Electrostatic Hazards

When two materials come into contact, electrons transfer from one material to another, causing the surface that acquires an excess of electrons to become negatively charged while the surface that loses electrons becomes positively charged. If the two contacting bodies are separated quickly enough, and one or both bodies remain isolated from ground or are insulating, they will retain their excess charges. In the chemical process industries, electrostatic hazards arise when unwanted or uncontrolled charging occurs, usually the result of a liquid or solid becoming charged by coming into contact with other materials/surfaces. Typical operations in a chemical processing plant that can give rise to electrostatic charging include liquid transfer through hoses and pipes, mixing, settling of two-phase mixtures, filtration, drying, grinding, blending, transfer, and packaging operations. This article discusses electrostatic hazards that may be associated with some common operations involving liquids and powders, and offers suggestions for the control of these hazards.