have performed an engineering study and developed a conceptual design that meets all the requirements for navigating and inspecting unpiggable transmission pipelines. Based on Foster-Miller's previous efforts developing the Pipe Mouse robot, the RoboScan inspection robot (Figure ES-1) meets the navigational and physical challenges of unpiggable pipelines through an innovative modular platform design, segmented MFL inspection modules and improvements to the inter-module coupling design. Figure

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... -1. RoboScan Inspection Robot for unpiggable pipelines Description of Problem North America is crisscrossed with an extensive system of gas transmission and distribution infrastructure including underground pipelines. There are hundreds of thousands of miles of high-pressure gas transmission lines that cross the country and are owned and operated by a large number of interstate pipeline operators. There are millions of miles of low-pressure distribution piping that are owned and operated by hundreds of local gas distribution companies. The safe and efficient function of this infrastructure is vital to the Nation's energy security, the commercial operations of many industries and the continuous delivery of fuel to millions of ii residential customers. Inspection, maintenance and repair of these pipelines are necessary elements of a pipeline integrity program. When access is practical, internal pipe inspection, maintenance and repair can offer a cost-effective approach to providing the services needed to ensure the safe and efficient operation of the infrastructure. However, difficulties in gaining physical access to and through these pipelines can present a potentially staggering economic burden on the owners/operators. Unpiggable Pipelines Physical Obstacles: There are many physical "obstacles" in the piping network that makes pigging impossible. The most intractable of these obstacles include: • Bends/elbows (90 degree) with bend radius less than 1.0 D. • Mitered joints/elbows greater than 10 degrees. • Back to back combinations of bends/joints. • Reduced port valves, including valves with full ports but smaller in diameter than the pipeline and/or plug valves that have neither full diameter ports nor circular openings. • Reduction/expansion in pipe diameter greater than 50 mm (2 in.). • Unbarred branch connections.