In this episode of the DustSafetyScience Podcast, we do a dust collector training mini-session with Matt Devitt, Director of Operations at BWF Envirotech, which is based out of Hebron, Kentucky. BWF Envirotech hosts a yearly dust collector training academy: this year it will be held from September 16th to 19th.
Dust collector safety has been a theme in several previous episodes. We’ve discussed:
- The Nova Scotia dust collector program with Jeramy Slaunwhite
- The top five mistakes companies make with their system design with Diane Cave
- Designing dust collector protection programs with Gilles Plourde
- Changes in the dust collection equipment landscape with Jeremiah Wann
Today’s episode with Matt Devitt goes over the fundamentals of dust collection equipment. If you’re new to the subject of dust collectors, Matt’s interview will clarify what they do and what varieties are available. Even those who work with this equipment all the time will find his insights and advice beneficial.
The BWF Group, which includes BWF Envirotech, is a fabric filtration company based in Germany. The felted rolled goods come to Matt’s company in northern Kentucky in Hebron, where they are converted into filter bags. As the Director of Operations, Matt’s responsibilities include:
- Supervising the manufacturing process
- Managing the environmental services, which is all of BWF Envirotech’s mechanical- based projects services
- Overseeing the technical services, which include training and higher-level process audits
What Are the Main Components of a Dust Collector System?
When asked to list the different parts of a correctly functioning dust collection system, Matt divided them into four main areas:
- The hood
- The ductwork
- The box, which is the dust collector itself
- The exhaust system, which is where the clean air is going
What Are the Different Types of Dust Collector?
The most commonly seen dust collection systems include:
- Pulse-jet, which blasts medium to high-pressure air into the top of the filter bag, expanding it out from the support cage and breaking off the dust cake, which moves down into the hopper.
- Reversed air, where the dust is captured on the inside of the bag by reversing the airflow through the compartment to break the dust cake and move it into the hopper.
- Shaker, which mechanically shakes the filter bag so that the dust cake is removed from the filter.
- Plenum cleaner, which collects dust on the outside of the filter bag while the clean air exits through the inside of the bag.
- Rotary arm, which has a rotating arm above the tube sheet that supports the bag and separates the dirty side from the clean side.
Matt explained that the equipment is also parsed down according to whether it is designed to clean in online or offline mode.
- Online systems allow the removal of the dust cake off of the filter while that filter is still taking on air/gas
- Offline systems isolate a section of the baghouse and prevent any new gas from entering while the filters are being clean.
Another way of categorizing dust collectors is the type of filter it uses: top load bag system, bottom load bag and cage system, or pleated filter.
What Should People Be Aware Of With Regard to Dust Collector Subsystems?
Matt explained that the hood supports a smooth transition by creating a physical distance between the transport duct and the enclosure. The desired face velocity at the hood is going to be somewhere between about 200 to 300 feet per minute, which is needed to move the fine dust particles.
The physical distance is needed because the speed at the inlet to the hood may only be 250 feet per minute but in the transport duct, it needs to be significantly faster: 3500 to 4000 feet per minute. If the transition is not created, the amount of resistance in the system increases and a lot of unwanted extra material is pulled into the baghouse.
To illustrate the relationship between the hood and the enclosure, Matt likened the enclosure to a paint booth and the slots behind it would be the hood section itself. Another analogy was a conveyor belt system: there is a transfer point from a chute down to a conveyor belt moving material around. Most of the dust generated from that transfer stays in the enclosure and the hood picks up and directs the fine dust up to the baghouse.
With regards to ducting, Matt said that moving the baghouse is sometimes a better idea than installing extra ductwork. Every time direction changes, about five to seven diameters of straight run are needed: otherwise, balance will be more difficult. He added that the duct diameter needs to be an appropriate size. If it is too large, the velocity will be too low and material will drop out. If it is too small, the velocity is going to be too high and can cause abrasion issues.
How Much Dust Should Be Picked Up By a Well-Functioning Dust Collection System?
Matt said that the amount of dust picked up will depend on the density of the material. The first thing you want to ask is what apparatus you are collecting dust from. The amount of volume needed for a 48-inch wide duct is going to be different than what is needed for a bin that’s taking on grain. If the duct is too big, the dust will settle on your ductwork and create a hazard. If it is too small, abrasions can appear in the duct line.
An Overview of Baghouses and Bags
When selecting the material and thickness for the dust collector bag, Matt said that it is important to understand the operating environment. This includes the gas composition and temperature and dust type. For example, what size are the dust particles? Are they dry and free-flowing or sticky and prone to clumping? If combustion is an issue, a stainless steel mesh material will be needed to make sure the whole bag is grounded out.
