Excavation and Direct Examination of buried piping using conventional non-destructive examination (NDE) has been the traditional inspection approach for decades and remains the only quantitative method for piping evaluations in plants when internal in-line inspection tools cannot be used due to geometry or other constraints. This “difficult to assess” piping presents many challenges, including limited effectiveness of traditional indirect inspection tools, high cost and operational concerns associated with excavations, and the ability to evaluate only a small sampling of a piping system. Many inspection technologies exist for buried pipe assessments; however, no indirect techniques provide the ability to yield quantitative wall loss values suitable for ASME fitness for service calculations beyond what’s exposed in the excavation. An evolving technology, guided wave testing (GWT), has many applications including the ability to provide assessment information beyond the excavation.

In this paper, the application of GWT for buried piping inspection will be discussed. We will review: principles behind its operation; the competitive technologies on the market; challenges for the technology; management of data within the Electric Power Research Institute (EPRI) industry standard buried pipe database (BPWorks™ 2.0); trending; case histories showing how GWT can be used to extend the knowledge gained during an excavation by screening adjacent areas for more significant corrosion than observed in the excavated and exposed area; coupling GWT results with other inspection technologies to gain an enhanced interpretation of the overall condition of the line; and how to incorporate this data into an effective structural and/or leakage integrity program as part of the reasonable assurance process.

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