Page 523 - Dust Explosions in the Process Industries

490 Dust Explosions in the Process Industries

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Figure 7.1 3 Silicon dust explosion in the welding
torch ignition test apparatus used in Norway. For a
much clearer picture, see Color Plate 9.

objective, no matter which test it is. Then, further, more specific testing may be required.
The various methods used can be grouped in three main categories:
Tests for ignition sensitivity of dust deposits and clouds.
Tests for limiting conditions for flame or glow propagation in dust clouds and deposits.
Tests for maximum rise and rate of rise of explosion pressure in dust clouds.
Before discussing the various test methods, however, some special tests concened
with evolution of explosible gases from heated dusts should be mentioned.

7.6
CAN HAZARDOUS QUANTITIES OF EXPLOSIBLE
GASES EVOLVE FROM THE DUST DURING HEATING?

7.6.1
THE INDUSTRIAL SITUATION

If the oxygen supply is limited, which often is the case if smoldering takes place in large
powder deposits in closed vessels, CO and other combustible gases can be produced,
which can mix with the air and form an explosible gas cloud above the powder deposit.
If the smoldering fire propagates to the surface of the powder deposit, the gas mixture