Does my industrial facility need a DHA?
By Ali Roth
While NFPA standards and codes give valuable insight to the safety of processing and manufacturing facilities, it is still undergoing changes and improvements. The NFPA 660 will combine other resources into one document that contains relevant information for other areas of focus.
Additional standards and codes relating to metals/alloys (NFPA 484), agricultural/food products (NFPA 61), wood processing/wood working (NFPA 664), and sulfur powders/solids (NFPA 655) are all available through the NFPA website.
A recent explosion at a grain elevator in Jefferson, Iowa, illustrates the potential severity of such accidents and the importance of dust hazard analysis (DHA) to expose the types of dust that pose a danger to processing facilities.
DHAs can be complicated, confusing, and invasive, but simple measures can be taken to determine if one is even needed in the first place.
NFPA 652-19 has a flow chart – frequently used by industry experts like those at IMEG – that can determine if your industrial or processing facility needs to conduct a DHA. The essence of the flow chart can be summarized with these questions:
Does your facility manufacture, process, blend, convey, re-package, generate, or handle dusts or particulate solids? If the answer to this question is yes, you may be required to do a DHA. Many dusts that cause catastrophic disasters are materials that the average person would not consider “hazardous” or “dangerous,” like flour, sugar, and plastic. It is important to follow NFPA guidelines to determine if a more in-depth analysis of your facility is needed.
Have you determined the combustibility or explosibility hazards of the material? The next step in determining the need for a DHA is checking to see if the materials in your facility are combustible or not. This information can sometimes be found on the material safety data sheet (SDS) for the material. Frequently, the SDS will simply state whether certain materials are combustible/flammable or not. If the material is listed as combustible, a DHA must be performed on the process handling the materials. If the material is not combustible, that information should be documented in accordance with NFPA 652 and meet the documentation requirements for the authority having jurisdiction (AHJ).
If the combustibility information is not readily available on the SDS, a simple “go/no-go” combustibility/explosibility test needs to be performed on the material. A more in-depth analysis can be conducted if more tests are performed. These additional tests can provide Kst, Pmax, MEC (minimum explosible concentration), and MIE (minimum ignition energy). This information is helpful when sizing dust collectors for combustible dust, deflagration venting, explosion vents, and examination of other hazards including ignition from electrostatic discharge.
A DHA should document what a facility is doing correctly to mitigate dust deflagration/explosion hazards as well as what they can improve on. After that, the owner and engineer should work as a team to implement the changes needed to bring the facility into compliance. The DHA should also foster an ongoing safety discussion guided by the engineer and including everyone from the operators to the plant manager.