Reportedly static electricity causes an average of 280 industrial incidents each year in the US alone. Additionally, static electricity is responsible for at least two serious industrial fires or explosions every day of the year somewhere in the world. Many companies see good reasons to implement protection measures in order to:

Static electricity can build up in a wide range of industrial situations where there is friction between two things made of different materials or substances. It can also be generated by repeated contact and separation between dissimilar materials.

Static charges can build up in certain liquids; for example, petroleum-based solvents and fuels such as benzene, toluene, mineral spirits, gasoline and jet fuel when the liquid flows through pipes, is poured, pumped, filtered, or agitated. When liquids are transported or handled in non-conductive containers, something brushing the outside surface of the container may cause an electrostatic charge to build up in the liquid. Generally, the amount of static charge that develops depends upon the quantity of liquid, how fast it is flowing, turbulence in the liquid, and the presence of impurities.

Non-conductive liquids tend to hold a charge because they do not conduct electricity well. Therefore, even when in contact with a conducting material, like a grounded metal pipe or container, the bound charge is not adequately dissipated. Conductive solvents may build up a charge in plastic or glass containers because the containers decrease the rate at which the charge in the solvent would otherwise dissipate. When enough charge is obtained, a difference in electrical potential can develop, and a spark may be produced. If the vapor concentration of the liquid in the air is in the “flammable range” and the spark has enough energy, a fire or explosion can result.

Typically, the conditions for igniting a liquid are most optimum when the liquid is at a temperature that produces surface vapors with air concentrations in the middle of its upper and lower flammability limits.

Depending upon the environment, static electricity might be a simple nuisance or constitute a major hazard. In an environment where the relative concentration of fuel and oxygen is in a flammable range, any spark, or “Electrostatic Discharge” (ESD), having sufficient energy may cause a fire or explosion. Flammable and combustible liquids can present a static electricity hazard depending upon their ability to generate static electricity, their electrical conductivity, and their flash point.

Typical processes at risk within flammable/combustible gas, liquid vapor or dust (powder) atmospheres: