Electricity: measuring and testing – Magnetic – With means to create magnetic field to test material
Patent
1993-01-28
1994-11-15
Strecker, Gerard R.
Electricity: measuring and testing
Magnetic
With means to create magnetic field to test material
324220, 324241, 324242, G01N 2790
Patent
active
053651693
ABSTRACT:
The present invention relates to a flaw detector for metal material for maintaining and managing pipelines using a remote field eddy current sensor. An AC signal having a constant level and shifted by predetermined phase angle is added to signals received in receiving coils of the remote field eddy current sensor to obtain accurate phase detection in a normal, nonflawed portion of the pipeline to be tested (e.g. uniform thickness, no holes, etc.). By preventing generation of abnormal flaw data, precise diagnosis of the pipeline can be performed. An AGC circuit may be used to maintain at a constant level of received signal. Two sets of spaced apart receiving coils are spaced from an exciting coil a distance greater than a predetermined distance (about two time the pipeline diameter). The set of receiving coils closest to the exciting coil has a greater number of coil turns than the other set. This coil configuration generates sensed coil differential signals having sufficient signal amplitude to permit stabilized and accurate phase detection and comparison for nonflawed and gradually flawed regions in the pipe.
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Fujiwara Shigeru
Hosohara Yasuharu
Kawabe Toshihide
Suzuki Kiwamu
CXR Co., Ltd.
Strecker Gerard R.
Tokyo Gas Co. Ltd.
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