An excellent article co-authored by Tony Supine and Mike Walters, “How to Make Sure Your Dust Collection System Complies with Combustible Dust Standards,” reveals the history for the purpose of combustible dust standards by OSHA, the NFPA, and the CSB but also provides knowledgeable insight into explosion prevention methods and the shortcomings thereof as well as of the types of explosion venting and prevention equipment available.
Most important are the NFPA standards to which compliance is mandatory. NFPA 654, “Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing and Handling of Combustible Particulate Solids,” is the go-to guide on designing safe dust collection systems. NFPA 654 directs the designing engineer to NFPA 68, “Standard on Explosion Protection by Deflagration Venting,” most importantly the 2007 edition, which provides stringent guidelines on the equipment necessary for venting combustible gases that ignite within an enclosed area; and NFPA 69, “Standard on Explosion Prevention Systems,” which provides guidelines for explosion protection methods to use when venting is not optional, such as suppression, containment, and extinguishment. Much of this is reflected in our special duct fabrications area under dust collection systems.
It is laudable that the authors provided many technologies capable of limiting, preventing, and extinguishing combustible dust explosions pertinent to a variety of specific industries. Those technologies outlined are passive, which includes explosion venting, flameless venting, passive float valve, flow operated flap valve, and flame front diverters; and active, which includes chemical isolation, chemical suppression, fast acting valve, and high-speed abort gate.
Most commendable was the attention paid to common mistakes that contribute to risks for explosions in a facility. The two key takeaways from this article for prevention and limitation of fire and explosions are:
- Know your dust. Have it analyzed for its combustibility. The lab will provide you with the Kst and Pmax values of the dust for you to pass on to your dust collection system supplier in order to correctly size the dust collector, components, and venting/suppression systems. A hazard analysis can help you avoid speculative “bargains,” purchasing more explosion equipment than you need or purchasing non-compliant equipment.
- Keep your facility dust-free. Any dust over 0 Kst is considered combustible and even a fine layer, whether on the floor or high above in the rafters, will result in citations. Regular inspections can seem like an annoyance but can help you avoid or limit catastrophic events.