Development of lower flammability limits testing apparatus for gasoline vapor – Air mixture using an internal vaporizer at ambient conditions

Fire accidents at public fuel stations in Indonesia have urged the need to characterize the causes of these fires. In the gas station area, the formation of gasoline vapor is the main concern of this research. Therefore, this study aims to analyze lower flammability limits (LFLs) of gasoline vapor-air mixtures of the selected gasoline samples. The LFL of gasoline vapor was characterized using a 1.2 L vertical tube integrated with an internal evaporator and a high voltage electric lighter with the energy of 10 J. The tube is made of glass with a diameter of 80 mm and a height of 300 mm with an open top end. This apparatus can run two test methods of upward and downward propagation. The experiment was conducted at the ambient condition with an evaporation temperature of the sample being 150 °C for the internal evaporator. Four gasoline samples were used with varying octane numbers (RON) obtained from arbitrary public gas stations. For validation, Iso-octane (IO) reference fluid with a purity level of 99.5% was tested for the assessment of LFL. The results with the upward propagation method showed that the LFL volume-based concentration were 1.62%, 1.61%, 1.64%, 1.60% and 1.05%, and downward propagation method were 2.48%, 2.39%, 2.30%, 2.11% and 1.57% for RON_88, RON_90, RON_92, RON_95 and IO_100 samples respectively. This study shows that a downward propagation flame has a higher gas temperature with lower velocity compared to an upward flame, which suggests that lower elevation fuel vapor sources at gas stations have a higher fire potential. This research topic is in an effort to provide input on the fire hazards at gas stations that are specific for tropical conditions with traffic practices such as in Indonesia and other countries that face similar hazards and threats. This study can provide input for further transportation safety policies and research.