Dynalene provides autoignition temperature testing in accordance with ASTM E659 for liquid and solid chemicals up to 750°C. A chemical’s autoignition temperature is the lowest temperature at which it will spontaneously ignite under normal atmosphere without an external source of ignition.
As the temperature of the chemical increases, the concentration of chemical vapors increases as does their kinetic energy. When these high-energy vapors mix with oxygen they can cause combustion even if no spark or flame is present. It differs from flash point temperature in that flash point requires a flame to ignite the vapors and the autoignition temperature occurs at a much higher temperature. Below is a list of some common chemicals and their autoignition temperatures (flash point is also there for comparison):
|Chemical||Autoignition temperature||Flash point temperature
|Mineral oil||330 – 350°C||100 – 150°C
|Wood||300 – 320°C||260 – 280°C
|Gasoline||245 – 280°C||-43°C
Autoignition analysis is very important for determining the safe handling and storage procedures for chemicals. In chemical processing systems the chemical is unlikely to reach its autoignition temperature is unlikely to be reached in properly designed systems. A situation where this could potentially happen is if something like a flammable liquid began leaking out of a pipe and landed on a heater. If the surface temperature of this heater was above the autoignition temperature of the fluid, the fluid will spontaneously combust (if there is oxygen present).
In some operations you may see a process operating above a fluid’s flash point, however these systems take extra precaution to ensure there are no leaks or ignition sources nearby. The chemical vapors would also have to be trapped in a confined space to reach a certain concentration near the ignition source. You would never see a fluid process that operates close to or above the autoignition temperature.
Dynalene’s autoignition instrument
We use a Kohler 47000 Autoignition Apparatus to perform autoignition testing. It can perform autoignition analysis between ambient temperature up to 750°C. The temperatures at which ‘cool flame’ and ‘hot flame’ ignitions occur, as evidenced by sudden temperature increases in the sample flask, are measured and recorded, and the delay time between introduction of the sample and ignition is timed.