Abstract
The execution of in-line inspection (ILI) as the primary assessment methodology to manage a specific pipeline integrity threat has become standard practice for pipeline operators. The ability for ILI to properly size and characterize pipeline anomalies is better than ever. However, there are challenges that operators should be aware of when it comes to understanding the limitations of ILI. These challenges can differ depending on the threat being managed.
The threat of cracking in a pipeline longitudinal seam weld can be particularly challenging to manage. Recent improvements in the detection capabilities of crack-detection ILI technology present a challenge for pipeline operators. It is not uncommon for ILI to report several hundred or even several thousand seam weld anomalies on a single pipeline. Managing this large number of features can be very difficult, and the repercussions of excavating features that do not pose a true integrity threat extend well beyond the financial. The elimination of unnecessary excavations will in turn decrease risk related to safety associated with every excavation and allow the operator to focus solely on the features that pose a true integrity threat.
This paper presents a case study in which a liquid pipeline operator was dealing with these exact challenges. A recent ultrasonic crack detection (UC) ILI reported several thousand linear longitudinal seam anomalies on a post-1980 vintage pipeline containing high-frequency electric resistance welded (HF-ERW) seams. To properly qualify the integrity threat, an integrated approach was executed that combined non-destructive evaluation (NDE), destructive material property testing, full-scale burst and fatigue testing, metallurgical analysis, raw ILI data review, and engineering critical assessment.
The results of the integrated testing and analysis identified that a large number of ILI-reported features were mis-characterized due to the presence of excessive internal trim associated with many of the seam welds contained in the pipeline. The analysis provided the necessary technical justification to forego excavations associated with the features that were mis-characterized by the ILI. Integrated testing and analysis provided the operator with a superior understanding of the true nature of the seam weld integrity threat for this pipeline.
