Comparative Analysis of Running Ductile Fractures in Dense-Phase and Supercritical CO2 Pipelines Designed Per DNV-RP-F104 and ISO-27913

Abstract Transmission pipelines carrying dense-phase and supercritical CO2 are susceptible to running ductile fractures (RDF). This vulnerability arises from the unique thermodynamic characteristics of dense-phase and supercritical CO2 during its release from an orifice in the pipeline. Dense-phase and supercritical CO2 pipelines operate at high pressures, and depressurization resulting from a through-wall fracture can lead to a phase change in CO2. The present study investigates the differences between two well-known standards DNV-RP-F104 and ISO-27913 in terms of the minimum wall thickness and Charpy v-notch (CVN) impact energy required for the RDF control for a set of analysis cases representative of dense-phase and supercritical CO2 pipelines. The prediction of RDF is commonly carried out using the Battelle two-curve method (BTCM). Given the long plateau in the decompression wave speed curve that is typical of CO2 pipelines, a simplified BTCM is employed in this study for the RDF assessment by comparing the arrest pressure with the saturation pressure. The arrest pressure is computed using the Battelle through-wall crack model with modifications based on full-scale experimental data reported in the literature. The open-source tool RAMDECOM is used to compute the saturation pressure for a given set of initial operating pressure and temperature based on the one-dimensional isentropic decompression assumption and rigorous equation of state. It was observed that the wall thickness and CVN impact energy values determined per ISO-27913 are higher than those determined per DNV-RP-F104, suggesting a more conservative design based on ISO-27913. DNV-RP-F104 emerged as more straightforward for designing the analysis cases considered in the present study, whereas ISO-27913 necessitated adjustments in the calculated wall thickness to adhere to its maximum CVN impact energy requirement.