Instrumentation of Cross Electromagnetic Eddy Current Sensing for Internal Pipeline Inspection

Eddy current (EC) detection technique has been applied for the inspection of small-diameter pipelines whereas it retains the limitation in detecting defects on the outer wall of the pipeline. This article proposes new instrumentation of cross electromagnetic EC sensing for internal pipeline inspection. The technique integrates the principles of remote field EC (RFEC) and near field EC and involves exciting two types of magnetic fields inside the pipeline. The first magnetic field is oriented perpendicular to the pipe wall, which allows for the detection of inner wall defects. The second magnetic field propagates along the pipeline direction, enabling the detection of outer wall defects. By combining these two magnetic fields, the proposed technique enables simultaneous detection of both inner and outer wall defects in small-diameter buried pipelines. A detection platform for an experimental laboratory system has been built, and an internally integrated system developed for pipelines with an 8-in diameter. By conducting inspections on various pipelines, defects on both the inner and outer walls were successfully detected. Results have validated the reliability and efficiency of the proposed detector.