The most difficult question to answer in guided wave is the inspection range. How far can your system inspect? It depends on the capability of guided wave system (how strongly it generates torsional or longitudinal mode and how much it reduces the generation of flexural modes), defect size, and attenuation (operating frequency, geometric features of pipe, corrosion condition, pipe coating, insulation, depth of burial, and the nature and degree of compaction of the surrounding soil).

The following shows a photo and data of a MsS guided wave test for a 16-inch OD aboveground straight gas transmission pipeline. The guided wave can detect about a 2.5- percent cross-sectional area defect (marked with couplet in the bottom graph) located at about 493 ft after passing 18 girth welds.

Please see that the MsS data has high spatial resolution compared to other guided wave systems. With the below inspection we can inspect over 500 ft length of piping in one direction for detection of 2 to 3 % defects on straight bare or painted lines. The inspection range and defect sensitivity depends on the type of probe used, guided wave system, operating frequency, and attenuation due to geometric features or insulation. With the strong generation of axial symmetric mode, MsS GWT system can detect 2% to 3% defects located at about 150 meter after passing 18 girth welds in a 16-inch OD aboveground straight gas transmission pipeline [Pipeline and Gas Technology, August (2006), pp 28-3 1].