Hydrogen and anthropogenic CO2 pipelines create unique inspection challenges, primarily due to hydrogen’s impact on fracture toughness and risk of hydrogen-assisted cracking. These damage mechanisms necessitate reliable technologies for the inspection of longitudinal cracks and elevated hardness locations. In-line inspection (ILI) tools that operate effectively in gases like H₂ and dense-phase CO₂ are less disruptive than liquid-based tools and also offer valuable applications for existing hydrocarbon pipelines.

Elevated hardness areas may appear as hard spots in the pipe body or as “hard seams”. These hard spots have been an integrity concern associated with stress corrosion cracking or crack-like flaws within hard seams. For H2/CO2 service, the presence of hydrogen can reduce fracture toughness and thus the incentive for effective ILI hardness measurement tools to mitigate crack threats in H2 or CO2. For hydrogen and hydrogen Blend Service, PRCI has developed Consensus Engineering Requirements for Pipelines to provide more comprehensive and current guidance. This document highlights the need for an engineering assessment for lines repurposed to hydrogen service to assess existing anomalies, including cracks and hard spots specifically.

Reduced fracture toughness in H₂/CO₂ service increases the need for advanced crack detection and sizing ILI tools. Industry and fracture mechanic assessments have indicated that lines repurposed for H2 or CO2 will benefit greatly from crack ILI tools that can achieve ultrasonic crack detection (UTCD) level performance. While EMAT ILI tools are commonly used in gas pipelines due to the challenges of liquid batching, their sizing and detection capabilities are generally lower than UTCD tools, which require liquid coupling.

This paper will highlight existing technology needs and gaps, and recent technology developments to address both the crack and hardness inspection topics for H2/CO2 pipelines as well as existing hydrocarbon pipelines.