There are four types of fabrics used in the construction of bulk bags:
Type A Bulk Bags & FIBCs
The majority of Bulk Bags and FIBC’s are produced from type A fabric. This type of bag is produced from standard woven polypropylene fabric that has no static protection. This type of bulk bag should not be used in an environment where there is an air dust mixture or explosive gas or flammable solvent atmosphere.
Type B Bulk Bags & FIBCs
Type B bulk bags are again produced from non-conductive woven polypropylene fabric having a breakdown voltage not exceeding 6kV. Like type A bulk bags they also cannot be considered as anti-static bulk bags as they do not have a mechanism for removing electro charge from the bag.
The fabrics used in type B bulk bags have a low breakdown voltage preventing the occurrence of propagating brush discharges which can ignite an air dust mixture, however explosive gas atmospheres can still be ignited.
Type B bulk bags are used to safely store and transport dry flammable powders.
Type C Bulk Bags & FIBCs
Type C Bulk Bags and FIBC’s are normally produced from non-conductive woven polypropylene fabric with interwoven conductive threads forming a connected grid that is maximum 50mm mesh size that have a distance between each other of no greater than 200mm if the threads are in one direction only.
Conductive threads are then grounded during the filling and discharging of the Bulk Bag. When grounded correctly there is no risk of incendive discharges.
Type C bulk bags are used in environments where there is an air dust mixture as well as explosive gas atmospheres.
Type D Bulk Bags & FIBCs
Type D Bulk Bags and FIBC’s are produced from non-conductive woven polypropylene fabric with conductive fibres that are not connected to each other. This type of Bulk Bag is not conductive but dissipates charge into the environment through corona discharge.
These Bulk Bags can be treated with antistatic coating reducing the surface resistance of the fabric.
Because the electro-charge is dissipated through corona discharge this type of bulk bag can charge conductive objects and operatives nearby. These objects or people can then cause electrostatic sparks with contact with grounded objects that could ignite air dust mixtures or explosive or flammable gas atmospheres nearby.
When filling or discharging a Type D Bulk Bag or FIBC in a hazardous area all conductive objects or people nearby must be grounded during the filling and discharge process.
Instructions for grounding will be printed on the label of a type D bulk bag.
Bulk Product: MIE (Minimum Ignition Energy) of Dust
Explosive Dust Atmosphere
Explosive Gas and Vapor Atmosphere
MIE > 1000 mJ (mega Joules)
1000 mJ ≥ MIE > 3 mJ
MIE ≤ 3 mJ