Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
2002-03-19
2004-10-05
Williams, Hezron (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
C073S628000, C073S638000
Reexamination Certificate
active
06799466
ABSTRACT:
BACKGROUND
1. Field of Endeavor
The present invention relates to inspection systems and more particularly to acoustic wave inspection systems.
2. State of Technology
U.S. Pat. No. 6,079,273 for EMAT inspection of header tube stubs by Paul J. Latimer, assigned to McDermott Technology, Inc. and The Babcock & Wilcox Company, patented Jun. 27, 2000, provides the following description, “A method for non-destructively testing closely-spaced objects, such as header tube stubs for a furnace or boiler using electromagnetic acoustic transducers (EMATs) having meander coil sensors. The small size of the sensor combined with the need to move the sensor only a small fraction of the circumference of a tube to scan the entire circumference of the tube under test permits easy and accurate testing of an entire tube, even when the tube is one of a closely-spaced bundle.”
U.S. Pat. No. 5,359,898 for hydrogen damage confirmation with EMATs by Paul J. Latimer, assigned to The Babcock & Wilcox Company, patented Nov. 1, 1994, provides the following description, “A method and apparatus for use in confirming hydrogen damage in a boiler tube comprises a pair of electromagnetic acoustic transducer coils which are mounted for movement toward and away from each other. An electromagnet produces pulses that generate acoustic beams across a chord and within the wall thickness of the boiler tube. For adapting to boiler tubes of different outside diameters, the transducers coils are mounted on a resilient member so that the coils can be pressed against the outer surface of coils having a variety of outside diameters. The angle of the acoustic beam between the coils must also be adjusted, however, and this is done by changing the frequency of energy applied to the coils.”
U.S. Pat. No. 6,148,672 for inspection of pipes by Peter Cawley, et al., assigned to Imperial College of Science, Technology of Medicine, patented Nov. 21, 2000, provides the following description, “An apparatus and a method for inspecting elongate members, especially pipes, using Lamb waves. The apparatus and method provide for the propagation of an axi-symmetric Lamb wave of a single mode in one direction along the pipe. A receiver is provided to receive the Lamb wave after its passage along the pipe and convert the received wave for storage, processing and analysis to determine whether or not there are faults present in the pipe. The apparatus includes at least one and usually several excitation rings each having a plurality of Lamb wave exciters deployed in equiangular spacing in a ring clamping structure whereby each exciter can be pressed with equal force against the surface of the pipe under inspection.”
U.S. Pat. No. 5,767,410 for Lamb wave ultrasonic probe for crack detection and measurement in thin-walled tubing by John P. Lareau, et al., assigned to Combustion Engineering, Inc., patented Jun. 16, 1998, provides the following description, “A probe inspects steam generator tubing for defects. The probe includes a transducer which generates a localized ultrasonic Lamb wave. The ultrasonic wave is transferred to the tubing by a coupling medium, such as water, that physically couples the transducer and the tubing. Defects in the tubing reflect the ultrasonic wave to the probe which detects the reflections. The results are then used to determine the length and depth of such defects as cracks, pitting, and thinning. The localized ultrasonic wave performs an inspection sensitive enough to detect ligaments between crack segments. This allows highly accurate predictions of tubing integrity and rupture strength.”
SUMMARY
Features and advantages of the present invention will become apparent from the following description. Applicants are providing this description, which includes drawings and examples of specific embodiments, to give a broad representation of the invention. Various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this description and by practice of the invention. The scope of the invention is not intended to be limited to the particular forms disclosed and the invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims.
The present invention provides a system for inspecting conduits such as tubes, pipes, etc., for undesirable characteristics. The system includes a transducer system that induces guided acoustic waves onto said conduit and detects defects. The transducer system induces guided acoustic waves in the conduit and detects the undesirable characteristics of the conduit by receiving guided acoustic waves that contain information about the undesirable characteristics. The conduit has at least two sides and the transducer system utilizes torsional modes of propagation to provide inspection using access from only the one side of the conduit. Cracking is detected with pulse-echo testing using one transducer to both send and receive the guided acoustic waves. Thinning is detected in through-transmission testing where one transducer sends and another transducer receives the guided acoustic waves.
The invention is susceptible to modifications and alternative forms. Specific embodiments are shown by way of example. It is to be understood that the invention is not limited to the particular forms disclosed. The invention covers all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims.
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Bauer, D. G., et al., et al., “Interpreting recovery boiler tube thickness data,” Tappi Journal, vol. 79, No. 11, pp. 161-169, Nov. 1996.
Bauer, D. G., et al., “The inspection of recovery boilers to detect factors that cause critical leaks,” Tappi Journal, pp. 92-100, Sep. 1991.
Saint-Surin Jacques M.
Scott Eddie E.
The Regents of the University of California
Thompson Alan H.
Williams Hezron
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