Consulting
Litigation Support
Laboratory Testing
Learning with Stonehouse
Training Topics
Consulting
Litigation Support
Laboratory Testing
Learning with Stonehouse
Training Topics

Search

January Safety Feature: Safe Use of Flexible Intermediate Bulk Containers (FIBCs) – Requirements of NFPA 652

Safe Use of Flexible Intermediate Bulk Containers (FIBCs) – Requirements of NFPA 652

 

Both users and manufacturers of FIBCs need to take action to prevent dust explosions caused by static electricity

A dust cloud of fine explosible particles in air with a concentration that is above its minimum explosible concentration (MEC) can be expected at some point when FIBCs are filled or emptied. The dust cloud could occur inside the bag – or even external to the bag in some cases. What’s more, movement of powder to the bag, inside the bag, or on emptying, can generate static electricity. The combination of static electricity and a flammable dust cloud can result in an explosion or deflagration (flashfire) putting people and the plant at risk. It should be no surprise, therefore, that FIBCs need to be type tested to avoid the electrostatic ignition risk – and that users are required by NFPA 652 to include FIBCs in their Dust Hazard Analyses (DHAs).

The amount of static generated and whether or not it accumulates on the bag or the powder, resulting in incendive discharges, depends on the properties of both the FIBC and the powder itself. It is therefore critical to ensure the correct type of FIBC is selected for the specific powders and circumstances in which it is to be used.

NFPA 652 requires that your Dust Hazard Analysis (DHA) must include the electrostatic ignition hazards associated with the combustible particulate solids inside or surrounding the FIBC.

The 2019 edition of NFPA 652 Standard on the Fundamentals of Combustible Dust provides minimum general requirements to manage combustible dust fire, flash fire, and explosion hazards. It also directs the user to other NFPA standards for industry- and commodity-specific requirements.  NFPA 652 requires that the owner/operator take the following steps:

NFPA 652 requires that the Dust Hazard Analysis (DHA) also include the electrostatic ignition hazards associated with the combustible particulate solids inside or surrounding the FIBC.

Table 1 summarizes the requirements of NFPA 652 for use of FIBCs.

Table 1. NFPA 652 Requirements for Use of FIBCs

FIBC Type and NFPA 652 Requirements

Type A 

  • Must only be used with noncombustible powders or combustible powders with MIE >1,000mJ
  • Must not be used in locations where flammable vapors or gases are present
  • Must not be used with conductive dusts

Type B

  • Can be used for combustible dusts with MIE >3mJ
  • Must not be used in locations where flammable vapors or gases are present
  • Must not be used for conductive dusts

Type C 

  • Can be used for combustible powders and in locations where flammable vapors or gases having MIE >0.14mJ are present
  • Conductive components (threads) of the FIBC must be electrically interconnected and terminate in a grounding tab. The resistance from any of the conductive components to the grounding tab must be ≤107ohms
  • Must be grounded during filling and emptying operations with a resistance-to-ground <25 ohms
  • Can be used for conductive dusts, provided that the dust is in contact with electrical ground

Type D 

  • Can be used with combustible powders and in locations where flammable vapor or gases with MIE >0.14mJ are present
  • Must not be used for conductive powders

“Type B, Type C, and Type D FIBCs shall be tested and verified as safe for their intended use by a recognized testing organization in accordance with the requirements and test procedures specified in IEC 61340-4-4, before being used in hazardous environments.

Intended use must include both the product being handled and the environment in which the FIBC will be used.

Table 2 summarizes the tests that are required by IEC 6130-4-4 for different FIBC Types.

Table 2. IEC 6130-4-4 Testing Requirements

FIBC Type and Test

For all types of FIBCs     

 Type B FIBCs     

 Type C FIBCs     

  • Electrical Resistance between the grounding strap and any conductive location on the FIBC surface

 Type D FIBCs     

  • Incendivity of Electrostatic Discharges from the surface of the FIBC during full-scale filling and emptying operations

 Liners for use in FIBCs   

According to NFPA 652, FIBCs that have not been tested and verified for type in accordance with IEC 61340-4-4, shall not be used for combustible dusts or in flammable vapor atmospheres.