Detection of Hydrogen induced Cracks During In-service inspection of Piping Using Ultrasonic Phased Arrays – Assessment of Fitness for Service (original) (raw)

Hydrogen induced cracking in Carbon steel in sour service is a common damage mechanism, particularly in older steel piping, which was generally non-compliant to NACE 0175. During inservice inspection of such an old pipeline in a gas processing plant, numerous mid wall indications were observed while performing conventional Pulse-echo ultrasonic examination. Previously it was assumed as laminations and stringers in the piping material during manufacturing process; however for reconfirmation, an automated phased array examination has been performed on the same location with longitudinal waves and several indications with depths around mid-wall thickness have been observed and recorded. A portion of the affected pipe where indications were observed has been cut and removed from the main pipe after complete shut down and it was observed that several blisters with cracks have been occurred in the inside surface of the piping which were not visible from the outer surface. Further assessme...

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