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A cylindrically guided wave technique (CGWT) was developed by scientists at Southwest Research Institute (SwRI) to inspect anchor rods for high-voltage transmission towers. These rods, ranging from 10 to 20 feet in length and 1 to 2 inches in diameter, are buried in the ground or in concrete and are susceptible to environmentally induced corrosion. When the rods fail, a transmission tower may fall, resulting in a power outage and expensive repairs. The cylindrically guided wave technique can detect corrosion damage at levels as small as 20%.
Evaluation of CGWT for Corrosion Detection in All-Thread Bolts
All-thread bolts are used in many applications to bind, clamp, and secure various types of machinery. For example, they can be used to clamp heat exchanger flanges together by putting a nut on each end of an all-thread bolt and tightening the nuts until the bolt has proper tension. In this application, most of the all-thread bolt is in a bolt hole in the heat exchanger flange and is not available for visual inspection.
In the operational mode, the bolts are susceptible to leakage of borated water around the flange region, which could lead to borated-water corrosion. Borated-water corrosion is unique because it causes all-thread material to corrode away so that the remaining material has a very smooth, almost polished surface.
The cylindrically guided wave technique has been useful in detecting borated-water corrosion. A preliminary evaluation indicated that CGWT could be used to inspect all-thread bolt test samples.
Simulated corrosion on these test samples consisted of removing the threads in a 2-inch-long region approximately two-thirds of the way down the length of the bolt to a diameter reduction of 20% and 50%. Initial results showed that the amount of diameter reduction could be measured using CGWT.
Based on the positive results obtained in the preliminary evaluation, SwRI:
For more information about our nondestructive evaluation (NDE) capabilities, cylindrically guided wave technique technology, or how you can contract with SwRI, please contact Glenn Light, Ph.D., at glight@swri.org or (210) 522-2218.
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| Sensor Systems and Nondestructive Evaluation (NDE) Technology Department | Mechanical Engineering Division | SwRI Home | |
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Southwest Research Institute® (SwRI®), headquartered in San Antonio, Texas, is a multidisciplinary, independent, nonprofit, applied engineering and physical sciences research and development organization with 11 technical divisions. |
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January 03, 2013 |
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