Bulking Brush Discharges

PLATE 3. Multiple bulking brush discharges on powder bed (time exposure). (From Bartkneeht in Industrial Dust Explosions, ASTM STP 9S8. p. 17S) 

It was initially thought that these discharges only occur during bulking of coarse powders with diameter 1-10 mm, such as pellets [25]. Later work demonstrated that this is not the case although the phenomenon is more frequently observed with coarse powders (6-3.1.1 and 6-4.2.1). 

Tests using vertical cylindrical silos have shown that the charge transferred by these discharges increases with silo diameter [161]. The maximum observed charge transfer Q varied with silo diameter D according to 

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Silo Inlet Neutralizers. Two types intended to reduce the intensity of bulking brush discharges in powder silos are described in [73]. The first is a pointed discharge rod mounted axially inside the filling pipe outlet so that it points upstream into the filling pipe. The second is a... 

As discussed in 2-6.3 and 6-4.2, powder ignition via bulking brush discharge requires the coincidence of several factors, each of which has an associated probability. The minimum conditions are... 

Effect of Particle Size on Bulking Brush Discharges... 

The minimum size of container for bulking brush discharges has not been established, but is probably about 1 m3. Their occurrence in such small containers might require coarse particles such as pellets and therefore represent a hazard only where flammable gas or hybrid mixtures are present. Assuming that the effective energy of the discharges is at the low end of the proposed... 

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