Consequence Analysis of High-Pressure Natural Gas Pipelines to Determine the Safe Zones Around the Pipelines by Using PHAST

Abstract Natural gas pipelines are essential for energy, but their failures can result in severe consequences. Egypt has established measures that include location classification for pipeline safety design and operation. Additionally, safe separation distances from communities are defined based on risk assessment principles. Nonetheless, a standardized method for determining these distances is lacking. This research introduces a methodology employing PHAST consequence modelling to ascertain safe separation distances, replacing the Fixed Distance/Rule-Based approach. Event Tree Analysis evaluates potential hazards from pipeline ruptures, such as dispersion and explosions. PHAST simulates these hazards, delineating zones for gas dispersion, thermal radiation, and overpressure. It models full-bore ruptures of varying pipeline sizes and pressures under different soil conditions. The modelling identifies safe distances for specific gas concentration, thermal radiation, and overpressure metrics. Results are illustrated through tables and graphs correlating safe distances with pipeline specifications. The PHAST modelling indicates that safe separation distances are directly proportional to pipeline size and pressure. Flammable gas dispersion is notably longer in sandy soil than in mixed soil. Stable weather conditions (2/F) produce larger dispersion areas but reduced thermal radiation and overpressure distances compared to neutral conditions (5/D). When compared to UKOPA and IGEM standards, PHAST modelling often predicts equal or greater safe distances. Methodological validation occurred by aligning the PHAST simulation of the 2021 Raven pipeline incident with observed flammable gas zones. Recommendations emphasize integrating safe distance findings into Egyptian legislation, exploring other hazardous materials, and mitigating ignition sources near pipelines due to flammable zone risks. The PHAST model serves as an effective tool for determining safe separation distances for natural gas pipelines, accounting for various operational factors.