Girth weld cracking threats

Jon Lawson

In 2013, a new gas line with internal stainless steel CRA cladding experienced a failure. This 16-in pipeline was commissioned early in 2013 and occasionally used.

The failure consisted of circumferential cracking in a girth weld at a pipe bend. The investigation team recommended a complete inspection of all weld joints on this 10 km (6 mile) line.

Ultrasonic ILI was the only feasible means to inspect this line, doing so required that a liquid coupling medium be introduced. Due to the importance of the pipeline, a sequence of two inspection runs was selected.

The first run was completed using an NDT Global ultrasonic circumferential crack (UCc) tool to address the detection of circumferential cracks and crack-like anomalies. The second tool selected was the ultrasonic metal loss with pitting resolution (UMp) tool to detect metal loss anomalies, pitting, laminations and inclusions.

Associated risks were reduced by NDT Global taking full responsibility to prepare and clean the line along with a complete re-establishment procedure. All inspection results were independently verified to be highly accurate.

This gas line is a critical asset, express reports were delivered within 5 days of each run and full reports within the agreed timelines. Express reporting has been instrumental in bringing back the pipeline to normal operation.

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