Transferred charge of brush discharges in explosive gas atmospheres – A verification of the ignition threshold limits

A wide series of experiments has been performed to check the incentivity of hydrogen/air, ethene/air and propane/air mixtures due to brush discharges. Thereby, the transferred charge as a criterion to judge the ignition potential is determined to verify the thresholds of transferred charge given in the standards IEC 60079-0 and in EN 13463-1. These thresholds have never been examined directly in an experiment before. It is stated that the thresholds for explosion group IIA, IIB and IIC represent different levels of safety. Using adequate thresholds the criterion of transferred charge is suitable for a judgement of potential electrostatic ignition sources.

► Probability of incendive brush discharges increases with amount of transferred charge.
► The current transferred charge thresholds represent different levels of safety.
► The ignition process is very much affected by statistics.