Combustible Dust — What You Should Know About NFPA 652

In this ioKinetic sponsored webinar, you’ll gain an overview of NFPA 652 and how it provides the basic principles and minimum requirements to manage fire, flash fire, and explosion hazards of combustible dusts. We’ll compare and contrast NFPA 652 with the legacy NFPA standards—including NFPA 654, 61, 484 and 664. If you work in one of the industries the new standard serves—agriculture, pharmaceutical, oil and gas, petrochemical or chemical—join this webinar to identify approaches for meeting the requirements.

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Live Webinar Q&A

Q. Does the NFPA Standard provide a rationale for the 8 cubic feet threshold for protecting and preventing explosion hazards? Is that limited to dust?

A. Yes, I believe that is limited to dust. I haven’t seen a reference to flammable gas in the standard, and I don’t think that NFPA provides details about why 8 cubic feet. My understanding is that the reason for the 8 cubic feet is that you cannot functionally vent a piece of equipment that size. Also, the piece of equipment is so small that the hazard associated with it is very limited so they made that the cut-off point.

Q. I work for a methanol facility that produces dry distillers grains, and often there is a question on the hazard of this product’s dust. The composition can vary depending on the process and the plant. What would be the minimum test you would suggest prior to classifying the dust hazard and are there labs readily available in the US that perform this testing?

A. I would suggest running a screening test. Maybe the materials are different sizes so maybe you can base the test plan on different particle sizes. If it is corn-based or grain-based, I am not sure that the composition is going to change all that much; it may really be a particle size at the end. If it is composition, you can also try taking a few different samples of different compositions. Then go through a screening process for the one that’s the most hazardous and take that most hazardous one into the detailed characterization test. In terms of labs that do this testing, yes, there are at least four labs that do. ioKinetic is one of them, but there are some other labs located throughout the U.S.

Q. Are DHA leader qualifications different from PHA leader qualifications?

A. I would say no, they are not. I don’t think they specify that in the standard. From my experience, PHA leaders make great DHA leaders as long as they have the background and the knowledge in the dust hazards that need to be evaluated. That is all that’s required.

Q. Three years is given to complete assessments but is there a length of time to get your processes in line with this NFPA standard?

A. Some of the requirements are retroactive and some are not. You have to look at each of the different pieces to see if it is a retroactive piece and if it’s retroactive, then I would say you need to start working on it right now. If it’s not, and this is something you want to incorporate into new design and new construction, you may want to consider it when you’re looking at your hazard analysis. Again, hazard analysis really is the hardest. If you do a process test analysis and look at the prescriptive requirements versus what you have in place, you can decide whether the hazard is really something that you need to address immediately or whether it’s something that can wait for the next modification.

Q. Can you recommend a good resource for combustible dust training materials? I’m looking for a more up-to-date powerpoint and also videos to train plant employees.

A. I don’t know that there is anything out there in the open literature. OSHA has been very quiet on this. The NFPA does training on this and individual consultants provide training. You might be able to speak to an individual consulting company that can provide you with the training materials that you could then use to continue your training.

Q. Has OSHA adopted NFPA 652 as an accepted industry practice and will they cite companies for failing to comply?

A. OSHA hasn’t officially adopted any of these standards, but they do rely on them to provide guidance in their client’s activities. If OSHA is out there doing their national emphasis program evaluations or if they are at your site for anything, OSHA can always rely on the general provisions and then reference NFPA standards as RAGAGEP. I have seen them do that many times. I haven’t seen them do it specifically for 652 yet but it’s very new.

Q. What’s an appropriate inspection period for grounding and bonding systems?

A. In my personal opinion, I would say a year, annually.

Q. On these standards, including 652, they allow for prescriptive compliance and performance compliance. Do you have a general recommendation for a company just getting into dust hazard management? For example, prescriptive versus performance and any recommendations for a PSM regulated company?

