The amount of sample required:
The procedure of the measurement
Checking the homogeneity of the tested powder sample and its compliance with the standard requirements.
During the test, the powder layer shall be placed in a metal ring with an internal diameter of 100 mm in a layer of 5±0,1 mm.
To perform the test, it is necessary to adjust the temperature of the heated surface to the desired value and to reach a steady state. The metal ring should be placed in the center of the surface and the powder layer described above should be formed in 2 minutes.
If no auto-ignition is detected after 30 minutes, the test should be terminated and repeated at a higher temperature. All tests must be performed with a fresh layer of powder.
If inflammation or spontaneous combustion is observed, the test should be repeated at a lower temperature. The result of the test is the temperature at which ignition or spontaneous combustion is still present, but not at a temperature 10 K lower. This needs to be confirmed by at least three tests. If no inflammation is observed at 400 °C, the test must be repeated at 200 and 300 °C to confirm the non-inflamed result.
Limitations of the test
The standard test examines 5 mm layers (thicker layers may result in lower values).
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