Advanced Methods for Determining the Origin of Vapor Cloud Explosions Case Study: The 2006 Danvers Explosion Investigation

Abstract

Gas dispersion and explosion dynamics can be very complex. Blast effects in the far field are less sensitive to the local dynamics of an explosion event, and simplified techniques have been developed to roughly estimate the amount of fuel involved (i.e., energy released) in an explosion based on the observed damage in the far field. However, these simple techniques are not suitable to predict the complex explosion dynamics that occur in the near field. The phenomena that drive explosions and resulting damage in the near field are complex in nature, as they depend on non-linear interactions between multiple variables (e.g., ignition location, flame accelerations due to object interaction, fuel reactivity, geometry of the facility regarding confinement and interconnected rooms, vent areas, etc.). Furthermore, the damage created in the near field by overpressure development, blast wave reflections and focusing, pressure impulse, pressure piling, blast wind and ensuing drag forces, may be difficult to interpret using simple methods. The origin of an explosion may, in fact, differ from the intuitive epicenter determined from oversimplified assumptions and may lead to incorrect conclusions regarding the cause and origin or initiating events of the accident. State-of-the-art 3D modeling tools, such as FLACS, are typically required to understand and evaluate complex explosions. FLACS was specifically developed to predict the consequences associated with complex explosions, especially in the near field, and has been extensively validated against hundreds of full-scale experiments. Therefore, FLACS simulations can be used to investigate the chain of events of the explosion and provide a more complete understanding of the evidence, including near-field blast damage. This paper presents the findings of how FLACS was used to help determine the explosion origin in the explosion that occurred at an ink and paint manufacturing facility in Danvers, Massachusetts, on November 22, 2006. This paper is not intended to provide complete investigation findings and will only provide the necessary background material to follow the explosion origin analysis.