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Magnetic response imaging monitors pipelines, detects corrosion Drawing from experience gained
through the development of magnetic resonance imaging (MRI), a medical technique used to form visual images of detailed structures inside the body, a group of physicists and engineers with 4D Imaging (Berkeley, California) have cre- ated a pipeline monitoring technology that generates a continuous magnetic ÅMTL IZW]VL I [\MMT XQXMTQVM \W LM\MK\ IVL measure corrosion. By wirelessly trans- mitting the raw inspection data upon demand to a processing center, the monitoring technology can provide a real-time visual representation of a pipe- line's percentage of metal loss, giving pipeline operators the ability to immedi- ately assess the health of a pipeline. The ZM[MIZKP QVQ\QI\ML Å^M aMIZ[ IOW QV ZM- sponse to a request to develop a system that could monitor clad and insulated pipelines, is supported in part by Berkeley Engineering and Research Corp. and Chevron Energy Technology. The monitoring technology, known as
magnetic response imaging, applies an M`\MZVIT UIOVM\QK ÅMTL \W I [\MMT XQXMTQVM by sending an electrical current through a series of wire coil pairs (referred to as saddle coils) that drape over the circum- ference of the pipe, says Jerome R. ;QVOMZ KPQMN [KQMV\QÅK LQZMK\WZ _Q\P , Imaging, professor emeritus of engineer- ing science at the University of California, Berkeley, and one of the researchers originally involved in the development of 5:1 ?PMV IV M`\MZVIT UIOVM\QK ÅMTL Q[ applied to a steel pipe (which is ferromag- netic), magnetic domains (trillions of small groupings of atoms) within the steel are forced to line up in the direction of \PM UIOVM\QK ÅMTL 1N \PM [\MMT Q[ KWZZWLML the number of magnetic domains de- creases because the corrosion compounds \aXQKITTa QZWV W`QLM[ QZWV []TÅLM[ IVL
iron chlorides) are not ferromagnetic. By determining the number of magnetic domains that remain intact, the monitor- ing technology can accurately measure the degree of corrosion in a pipeline.
NACE International, Vol. 51, No. 4
A 12-in pipe is instrumented with two saddle coils, which are part of the magnetic response imaging system. Photo courtesy of 4D Imaging.
The magnetic response imaging sys-
tem is designed to be a permanently in- stalled monitoring system with saddle coils placed approximately every 2 m along the length of the pipeline. The electric current is provided by a power supply at one end of the pipeline. When activated, the system sends pulses of electrical current to the saddle coils, one after the other along the length of the pipeline, to magnetize the segments of XQXM JM\_MMV \PM [ILLTM KWQT[