Within the last decade, axial cracking became a significant and well-known threat to pipeline systems. The defects are commonly in/at the longitudinal welds or in combination with external corrosion/coating disbondment (SCC). Inline Inspection (ILI) service providers developed inspection technologies for liquid and gas lines that are now utilized regularly. In comparison to axial cracking, circumferential cracking does not yet show a significant role in pipeline integrity. Nevertheless, pipeline operators observe these defects, often in combination with circumferential welds and/or local stress/strain accumulation. Such features are often caused by soil movement, which may occur more readily in mountainous areas.
Over the course of the 2014/2015 calendar years, NDT Global inspected 12” pipeline segments for circumferentially oriented crack-like indications. The pipeline segments totaled 814 km in length and transported light crude oil. The 6 pipeline segments range in length from 61 km to 251 km each. The pipelines were considered to be susceptible to axial stresses (both in the base material as well in the girth welds) due to slope subsidence and outside forces acting on the pipe. In previous integrity digs, circumferential crack-like indications were found in conjunction with slope movement and these segments needed to be further investigated.
This paper provides information on the challenges solved during the course of the project. Lessons learned from previously inspected sections have been applied to future inspections. The authors will provide information on the inspection campaign, a discussion regarding field verification findings and ILI results, and project conclusions.