Join ioKinetic for this 60-minute webinar to learn how to complete the pre-planning, execution and follow-up tasks required by a NFPA-compliant dust hazards analysis. You’ll learn how to generate and gather process safety information — including the appropriate dust characteristics to measure, choosing a qualified DHA leader, staffing your team, selecting a methodology to apply, evaluating process operations and building compartments, documenting the discussion, and follow up.
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Q. Do you anticipate that OSHA will enforce these NFPA DHA deadlines?
A. I think if history is any indication, then we can expect that they will be enforcing these DHA deadlines. As you are probably aware OSHA does not have its own standards related to most of these types of combustible dust. They have some grain standard and some other stuff has come and such, but it doesn’t have a consolidated combustible dust standard. People have been asking industries and the CFE has been commenting, various groups have been asking them too but that’s not where their focus is. But what they do is they rely on these other standards, housekeeping standards, the general requirements to operate as to provide a safe environment. They rely on those if they need to put a citation or something against them if a company is not complying with some of these NFPA standards; which under a definition that’s getting more and more popular is RAGAGEP, Recognized and Generally Accepted Good Engineering Practices.
Q. Industry worldwide has been managing dust for hundreds of years; for example grain silos near rail roads have been around since the early 1800s. It seems like dust explosions have been more frequent within recent times. What has caused the dust hazards to increase?
A. I don’t know if they have been more frequent or if we just hear about them more because we have much more access to information than we used to have. It would be interesting to do that comparison to see how many used to occur. I think manufacturing is changing and information is changing at a fast rate. It’s a little difficult to say what’s causing them to be more frequent, if in fact they are, but I just know they are quite frequent, and we need to do our best to reduce risk and reduce the number of incidents that are occurring.
Q. Do you have examples of the time needed to conduct a DHA for a given process?
A. I would say for a smaller, say an agricultural maybe a food production company, maybe three to five days. If we start talking about chemical plants, we are probably talking one to two weeks. Larger ones obviously more than that. Things that aren’t considered in the chemical industry, it’s up to a week, and then a little or a lot higher for more chemical operations.
Q. Does conducting the DHA preclude you from having to fully comply with the prescriptive requirements of the NFPA Standards?
A. Not according to how it’s written. I am not sure how OSHA would interpret that. I think what you are asking is, can you use the DHA to avoid doing the prescriptive standard? So if you evaluate something during a DHA and you decide there is not a hazard or you don’t think a hazard is large enough to warrant this, do you not need to implement the prescriptive standard? What I would say about that is, if you take a multi-disciplinary team of people that are knowledgeable in the process, knowledgeable in hazard analysis identification, and all that and do an analysis; at least you have addressed it. Somebody like OSHA might be able to come in and argue with the choice that you made but at least you have looked at it and said we think the risk is low, it’s not a problem. Does it preclude you from having to? Not the way the standards are written.
Q. Where would I find a list of potential “What if” questions for an agricultural DHA?
A. Our software Process Safety Enterprise® PHAGlobal® does have a list of questions for agricultural DHA, and then I would also point you towards some of the CCPS books. I don’t know if they have specific ones on agriculture, but they would have dust hazard analysis checklists. The new book 2017 that was referenced, the CCPS Guidelines for Combustible Dust Hazard Analysis, Publisher, Wiley (2017), has some checklists in there.
Q. Is it true that if I have combustible dust in a dust collector, that I need to install an explosion vent compression system per code? Or can I have other means to eliminate the risk?
A. If the dust collector has an explosion hazard, and that means it has a dust and it has a credible ignition source, and it has a means to put that dust into a dispersed cloud which in a dust collector, it’s generally always a dispersed cloud. So, if it has all those potential things present than according to NFPA, you need to have some sort of explosion protection. Whether it be venting or suppression, I would refer you to NFPA 69 for the appropriate or applicable dust explosion protection method.
Q. Is a separate DHA required or recommended if you already have site PHAs in place?
A. As long as the PHA evaluated the dust hazard, that should suffice. PHAs are generally more comprehensive than what’s required for a DHA. I would stress the caveat is that the PHA looked at the dust characterization data, it looked at the safe operating ranges and considered fire flash and fire explosion hazard, then it’s the same analysis.
