Many processes and operations in a chemical plant involve handling and processing of liquids and powders, most of which could under certain conditions be flammable. Flammable gas, vapor, and dust cloud atmospheres can be ignited if a sufficiently energetic ignition source is present. It is noteworthy that most flammable gas/vapor atmospheres and some dust clouds can ignite by very small energy ignition sources. One potential ignition source that, in many cases could be an inherent part of the process/operation is an electrostatic discharge. Electrostatic discharges result from the generation and accumulation of electrostatic charges. Electrostatic charge generation most commonly occurs whenever two materials, liquids and/or solids, make and then break contact with each other. The accumulation of the electrostatic charge can result in electrostatic discharges. This suggests that there are many occasions during the transfer, handling, processing, and packaging of flammable liquids and powders in a chemical plant flash fire and explosion hazards exist.
This paper shall discuss the practical measures that can be considered to prevent/control electrostatic ignition hazards that are associated with some common liquid and powder handling/processing operations in the chemical industry.
What is Static Electricity?
Static electricity is the charge that is generated whenever any two contacting surfaces move relative to each other. Static electricity is generated during many common chemical processing operations, such as when liquids flow relative to pipe walls or when powder particles come into contact with the surfaces of the processing and conveying equipment, among other mechanisms.
Contrary to some common belief, static electricity is predictable, quantifiable, and controllable and in fact the predictable and controllable nature of electrostatic charge is used to our benefit in a multitude of applications, including photocopying, air pollution control, and spray coating. There are also many negative instances of static electricity, including electrostatic nuisances, problems, and hazards.