Risks of ignition from ‘Type D’ ungrounded fibc

Avoidance of risks of ignition with unearthed Type D FIBC requires that electrostatic discharges cannot quickly access large quantities of charge via any conductive features of the material. The present studies show how the effective resistivity of conductive features within FIBC type fabrics can be measured, without electrical contact, from the variation of shielding performance with frequency. From such measurements an empirical acceptance criterion has been derived that matches well to the results of gas probe ignition tests. Studies are proposed to provide reliable criteria for assessing FIBC Type D bag materials and to help optimize FIBC fabric design.