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Proceedings Paper

Thermographic detection and quantitative characterization of corrosion by application of thermal line source
Author(s): K. Elliott Cramer; William P. Winfree; Dan Reid; Jane Johnson
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Paper Abstract

Wall thinning in utility boiler waterwall tubing is a significant inspection concern for boiler operators. Historically, conventional ultrasonics has been used for inspection of these tubes. This technique has proved to be very labor intensive and slow. This has resulted in a `spot check' approach to inspections, making thickness measurements over a relatively small percentage of the total boiler wall area. NASA Langley Research Center has developed a thermal NDE technique designed to image and quantitatively characterize the amount of material thinning present in steel tubing. The technique involves the movement of a thermal line source across the outer surface of the tubing followed by an infrared imager at a fixed distance behind the line source. Quantitative images of the material loss due to corrosion are reconstructed from measurements of the induced surface temperature variations. This paper will present a discussion of the development of the thermal imaging system as well as the techniques used to reconstruct images of flaws. The application of the thermal line source, coupled with this analysis technique, represents a significant improvement in the inspection speed for large structures such as boiler waterwalls while still providing high-resolution thickness measurements. A theoretical basis for the technique will be presented thus demonstrating the quantitative nature of the technique. Further, results of laboratory experiments on flat panel specimens with fabricated material loss regions will be presented to demonstrate the capabilities of the technique. Additionally, the results of applying this technology to actual waterwall tubing samples will be presented.

Paper Details

Date Published: 5 February 1999
PDF: 10 pages
Proc. SPIE 3588, Nondestructive Evaluation of Utilities and Pipelines III, (5 February 1999); doi: 10.1117/12.339947
Show Author Affiliations
K. Elliott Cramer, NASA Langley Research Ctr. (United States)
William P. Winfree, NASA Langley Research Ctr. (United States)
Dan Reid, College of William and Mary (United States)
Jane Johnson, College of William and Mary (United States)

Published in SPIE Proceedings Vol. 3588:
Nondestructive Evaluation of Utilities and Pipelines III
Walter G. Reuter, Editor(s)

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