(47s) Liquid Fuels Release Rate Calculation in Transport Pipelines with Complex Topographical Conditions

Pipelines are the most efficient and economical mean of hazardous materials (HazMat) transportation through long distances. In the particular case of hydrocarbons, production sites are often far away from processing facilities and/or final users, therefore, this industry uses the greatest amount of transmission pipelines. The main concern related to the operation of these systems is the loss of containment events (LoC), due to the fact that the fluid itself constitutes a source of hazard. Such events, despite their low frequency, might have severe consequences on the surrounding communities, the environment and the assets of the operating company or any other company in the vicinity of the pipeline.

In order to ensure a safe and reliable operation of these systems, and to support decision-making processes in a risk management framework, it is required to perform risk analysis. This analysis will allow establishing possible consequences of the accidental events and the required measures to reduce the frequency of events and/or the effects magnitude. One of the main inputs to risk analysis is the release rate, i.e., the rate at which the material is released to the surroundings once the loss containment takes place. Modeling the release rate is particularly important in countries with complex topographic conditions, in which a pipeline undergoes several geographical changes along its route. The amount and manner in which a HazMat is released to the surroundings will define the possible accidental events and therefore the consequences on the elements of interest, such as population, environment or infrastructure. Therefore, it is necessary to properly quantify the available volume for release at each segment of the pipeline and estimate the related release rate profile. As a result, several models have been developed to model hydrocarbon release scenarios, including phenomenological approaches that consider one (axial) and two-dimensional (axial and radial) flow patterns, with or without phase change, transient effects, and more. Although the phenomenological models offer the best representation of reality, their computational cost is extremely high, with computing times on the order of days.

This work presents a tool that supports decision making processes during the design, operation and/or revamping of hydrocarbons transmission pipelines. The tool allows a simple, non-phenomenological calculation for a quick estimation of available volume for release, and the related release profile. The tool considers the presence of active-automatic safety barriers (such as emergency shutdown valves and check valves) in pipelines with complex topographical conditions, given a failure in any point of the pipeline. These calculations are performed at a very low computational cost, with computing times on the order of minutes. The results provided by this tool become a key input to perform a priori risk analyses of pipeline systems to identify its critical segments (those with the highest release rates and times). Such information is crucial to define the layers of protection to be implemented (e.g., determine segmentation requirements, application of other safety barriers) and for the strategic design of emergency response plans in case a failure occurs (e.g., establish the critical areas of the pipeline, location of sensing devices, emergency response brigade).