Chapter 13 - Static electricity

Abstract

The basic concept of static electricity is the generation of an electrical charge after two bodies are brought into close physical contact and then separated, for instance, a belt running over a pulley. When two bodies, particularly when they are of different materials, are brought into close physical contact a redistribution of electrons in the bodies occurs, causing the bodies to produce an attractive force. When the bodies are separated, a counter force is created and appears as energy between the bodies causing them to be charged. The charges appear as a potential difference or a voltage between the two bodies. The voltage so obtained is the result of numerous physical contacts and separations. One body will become positively charged because it is left with an excess of protons and another will become negatively charged because of an excess of electrons. If the body has sufficient energy a spark may occur and if the spark occurs in the presence of a flammable vapor-air mixture, ignition may result. The ability of a spark to produce ignition is mainly a function of its energy. The possibility of a spark is reduced when the loading product consists of crude oil or Class II and Class III flammable liquids. However, for a rapid reduction of such accumulated charges, all equipments used in a hazardous area should be adequately bonded and grounded.