Independent Comparison of Electromagnetic Inspection Tools for AWWA C303 Bar-Wrapped Pipe by Blind Verification Testing

While much of the effort on condition assessment of concrete pressure pipe has focused on prestressed concrete cylinder pipe (PCCP) for many years, a significant amount of AWWA C303 bar-wrapped concrete cylinder pipe (BWP) installed across the United States, since the 1940s has also been degrading. Due to increasing awareness on degrading BWP pipelines supported by concerns after high-consequence failures, high-resolution electromagnetic (EM) inspection technologies are now also in demand for BWP to detect defects in the steel cylinder and reinforcing bars. Pipeline inspection vendors have been investing in improving their inspection technologies, tools, and platforms. Currently, two primary inspection technologies are being offered by a few vendors with varying claims of accuracy and resolution: the Remote-Field Technology (RFT) and the Near-Field Technology (NFT). Platforms include modular, non-modular, robotic, and others. Although the theoretical basis of the inspection technologies may be similar, the results are likely affected by many proprietary factors considered by each vendor, such as sensor types and configuration, calibration and inspection procedures, and differences in data processing and interpretation. Many BWP pipelines have been and continue to be inspected with these technologies using different tools and platforms; however, independent field verification of their results has been limited, precluding development of full confidence in their capabilities and limitations. This paper expands the results of a recent blind verification study performed with one of the pipeline inspection vendors, with results from a second inspection vendor on the same test pipes, 30 in. and 36 in. diameter BWP. To allow for direct and fair comparison of results from the two vendors, additional defects were introduced into both test pipes, and the first vendor was invited to rescan the pipes and update their results.