Pulse Echo Ultrasonic Techniques for Underwater Inspection of Steel Waterfront Structures.

Laboratory tests were made to 1 determine the measurement accuracy using three different methods of acquiring and interpreting the ultrasonic data, 2 identify operator training requirements and optimum information feedback techniques for the diver, and 3 analyze the electrical power transmission characteristics of the ultrasonic system and identify any potential safety hazards to the diver. Due to the problems associated with multiple front surface echoes, digital ultrasonic thickness gages should not be used as the only means of inspecting steel structures in areas found to have irregular front surface conditions or where the thickness readings are found to fluctuate rapidly over a small area. Field tests of the ultrasonic scanner and surface milling adapter have confirmed that results comparable to those obtained during laboratory tests are attainable during in-situ inspection of steel pilings since the ultrasonic scanner and milling adapter technique is not truly nondestructive in nature, however, it should be considered an interim inspection procedure. Investigation of alternative inspection techniques that do not require material removal should be continued. A power system test circuit should be incorporated into any 100-VAC circuit used to power underwater ultrasonic test equipment. As an additional safety precaution, inspection divers should be required to wear neoprene wetsuit gloves and should be instructed not to reach through the airwater interface while holding any grounded electronic equipment in their hands.