2020 Volume 13 Issue 1 Pages 57-63
Powder handling operations are conducted to support our daily lives and industrial society. However, industrial accidents caused by electrostatic charges or/and discharges on powder still happen along with the use of insulating flexible intermediate bulk containers（ FIBC）. This paper examines the surface voltages of charged FIBC along with the electrostatic discharges generated from charged FIBE during powder loading and unloading. A conveyor type test facility including FIBC and about 300 kg of polypropylene powder（ PP, 2 mm） was used for this test. As a result, the maximum surface voltage exceeded 100 kV during both loading and unloading. As for the polarity, the charge was negative during loading and positive during unloading in this study. The surface voltage decreased with increasing relative humidity, However, even at above 75% humidity, about -50 kV with loading（ about 45 kV in unlading） still remained, which still does not meet the safety level. In the case where the grounded metal spheres approached the charged FIBC, the maximum discharge amount of electrostatic （brush） discharges was above 200 nC, which may ignite combustible liquids and very sensitive powders.
