Cone discharge


Procedures involving non-conductive powder can cause ignition sources by electrostatic cone discharge when large quantities of powder are processed. If initial analysis shows the possibility of incendive cone discharges, measures for prevention exceedingly high electrostatic charging are usually implemented. The video below shows numerical analysis of the filling of a container in the event when electrostatic field above the powder heap rises to the value of 3 kV/mm, meaning that cone discharges may be expected.


Electrostatic field inside earthed metal container during the introduction of low conductivity powder. When this process is fast, electrostatic field above the heap rises to a hazardous level of 3 kV/mm (the colour red represents electrostatic field of 3 kV/mm or more, orange 2 kV/mm, green 1.5 kV/mm, blue 1 kV/mm and white below 0.5 kV/mm; grey surface represents upper level of the powder heap). Note that after the filling procedure is finished, the strength of the electrostatic field starts to decrease due to slow relaxation of electrostatic charge to the earth. Video is time lapsed.

 

Numerical simulations help assess hazards during procedures and ways to avoid them. The video below shows a situatuion where the filling procedure is appropriately slowed down, so that the strength of th electrostatic field doesn't reach a hazardous level.


Same data as above, but with slower loading of container. Strength of the electrostatic field above the powder heap remains below 3 kV/mm.