Dynamic Leakage Characteristics and Emergency Shutdown Valve Optimization for Urban High-Pressure Gas Pipelines

Addressing the lack of quantitative basis for dynamic response characterization and emergency shutdown decision-making in urban high-pressure gas pipeline leaks, this study takes a JS pipeline as the engineering case and establishes a dynamic simulation model based on OLGA incorporating leak and shutoff valve modules. The effects of aperture size, leak location, inlet flow rate, and valve operation on release intensity and economic losses are systematically analyzed. Results reveal that without intervention, leak-point pressure follows a four-stage evolution—steady operation, sharp drop, gradual decline to equilibrium, and post-plugging recovery—while leakage rate exhibits positively coupled synchronous behavior. Aperture size acts as an exponential-level hazard control factor; apertures ≥150 mm and rupture cases mandate immediate valve closure. Upstream leaks primarily threaten supply continuity, whereas downstream leaks exhibit sustained high-rate venting with greater release intensity, which may lead to more severe accident consequences depending on local atmospheric conditions and dispersion patterns. Inlet flow mainly modulates pressure equilibrium with limited influence on release rate. Emergency shutoff valves achieve loss reductions of 46.9–67.6% for apertures ≥150 mm, corresponding to savings of 0.47–3.48 million CNY within 4 h. These findings provide dynamic quantitative support for leak classification, coordinated valve control strategies, and emergency repair decision-making.