A Spill Volume Calculation Approach and its Positive Impacts on Pipeline Risk Management

Abstract The loss of containment in liquid pipelines is a significant concern for pipeline operators, service providers, and regulators. Estimating the potential spillage volume at a designated pipeline location is critical for societal risk analysis, environmental impact assessment, and emergency response planning. The total spillage volume, after loss of containment, in each scenario consists of two parts: (a) the spill volume during operation while the pumps are active, and (b) the gravitational spillage volume after the pumps are shut down. A common industry practice to determine the operational spillage volume involves using commercial transient thermo-hydraulic simulation software. This software allows modeling the intended bore opening at a specified location and, through numerical simulation, defines the spillage volume within the time span required for the control room to detect the issue and respond by deactivating the pumps. Calculating this time span in advance for each scenario is essential. In recent years, there has been a notable increase in the demand for spillage volume simulation in Brazil, propelled by the regulatory requirement for risk studies. This surge is particularly driven by the need for comprehensive environmental analyses related to pipeline water-crossings and quantitative risk assessments that consider the population residing in high-consequence areas. Brazilian environmental agencies now mandate the evaluation of three distinct pipeline failure scenarios: (i) a pinhole with a diameter ratio d/D of 5%, (ii) a hole with a 20% diameter ratio, and (iii) a rupture with 100% internal diameter size. The increased demand has led to a significant rise in the utilization of numerical models and simulations. To meet this challenge, simplified hypotheses have been formulated. These hypotheses facilitate the computation of potential spillage volume during operation without relying on transient thermohydraulic software. Through the development and implementation of an algorithm, it becomes feasible to derive a comprehensive profile of the total spillage volume (both operational and gravitational) along the pipeline, based on the chosen discretization. The innovative tool, MAVAZ, developed by SIMDUT/PUC and TRANSPETRO, has proven effective in meeting the requirements of Brazilian regulators. MAVAZ’s calculation modules consider factors such as valve closure and spill containment times, offering a comprehensive approach to spill event analysis. The continuous development of MAVAZ calculation modules over the years has enhanced the realism of potential maximum leaked inventories, resulting in a more accurate calculation, and reducing the level of conservatism. Consequently, there have been positive impacts on cost optimization associated with pipeline risk management, both in risk analysis studies and in mitigating potential consequences through improved emergency response resources.