This report on the liquid flow from the overfilled tank leading to the formation of flammable vapour in the Buncefield Incident was prepared for the HSE incident investigation. The purpose of the work was to provide a connection between the loss of containment and the formation of a flammable vapour cloud. Practical and numerical investigations have demonstrated that the bulk of fuel vaporisation and entrainment of air occurred during the cascading of fuel from the top of the tank into the bund.
The work involved the construction of a full scale replica of a section of top of the tank involved at Buncefield and also a full height section of the tank wall. Liquid flow experiments were carried out.The overall liquid flow results in a relatively fine spray, with droplets a few millimetres in diameter.Numerical analysis of heat, mass and momentum transfer (between droplets in the fuel cascade and the air that surrounds them) has shown that the fuel cascade drives a significant downward flow of air. The air is contaminated by high concentrations of light hydrocarbons and is cooled. Final temperatures and concentrations within liquid and vapour are likely to be very close to equilibrium values.
This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.
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