Pipeline seam welds are often inspected using ultrasonic In-Line Inspection (ILI) technologies. The thru-wall height of the detected crack-like anomalies are usually determined using the reflected amplitude of the ultrasonic signal. However, amplitude-based techniques can have significant errors due to unknown and variable geometrical aspects of the cracks, and most vendor specifications are based on planar, perpendicular notches, versus the complex shapes associated with natural cracks.

Accurate and reliable height sizing of cracks is necessary for proper risk management in pipelines. Therefore, improved sizing performance is highly advantageous in both deterministic and probabilistic assessments.  Alternative time-based technique, e.g., tip diffraction, is known to be more reliable than amplitude-based techniques, but tip measurements are often not possible due to the capability current ultrasonic testing (UT) ILI tools.

A new ILI tool with consistent and repeatable tip diffraction sizing capability has been developed and validated successfully in both a 1970’s High Frequency ERW Pipeline and validation spool with synthetic cracks. The increased sizing performance will improve integrity assessments for both greater reliability and maintenance efficiency.