2. Experimental
The Hartman explosion tube was used mainly to test the explosibility of dusts
because of the possibility of exchanging gas in the explosion tube. Great attention
was paid to form as homogeneous a dust cloud as possible. The tapping sieve
apparatus [5], which is regarded as optimum for producing a homogeneous dust
cloud, was used to confirm the explosive concentration by the Hartman explosion
tube. A high-voltage transformer for the Hartman tube (output voltage : 15 kV,
output current : 20 mA) was used to measure the explosive concentration, with a
discharging period of a few seconds. Test dusts used was polyurethane, plastic, etc.,
which were collected during the recycling of refrigerators and other appliances.
For the investigation of explosibility of dust-flammable gas mixture, the gas in the
experimental system was replaced by pre-mixed gas with a specific concentration
value. Cyclopentane was used as a sample gas, because cyclopentane is widely used
to foam insulating material. The ignition temperature of the dust cloud was
measured by a modified Greenwald–Godbert furnace. Minimum ignition energy was
measured by using a single pulse generator.