Multiple inspection jobs were recently completed for a western-US natural gas pipeline operator. The sections of line required reassessment as part of the operator’s ICDA program. For multiple reasons the lines were deemed unpiggable, which necessitated the use of robotic ILI tools rather than flow-driven pigs.

A video-crawler inspection conducted by the operator discovered a possible indication of internal corrosion at a low point in the line. A neighboring line had dense internal buildup too extensive to rely upon a visual-only inspection. Due to these preliminary findings the operator made the decision to perform a comprehensive in-line inspection using robotic EMAT tools, and to extend the scope of the inspection beyond the original plan.

A high-resolution internal examination of the pipe sections was conducted using the tool’s non-contact EMAT probes. The EMAT scan of the indication did confirm some wall loss in one of the pipe sections, however it was measured to be at a minimal depth, so a drip line was installed and the pipeline was returned to service.

By utilizing robotic ILI tools to perform the inspection of the unpiggable lines, the pipeline operator was able to complete their reassessment obligation on an expedited timeframe, gain valuable previously-unknown data about the pipeline features, and validate the integrity of the pipeline.

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