Multi-Coil Eddy Current Probe for the Detection of Circumferential Cracks in Tubing

Conventional eddy current bobbin probes, multi-pancake and/or rotating pancake probes, and transmit-receive eddy current probes are currently utilized in testing metal tubing. Each method has respective strengths and weaknesses. This paper proposes another eddy current probe with new features. The structure is designed to be sensitive to circumferential cracks, which are not easily detected with ordinary bobbin coil probes. The directions of the magnetic field and the eddy current around the coil were considered in design of the probe structure. Signals of these probes from the artificial defects were acquired and analyzed. Experimental results show that the developed probes are more sensitive to circumferential defects than comparable ordinary bobbin probes. In addition, the new probes are insensitive to axial defects. By employing both the new probes and ordinary bobbin probes, more reliable ECT can be performed.