A coal dust explosion occurs when, by some means, a combustible concentration of coal dust is lifted into mine roadways and ignited.

For example, the ignition of a small quantity of methane gas generates a pressure wave which lifts coal dust that has accumulated on the roadway surfaces into the air. The associated methane flame ignites the coal dust.

Without some means of limiting the reaction, coal dust will continue to lift and burn and creating an even larger pressure wave, and a coal dust explosion propagates through the mine.

This behaviour can be seen in the images below. The explosion was staged in a surface gallery about 150m long. There is an initial methane explosion which lifts coal dust into the air which is ignited (frame 3) The ensuing explosion propels dust into the air and out of the tunnel mouth and ignites the airborne coal dust. The coal dust burns and drives a pressure wave ahead of itself causing more dust to be ejected from the tunnel and eventually burning all the way out of the gallery.

Passive explosion barriers generally consist of some form of framework upon which loose stone dust is placed or water tubs are suspended. The successful operation of any passive barrier is dependent on the explosion pressure and time delay between arrival of pressure front and flame at barrier site to distribute the inertant into the flame. Traditional stone dust shelf and water trough passive barriers require high triggering pressures to operate, and this why they will not stop a methane only explosion.

The SkillPro-CSIR bag barrier has been subjected to extensive testing in Germany, the USA and South Africa

At Tremonia Mine in Germany, the bag barriers were tested in a full scale gallery against a wide range of explosion conditions. The images below show the bag barrier in operation in an underground explosion gallery.

Note the development of the initial methane explosion as it expands from the point of ignition (frames 1 to 3) The flame ignites coal dust which becomes involved in the explosion (Frame 4) and is then extinguished by the barrier (frame 5)

The bag barriers can be seen in the foreground silhouetted against the flame and the effectiveness of the barrier is evident when the flame is extinguished.

At the Lake Lynn Experimental Mine in the USA the bag barriers were tested in a number of configurations in a multiple heading mine layout, the first time that an explosion barrier has been tested in this way

The area of the mine used for explosion testing of the Bag Barriers consisted of three headings joined by seven cut-throughs

Testing commenced with a Base Case Explosion where the flame extension was measured. Subsequent tests measured the reduction in flame extension as the more barriers were installed in various configurations. This test work has been comprehensively documented by CSIR and SkillPro.

At Kloppersbos in South Africa where the bag was originally developed extensive preliminary testing was undertaken on the initial design and continues today to ensure the quality of the product.