Accurate prediction of the gas release rate following a full-bore pipeline rupture is key to risk assessment, safe pipeline routing, effective emergency planning and valve closure strategy. Typical tools adopted by the pipeline industry are developed for a perfect gas and are designed to simulate an isolated line rupture event or for simplistic boundary conditions (e.g. constant inlet pressure or no inflow). In the case of a real-life rupture event, a mainline block valve (MLBV) does not respond instantaneously at the time of rupture. Depending on the operation of the pipeline and the configuration of the network itself, the ruptured section might not be isolated for a period of time. Meanwhile, the inlet boundary condition is driven by the upstream network configuration, valve characteristics and operation protocols. As a result, the amount of mass release can be significantly under-estimated by a predictive tool that does not account for these factors.
A program based on the Method of Characteristics was developed, which allows an accurate equation of state and complex boundary conditions that reflect proper upstream conditions and valve closure strategy to be incorporated. An example case demonstrates that a shut-in scenario cannot provide correct out-flow prediction. The resulting outflow amount in a real-life rupture can be a few times higher than a shut-in scenario. This holds important implications in pipeline design, valve closure strategy and risk management.