The peak amplitude of the fundamental torsional
mode, T(0,1), ultrasonic guided wave, excited and
sensed by commercially available equipment using
permanently mounted magnetostrictive transducers,
was used to monitor the growth of electrochemically
induced, external discontinuities in a
steel pipeline (216 mm outside diameter). The
pipeline was more than 30.5 m long, had multiple
welds and two 90° elbows. Over the course of
eight months, two discontinuities, hidden from
ultrasonic testing (UT) technicians, grew systematically
in both area and depth, providing the opportunity
to experimentally evaluate the effects of
complex geometry on signal characteristics.
Corrosion around a weld was also studied. The
obtained results were compared with a surface
discontinuity that was unaffected by intermediate
welds located between the transducer and the
discontinuity. It was found that the effects of
multiple welds and an elbow decreased the sensitivity
for discontinuity growth monitoring by a
factor of less than two. This was established by
examining the scaling of discontinuity signal peak
heights against a weld peak instead of using a
conventional distance-amplitude-correction (DAC)
curve to account for material attenuation, by
comparing the signals from a discontinuity viewed
along the forward and the reverse direction, and
by allowing the discontinuities to change in all
three dimensions in the course of this monitoring
effort. This controlled study for discontinuity
growth monitoring can be useful to guide efforts
on discontinuity growth monitoring of complex
pipelines in the field.
Alleyne, D. N. and P. Cawley, “Long Range Propagation of Lamb Waves
in Chemical Plant Pipework,” Materials Evaluation, Vol. 45, No. 4, 1997,
Demma, A., P. Cawley, M. Lowe and A. Roosenbrand, “The Reflection of
the Fundamental Torsional Mode from Cracks and Notches in Pipes,”
Journal of the Acoustical Society of America, Vol. 114, No. 2, 2003,
Demma, A., P. Cawley, M. Lowe, A. Roosenbrand and B. Pavlakovic, “The
Reflection of Guided Waves from Notches in Pipes: A Guide for Interpreting
Corrosion Measurements,” NDT & E International, Vol. 37, No. 3,
2004, pp. 167–180.
Demma, A., P. Cawley, M. Lowe and B. Pavlakovic, “The Effect of Bends
on the Propagation of Guided Waves in Pipes,” Journal of Pressure Vessel
Technology – Transactions of the ASME, Vol. 127, No. 3, 2005, pp. 328–335.
Kwun, H., S. Y. Kim and G. M. Light, “The Magnetostrictive Sensor Technology
for Long Range Guided Wave Testing and Monitoring of Structures,”
Materials Evaluation, Vol. 61, No. 1, 2003, pp. 80–84,
Kwun, H., S. Y. Kim and A Crouch, “Method and Apparatus Generating
and Detecting Torsional Waves for Long Range Inspection of Pipes and
Tubes,” U.S. Patent 6624628, 2003.
Kwun, H., J. Crane, S. Y. Kim, A. Parvin and G. M. Light, “A Torsional
Mode Guided Wave Probe for Long range In-bore Testing of Heat
Exchanger Tubing,” Materials Evaluation, Vol. 63, No. 4, 2005,
Ledesma, V., E. Perez Baruch, A. Demma and M. J. S. Lowe, “Guided Wave
Testing of an Immersed Gas Pipeline,” Materials Evaluation, Vol. 67, No. 2,
2009, pp. 102–115.
Liu, J. M. and C. E. Davis, “Laboratory Assessment of Ultrasonic Guided
Wave Technology for Corrosion Damage Detection in Piping with a Deck
Joint and an Elbow,” Technical Report NSWCCD-61-TR-2005/26, April
Liu, J. M. and C. P. Nemarich, “Remote NDE Technology for Inaccessible
Shipboard Piping Inspection,” Journal of Failure Analysis and Prevention,
Vol. 8, No. 2, 2008, pp. 193–198.
Mu, J., M. J. Avioli, and J. L. Rose, “Long-range Pipe Imaging with a
Guided Wave Focal Scan,” Materials Evaluation, Vol. 66, No. 6, 2008,
Rose, J. L., Ultrasonic Waves in Solid Media, Cambridge University Press,
New York, New York, 1999.
Rose, J. L., Z. Sun, P. J. Mudge and M. J. Avioli, “Guided Wave Flexural
Mode Tuning and Focusing for Pipe Testing,” Materials Evaluation,
Vol. 61, No. 2, 2003, pp. 162–167.
Rose, J. L., L. Zhang, M. J. Avioli and P. J. Mudge, “A Natural Focusing
Low Frequency Guided Wave Experiment for the Detection of Defects
Beyond Elbows,” Journal of Pressure Vessel Technology, Vol. 127, No. 3,
2005, pp. 310–316.
Rose, J. L., J. Mu and J. K. Van Velsor, “New Directions in Guided Wave
Pipe Testing,” Materials Evaluation, Vol. 65, No. 4, 2007, pp. 375–378.