Authors: Prof R Bris, VSB-Technical University of Ostrava, S Medonos, Petrellus Engineering Ltd, Chris Wilkins, Petrellus Engineering Ltd, Dr A Zdrahala, VSB-Technical University of Ostrava. Proceedings of the European Safety and Reliability Conference ESREL 2012.
Risk to safety of personnel in process industries is normally modelled in the application of Event Trees, where the risk is defined as a product of event frequency and its consequences. This method is steady state whilst the actual event is time dependent, comprising, for a gas release, as for example, the size of gas cloud being released, probabilities of ignition, fire or explosion, fatality, escalation to new releases and fire and/or explosion, and the probability of fatality, all varying with time.
This paper presents modelling of the time-dependent events and the time-dependent probability of fatality by means of two methods: direct Monte Carlo simulation on one hand and analytical computation based on modelling of scenarios by the use of directed acyclic graph (DAG) on the other. Using these methods the modeled scenarios change with relevant probabilities at defined times to configurations with appropriate probabilities of fatalities. The Paper uses a realistic example from the offshore industry and compares it with the simulation method.
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