This paper presents the method of magnetic-flux-leakage (MFL) detection and the characteristics of a giant-magnetoresistance (GMR) sensor. An experimental apparatus that uses a GMR sensor for oil-pipeline inspection is described. A permanent-magnet assembly was used to excite MFL signals. The magnet-assembly motion is in the inner pipeline and out the artificial defects. The GMR sensor liftoff is 2 mm. The result is shown. We can see that the artificial defects can be reliably detected with the GMR sensor. The magnetic field is a three-dimensional vector. For the Hall sensor, the measured magnetic field is parallel to the sensor chip. In contrast, for the GMR sensor, the measured magnetic field is perpendicular to the sensor chip. Thus, the sensor array can be designed on the basis of the Hall sensor and the GMR sensor. A Hall sensor and a GMR sensor can be arranged in a line along the axis orientation. A more useful signal will be produced; consequently, the pipeline defects nondestructive evaluation will become easier and more reliable.
A giant-magnetoresistance sensor for magnetic-flux-leakage nondestructive testing of a pipeline
Ein Riesenmagnetowiderstand zur zerstörungsfreien magnetischen Streuflussprüfung einer Pipeline
Russian Journal of Nondestructive Testing ; 41 , 7 ; 462-465
2005
4 Seiten, 5 Bilder, 7 Quellen
Article (Journal)
English
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