A. My recommendation is generally to start with prescriptive compliance. If you meet the prescriptive requirements, then you’re done. If you don’t meet the prescriptive requirement, now you need to look at a performance-based approach. Decide whether you really do have a hazard that requires you to meet the prescriptive requirement or maybe the hazard is such that you can do an evaluation. There are multiple levels of prescriptive and performance-based approaches in terms of doing engineering analysis. You can have people come in and do modeling work, facility siting modeling, and such if you want to try to justify not having a prescriptive-based control that’s been required specifically. In terms of PSM, I would just say include the combustible dust hazard and the process hazard analysis that you’re doing now, and that should pretty much cover it. In terms of the management system, you will already have all those management systems and then some because OSHA’s is more comprehensive than what’s here.

Q. Is there a material difference in complying with your NFPA standard and NFPA 652 then just complying with OSHA PSM? Is this OSHA’s way of dealing with combustible dust NEP?

A. I can’t speak for OSHA and what they are thinking but they have up until now relied on NFPA as the standard maker and as the expert on managing combustible dust. I do think OSHA will probably come up with a standard but I’m not privy to know if they’re going to have their own specific requirements or if they will just reference back to NFPA. That’s hard to know; they haven’t put any focus on combustible dust in the current administration so we are not sure what the next one will bring.

Q. Do you normally consider propagating dust XP hazards in connections of less than four inches in diameter a credible event?

A. Yes, there have been studies shown that you can propagate an explosion in a piece of ductwork that’s less than four inches. There are modeling simulations that can be done to evaluate a specific composition of a material and a specific diameter pipe. You can propagate through a four-inch diameter pipe, which is why they have taken that exclusion out of the newest 654 and 652 standards. With the four-inch duct, it’s truly less likely that you will propagate but there are certain materials that can propagate in that size ductwork.

Q. What kind of source do you recommend to find valuable Minimum Ignition Energy (MIE) of different substances?

A. There are some MIE values in NFPA 68 I believe, which is the explosion design of deflagration vents standard NFPA 68. There’s also the European website and they also provide MIE data. The only thing I would caution is that you make sure that you have the particle size and the moisture content and then add the composition of those materials if you want to apply those directly to your processes.

Q. What does hazard analysis really consist of, especially when it comes to metals?

A. It’s not very specific, it just says that you need to do one. If I were operating that process, I would fall back on the guidance in 654 and 652 and do a comprehensive PHA. These don’t need to be extremely long. Doing a comprehensive PHA doesn’t mean it needs to take a week. It will depend on the size of the operation. I’ve done some in as short a time as four hours, and some take up to three days. Metal facilities don’t tend to have a huge amount of unit operations, so they don’t have to take an extreme amount of time, but you just want to make sure that you have looked at the different unit operations that you are involved in. Metals usually have dust collection, material separators, and all that, so guidance in metal standards are not really there.

Q. Does the burn rate test for chloral flame initiate the test, and can other heating mediums be used?

A. Not for a burn rate test but for other tests we do have something called a hot surface ignitor which we just subject to temperature. There are other tests that can address different ignition sources from a temperature and flame perspective, but the burn rate is specific to that torch.

Q. Do sites need to implement the management system of climate in chapter 9 if they have identified a combustible dust hazard? Or is there an exemption from implementing these elements?

A. There’s not an exemption that I am aware of. If you have combustible dust, then the management systems need to come into play and need to be implemented. Most likely you have many of them – operating procedures, training, contractor management – they are not a new science. They’ve been around a long time and I would suspect that you have a lot of them in place, maybe just not in an organized way.

Q. Fire protection is not necessarily required within the equipment, correct?

A. That’s a tough one, I was looking for that myself earlier today. I don’t think that it’s specifically called out, I think it’s more for external to the equipment.

Q. Does NFPA 652 have any specific experience training requirements that DHA personnel must meet to be considered qualified?

A. No. I think it’s similar to the question that was asked earlier about DHA qualification requirements for leaders: there isn’t anything there. I think anyone who has Process Hazard Analysis training would be able to manage a dust hazard analysis.

Q. Can you please provide a specific NFPA standard on static electricity, explosion protection systems, and deflagration vent sizing?

A. Static electricity is NFPA 77, explosion protection systems are NFPA 69, and deflagration vent sizing is NFPA 68.

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