A third full-scale fracture propagation test has been conducted using a dense phase carbon dioxide (CO2)-rich mixture (approximately 10 mole percent of non-condensables), at the DNV GL Spadeadam Test & Research Centre, Cumbria, UK, on behalf of National Grid, UK.
The first and second tests, in 914 mm (36 inch) outside diameter pipe, also conducted at the Spadeadam Test & Research Centre, showed that predictions made using the Two Curve Model and the (notionally conservative) Wilkowski et al., 1977 correction factor were incorrect and non-conservative. An additional correction was required in order to conservatively predict the results of the two tests.
A third full-scale test was necessary to evaluate the fracture arrest capability of the line pipe for the proposed 610 mm (24 inch) outside diameter Yorkshire and Humber CCS Cross-Country Pipeline, because the predictions of the first and second tests were non-conservative, and it was unclear if and how the results of these tests could be extrapolated to a different diameter and wall thickness.
The third test was designed to be representative of the proposed cross-country pipeline, both in terms of the grade and geometry of the pipe, and the operating conditions.
The test section consisted of seven lengths of pipe: an initiation pipe and then, on either side of the initiation pipe, one transition pipe and two production pipes. The (in total) four production pipes are representative of the type of line pipe that would be used in the proposed cross-country pipeline.
A running ductile fracture was successfully initiated; it propagated through the transition pipes on both sides, and then rapidly arrested in the production pipes. The result of the test demonstrates that a running ductile fracture would arrest in the proposed Yorkshire and Humber CCS Cross-Country Pipeline.
The main experimental data, including the layout of the test section, and the decompression and timing wire data, are summarised and discussed.
Furthermore, the implications of the three tests, in two different pipe geometries, for setting toughness requirements for pipelines transporting CO2-rich mixtures in the dense phase are considered.