Pipelines frequently develop an induced magnetic field caused by any one of the following: pipeline inspection methods; induced electrical currents in the pipe; adjacent pipelines; terrestrial currents; and/or the interaction with geomagnetic fields. The induced magnetic field can become intense enough to interfere with pipeline repair procedures that involve arc welding. This report provides some background on the origins of magnetic fields in pipelines, and presents a technique for demagnetizing the area immediately surrounding any surfaces to be welded. A step-by-step procedure is given for...
Pipelines frequently develop an induced magnetic field caused by any one of the following: pipeline inspection methods; induced electrical currents in the pipe; adjacent pipelines; terrestrial currents; and/or the interaction with geomagnetic fields. The induced magnetic field can become intense enough to interfere with pipeline repair procedures that involve arc welding. This report provides some background on the origins of magnetic fields in pipelines, and presents a technique for demagnetizing the area immediately surrounding any surfaces to be welded. A step-by-step procedure is given for reducing the residual magnetic field to a practical level low enough for welding purposes.