Near-field testing (NFT) is a technique commonly used to inspect air coolers and ferromagnetic heat exchanger tubing. This technology has proven efficient in detecting internal pits and general wall loss. It is generally the preferred technique for air cooler inspection. NFT probe design has major limitations, however. Other tube inspection technologies have been available for decades, each offering various levels of performance. MFL and IRIS are somewhat harder to deploy than NFT; MFL probes use permanent magnets, while IRIS is time consuming, involves rather complex tooling, and requires water. Near-field array (NFA) technology represents a unique alternative for this application. It provides scan results in the form of intuitive C-scan imaging, offers better sensitivity over other inspection methods, and is much faster. The development of NFA posed an impressive technical challenge, especially in terms of multiplexing and probe design. NFA probes have proven to offer excellent circumferential resolution, optimized pulling speed and ease of deployment. This paper discusses the development of NFA technology and its benefits, including laboratory and field-testing results on typical air cooler tubing. NFA performances are compared to others techniques for further insight.

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