

Coal Dust

Coal Dust Was Slowly Being Realised

In an underground explosion the blast preceding the flame kicks up the dust from the roof, floor and sides and while it is suspended in the air it is ignited by the following flame and this carries on as long as there is dust to supply it. Burning of the coal dust uses up the oxygen in the atmosphere and the incomplete combustion produces a deadly carbon monoxide.

At the beginning of the 19th century, coal dust was slowly being realised and there was reference to the explodablity of coal dust in several reports including that of the celebrated North of England viewer by the name of Buddle on the Wallsend explosion of 1803 and that of the Reverend John Hodgson describing the Felling explosion of 1812 where 92 men and boys were killed, the boys being 7 and 8 years of age.

More emphatic and detailed is the description of Lyall and Farriday on the Haskell explosions of 1844. These were scientists of their day and they stated, "In considering the extent of the fire at the moment of the explosion it is not be to supposed that firedamp was the only fuel,- the coal dust, swept by the rush of flame and wind from the roof, floor and walls of the workings would instantly take fire and burn if there was enough oxygen in the air present to support its combustion".

Dickinson, in his report of the Ince colliery explosion of 1854 stated, "As the workings were very dry they would be aggravated by coal dust raised by the blast".

Another interesting reference was made by two colliery managers at the inquest following the Winstay explosion of 1873 when they said in their evidence that coal dust would be ignited by firing a shot, and incidentally investigations were also going on in Europe with the same conclusions.

In 1875 Galway commenced experimental work on the explosability of coal dust. First he demonstrated that mixtures of firedamp and air containing less than 1% of firedamp became inflammable when charged with fine coal dust.

Later investigations of certain colliery explosions disclosed the dominant part that coal dust had played in them. Midlands experiments were reported before the Chesterfield and Derbyshire Institute of Mining in 1878 "Explosions of coal dust and air were obtained in the absence of firedamp" and this increased activity led to the problem being considered more seriously.

In 1879 the Royal Commission of Accidents was appointed and attention was directed to the coal dust problem, after the Seaham explosion in 1880 the problem assumed great public importance. The Government sanctioned official experiments and the first mention of stone dust to conduct the inflammability of coal dust was mentioned. Mr. Atkinson, H M Inspector of Mines, the same one that conducted the 0ld-Sal inquiry, stated on this experiment that the intake traveling way was not damaged by the explosion but the parallel haulage road was completely wrecked. The difference in effect he attributed to the presence of stone dust in the traveling road and this foreshadowed the future methods of combating this problem.

At the Elmore colliery explosion in Durham in 1886 Atkinson said he believed the explosion to be entirely due to coal dust combustion in pure air. He suggested that concussion caused by a shot raised the cloud of dust which was ignited by the issue of a flame at the same moment, and that same day Atkinson with his brother, who was also a mines inspector, published the results of their investigations in a book called Explosions in Coal Mines which also incorporated Galway's and other scientists' views. On that evidence all senior management would be aware of the potential hazards of coal dust.

In those days, safety was often diluted in the pursuit of profit and at the Mossfield Colliery inquiry it was stated that the Cockshead seam was a dusty seam and in both the intake and return roads it was about 2 or 3 inches deep on the floor. The men had used water to lay the dust until Mr. Potts had objected because this made the floor heave up and lift and of course this had to be repaired and this added costs to production. He had also reduced the number of men doing repairs in the pit to cut costs and in the Bambury seam the dust was only removed when it covered the rails and wagons of coal could no longer run so if it was preventing production they cleared it up and it was due to these conditions that the 37 victims died, not by the direct violence of the blast but from its toxic effects.

In the Mossfield colliery explosion of 21st March 1940 in which 11 miners were killed. The inspector's report stated, "The loss of life in the 1889 explosion was catastrophic compared to the present occurrence. There is little or no doubt that this was because that explosion was propagated by coal dust there is also little doubt that the effects of the recent explosion would have been greatly magnified but for the fact that the roadways were copiously treated with stone dust". As it was, the explosion was limited both in extent and violence.

(Stonedust :- Crushed limestone (calcium carbonate). The ignition of naturally occurring methane gas is serious enough, but if this propagated a coal dust explosion then the consequences could be devastating throughout the mine. To help reduce the risk of this happening stone dust was introduced, the idea being that it would provide a concentration of suspended dust particles in the path of the flame of an explosion, it was hoped that this would reduce temperatures and arrest an explosion.)






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