Electrostatic Hazards Associated with Powder Handling in Silo Installations

Pneumatic delivery and general movement of powdered products inevitably results in some degree of charge separation between the product and its containing walls. Unlike electrostatic charging associated with high-velocity pumping of insulating liquids, where addition of an antistatic additive is a standard means of quenching the charge, the situation is a little more difficult to control with powder. There is as yet no antistatic additive commercially available for powders, and therefore the standard procedure of grounding all plant hardware does not give sufficient protection against charge accumulation. The powder itself, will still emerge at the end of the delivery sequence in a highly charged state, and it is this which usually results in a potentially hazardous situation. A case study on a powder handling silo installation following a severe explosion during filling operations is described.