Fluxys, the Belgian gas transmission system operator (TSO), is advancing its strategy to supply hydrogen (H₂) to industrial clients, with the first H₂ transport capacity targeted for launch by 2026. As part of this initiative, selected pipelines within the existing natural gas network are being earmarked for conversion to hydrogen service. However, threats that are typically negligible in natural gas environments, such as hydrogen embrittlement and cracking, can present significant integrity risks when transporting H₂.

Fluxys initiated an evaluation to determine whether a combination inline inspection (ILI) tool equipped with low-field magnetic flux leakage (LFM) technology could effectively detect features of interest prior to introducing H₂ into the system. In June 2024, the tool was deployed on a 15.09 km, 12.75" natural gas pipeline in Belgium.

In addition to typical metal loss features, the inspection revealed several atypical anomalies that, while not posing an immediate threat to pipeline integrity, may warrant closer scrutiny ahead of H₂ conversion. These features could present risks in H₂ service environments. The paper introduces the application of LFM technology as a critical component in enhancing detection capabilities when used alongside other sensors. This approach enables identification of features such as areas of increased hardness, gouging, re-rounded dents, arc strikes, and crack-like indications—many of which may go undetected using conventional ILI methods. Fluxys is currently conducting targeted excavations and non-destructive examinations (NDE) to investigate these findings further.

The paper presents both the ILI results and the subsequent field evaluations carried out during the post-ILI dig programme.

Key words: hydrogen, pipeline conversion, in-line inspection, low field magnetic flux leakage (LFM), hardness, gouging, re-rounded dents, arc strikes, crack-like