Loosening Monitoring of a Threaded Pipe Connection Using the Electro-Mechanical Impedance Technique—Experimental and Numerical Studies

Threaded connections are the most common pipe fittings used in oil and gas transportation systems. Due to external vibrations, cyclic loads, and pollution, the fitting parts may start getting loose, which could result in pipeline leaks and other environmental disasters. It is of great significance to develop a reliable technique that could provide real-time monitoring of the looseness of pipeline fittings. In this paper, a piezoceramic-based active sensing method combined with the electro-mechanical impedance (EMI) technique was developed to monitor the health condition of threaded pipe connections in real time. Two pipe segments coupled with a threaded coupling fitting were assembled in the laboratory, and a lead zirconate titanate (PZT) patch was surface bonded onto the coupling part. In the experiment, the PZT impedance signatures were measured at each simulated loosening condition. A root-mean-square deviation (RMSD) method was employed to build a looseness index from the measured impedance signatures. To verify the effectiveness of the developed EMI technique, the experimental results were compared with those computed from a numerical simulation. The good agreement from experimental and numerical results highlights that the developed piezoceramic-based EMI technique has great potential for determining early looseness, as well as for monitoring the health status of the pipeline fitting during its service life.