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 pa (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 pe flows abruptly into the pipe and sample tube.
In this way, the oxygen in the sample tube is almost adiabatically compressed from
initial pressure pa to final pressure pe 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 pe/pa
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.