Abstract
Abstract Large-scale wall venting experiments were conducted in the same steel silo of 22 m height, 3.7 m diameter and 236 m3 volume used in previously published roof venting experiments. Maize starch test dust (125 kg), was blown into the silo at the top through a conventional pneumatic pipeline. The dust injection process lasted for 28 s, whereafter the air flow in the pipeline was terminated and the ignition source activated. The dust concentration in the silo was measured during dust injection. Pressure as a function of time and flame speed at different locations in the silo were recorded during each explosion experiment. In the case of an uncovered vent of 4.4 m2 in the cylindrical silo wall close to the silo top, the maximum explosion pressures in the silo were generally considerably lower than with a 3.6 m2 roof vent, and even somewhat lower than with a roof vent of 5.7 m2. Lower turbulence, and hence combustion rate in the dust cloud in the silo, due to more restricted flow out of the vent, may be the reason for this. On the condition that adequate precautions are taken to prevent destructive effects of reaction forces, venting through the silo wall may therefore be preferential to roof venting even from the of view of minimizing the explosion pressure.
Published Version
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