In the mid-1990s, the oil and petrochemical industry had an inspection requirement to detect corrosion under insulation (CUI). CUI occurred when a leak path from the outside of the insulation to the OD of the pipe allowed moisture to condensate and active corrosion on the pipe OD. Using conventional inspection approaches to find the CUI required removal of the insulation and the inspection of every square inch of the pipe OD surface. In work done in the early 1990s, Dr. Hegeon Kwun showed that guided waves could be directly generated on ferromagnetic material based on the magnetostrictive effects and that the waves travel hundreds of feet from one sensor location to detect broken wires in wire ropes. This approach seemed to hold promise for the CUI inspection on pipes. The feasibility of generating and detecting longitudinal guided waves was subsequently proven in the laboratory. Encouraged by the laboratory results, a prototype field instrument system, including electronics and probes, was developed under a joint industry funding project in the latter part of 1990s. The developed system performed well in the field. However, it was soon found that the longitudinal wave mode interacts with liquids in the pipe and, as a result, causes additional signals which make the defect detection difficult. It became obvious that, to inspect pipelines carrying liquid products, torsional waves that do not interact with liquids need to be used. Work quickly began on ways to generate torsional waves magnetostrictively and the magnetostrictive sensor MsS torsional mode technology was developed in early 2000s. The torsional mode probes used the same instrument developed for the longitudinal mode and subsequent field evaluations of the torsional wave pipeline inspection were very successful. Following a couple of years of field testing and evaluating the technology for many applications, Southwest Research Institute (SwRI®) developed the MsSR2020 and began commercialization of the system. As the success of the technology began to grow, SwRI® updated the system to make it more portable, battery powered, and easier to operate. Over the years there have been three system revisions and the MsSR3030R is the third version and development of the fourth version is currently ongoing. The MsS system is now used globally by many industrial companies and organizations for various applications including inspection of pipelines, cables, heat exchanger tubes, and anchor rods. There are many more applications of the technology that SwRI is also trying to transfer, not only for inspection but for monitoring as well. These include inspection and monitoring for tank bottoms, aircraft structures, and vessels.

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