Paradigm Busted - Pinhole Detection Utilizing UHR Axial MFL and Caliper ILI
Mark Olson
Mark Olson
Part of the proceedings of

Shifting paradigms is difficult. In a past life (late 1990’s/early 2000’s), the ENTEGRA® team experienced this, when they commercialized the first XHR MFL tools that could reliably differentiate plain dents from dents potentially containing metal loss. Industry then had to adapt its thinking regarding the assumed limitations of ILI technology development. With the advent of ENTEGRA’s UHR MFL/Caliper combination tools, the detection, characterization, and sizing of true pinhole anomalies is a new frontier for axial Magnetic Flux Leakage (“MFL”) In-line Inspection (“ILI”).

The paradigms to be challenged are that: 1) existing MFL technology isn’t capable of sufficient detection/accuracy for true pinholes, and 2) in-the-ditch NDE techniques are more reliable than MFL In-line inspection results for internal pinholes.

This paper will discuss the past 4 years of experience with UHR MFL in-line inspection. Pull testing on machined defects demonstrated that 3mm (~0.125” inch) defects could be reliably detected, characterized, and sized to depths of 10% internally and 20% externally at lower ILI speeds (20% / 25% at full tool specification speeds). Subsequently, field correlation on hundreds of internal and external pinhole corrosion features validated the sizing specifications. Regrettably, this exposed the real-world challenges facing in-the-ditch NDE techniques, and technician experience locating the pits and reliably measuring the true pit depths. Further laboratory testing compared the effectiveness of various in-the-ditch NDE techniques and identified recommended best practices.

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