FIBC Types A, B, C and D: Static Grounding Requirements for Bulk Bags
A practical guide to how Type A, Type B, Type C and Type D FIBCs control electrostatic charge, and what each type requires for safe use in bulk handling operations.
FIBC static grounding requirements: the short answer
FIBC Types A, B, C and D control static electricity differently. Type C FIBCs must be grounded during filling and emptying. Type D FIBCs do not require a direct bag ground, while Type A and Type B FIBCs have restricted or unsuitable hazardous location use.
- Use the correct FIBC type for the hazard. Bag selection should be based on material MIE, hazardous location classification and site risk assessment.
- Ground Type C FIBCs directly. Connect the bag to a verified ground/ground point and maintain a reliable path during transfer.
- Control the wider electrostatic risk. Nearby conductive items, contaminated bag surfaces and operator procedures all affect safe use.
What are the four FIBC types?
Flexible intermediate bulk containers (FIBCs) are divided into four groups: A, B, C, and D.
Quick comparison: FIBC type vs grounding requirement
The use of these different types of FIBC is set out in the international guidance document IEC TS 60079-32-1:
For more detailed technical background, read Newson Gale’s whitepaper on the theory and practice of controlling static electricity in FIBC operations.
While this may seem complicated at first glance, safe electrostatic grounding procedures for each type of bag can be defined and applied consistently to their use in hazardous location operations.
Type A FIBC: non-conductive bags for non-flammable environments
Type A FIBCs are simple containers made of polypropylene or other flexible, non-conductive fabric.
Due to their non-conductive construction and lack of any means to provide effective electrostatic grounding, Type A FIBCs are not suitable for hazardous location operations.
They should only be used in non-flammable atmospheres with materials that have a Minimum Ignition Energy, or MIE, of greater than 1,000 mJ.
Type B FIBC: low breakdown voltage bags with limited hazardous location use
Type B FIBCs are of similar construction to Type A bags, but are made from flexible materials that have a low breakdown voltage to help prevent propagating brush discharges.
When electrostatic charge builds up on the bag and its contents, the goal is to allow it to discharge in small, frequent static shocks with low energies, rather than build up into one larger discharge that could ignite the materials being handled or the flammable atmosphere they have created.
Beyond this, Type B FIBCs have no designated mechanism to safely dissipate electrostatic charge.
This can work for some materials with higher minimum ignition energies and in some hazardous location zones, but Type B containers are not suitable for lower-MIE materials or certain hazardous location zones.
Image source and licence details: Tesla-coil-discharge.jpg by Iantresman / Caroline Tresman, via Wikimedia Commons. Licensed under CC BY 2.5, CC BY-SA 3.0, and GFDL. No changes made.
Type C FIBC: conductive bags that must be connected to ground
Type C FIBCs are constructed from flexible materials interwoven with conducting threads designed to allow the bag to safely dissipate electrostatic charge when connected to a grounding point.
The nature of this connection to ground is defined by standards and industry best practice:
NFPA 77 and IEC TS 60079-32-1 states that Type C FIBCs are designed to be connected to ground during filling and emptying operations.
NFPA 77 and IEC 61340-4-4 state that a reliable connection to ground must be in place, with a maximum resistance level of 1 x 108 Ω.
This connection is best achieved via a clamp attached to one of the designated grounding tabs built into the FIBC, connecting the bag to a local verified grounding point on site.
Passive vs active FIBC grounding systems
The connection can take the form of a passive grounding solution or an active grounding solution. Passive systems must be manually confirmed by an operator, while active systems add the benefits of continuous monitoring, visual indication via LED displays, and automation of functions such as an automatic shutoff in the event of unsafe conditions through interlocks to process equipment.
An active grounding solution that is well designed in line with the resistance values put forward by the relevant standards and guidance documents also confirms conformance to requirements of the standards and best practice detailed above.
Type C FIBCs are specifically designed for hazardous location operations and must have a suitable connection to ground before and during all hazardous location bulk material transfer operations. In addition, IEC TS 60079-32-1 also recommends that all conductive items within 1m of any FIBC used in hazardous location operations should be properly grounded. These grounding provisions can take the form of permanent, semi-permanent, or removable connections, separate to the grounding solution for the FIBC itself, and can be passive or active.
Type D FIBC: static dissipative bags that do not need direct grounding
Type D FIBCs are constructed from static dissipative material and work on the principle of safely allowing electrostatic charge to dissipate via low-energy corona discharge.
This means that the bag itself does not need its own grounding connection.
Operators should still ensure safe conditions for electrostatic charge dissipation via corona discharge. This includes making sure that the surface of a Type D FIBC does not become contaminated with conductive or flammable materials such as grease before or during operation.
Why conductive items near FIBCs also need grounding
As with Type C or any other FIBCs used in hazardous location operations, any conductive item within a 1m radius of the FIBC when in operation must have its own reliable connection to ground.
FIBC grounding requirements summary table
| FIBC type | Electrostatic grounding requirement | Practical safety measures |
|---|---|---|
| Type A | N/A — No safe electrostatic grounding route. | Not suitable for hazardous location operations. Use only in non-flammable atmospheres and appropriate material conditions. |
| Type B | N/A — No mechanism for dissipating electrostatic charge. | Only suitable for some materials and some hazardous locations, subject to risk assessment. |
| Type C | Direct ground connection required. | Direct connection to a local site grounding point with maximum resistance level of 1 x 108 Ω. |
| Type D | No direct grounding connection for bag. | Charge dissipation occurs via corona discharge into the surrounding atmosphere. |
Which FIBC type is best for hazardous location operations?
When undertaking hazardous location bulk material transfer operations, it is vital to use the appropriate equipment for safe operational procedures.
In practical terms, this means using Type B FIBCs only in certain and limited hazardous location operations when deemed suitable, and using Type C or Type D FIBCs, each with the appropriate electrostatic control measures in place, more generally for hazardous locations.
For Type C FIBCs, this means establishing and maintaining a direct connection between the bag and a local grounding point. For Type D FIBCs, it means ensuring safe conditions for corona discharge and controlling nearby conductive items.
Need help applying FIBC grounding requirements?
Explore practical static grounding guidance or speak to Newson Gale about selecting the right FIBC grounding solution for your application.