(60a) Risk Ranking Criteria for Catastrophic Vessel Failures Due to Fire Exposure. Vessel Wall Dynamics & Consequence Analysis

Vessel rupture is caused by an increase in the internal energy of the contents and insufficient emergency relief. Under fire exposure or internal heating by a runaway reaction, or both, the vessel walls temperature increases, the yield and tensile strength of the vessel walls decrease, and resistance to internal pressure decreases. Vessel wall dynamics analysis is a valued tool capable to predict not only when the vessel is expected to fail; i.e., stress due to internal pressure is greater than the ultimate tensile strength, but also to predict which conditions remain in the sytem. These conditions are the basis for consequence analysis, study which is based on ensuring knowledge of how the available internal energy in the system is being transformed: a source of fragmentation and deformation energy for the vessel shell, kinetic energy imparted to contents and fragments, and blast wave energy.

The paper analyzes two selected systems considered to be under a pool fire; i.e., vessel wall dynamics and consequence analyses have been performed. A detailed discussion of the parameters that impact on the predicted time to vessel failure and consequences of a Boiling Liquid Expanding Vapor Explosion (BLEVE) is provied. Finally, a specific risk ranking criteria able to quantitatively rank these scenarios is illustrated. The key two parameters able to define both the frequency of occurrence and consequence levels are the “time to vessel failure” and “energy available” in the system, respectively.