Interconnected Conductive Threads
Dissipates Charge to Ground
RG < 107 ohm
Do not use:
Type C FIBC are also known as conductive FIBC or groundable FIBC. Originally they were made from entirely conductive materials. Today, groundable Type C FIBC are more commonly made from non-conductive polypropylene interwoven with conducting yarns, normally in a grid pattern. The conductive yarns must be electrically interconnected and connected to designated ground or earth bonding points. The ground or earth bonding points must in turn be connected to a system ground or earth during all bulk bag filling and emptying operations.
The interconnection of conductive yarns and the connection to ground or earth are critical to the safe use of Type C FIBC. The interconnection of conductive yarns throughout the bulk bag is achieved by correctly sewing together the panels of fabric that make up the groundable bulk bag. Sewing is a manual operation, as is the connection of the groundable bulk bag to a system ground or earth. As with any manual operation, ensuring interconnection and grounding of Type C FIBC is subject to human error.
|Inside FIBC||Atmosphere Surrounding FIBC|
|Non-Flammable Atmosphere||Explosive Dust Atmosphere||Explosive Gas or Vapour|
MIE > 1000 mJ
|A B C D||B C D||C D|
|MIE 3 mJ to 1000 mJ||B C D||B C D||C D|
|MIE < 3 mJ||C D||C D||C D|
|FIBC Type A||FIBC Type A are made from non-conductive fabric and provide no protection against static electricity.|
|FIBC Type B||FIBC Type B are made from non-conductive fabric. They differ from FIBC Type A in that the breakdown voltage through the fabric, including any coating, shall be low enough to prevent propagating brush discharges.Spark discharges may occur from the surface of FIBC Type B if they become contaminated or coated with conductive material (e.g. water, grease or oil). Precautions should be taken to avoid such contamination and to avoid conductive objects such as tools or metal clips being placed on the FIBC.|
|FIBC Type C||FIBC Type C are made entirely from conductive fabric or from a non-conductive fabric with interconnected conductive threads or filaments. The pattern of conductive threads or filaments is either:a grid enclosing an area of non-conductive fabric no greater than 25 cm2,
or a 20 mm stripe, in which case each thread or filament must be interconnected at two separate places (usually at both ends).
FIBC Type C must be provided with a grounding point to which all conductive panels, threads or filaments are electrically bonded. The resistance to the grounding point from anywhere on a conductive fabric and from conductive threads or filaments must be less than 108 ohm (updated to less than 107 ohm in the second edition of IEC 61340-4-4 – see below).
The lift loops of FIBC Type C must also contain conductive threads or filaments with a resistance to the grounding point of less than 108ohm (updated to less than 107 ohm in the second edition of IEC 61340-4-4 – see below).
FIBC Type C must also meet the breakdown voltage requirements of FIBC Type B.
In order to prevent spark discharges that might ignite a flammable or explosive atmosphere, it is essential that FIBC Type C are always securely grounded. A label should be attached to the FIBC indicating the position of the grounding point(s) and clearly stating the requirement for grounding. Ungrounded people may become charged through normal activity and could then discharge to ground when touching Type C FIBC. It is essential to follow normal safe practice and ensure that all conductors, including people, are grounded in the presence of flammable or explosive atmospheres.
|FIBC Type D||FIBC Type D are made from fabric that allows charge to be dissipated without being connected to ground. FIBC Type D fabrics usually contain conductive threads or filaments that dissipate charge safely into the atmosphere by low energy corona discharges. Some FIBC Type D have low resistivity coating that may reduce the risk of incendiary discharges.Grounding of FIBC Type D is not required.
To be qualified as safe for use in the presence of flammable or explosive atmospheres it must be first demonstrated that FIBC Type D do not produce incendiary discharges under realistic conditions.
Note: The conditions and procedures of test used to demonstrate the absence of incendiary discharges are specified in the draft IEC 61340-4-4.
FIBC Type D must also meet the breakdown voltage requirements of FIBC Type B.
Ungrounded conductors such a metal drums or people may become charged when positioned close to some FIBC Type D. It is essential to follow normal safe practice and ensure that all conductors are grounded in the presence of flammable or explosive atmospheres.
Spark discharges may occur from the surface of FIBC Type D if they become contaminated or coated with conductive material (e.g. water, grease or oil). Precautions should be taken to avoid such contamination and to avoid conductive objects such as tools or metal clips being placed on the FIBC.