PR-462-143703-R01 Development and Evaluation of Guided Wave Structural Health Monitoring for Buried Pipe

Abstract

Excavations to inspect buried piping are often costly and risk damaging other plant assets during the digging. Some utilities have used permanently installed guided wave sensors to monitor piping condition and reduce the excavations. The project that is the subject of this report has two objectives-to evaluate the current state-of-the-art and to create a test bed for vendors to improve their technology and data analysis algorithms. Understanding the state-of-the-art will enable utilities to effectively use guided wave structural health monitoring in support of their underground piping aging management plans and their license renewal activities. Guided wave effectiveness in buried pipe applications depends on many variables, including coating, backfill, temperature, soil moisture, and environmental noise. An important aspect of monitoring is the effectiveness of data analysis algorithms in distinguishing changes in data due to damage to the pipe wall from those resulting from the environment. A buried mockup was constructed with common coatings and backfills, and two vendors installed commercially available guided wave systems. An initial flaw set was initiated in the mockup. Then, about every three months, holes were dug to modify some existing flaws, initiate new flaws, and leave some unchanged. Data were collected over a timeframe that included all four seasons. Damage was generally initiated with grinding tools to produce irregular shapes and sizes and to simulate corrosion. Flaws were characterized with a structured white light camera technology. Flaw information was kept confidential from the vendors until all data were complete and vendors had provided their assessment of the mockup at each stage. After the results were reviewed with the vendors, the flaw information at each stage was provided to the vendors for continued development of their technology. This enables the vendors to conduct lessons learned and improve their procedures, data analysis algorithms, and hardware designs. Utility operators can use the results of this report to better apply guided wave structural health monitoring technology. Benefits will also result from lessons learned and improvements by vendors. It is better for vendors to learn about needed improvements and data analysis through a test bed than to find them out in the field. The buried pipe mockup also provides a potential test bed for future studies and evaluations of structural health monitoring technologies or in-line pipe devices.