operates approximately 115,000 km of oil and gas transmission pipelines. Maintaining the integrity and safe operation of this vast pipeline network has significant social and economic implications. New knowledge, models and methodologies that will assist the pipeline operators in achieving this goal are of significant practical value. The proposed research program is aimed at maintaining the structural integrity of steel pipelines under various threats, and consists of the following projects, namely 1) developing reliability-based pipeline corrosion management methodologies, 2) developing multi-objective optimal maintenance strategies, and 3) investigating the single-edge tension specimen for determining the fracture toughness. Over the last decade, the reliability-based pipeline corrosion management program has received growing attentions from pipeline operators because such a program provides an appropriate framework to account for various uncertainties involved in the corrosion inspection and assessment. The outcome of project 1) will fill the knowledge gap with respect to the spatial correlation of corrosion defects and provide a probabilistic framework to simultaneously make inference of the number and growth of corrosion defects on pipelines based on the inspection data. These methodologies will lead to realistic modeling of the degradation process associated with a corroding pipelines, which is critical to the determination of re-inspection interval, accurate evaluation of the time-dependent reliability of the pipeline and development of a phased defect mitigation plan that satisfies both the resource and reliability constraints. Optimal maintenance decisions for pipelines have significant safety and economic benefit to the society and the. The outcome of project 2) will provide guidance to pipeline engineers on the selection of maintenance plans to maximize reliability/safety and minimize cost at the same time. This is valuable not only from the perspective of the pipeline operators but also from the perspective of general public located in the vicinity of the pipelines. The strain-based assessment is being increasingly used to address large plastic deformation imposed on pipelines due to, for example, slope movement and ground subsidence. The fracture toughness resistance curve is a key input in the strain-based assessment of pipelines containing planar defects (i.e. cracks). The use of the single-edge tension specimen to experimentally determine the fracture toughness has gained much attention in the pipeline industry over the last decade, because the fracture toughness determined from such type of the specimen is more relevant to that of the full-scale pipe. The outcome of project 3) will facilitate the development and standardization of the single-edge tension specimen-based fracture toughness testing procedure, which can lead to more accurate evaluation of the fracture toughness and consequently more accurate strain-based assessment of pipelines containing cracks.