Guided Wave Testing

Guided waves are structure-borne ultrasonic waves that propagate along the structure confined and guided by its geometric boundaries.  As shown in the Figure 1, the guided wave in the pipeline propagates along the pipe axis and reflects back from any local cross-sectional area change such as corrosion defects. The GWT is a technique for finding defect location with the measured arrival time and the known velocity of guided wave and estimating the defect size with the signal amplitude. The GWT uses low-frequency of 5 to 250 kHz in order to have a  wavelength that is usually longer than the pipe wall thickness and to obtain less attenuation for long-range inspection.



 How does the inspector perform Guided Wave Testing?


The MsS equipment for guided wave testing or long-range ultrasonic testing is compact and easily operated by inspectors in facilities. Like ordinary ultrasonic thickness measurement tool, inspector can carry it to the pipe and quickly test the pipe using MsS probe and shear couplant. The surface preparation of guided wave testing is the same as that of ordinary ultrasonic inspection except that we need to access to the whole pipe circumference for long-range inspection. If MsS sector probe is used, the guided wave inspection of pipe is the same as the ordinary UT thickness measurement in preparation and procedure. The only difference is that the guided wave testing checks defects along the axial length of pipe instead of wall thickness.