In the manufacture of spirally welded pipe, the “skelp” or plate used is joined using a weld to allow continuous flow of the plate through the forming section of the production mill. For large diameter spiral pipes, there can be one skelp-end weld (SEW) in every 5-7 joints of pipes. The weld is oriented neither longitudinally nor circumferential. Hence, in-service inspection of SEW in a pipeline is challenging.

In 2017, Kuwait Oil Company (KOC) commissioned two nos. 24-inch high-pressure gas pipeline constructed from spirally welded pipe. During the repair of one of the pipelines, cracks were discovered in the SEW. Further inspection by radiography technique revealed cracks on another SEW. It was decided to cut out and replace all SEW in that pipeline. Random inspection on another shorter pipeline also revealed cracks though at a lesser extent. These cracks presented themselves along the line of the SEW, randomly spaced and perpendicular to the SEW.

KOC wanted to ensure that there were no integrity issues related to the SEWs and hence looked for an in-line inspection (ILI) technology that would find these anomalies and potentially prioritise them for further investigation. KOC selected the TDW combination tool – multiple dataset (MDS) – as a trial to assess the capability for this application. The MDS ILI tool was run in 2023 and successfully identified some areas where these features existed and with dig feedback, confirmed their existence.

The paper describes the problem and the deployment of the ILI solution. Dig feedback will also be shared to highlight the nature of these features and how the ILI tool performed.