A Compelling Comparison of Field Measurements and Numerical Modeling in Pipeline Surge Pressure Mitigation

Transient pressures can cause damage to force mains and pumping systems, leading to pump station down-time, sewage overflows, and costly repairs. In this case, the collection system owner detected that excessive surge pressures were occurring in a sewage force main system. The owner undertook a surge analysis study to determine the magnitude of surge pressures in the system, and to develop a solution for reducing surge pressures to acceptable levels. The surge analysis study included numerical modeling of the system and field measurements of transient pressures along the force main both before and after installing a surge tank at the pump station. This study provides convincing evidence for two conclusions relevant to managing transient pressures in pipeline systems: (1) numerical modeling can provide reliable data for sizing a surge tank to mitigate surge pressures, and (2) measured peak pressures may exceed modeling predictions by significant amounts when the system is subject to vaporous column separation. Modeling results will be most reliable when a surge mitigation strategy is in place that can fully prevent vaporous column separation within the system.