An NDT guided wave technique for the identification of corrosion defects at support locations

• A rapid screening technique for defects detection at pipe-support interfaces is presented.
• Axially orientated PPM EMAT’s are used to generate SH1 guided waves.
• Support contact and defect effects are evaluated through FE models and experiments.
• The technique is insensitive to support contact, but has a high defect sensitivity.

Due to the large number of pipe supports over a piping run, a rapid reliable NDT system is needed to identify hidden corrosion defects at a pipe-support interface. To accomplish this, a system using Periodic Permanent Magnet (PPM) Electromagnetic Acoustic Transducers (EMAT׳s) to generate dispersive SH1 guided waves is implemented. For this study, both the effect of the support contact and a corrosion type defect are evaluated independently through finite element models and experiments utilizing a flat plate approximation. It was found that utilizing the SH1 plate wave near the inflection point or ‘knee’ of the dispersion curve yields a high sensitivity to gradual wall loss defects while experiencing a minimal effect from the support contact.