Once you understand what the baghouse is supposed to do for your process, it is easier to select a fabric type and finish as well as the type of cage needed (e.g., mild steel or galvanized).
The Exhaust System
Matt said that the exhaust system will follow the same principles for inlet ducting. The only difference is that everything in the exhaust system is supposed to be clean air. All of the dust should be captured in the baghouse so the minimum velocity requirements can be relaxed and the diameter can be a bit larger, resulting in less resistance.
“That would be one where you’re going to exhaust the system, you know, as it’s going to exhaust back into a building,” he explained. “Is it in a large warehouse where it’s not a big deal? Is it going to go through the roof through the side of the building? Things of that nature.”
The Fans
He said that he had seen a lot of what appeared to be good systems, only to learn that the fan was on the roof with a 90-degree elbow coming off of it.
“To me, that’s like the perfect routine at the Olympics on the balance beam and then you just don’t stick the landing,” he said. “Everything was right up until that point.”
When modifications are made after the original design or the system does not match the design, the fan may have to be adjusted to compensate. If three or four more pickup points are added, the fan doesn’t have the extra capacity to handle it.
“The fan is the arbiter of truth. You can do whatever you want to that system but the fan is going to know and it’s going to call you out on any changes that you make.”
Conclusion
Matt left the listeners with two recommendations:
- General TLC on your dust collection equipment. Components like ducting and the hood don’t last forever and will need to be repaired or replaced if they lose capacity.
- Use of added controls like hopper level indicators, which can prevent dust from accumulating to a dangerous level.
Both measures can improve the working life of your dust collector and contribute to a safer working environment.
If you would like to discuss further, leave your thoughts in the comments section below. You can also reach Matt Devitt directly:
Email: [email protected]
LinkedIn: https://www.linkedin.com/in/devittm/
If you have questions about the contents of this or any other podcast episode, you can go to our ‘Questions from the Community’ page and submit a text message or video recording. We will then bring someone on to answer these questions in a future episode.
Resources Mentioned
DustSafetyScience
Combustible Dust Incident Database
DustSafetyScience Podcast
Questions from the Community
Education
Dust Collector Training Academy
Companies
BWF Envirotech
Previous Episodes
DSS029: Changes in the Dust Collection Equipment Landscape with Jeremiah Wann
DSS018: Top Five Mistakes Companies Make in their Dust Collection System Design with Diane Cave
DSS016: Designing Dust Explosion Protection Systems with Gilles Plourde
DSS004: Nova Scotia Dust Collector Safety Program and Explosion Safety with Jeramy Slaunwhite
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DSS032: Dust Collector Training Mini-Session with Matt Devitt
Full Episode Transcript
Chris Cloney: [00:09] Welcome to episode number 32 of the Dust Safety Science Podcast. We’re creating a worldwide community around process safety and industries handling combustible dust. I’m your host, Dr. Chris Cloney.. Today’s episode, we’re doing a dust collector training mini session with Matt Devitt, Matt’s Director of Operations at BWF Envirotec, based out of Hebron, Kentucky. And he’s really knowledgeable in this area, so I’m really happy to have him on the show. So Matt, thank you for spending your time to help us learn about this topic.
Matt Devitt: [00:37] Not a problem. Definitely happy to be here, Chris. Thanks for having me.
Chris: [00:41] So I met Matt across LinkedIn. If you happen to be connected with him, he’s the guy who’s always posting videos that are a mix of productivity, personal effectiveness, and then lots of dust collector and baghouse training and design technical aspects mixed in there. So he’s kind of hard to miss in that space. In the previous podcast episodes, we’ve talked a lot about Dust Collector safety. Episode four, we talked about the Nova Scotia Dust Collector program with Jeremy Slaunwhite in 18. We talked about five top mistakes companies make with their system design with Diane Cave. Episode 16. We talked about designing dust protection programs with Jill Plourde and more recently in 29, we talked about changes in the dust collection equipment landscape with Jeremy Jeremiah one but it just kind of occurred to me as I went through these, that we haven’t done a kind of a fundamental episode on what is a dust collector, what are the components? And just giving the listeners, you know, a lay of the land for this piece of equipment. So that’s really what I brought Matt on here to do today. I know BWF Envirotec does their dust collector training academy each year, their bag House training Academy in September this year it’s September 16th and 19th. That’s a two or maybe three day seminar covering everything for dust collection systems. And hopefully we have this next 25 minutes. We can pull over a mini training session from that. So if you’re just a complete beginner in dust collection, this should be really helpful. And just give me the lay of the land. And if you’re more advanced than you, you work with these systems all the time. I’m pretty sure Matt’s going to also throw a lot of, you know, tips in there on things that we need to know and understand. So I think it’s going to be a really great episode for that. So maybe by way of just getting started, Matt, what does BWF Envirotec do and kind of what’s your role or roles within the company today?
