Abstract
The frequency of an accident scenario is most commonly assessed by a generic failure frequency approach; the accuracy of the calculations is based on the quality of the data used. There exist different sources of generic failure frequencies such as the Reference Manual Bevi Risk Assessments (2009), the Failure Rate and Event Data for use within Risk Assessments of the HSE (2012), and the Handbook of Failure Frequencies of the Flemish Government (2009). The differences between them rely on the factors considered for their calculation and on the way the failures have been classified.
Each one of the aforementioned sources takes into account different variables, but aspects such as the mechanical failures or the human factor are not explicitly detailed. Although the mechanical failures may have been considered indirectly, the human factor is difficult to quantify. The latter is a major cause of undesired events in process industries. Due to the complexity of quantifying human error and the causes that lead to it, this factor is not often considered in most of the generic failure frequencies databases.
Through the use of fuzzy logic, the human factor is going to be introduced in the failure frequency estimation of storage vessels in chemical plants. This theory allows including qualitative variables not considered by traditional methods and deal with the uncertainty involved. In this way, the failure frequency estimation for storage vessels will be more realistic and accurate. To design the model the expert’s opinion is going to be taken into account through a questionnaire.
