38 Pipeline Technology Journal - 3/2022 RESEARCH • DEVELOPMENT • TECHNOLOGY the (new) inlet end. This will require that the expan- sion potential and forces are evaluated and may lead to additional intervention to accommodate the increased expansion forces, by e.g. increased burial to avoid up- heaval buckling or by allowing the pipeline to expand in a controlled manner. Effects of weight and mass of fluid: The density of the CO2 in dense phase could be in the range of 10 times higher than the density of the natural gas, while the density of CO2 in gas phase is more similar to natural gas. Hence, if CO2 is transported in gas phase the weight and mass of the pipe- line may not change significantly, however, for dense phase CO2 the weight may increase significantly. If the weight of the pipeline increases, this may decrease the acceptable free span lengths as the bending of the pipe- line increases on supported shoulders, and additional mitigation may be required. Further, an increased mass will change the natural frequencies of e.g. free spans and hence the acceptable free span length may be shorter due to changes in the fatigue/fracture loading response, and additional mitigation may be required. The dynamic loads from e.g. waves and current may also change due to changes in weight and mass. Changes in weight will also influence on-bottom stability. Third party loads: Loads from third party are generally not changed when changing from natural gas to CO2 transport, however, if weight and mass of the pipe- line is changed this may change the response of the pipeline. 8. Summary and Conclusion This paper has discussed a general approach for re-qualification of pipelines for CO2 transport. There are several key criteria that need to be considered carefully, and checks that need to be made, before ap- proving a piece of onshore or offshore infrastructure for re-use. Implicitly the feasibility of repurposing of a specific pipeline needs to be confirmed and docu- mented through a re-qualification process to ensure acceptable integrity, safety as well as transport capac- ity. General codes and recommended practices that lay out requirements and guidelines for design an opera- tion of CO2 pipelines are already available and can be used as basis for re-qualification of CO2 pipelines. It is foreseen that these standards will evolve with the CCS industry to incorporate latest research. In this paper, the various steps in the re-qualification process in DNV-RP-F104 has been outlined. There are however aspects that could benefit from fur- ther research, e.g. formulation of requirements for running ductile fracture and eventual environmental embrittlement. Impurities in captured CO2 affect crit- ical pressure, critical temperature, and phase behavior, which may affect pipeline materials and design param- eters. Other challenges related to repurposing of pipe- lines may be general lack of design and construction documentation for older pipelines. Also, repurposing of pipelines for CO2 transport may be challenged by local rules and regulations, and interpretation of such. Thus, re-qualification of pipelines, especially for CO2 transport in dense phase, is therefore not considered trivial and requires a careful evaluation but is never- theless considered as fully possible in many cases. ‘The feasibility of repurposing of a spe- cific pipeline needs to be confirmed and documented through a re-qualification process to confirm acceptable pipeline integrity as well as transport capacity.’ References IEAGHG, “CO2 Pipeline infrastructure”, 2013/18, December 2013 1. 2. DNV-ST-F101 ‘Submarine pipeline systems’, 2021 3. DNV-RP-F104 ‘Design and Operation of carbon dioxide pipelines’, 2021 4. Rabindran, P. et. 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