Observation of propagating brush discharge on insulating film with grounded antistatic materials

A propagating brush discharge (PBD) usually occurs on a highly charged thin film with a grounded metal backing plate and often becomes energetic enough to ignite a flammable gas/vapor and even a dust cloud. In an actual situation, a PBD is seen on the surface of a large-sized flexible intermediate bulk container (FIBC) during its filling and/or emptying processes in an industrial site when the fabric of the FIBC is highly insulating. Anticipating that a PBD could occur even on an antistatic FIBC if it were used with an insulating inner bag, various types of antistatic fabrics for FIBCs in contact with an insulating polyethylene terephthalate (PET) sheet were put to the test. An antistatic fabric was grounded, and the PET sheet on the fabric was charged with a corona charger. A PBD was then generated by approaching a grounded spherical electrode. The discharge patterns were observed, and the currents and charge amounts were measured. A thin metallic fiber woven on an insulating fabric was found to drastically enhance the transferring of charge during a PBD, probably because of the corona discharges emanating from the metallic fiber. The resistivity of the fabric also affected the charge transference. The incendiary nature of each mode of PBD was discussed.