Magnetic Flux Leakage Testing for Internal and External Defect Identification in Rotating Pipe Inspections

Abstract

This study proposes a magnetic flux leakage inspection capable of identifying internal and external defects in rotating pipe inspections. The proposed identification between internal and external defects employs the effect of motion-induced eddy current that has been an adverse effect on the conventional magnetic flux leakage testing. A three-dimensional finite element analysis was conducted to assess the feasibility of detecting and classifying these defects. Two hall sensors, symmetrically positioned from the pole structure, exhibit asymmetric defect signals with inverse signal variations for the internal and external defects. Simulation studies were performed to investigate the effect of flux density and rotational speed on defect signals. A prototype sensor was fabricated, and the measurement shows peak-to-peak variations as - 43.1% for internal defects and + 25.7% for external defects, indicating a strong correlation with the simulation results. These findings suggest that the proposed inspection can represent an effective alternative to the conventional ultrasonic testing for monitoring pipe integrity at the pipe production stage.