Ignition risk due to electrostatic discharges obtained from small scoops

Abstract

Small scoops such as might be used to handle powders were tested by rubbing with materials based on IEC 60079-32-2 and also by scooping a sample material (glass beads). Discharges from the scoops were evaluated against the criteria given in IEC 60079-32-1. Although the projected areas of the scoops were less than 10000 mm², ESD with charge transfer greater than 25 nC or 60 nC were regularly obtained. Tribocharging the scoops based on the IEC 60079-32-2 test gave charge transferred in discharges greater than when charging by scooping glass beads. It is concluded that some risk of ignition could occur to near optimum flammable atmospheres from Group IIA and IIB materials.