Measuring and testing – Vibration – By mechanical waves
Reexamination Certificate
1999-09-17
2001-09-04
Moller, Richard A. (Department: 2856)
Measuring and testing
Vibration
By mechanical waves
Reexamination Certificate
active
06282964
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates generally to the field of non-destructive testing of components and in particular to a new and useful method and apparatus for the non-destructive inspection of boiler tubes for cracks using electromagnetic acoustic transducer technology.
Various nondestructive methods such as ultrasonic (UT), eddy current (ET), magnetic particle (MT), and dye penetrant (PT), have been used for the detection of cracks in boiler tubes. All have serious limitations that prevent their use for real time, high speed inspection of boilers for surface breaking cracks. UT requires a liquid couplant which can produce extraneous signals. EC is very susceptible to material properties/variations inherent within a material which can produce signals that mask the defect signals or can be mistakenly interpreted as defects. Both MT and PT require large amounts of chemicals and are not suited for high speed inspection of boilers due to the time required for chemical application and signal interpretation, plus disposal of used chemicals.
Electromagnetic acoustic transducers (here EMATs or emats) are known for use in testing materials for defects. In known systems, a signal generator creates an acoustic wave which propagates through a test material and either the original signal or a reflection is received by a single sensor having a coil for converting acoustic wave energy to an electrical current. EMATs are typically used on planar surfaces of a test material to detect both surface and sub-surface defects in the test material.
Tubes present a challenge for testing due to their curved surfaces. Tubes used in industrial boilers present a further challenge, as the space around and access to the tubes is typically very limited. These tubes must be as free of defects as possible, and coated with materials to resist corrosion and breakdown in the harsh environment of an industrial boiler.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an EMAT device for non-destructive inspection of the surface of a tube for cracks using acoustic surface waves which includes a pulsed magnet having an active surface for facing the surface of a tube to be inspected. A receive emat coil is on the active surface and a transmit emat coil is on the opposite surface of the receive coil. The transmit emat coil has a scan surface for scanning over the tube surface. A transmitter for generating and transmitting an RF signal to the transmit emat coil is provided for generating a transmitted acoustic wave signal around the tube, the transmitted wave creating a reflected acoustic wave if a crack in the tube is encountered, the reflected wave generating a reflection signal in the receive emat coil. A receiver is connected to the receive emat coil for receiving the reflection signal. A digital computer is connected to the receiver for receiving and for processing the reflection signal and a display displays position information about a crack in the tube which created the reflected acoustic wave and resulting reflection signal.
REFERENCES:
patent: 5035143 (1991-07-01), Latimer et al.
patent: 5085082 (1992-02-01), Cantor et al.
patent: 5359898 (1994-11-01), Latimer
patent: 5456113 (1995-10-01), Kwun et al.
patent: 5526691 (1996-06-01), Latimer et al.
patent: 5763786 (1998-06-01), Camplin et al.
patent: 5907100 (1999-05-01), Cook
patent: 6009756 (2000-01-01), Willems et al.
patent: 6070467 (2000-06-01), Rosenberg et al.
Hancock Jimmy W.
MacLauchlan Daniel T.
Murphy Ralph D.
Edwards Robert J.
Marich Eric
Moller Richard A.
The Babcock & Wilcox Co
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