ABSTRACT
I. INTRODUCTION Sea spray, waterfall spray, the spray from a domestic shower, or indeed any spray of liquid, either naturally or artificially generated, consists of electrically charged drops. Some of the earliest recorded observations of natural spray electrification were made by Elster and Geitel (1890), who detected considerable charge in the vicinity of waterfalls. It is believed that the charged spray and ions emanating from the oceans of the world contribute significantly to the electrification of the atmosphere. In a num ber of industrial situations jets or sprays of various liquids are used to clean down equipment, including the insides of storage and cargo tanks. During tank cleaning a residual amount of the previously stored product is usually present and may produce significant quantities of flammable vapor that can be ignited by electrostatic discharges of quite low energy. For example, a propane/air mixture, which may be present in a fuel oil tank, has a mihimum ignition energy (MIE) of about 0.4 mJ, while naphtha may be ignited by discharges of energy of about half this value. When using liquid jets and sprays from nozzles it is therefore important to have an awareness of certain factors that tend to promote spray charging, so that this can be minimized if necessary.
