Experiment study of long pulse eddy current / eddy current pulse-compression thermography detection on large area with low-frequency and low-current

Eddy current pulsed thermography (ECPT) excited by high-frequency and high-current is at risk of causing irreparable damage to the detection object. Furthermore, using a high-current excitation pattern in flammable and explosive environments is strictly prohibited. To cope with that limitation, long pulse eddy current thermography (LPECT) and eddy current pulse-compression thermography (ECPuCT), which work in weakened excitation conditions, are two reasonable technologies. The LPECT experiment in low-frequency (50 Hz) excitation shows that subsurface defects are detected when the current is 8.3 A. Compared with LPECT, the experiment results of 13-bit barker-coded ECPuCT show the possibility of further reducing the excitation current and improving the defect detection signal–noise ratio (SNR). With a two-coil magnetic core inductor, defects whose aspect ratio is over 6 in a large area are effectively detected by ECPuCT. That confirms LPECT and ECPuCT are suited for high-risk environments, such as the petrochemical field.