This paper presents progress in the development of an EMAT device for detection and sizing of axial cracks in unpiggable gas pipelines of small diameter. This collaborative work is jointly funded by Quest Integrated LLC (Qi2), Quanta inline devices (Q-inline), Gas Technology Institute (GTI), Operations Technology Development (OTD), The United States Department of Transportation (USDOT) and Pipeline Hazardous Material Safety Administration (PHMSA). The project is in its third phase. Phase I focused on bench scale proof of principle demonstration in 8-inch diameter pipes, wherein the core physical principles of operation were finalized and limitations were identified. The core principle is comprised of using shear horizontal circumferential guided waves. The prototype developed in Phase I was bi-directional and capable negotiating a bend of radius that is 1.5 times the diameter of the pipe (1.5D bend). The primary limitation, later termed as signal congestion, is the obscuring of flaw signals by the transmitted signals and modal noise which are characteristic of circumferential guided waves in small diameter pipelines. During the interim period between the Phase I and Phase II, Qi2 carried out an internally funded study to find a solution to the problem of signal congestion. The solution resulted in a tool that has potential for zero blind spots for detection and sizing of cracks. Phase II achieved multiple objectives including a shop demonstrable tool as well as a preliminary demonstration of the ability of the tool in sizing of crack for a wide range of tool orientations relative to the cracks and flaw configurations. The ultimate goal of the project is the development of tethered (robotic) towed device. Q-inline joined the collaborative effort during Phase III of the project and the objective was subsequently augmented to include taking significant steps toward a future free-swimming tool. The paper discusses the sensor development and the most recent flaw sizing results.
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