Flammability hazards of fuel system leak testing

To meet current emission regulations, automotive evaporative emissions systems must meet maximum leak rate specifications. Leaks exceeding the required rate must be located and repaired. Evaporative emissions systems are commonly leak tested with smokes or aerosols. Under normal conditions, the contents of automotive fuel tanks are inherently safe from fire and explosions because the gasoline vapour contained within is too rich to burn. Introducing a typical leak testing flow will dilute the over-rich mixture, creating flammable volumes within the tank if air is used as the carrier gas for the leak test fluid.;This thesis considers the gasoline vapour behaviour in an automotive gasoline tank under leak testing conditions. An experimental study was performed on a typical gas tank and was used to verify the results obtained from a numerical model. Significant flammable volumes were found under some conditions. Recommendations for preventing flammable mixture formation during leak testing are included.