Q. Does the NFPA have any requirements for how long companies have to implement changes recommended based on the DHA?
A. There are no recommendations as to the timeline of the action items. If I were going to look at it as though I am doing a revalidation in 5 years, I would want – it just says you need to do a plan as soon as possible – so if you have a plan in place and you are taking steps to accomplish some of those action items and you have them, say, on a capitol budget, and that sort of stuff, then I think that would be appropriate but there is no specific timeline that I have seen.
Q. Have you experienced clients wanting to implement LOPA to their DHA? If so, how would your DHA preparation change?
A. In order for it to do LOPA you need some more details, failure rate information. There would have to be some research into understanding the failure rates for the dust equipment and control systems and all of that, in order to implement an effective LOPA.
Q. Prescribed DHA leader criteria seems to be the same as a PHA leader in chemical processes. Is that true?
A. Yes, and it is very similar. Someone that knows how to lead a hazard analysis uses the same approach. The difference is, in the chemical DHA you want someone familiar with chemical operations and the chemical hazards that you are considering. For DHA you would want someone familiar with how to apply the dust characteristics and understand dust operations.
Q. When is a DHA recommended to be performed for a new plant of a new technology?
A. If you are asking about when in the design steps, I would say similar to when you would apply a PHA, once the detailed design is done but before the equipment has been ordered. Because if changes need to be made, you want to do that before you order the equipment.
Q. How in depth do you address potential ignition sources? Are they just assumed to be there, or can they be controlled?
A. That’s really where the dust characteristics come into play. Dust ignition sources can be controlled depending on the sensitivity of the material to the different types of ignition sources. I’d typically look at every ignition source possible for each unit operation. So do we have heated air, do we have heated equipment, do we have electro static hazards, do we have any temperature issues, for each piece of equipment and compare that against a dust’s susceptibility to that type of ignition source. I can’t heat my system up over say 400 degrees Celsius if I have measured a minimum auto ignition temperature of 450 degrees Celsius, and adherently state I can’t get there. So those two things would need to be compared. It is possible to exclude certain ignition sources as long as you understand the dust characteristics to a significant degree, and how they are going to be impacted by the different types of ignition sources that could be present.
Q. Does your company offer DHA services? Are there companies that do?
A. Yes, our company offers DHA services and there are a lot of companies out there that do. Typically, people who do dust characterization testing, as we do, offer DHA services.
Q. Is a “What if” DHA assessment better suited for new plants and technology in the process of being constructed versus a more rigorous HAZAP? Checklist is obviously not possible.
A. “What ifs” are usually done early in the design phase so in a “what if” you want to capture the big things in the early design so you can make changes before it gets too costly to redo the design work. As you get closer towards the end, you can still apply a checklist if it’s a well-known unit operation. If it’s something that is outside of the ordinary then you would want to go to a HAZAP but if it’s something you know in terms of use spin, new amount of conveying, dust collection filters, backhouses, silos, typical dust handling equipment: conveyors, extruders, screens, and sifters, then you can still apply a checklist even if it hasn’t been designed. I would say to summarize early on in the process with the “what if’s” and as we get to more detailed design over to a checklist or HAZAP depending on the type of unit operation that you are looking at.
Q. Is applicability of NFPA 652-64 only in the US or seen as RAGAGEP for the rest of the world?
A. It often depends on the plant or the company. If the company is an international company, they will generally want to apply those things across the board. I’ve seen many European companies that have adopted some NFPA standards. But as you might be aware, ATEX is the more popular standard in Europe, and it’s a requirement. There are some similarities and differences between ATEX and the NFPA standards. Their focus is a little bit different. ATEX is more focused on equipment while NFPA and DHAs are more focused on operations. There are some differences there, but we do see it becoming more and more RAGAGEP throughout the world.
Q. For HAZOP style DHA is there a standard list of guide words or deviations?
A. We would just use the standard ones for hi flow, low flow, high pressure, low pressure, and temperature. There might be some individual ones for things like batch operations and such but we already have those in our standard list of guide words so we don’t use anything out of the ordinary when doing a HAZOP for a dust then we would for a standard DHA.
Q. If I have a plant in Europe, can we use the US NFPA standards for DHAs or would the Europeans want to see their own?
A. You will have to comply with the ATEX requirements. ATEX requires an onsite evaluation of equipment and building spaces as well. Like I said it’s different, it is more based on defining zones and specifying pieces of equipment, so you are going to have to do that to meet ATEX requirements in Europe no matter what. Using the NFPA standards can help you do more of a risk-based approach using the hazard analysis so it’s really not so much of what the government is going to want to see, it’s more what you think is going to get you to the ultimate goal.