Firedamp ignitions

The particular hazard of firedamp ignition relates to the circumstance when a hole fired early in the round breaks the coal at another hole and exposes the explosive before it detonates. This is simulated by firing gallery tests similar to those described above, but with inverse initiation of a... 

Two approaches are now used in attempts to prevent firedamp ignition by explosives. 

Note The safer the expl from the point of view of firedamp ignition, the larger is the "after-flame ratio and the lower duration of flame and its length (See Donarite and Carbonite)... 

Maximum Charge (Charge Umite in Fr) is the max charge of an expl that can be fired in a coal mine without causing ignition of firedamp and/or coal dust in air Ref Marshall 2, 585 (1917)... 

When used in permitted expls Cu tube must be used because A1 might ignite and its flame will cause firedamp explosion... 

Heath and Frost patented in 1877 the use of a water-retaining paste such as soap 5, starch 0.5, glue 0.5 water 94% for tamping bore-holes, loaded with dynamite, in order to prevent the ignition of firedamp Ref Daniel (1902), 371... 

A Commission was appointed in France to investigate the problem of ignition of firedamp. In the report made in 1880, it admitted that there was then no explosive known that would not ignite fire-damp (called coal-... 

Elementary Theory of Ignition 2) Ignition Cartridge 3) Ignition Compositions for use with Pyrotechnics 5) Ignition of Firedamp ... 

J. Taylor W. Young, 30, 4324 (1936) A complicated device suitable for igniting safety blasting explosives without igniting firedamp ... 

References, brief abstracts when available, to studies of firedamp and/or coal dust ignitions explosions, not listed in previous Encyclopedia Vols are given below ... 

H. G. Wolfhard M. Vanpee, Ignition of Fuel-Air Mixtures by Hot Gases and Its Relationship to Firedamp Explosions, pp 446-53 in 7th Symp Combstn (1959)... 

In this writer s opinion, Cook s values (Table 12.20 of Ref 18a) of TCJ are too high and his Pfj are too low the products probably contain more free carbon than shown. However, there is little doubt that most LOX detonations are hot , ie, they will readily ignite firedamp (Refs 2, 3, 12 14). Also the computed detonation velocities (estimated from Cook s PCj) show a much greater variation with compn and density than the experimental data of Table 3... 

C2H2 0.53%. Such a gas can easily form expl mistures with air and, if a source of ignition is available (See Firedamp Explosions), a serious expln can result. A firedamp expln can also stir up coal dust and set off a far more serious coal dust expln (See Coal Mine Explosions and Fires, Vol 3, p C360... 

Firedamp Explosions. Firedamp may be ignited by die flame from an explosive (Ref 2) or detonator (Ref 4), by jets of compressed air (Ref 5), and by friction (Ref 6). Ignition of firedamp by expls is avoided by use of especially formulated expls called Permis-sibles. These expls usually contain inorg salts that absorb heat and thus cool the deton gases. The cooled gases in turn help to choke the flame of the firedamp (Ref 8). The salt may also inhibit chain propagation... 

Flame. Accdg to the Encyclopedia Britannica (1964) 9, 413—16, flame, as a phenomenon of the physical world, is generally understood to be burning gas. Its prerequisite is (he formation of an explosive mixture, eg firedamp and air. If such a mixture is ignited (by spark or small flame), combustion spreads... 

The expls with long, durable flame (as Black Powder) almost always ignite the firedamp, even if the temperature is comparatively low... 

The flames from permissible expls have shorter duration than those of other types and that is the main reason why they are safer to use however, if the charge limit established for these expls is exceeded, there is danger of igniting the firedamp... 

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