1   Testing of materials for ignition sensitivity to gaseous oxygen impacts

For testing, solid materials are divided and liquids are applied onto ceramic fibers. A sample mass of ca. 0.1 g to 0.5 g is placed into a heatable sample tube of 15 cm³ in volume.

The sample tube is connected by a pipe and a pneumatically operated quick opening valve to a high-pressure oxygen accumulator. After the pipe and sample tube are at initial pressure p_a (generally ambient pressure) and the sample has reached the test temperature, the quick opening valve is opened and preheated oxygen (generally 60 °C) of final pressure p_e flows abruptly into the pipe and sample tube.

In this way, the oxygen in the sample tube is almost adiabatically compressed from initial pressure p_a to final pressure p_e and heated. A possible reaction of the sample with oxygen is indicated by a steep temperature rise in the sample tube.

If there is a reaction, further test series are performed at a lower pressure ratio p_e/p_a until the compression ratio is found, where no reaction of the sample with oxygen can be detected in a series of five consecutive gaseous impacts. If this result is confirmed in a second test series of five consecutive oxygen impacts, the tests can be finished or continued at a different test temperature.