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Using Passive-Axis Focusing Wedges to Decrease Inspection Reject Rates

When pipe welds are inspected using phased array ultrasonic testing (PAUT), the common problem of beam divergence is amplified by the curved geometry. To compensate the adverse effects of beam divergence in curved parts, a focusing wedge can be used. Many acoustic and inspection setup parameter validations are performed on flat blocks or plates even though the inspections are conducted on curved surfaces. Since the beam is affected by the radius of curvature at the various interfaces (for example, the wedge-to-part interface and back wall interface), the response to a discontinuity measured on a plate can be quite different from the response measured on a pipe. Recently developed passive-axis focusing (PAF) wedge technology can be used to address this challenge.


ASME, 2020, ASME B31: Pressure Piping, American Society of Mechanical Engineers, New York, NY

Zhang, J., C.T. Liu, and J. Habermehl, 2015, “Focusing Wedge for Ultrasonic Testing,” US Patent 9,952,183, filed 11 September 2015, and published 24 April 2018

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