Detection and sizing of corrosion are required across many industries. The oil, gas, and petrochemical industries need reliable, easy, and rapid nondestructive testing methods to evaluate the remaining wall thickness in pipelines. These techniques must be able to perform the measurement on difficult to access structures such as pipe supports. In this sense, ultrasonic guided waves are interesting because of their ability to propagate over long distances. Ultrasonic tomography is a potential solution but it is complex to implement due to the number of transducers, the precision in their positioning and the heavy data processing required [1]. In previous studies, it has been shown that the use of shear horizontal (SH) guided wave, and their cutoff frequency-thickness product can be used in medium to long-range remnant thickness gauging [2-3]. Using a pitch-catch configuration, it is possible to estimate the minimum thickness of the waveguide between the emitting and receiving probes. By repeating this measurement in several positions around the circumference, it is then possible to reconstruct the pipe's thickness profile. In this project, periodic permanent magnet electromagnetic acoustic transducers, or PPM EMAT, were used to generate narrow-band excitations centered on the excitation frequencies of the different modes. Individually exciting the modes allows for easier data processing than with a multimodal waveform. The detection of the cut-off of a mode can then be done using a one-dimensional Fourier transform. Considering a pitch of 6.2 mm, a steel pipe with an outside diameter equal to 323.8 mm and a thickness of 10.2 mm, the use of SH1 to SH4 allows to obtain four residual thickness detection thresholds equal to: 3, 5.3, 6.7 and 7.6 mm. EMAT probes were designed and validated by simulation with Comsol Multiphysics 5.5 and Pogo FEA. To better adapt to the pipe geometry, they are composed of curved neodymium grade N55 magnets and a flexible coil covering the surface under the magnets. By scanning the inspection line along the circumference it was possible to accurately size the thickness profile of a pipe with a thickness reduction varying from 3 mm to 10.2 mm, the nominal thickness of the pipe.[1]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;P. Belanger, P. Cawley, et F. Simonetti, «&nbsp;Guided wave diffraction tomography within the born approximation&nbsp;»,&nbsp;IEEE Trans. Ultrason. Ferroelectr. Freq. Control, vol. 57, no 6, p. 1405‑1418, juin 2010, doi: 10.1109/TUFFC.2010.1559. 
[2]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;P. Belanger, «&nbsp;High order shear horizontal modes for minimum remnant thickness&nbsp;»,&nbsp;Ultrasonics, vol. 54, no 4, p. 1078‑1087, avr. 2014, doi: 10.1016/j.ultras.2013.12.013. 
[3]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;A. Thon et P. Bélanger, «&nbsp;EMAT design for minimum remnant thickness gauging using high order shear horizontal modes&nbsp;»,&nbsp;Ultrasonics, vol. 95, p. 70‑78, mai 2019, doi: 10.1016/j.ultras.2019.03.006.

Reconstruction of the Remnant Thickness Circumferential Profile of a Steel Pipe Using High Order Shear Horizontal Waves and Emats

Paper Proceedings: https://asmedigitalcollection.asme.org/qnde/QNDE2021/volume/85529

ASME 2021 48th Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE2021)

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