The UT data software can be set up to directly measure two out of three characteristics: top-side surface profile; bottom-side profile; and, metal thickness. The third characteristic can then be developed computationally by direct export to Excel. Scanning and data acquisition is in real time and continuous. Within a discrete time or distance traveled interval, Maverick records the worst data point observed. Currently, Maverick makes a record of the data acquired during one-inch intervals. The recording system is infinitely adjustable. In two hours of actual scanning, 31,500 UT data points were collected. This amounted to 390 square feet (3.5%) of the tank floor. The inspection company that had provided the previous visual inspection considered the data acquired by Maverick to be reliable.
The sonar tracking system was also challenged by the tank's internal geometry. The roof was supported by several pillars which occasionally blocked sound from reaching the listening transducers. As a result, there were blind spots within the tank where the positioning system was unable to function. The operators were able to work effectively around this deficiency in most situations. On one occasion, the robot was driven too close to the sump due to positioning error and fell in, but was pulled out with minimal effort. The sound blockage problem had been previously anticipated. To solve the problem, additional listening transducers will be used eliminate the blind spots.
The tank roof pillars also posed a navigational problem inside the tank. Both the location and the number of pillars within the tank were in question, since drawings of the tank were unavailable. Throughout the week, visual surveys of the inside of the tank were conducted to identify obstacles like the roof pillars and to demonstrate the visual capabilities of the robot. The pillars are constructed from large back-to-back welded steel channels, with support angles along the tank floor at the base, as seen clearly in the robot's cameras. The cable tended to catch on the edges of the channels when the robot was driven around a pillar. In the future, surveys will be conducted in a way to avoid wrapping the cabling around roof pillars.
The demonstration proved to be successful and concluded a series of important engineering developments to make Maverick commercially ready. We want to say thank you to the Department of Energy, Lockheed Martin, General Electric, Texas Natural Resource Conservation Commission, American Petroleum Institute, Independent Liquid Tank Association, Mobil, Colonial Pipeline, Amoco, Shell Oil, Exxon, Al Mansoori Specialized Engineering, United Arab Emirates Offset Group, Regional Development Alliance, Idaho Department of Commerce, City of Idaho Falls, and the many others who have helped by being a part of the beginning of this success.
References available upon request.