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Method and apparatus for detecting external cracks from within a metal tube

United States Patent

August 7, 2001
View the Complete Patent at the US Patent & Trademark Office
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A method and tool using a continuous electromagnetic wave from a transverse magnetic-dipole source with a coaxial electric-dipole receiver is described for the detection of external sidewall cracks and other anomalies in boiler tubes and other enclosures. The invention utilizes the concept of radar backscatter rather than eddy-currents or ultrasound, which are sometimes used in prior art crack-detection methods. A numerical study of the distribution of the fields shows that the direct transmission from the source to the receiver is reduced from that in free space. Further, if the diameter of the receiver dipole is made sufficiently small, it should be possible to detect cracks with a scattering loss of up to -40 dB in thin-walled boiler tubes.
Caffey; Thurlow W. H. (Albuquerque, NM)
Sandia Corporation (Albuquerque, NM)
09/ 246,262
February 8, 1999
GOVERNMENT RIGHTS This invention was made with support from the United States Government under Contract DE-AC04-96AL85000 awarded by the U.S. Department of Energy. The Government has certain rights in this invention.