- Method ASTM D93/ASTM D56
- Repeatability below 140° F 2.0
- Reproducibility below 140F 8.0
- Blending non-linear
- Additive Correction No
When heat is applied to a petroleum product it will eventually reach a point where it starts to boil and turn from a liquid to a flammable gas. The flash point is the first point at which there are enough of these flammable vapors present to be ignited when a flame or heating element is introduced to the air/vapor mixture.
Both D56 and D93 methods are closed cup flash methods. In these methods sample is poured into a sample cup and placed into an instrument that seals the sample from the outside air around it. The sample cup is then heated. Once it reaches a temperature where the flash point is expected to be the cup is opened and an electric igniter or flame is dropped into the cup. If the mixture does not light it closes and continues heating until the instrument checks again. Once the sample is ignited the instrument will record the flash point and stop. The major differences between D56 Jet fuel flash and D93 Diesel flash is the use of the stirrer. In D93 a stirrer is used and in D56 it is not.
There are other methods of flash that use open cups. These are used to test high temperature flashes such as lube oil. In these methods the sample is heated and the flame is passed over the sample until the top catches on fire.
Flash testing is very important to determine how the products should be handled when shipping, storing, or using them.