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Category: Safety
Question: How can I predict the pressure drop per unit time if a rupture occurs in a full sized gas line?
Keywords: pipeline,failure,pipe,line,predict,predictions,pressure,drop
Answer: Set up an excel spread sheet that first caluculates the amount in the pipe section (assume a 20 mile block valve section, then calculates the amount of fluid lost trough a fixed orifice (or hole) in the line with a given pressure (use sonic flow equation used in relief valves). Then calculate how much gas was released in 1 second. Now recalculate how much gas is left in the line and the corresponding pressure it would take to represent the new volume. Replicate the lines with these equations and watch the pressure drop over 1 second intervals. This is an approximation because there will actually be a flow and pressure drop toward the leak point an pressure profile will occur. From experience, people often start with a 15 psi/minute rate of change alarm and then adjusted it based on typical flowing conditions. Line balancing is performed from SCADA data every 5 minutes. If the trend kept going in a loss for several cycles we started a detailed pressure watch.The link below will show you a report that details the accuracy of various methods in modeling pipeline failures.
Links: Pipeline Failure Study