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Science Direct |
An SH-wave EMAT technique for gas pipeline inspection | |
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In this paper we concentrated on natural-gas transmission steel piping of 216 mm outer diameter, 5.4 mm (or 6.3 mm) thick, and 70 cm long. The pipes were manufactured by bending rolled plates into a cylinder and then electric-resistance welding; the welding debris was removed and no reflection signal from the weldment was observed. The outer surfaces were painted and the inner surfaces were left in rust. Two types of artificial defects on the pipe’s outer surfaces were introduced by grinding and machining; dish-shaped depressions, in which the depth gradually changes in the axial and circumferential directions and flat-bottom rectangular defects.
Fig. 2. Dispersion curves of guided SH waves for t=5.4 mm. There are cut-off thicknesses for the dispersive modes SHn (n>0). |
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