Dust explosions Calculations

Dowtherm(R) pressure drop, charts, 94,113 Draft tubes, mixing, 309, 313 Dust clouds, 517 Dust explosions, 513 Calculations, 513 Dust separator, applications, 278 Characteristics, 234 Table, 232... 

Explosion calculations, 499-504 Estimating destruction, 501 Overpressure, 502 Pressure piling, 501, 504 Relief sizing, 505 Scaled distance, 502, 503 Schock from velocity, 503 TNT equivalent, 499-504 Explosion characteristics of dusts, 515 Explosion suppression, 518 Explosion venting, gases/vapors, 504 Bleves, 504 Explosions, 482 Blast pressure. 496 Combustion, 482 Confined, 482 Damage, 498-501 Deflagration, 482 Detonation, 483... 

As the loading density of a powdered solid explosive is reduced the detonation velocity becomes less. This follows from equation (5) of Chapter 2, asp2 is smaller the lower the density. Calculation shows that at the lowest densities the detonation velocity tends towards a limiting lower value, typically about 2000 m s-1. This is also the detonation velocity in a dust explosion of these substances. 

The finely powdered silicide is a significant dust explosion hazard [1]. The lower explosion limit for a calcium-silicon dust cloud of mean particle size 9.7 pm was measured as 79 g/m3, in good agreement with a calculated value [2], Other dust cloud parameters are presented and related to predictions [3],... 

The maximum explosion pressure and maximum rate of pressure rise values are determined by using the 20 L sphere apparatus. The dust sample is dispersed within the sphere, ignited by chemical igniters, and the pressure of the resulting explosion is measured. The sample size is varied to determine the optimal dust cloud concentration. The maximum pressure and rate of pressure rise are measured and used to calculate the explosion severity (Kst) value of the dust cloud. These data can be used for the purpose of designing dust explosion protection measures. 

The violence of the confined explosions (flammable v apor, gas, and dust) can be calculaled by the e.xplosion pressme mid energy eqmitions introduced earlier. The behavior of flammability (or e.xplosivity) limits of flammable mixtures and dusts is also covered in preceding sections. 

Dusts, particle sizes, 225 Dusts, hazard class, 521-523 Explosion characteristics, 524 Efficiency, centrifugal pumps, 200 Ejector control, 380 Ejector systems, 343, 344, 351 Air inleakage, table, 366, 367 Applications, 345 Calculations, 359-366 Chilled water refrigeration, 350 Comparison guide, 357, 375 Evacuation lime, 380, 381 Charts, 382 Example, 381 Features, 345... 

Dust samples were collected by the probe/filter configuration shown in Figure 2. The filter used to trap the explosive dust was a 37mm plastic filter cassette. To monitor the actual flow rate, a rotometer was used. The calculation for each traverse point dust concentration was obtained from... 

The theoretical calculation of the detonation temperature as a safety criterion was adopted only in France. In all other countries (and more recently also in France) a practical criterion has been introduced based on an experimental evaluation of the effect of explosion of a sample of the explosive on a mixture of air and methane, or on a suspension of coal-dust in air, under conditions similar to those existing in mines. For this purpose testing galleries were devised, simulating the conditions of mine galleries. 

The following empirical equations, Eqs. (23-15) to (23-17), allow the calculation of the size of a vent area A for combustible dust-air-mixture explosions. 

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