The mission was to identify the conditions of atmospheric pressure and ambient temperature under which a so-called empty-fuel-tank, containing residual fuel, could contain hazardous air/fuel mixtures. The issues are limited to two applications: explosion safety concerns in gasoline fueled automotive vehicles and explosion safety in jet fueled jet aircraft. In general, we concluded that flammable mixtures, under certain conditions, may exist in an empty fuel tank containing residual fuel, at ambient temperatures ranging from -51/spl deg/C (-60/spl deg/F) through 93/spl deg/C (200/spl deg/F), at or below atmospheric pressure. However, in the case of a gasoline automotive fuel tank, at normal ambient temperatures above -18/spl deg/C (0/spl deg/F), it is absolutely certain that the fuel tank head space contains an over-rich mixture, which cannot explode, unless the automotive fuel tank is completely drained of liquid fuel. Further, in the case of a fixed wing jet aircraft, a combustible mixture also does not exist in a fuel tank containing JetA type fuel at ambient temperatures below 38/spl deg/C (100/spl deg/F) which is about the lean limit flash point for commercial jet fuel at sea level. Nevertheless, this study identified six highly unlikely, but rationally possible critical conditions which can occur in a combination which may permit a combustible mixture to exist within a jet aircraft fuel tank and pose a potential hazard. While the scope of this summary paper is limited to fixed wing jet aircraft fuels, details of the automotive vehicle gasoline fueled application are contained in the original paper.
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