A Canadian pipeline company operates a 12 inch, nominal wall thickness 5.08mm and 25 km long partially buried insulated pipeline that transports hot liquid oil from an oil refinery, supplying product to a customer in Canada. In addition to the economic importance, this pipeline crosses a city intersecting several high consequence areas (HCA’s). Therefore ensuring the public safety and reliability of the pipeline is critical. One of the primary threats to the integrity of the system is external corrosion associated with areas of damage to the yellow jacket external coating. In buried sections this is due to a combination of water ingress in the damaged coating and CP shielding in these localized areas. The above ground sections are at a higher risk since they are open to the environment and any water ingress can be replenished. This corrosion mechanism can lead to potentially high corrosion rates. Such localized damage is difficult or impossible to detect in above-ground surveys. In addition to routine above-ground surveys and site examinations, high resolution in-line inspection is a key component of the pipeline operator’s overall integrity management strategy. It is conducted at appropriate frequencies to confirm the condition of the pipeline and to optimize maintenance plans to ensure the future safe, reliable and cost effective operation of the pipeline. To date three in-line inspections have been conducted on this pipeline. This paper presents an innovative technique for conducting a detailed corrosion growth comparison of the three inspection data sets and demonstrates the practical use of this methodology to optimize the future integrity management strategy.

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