Crack Management of Hydrogen Pipelines

The climate emergency is one of the biggest challenges humanity must face in the 21st century. The global energy transition faces many challenges when it comes to ensuring a sustainable, reliable and affordable energy supply. A likely outcome is decarbonizing the existing gas infrastructure. This will inevitably lead to greater penetration of hydrogen. While the introduction of hydrogen into natural gas  transmission and distribution networks creates challenges, there is nothing new or inherently impossible about the concept. Indeed, more than 4,000 kilometers of hydrogen pipelines are currently in operation. These pipelines, however, were (almost) all built and operated exclusively in accordance with specific hydrogen codes, which tend to be much more restrictive than their natural gas equivalents. This means that the conversion of natural gas pipelines, which have often been in service for decades and have accumulated damage and been subject to cracking threats (e.g. fatigue or stress corrosion cracking (SCC)) throughout their lifetime, can be challenging. This paper will investigate the impact of transporting hydrogen on the crack management of existing natural gas pipelines from an overall integrity perspective. Different cracking threats will be described, including recent industry experience of those which are generic to all steel pipelines but exacerbated by hydrogen and those which are hydrogen specific. The application of a Hydrogen Framework to identify, characterise, and manage credible cracking threats to pipelines in order to help enable the safe, economic and successful introduction of hydrogen into the natural gas network will be discussed.