Citation

Eckhoff RK, Fuhre K, Pedersen GH. J. Occup. Accid. 1987; 9(3): 161-175.

Copyright

(Copyright © 1987, Elsevier Publishing)

DOI

unavailable

PMID

unavailable

Abstract

The influence of dust concentration and location of the ignition point, on flame propagation and pressure development, has been studied in a series of vented maize starch explosions in a new 236 m3 steel silo, constructed specially for dust explosion experiments. The investigation constitutes a continuation of the experiments in a 500 m3 silo, reported previously. However, the new silo of height 22 m has a diameter of 3.7 m, and thus L/D = 6, whereas the 500 m3 silo had L/D = 4. Explosible clouds of maize starch were generated in the silo by conventional pneumatic injection, either at the top or at the bottom of the silo. Two vent areas of either 3.4 or 5.7 m2, were used.The most explosible dust concentration was found to be 400-500 3. The average minimum explosible concentration was about 100 3.The experiments confirmed that for explosions in large, slim silos, vented at the top, the maximum explosion pressure depends strongly on the vertical distance between the vent and the ignition point further down. Therefore no straight-forward correlation between vent area and maximum explosion pressure exists. Ignition close to the silo bottom generated pressures exceeding 1 bar (g) and flame speeds exceeding 100 , whereas ignition close to the vent at the silo top gave only marginal pressures, of the order of 10-20 mbar (g), and flame speeds of a few .Realistic sizing of vents for slim silos must imply identification of likely ignition source locations and be performed within an overall context of risk assessment.