Flash Point Fire Point Auto Ignition Temperature

three major technical terms describe flammability conditions in hydrocarbon liquids in their vapors flashpoint fire point and auto ignition temperature flashpoint defined the lowest temperature at which a heat in liquids vapor air mixture can be ignited flashed by a flame or spark or other ignition source placed above the liquid surface fire point defined the lowest temperature at which a heat in liquids vapor air mixture will burn continuously when combustion is supported by ignition sources such as the above auto-ignition temperature defined the lowest temperature at which a heated liquids vapors and air will say finite and burn without exposure to any ignition source flash point and fire point testing the liquid to be tested as heated in a cup and the rising liquid temperature is continuously measured a small flame is mechanically passed back and forth just above the surface of the liquid as the liquid gets hotter more of it evaporates causing the fuel-air mixture above the liquid to gradually become richer when the lower flammability limit is reached the ignition source will ignite the vapor air mixture causing a pop the observed temperature when the flame momentarily ignites the vapor air mixture is the flashpoint the ignitions repeat as the liquid temperature continues to rise the observed temperature when the burning becomes continuous is the fire point auto ignition point testing liquid is heated but without an ignition source when the vapor air mixture reaches a temperature sufficient to self ignite the observed temperature is the auto ignition point for a flash point related fire to occur all three conditions must be met vapor concentration these combustion tests allow vapor to concentrate in real life the vapors turn to smoke as they encounter air and dissipate temperature thermal oils cool rapidly when exposed to air source of ignition thermal fluid leaks are difficult to ignite unless a significant amount of very hot fluid leaks into a closed area where inadequate ventilation allows unreacted Vapor to collect and mix with air an exception occurs when fluid leaks onto an extremely hot surface such as the housing of a pump that is failing or a rotary union that has seized technically this is not a flashpoint related problem but one of auto ignition heat transfer fluids and closed-loop systems whether natural or synthetic are routinely used well in excess of their flash and fire points but never above their auto ignition points

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