An in-line inspection device called a smart pig deploys nonlinear harmonic (NLH) sensors against the inside surface of a pipe. Fluid flow propels the pig through the pipeline. The sensors look for anomalies along the entire inside pipe surface. According to the U.S. Department of Transportation's Office of Pipeline Safety, the leading cause of pipeline incidents is external force, such as impacts from construction equipment during excavation. Unlike conventional inline inspection methods, NLH sensors detect stresses and strains generated on the inside of the pipe by outside force. NLH contour plots show the presence and size of defects. "These multiple capabilities haven't been possible with any commercially available inline-inspection tools," says Graham Chell, Institute scientist at SwRI's materials engineering department.
