Modelling emergency isolation of carbon dioxide pipelines

• A model for simulating valve closure in failed pipelines is developed.
• Model predictions are compared against large scale experimental data.
• Close agreement between model and recorded data is reported.
• The minimum fluid temperature downstream of valve falls below the CO2 triple point.

The development and experimental validation of a mathematical model for simulating the dynamic response of in-line Emergency Shutdown Valves (ESDVs) for high pressure Carbon Dioxide (CO2) transportation pipelines is presented. Based on the homogeneous flow assumption, the model accounts for the pertinent valve characteristics, including the activation and closure times, as well as its proximity to the rupture location. The validation of the model is based on the comparison of its predictions against measurements taken following the controlled Full Bore Rupture (FBR) of a 113-m long, 148 mm i.d. pipeline containing CO2 at 15.1 MPa and 300 K, incorporating a ball valve along its length. The data recorded and simulated include the transient fluid temperatures and pressures immediately upstream and downstream of the closing valve following FBR. In all cases, very good agreement between the model predictions and recorded data is reported. Importantly, the minimum fluid temperature downstream of the closing valve is found to fall below the CO2 triple point indicating solid CO2 formation.