(553c) Consequence Assessment for Event Tree Analysis in Transitions Using Dynamic Simulation

Incidents that occur in industrial facilities can lead to the release of hazardous materials, uncontrolled fire and explosions, economic losses and environmental contamination. Consequence assessment is an examination of the undesirable impacts of an accident. Fuzzy logic combined with Event Tree Analysis (ETA) is used for quantitative risk assessment (QRA).

In this work dynamic simulation was used to assess the consequences of event tree branches for two examples of equipment switching transitions in chemical plants. The first example was switching between two solid desiccant dryers in an ethylene plant. The other example was the switching of a reflux pump with its spare in a reformate stabilizer column. Both examples have standard operating procedures (SOP) commonly accomplished manually by operators. Numerous operator induced fault cases were considered. These SOPs and fault cases were simulated in Aspen HYSYS V8.0 using the event scheduler feature. The consequences were identified by monitoring variables during dynamic simulation of each case. Thus, the fuzzy ETA algorithm was used to evaluate the risk of equipment switching transition faults while dynamic simulation was used to assess the consequence.