Multiple type defect detection in pipe by Helmholtz electromagnetic array probe

Non-destructive testing plays a key role in the detection of pipe. In this paper, a Helmholtz electromagnetic array probe, with the advantages of multiple type defect detection, quantification, non-contacting and good applicability on ferromagnetic pipe, is presented. A designed structure, containing a high precision tunnel magneto-resistive (TMR) array sensor, is used to scan the full circumference of pipe in a single pass. In the experiments, multiple types of detects, e.g. hole, axial crack and circumferential crack are detected through the probe. The profile of the defects can be inferred approximately. Moreover, the pipe of different radius are inspected showing that the radius of pipe has little effect on the detection sensitivity if the Helmholtz Probe proposed in this paper is used.