Resumen de Contribución al análisis de riesgos en el transporte de materiales peligrosos por tubería
Jaime Giovanni Ramírez Camacho
The highly complex and interconnected today's societies require a continuous flow of materials and energy from one geographical area to another. In particular, huge amounts of often-hazardous materials, mainly liquids or gases, are transported from production/extraction sites, through processing plants, to the final consumption areas.
The transportation can be performed by different modes: road, rail, ship (sea/river) or pipeline. Most of these modes have a strong interaction with the landscape, as often the transport takes place over long distances, crossing both rural and urban areas.
Pipeline transport is one of the most commonly used modalities for the transport of fluids and is commonly regarded as a safer alternative compared to other transportation modes, based on the low accident frequency and the generally limited number of fatalities historically registered. Nonetheless, due to the continually increasing extension of their network, pipelines often cross highly populated and industrialized areas, so that in case of a loss of containment involving a hazardous substance, significant damages can affect a large number of people. At the same time, given the close interaction between pipelines and human activities, the frequency of occurrence of failures can become significant. On the other hand, when crossing rural areas or with high biological diversity, a serious environmental impact can result. In some of these accidents, the scale of the event and the severity of its consequences have increased due to the so-called domino effect.
Consequently, an increasing attention has been devoted in recent years to the quantification of the risk associated with this transportation mode based on the well-known techniques of Quantitative Risk Analysis (QRA). This methodology consists in a step-wise procedure where the following main phases are carried out: identification of the accident scenarios, estimation of their frequency of occurrence, calculation of their consequences in terms of damaged areas and people involved and, finally, quantification of the overall risk.
On the basis of the above considerations, and with the aim of improving the knowledge of the data required to carry out a QRA, in this paper a statistical analysis of historical data on accidents involving onshore pipelines occurred all over the world has been carried out, to illustrate the risk associated to these systems. Detailed event trees have been developed for the different substance categories identified, and the conditional probabilities for each specific release sequence have been calculated.
The historical study of accidents in buried natural gas pipelines that have involved the formation of a crater has allowed the assessment of the influence of the pipeline parameters on the dimensions of the crater resulting from the rupture of the pipeline. Mathematical expressions have been obtained to represent the proportionality relationships found.
Finally, a mathematical model, based on a historical survey of pipeline accidents, is proposed to estimate the probability of domino effect in parallel pipelines, aerial or buried, associated to a jet of fluid and to the resulting erosion or thermal effects.
The results obtained represent a useful and needed starting point in QRA of hazardous materials transportation via pipelines.
