An ultrasonic laboratory prototype system has been developed for the investigation of removal of marine-fouling from offshore installations via cavitations' cleaning. It comprises a 270 element, 50kHz array and associated programmable controller unit. The work- is based on experimental as well as simulation studies. This paper gives a short description of the system components together with calibration and preliminary cleaning test results. It is hoped that such an array may form an integral part of a fully automated, single technology, maintenance system.
Inspection of offshore oil and gas production structures is of vital importance for safe operation. Marine fouling attached to the structures impedes this task and various methods for removing the growth have been considered by the industry. Among the more popular methods currently being employed are manual scrapers and brushes, water jetting and rotary brushes. A variety of inspection techniques are applied, including eddy current and magnetic particle inspection for location of surface breaking flaws, and ultrasonics for detection of internal flaws and in flooded member detection. These techniques all require a good surface contact to produce reliable test results. Cleaning is therefore required prior to their application. Most offshore inspection and cleaning techniques currently in operation require some degree of diver intervention. From both a cost and safety point of view the amount of diver activity should be reduced or even be made totally redundant. As offshore activities move into ever deeper waters, the use of diver based systems becomes unrealistic. Automation of both the inspection and cleaning tasks are therefore of increasing importance. Further, if tool manipulation could be reduced by combining the two main tasks (Le. cleaning and inspection) into a single system, the operation procedure may be simplified and made more time efficient.
