Many things can cause rapid transients in gas pipelines, such as the sudden shutdown of compressors, or the abrupt changes in flow rate due to leaks. The hydraulic simulation of these rapid transients requires a mathematical model capable of modelling the detailed rarefaction wave. This also enables the accurate analysis of the impact of sequential valve closures along the pipeline. To minimize potential flow interruptions the highly accurate modelling of the pipeline dynamics can be used to understand and tune the behavior of the automatic shutdown valve (SDV's). By simulating the pipeline behavior, offline analysis can be performed in a safe environment without interrupting pipeline operations.
Automatic shutdown valves are designed to automatically close mainline valves in the case of a major pipeline leak or rupture to minimize pipeline leakage. Calibrated to detect a sudden pressure differential drop between a reference reservoir and the pipeline, automatic shutdown valves can respond to more than just pipeline leaks. Improper actuation of the line break mechanisms during pipeline operations can result in unwanted interruption of the pipeline flow if the calibration is not optimized.
This paper discusses the pipeline behavior during the transient, the dynamic effects on the automatic shutdown valves, and covers an analysis of first and second order mathematical solvers. The results of the simulations are validated throughout with a comparison with field test measurements.
A piping system is the most common method for transporting fluids between two locations. There are many challenges in the safe transportation of fluids in pipeline systems, particularly during rapid transients. The use of mathematical models to simulate these rapid transients makes pipeline operations safer.
Mathematical models enable detailed analysis of transients following sudden compressor shutdowns, and abrupt flow rate changes caused by leakages. This detailed analysis provides an understanding of the behavior of the rarefaction wave as it propagates from the source of the change.