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Selection of Calibration Reflectors for Corrosion Resistant Alloy Piping

The four primary calibration reflectors for weld inspections in piping are side-drilled holes, flat-bottomed holes, notches, and through-holes. The specific reflector to be used depends on the code required for the inspection. All reflectors work well with shear waves in carbon steel. There is, however, an issue when some of the reflectors are used with refracted longitudinal waves in corrosion resistant alloys (CRAs). CRA materials are typically UNS N06625 (alloy 625) and UNS 31803 (duplex stainless steel) and are generally inspected by refracted longitudinal waves. Refracted longitudinal waves mode convert on some of these calibration reflectors, and the reflection is not the same as that with shear waves.

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