Electromagnetic Acoustic Transducers for Inspection of Steel Pipes

Electromagnetic acoustic transducers (EMATs) were developed for flaw detection in steel pipes. The EMAT, which consists of an electromagnet and a coil surrounding the pipe, can generate and detect the longitudinal wave propagating along the axial direction of the pipe. In this study, we investigated the properties of the EMAT. It was ensured that the optimum strength of the static magnetic field exists for transmitter and receiver, respectively, because the magnetostriction concerns the operating mechanism of the EMAT for ferromagnetic steel pipes. Thus the dual EMAT configuration is recommended to obtain the high amplitude signal, while narrowband burst wave should be used as excitation signal to avoid the distortion of the signal by dispersion. On the other hand, broadband pulse excitation is accessible for the single EMAT configuration. We compared the flaw detectability of both configurations.