A Microwave Measuring System for Detecting and Localizing Anomalies in Metallic Pipelines

In this work, an innovative system for structural health monitoring of metallic pipes is presented. The proposed system relies on using the pipeline as a waveguide for the propagation of an electromagnetic (EM) signal; possible anomalies in the pipe provoke the partial reflection of the propagating EM signal. Different from previous works that address similar applications, in this work, the EM test signal is injected in the pipeline/waveguide through a coaxial/waveguide transition that is made on the pipe surface (rather than on a cross section as generally done). In practical applications, this strategy would allow connecting more easily the test equipment to the operating, buried pipes. In addition, because reflections caused by anomalies may be difficult to identify with adequate accuracy, the authors have developed a dedicated processing strategy for the analysis of the reflections caused by anomalies. More specifically, by analyzing the measured reflected signal and correlating it to the ideal reflected signal, it is possible to improve the localization of anomalies along the pipe. The proposed system, along with the processing and operating strategies, was validated through full-wave simulations and experimental tests carried out on a steel pipe in the presence of intentionally provoked anomalies.