Application of flammability limit criteria on non-ASTM standard equipment

Accurate data of flammability limits for flammable gases and vapors are needed to prevent fires and explosions. The flammability limit, which is the maximum or minimum fuel concentration at which a gas mixture is flammable in a given atmosphere, has been studied for decades. However, due to differences in measurement conditions and equipment used, the flammability values exhibit significant variations, especially at elevated temperature and pressure. In this study, the flammability limits of methane-air were measured in a closed cylindrical vessel with upward flame propagation at a maximum initial temperature of 300 degrees C and a maximum initial pressure of 2atm. The combustion behavior and flame propagation properties are compared using different flammability criteria. Test results have shown that 7% pressure criterion is a conservative standard that can be applied for nonstandard vessel flammability test. Also, experimentally measured values are compared with existing data in the literature to study the influence of temperature, pressure and apparatus. In consideration of safe usage and storage, for each flammable gas substance at elevated condition, experimentally determined values should be used rather than extrapolated ones using estimation correlations.