Minimizing the risks resulting from hazardous scenarios during the design of a given system is of superior importance in order to ensure a safe operation and to demonstrate and satisfy regulatory requirements. A common approach in the process industry for this purpose is to use Quantitative Risk Assessment (QRA) as a decision-making tool to effectively apply risk mitigation measures. The results of a QRA allow quantifying individual and societal risks and assessing them against risk criteria. While individual risk is usually presented in risk contours showing the acceptable and tolerable risk limits, societal risk is often shown in an FN-curve which presents the cumulative frequency F of all system-related hazardous events that result in N or more fatalities.
Regarding cross-country pipelines, societal risk and hence the FN-curve results are related to the pipe length. However, the likelihood and the consequences of hazardous events and subsequently the risk vary along the alignment of a pipeline due to e.g. different environmental, geological and operational conditions, different pipe geometries and population densities. Therefore, using an overall FN-curve approach for a cross-country pipeline has a major shortcoming: A precise detection of the pipe sections which are mainly contributing to the risk is not possible, which makes an effective application of risk mitigation measures difficult.
This can be overcome by presenting the societal risk using the Linear Risk Integral (LRI) approach which addresses the societal risk along the length of the pipe route. The LRI can be interpreted as the cumulative risk for the society, i.e. sum of individual risks caused by the pipeline at the related location. The LRI approach allows comparing different pipeline systems and routes, providing an integrated overview of the pipe related risks and applying risk mitigation measures in a highly efficient manner.