ELECTROMAGNETIC ACOUSTIC TECHNIQUES FOR INSPECTION OF PIPE COVERED WITH MARINE GROWTH

Undersea inspection of pipelines and support structures is very difficult at best because of accessibility problems. An additional problem is the accumulation of marine growth on the surfaces of the component to be inspected. To apply ultrasonic, magnetic particle, or eddy current methods, the marine growth must be completely removed at considerable cost. A study has been conducted to evaluate methods of inspecting such components without removal (or with minimal removal) of the marine growth. A method is described that uses an electromagnetic acoustic transducer (EMAT) Lamb-wave method to inspect a large pipe by removing only a narrow strip of the marine growth for access. It has also been shown that a deep-penetrating eddy current (DPEC) technique can be used for inspection of a pipe completely covered by a 2 in. (5 cm) thick layer of marine growth. In both cases, simulated defects resembling those referenced in applicable industry inspection codes were detected in a pipe sample with the two methods.