Matt: [02:23] Yeah, absolutely. Chris. So BWF Envirotec, we are a fabric filtration company and the Envirotech group, which I’m a part of. We focus on air filtration. So in our German manufacturing office in Offingen, Germany is where we make our felted rolled goods. And then those rolled goods come over to us in Northern Kentucky and Hebron. And that’s where we do conversion into filter bags. So that’s really our bread and butter is the filtration, the material, the engineering of the felt for specific applications. But then what we’ve done is we’ve broadened out our scope of services because we understand the filter. Like we’re going to talk about in this session is just one piece of an overall system. And all of those parts of the system need to work properly. So we’ve started to expand our services with training and education on how to get your system working right to mechanical maintenance, installation, turnkey, so on and so forth, all focused on the baghouse and air filtration. But that’s that in a nutshell, is what BWF Envirotec does and the way I support the company as the Director of operations. So I watch over the manufacturing process, which is the conversion of rolled goods into filter bags, as well as our environmental services, which is all of our mechanical based project services. And then lastly, the third pillar we have is our technical services, which is where we do maybe higher level process audits. All of the training, both hands on, on site, off site, etc. all falls into that category as well. So that’s what I watch over within the company.
Chris: [04:02] Yeah, that’s a good background. It’s already kind of readily apparent why it makes sense to have you talking about this. Just what is a dust collection system starting with, you know, the one of the critical elements of the bags and the filters and the material that’s used, and then all the way out to the, you know, the full solution. It sounds like you guys have your hand in, in different pieces the whole way through for introduction. And this is, this is a little bit greedy for me because I’ve never actually taken a dust collector course or anything like that, so it’s a little bit helpful for me. And then even for someone that’s more advanced, I’m hoping it’ll be helpful. But what are the different parts of a correctly functioning dust collection system?
Matt: [04:39] The different parts that you have in the overall system? I’m going to lump them together in relatively large areas, though. There’s a lot of, you know, I guess sub assemblies that would go into each one of those. But the four main areas that I really look at when it comes to a properly functioning dust collection system is going to be the hood, the ductwork, the box for lack of a better word. But this is really, you know, also known as the dust collector itself. So everything that’s attached to that box and then finally the exhaust system. So where the clean air is going and so on and so forth. So it’s really those four areas: the hood, the ductwork, the bag house itself or dust collector itself, and then the exhaust system.
Chris: [05:20] Okay. And I know people say that they deal with different types of dust collection systems. And could you just give us we don’t need to go really in detail of the different types, but what are the maybe the names or the distinguishing between different types of systems? Just so when people hear them, they have a better idea of what people are talking about.
Matt: [05:39] Sure. So there’s a couple of ways to, I guess, to cut that pie, most commonly, the systems that people will work with out there are what are called a pulse jet dust collection system or medium pressure or high pressure pulse jet system. But really, if we step back, if we want to look at how we parse down the equipment itself, the first way I look at is, was the system designed to clean either in an online or an offline cleaning mode? And what that means is when it’s cleaning online, I am doing something to remove the dust cake off of the filter while that filter is still taking on gas to be cleaned, whereas an offline system, I’m actually going to isolate a section of the baghouse and prevent any new gas from coming into it with particulate, and then clean the filters down at that point. So that’s one way. And the reason I bring that up is because you can have a pulse jet system that’s designed to either run online or offline cleaning. And that’s where you can get into some of the subcategories that you have here. You know, some of the other ways that you can take a look at it as well, as far as breaking them out is just the general way you get the dust kicked off of the filter bag. So like I said, there’s pulsejet where you’re using high pressure air that you’re blasting in from the top into the bag. And what it’s doing is expanding that filter bag out from the support cage and breaking the dust cake off that way, so it moves its way down into the hopper.
Matt: [07:09] Another one is reverse air. And so this is a different configuration. This is where the dust is actually captured on the inside of the bag. And what you’re doing is you’re using the process gases, and you’re reversing the airflow through the compartment to break the dust cake and move it into the hopper that way. Another one is called a shaker, which is just the way it sounds. You are mechanically shaking the filter bag so that you can get the dust cake off of the filter. There’s also, you know, plenum, Paul Styles. And then the last one is like a rotary arm where you will have a rotating arm above the tube sheet. And for jargon terms, the tube sheet is where you’re actually putting the bag. So that’s what’s adhering to or supporting the bag. It’s what separates the dirty side from the clean side. So you’ll have this rotating arm that’s going above the tube sheet. And it will index to a certain point. And then it will blow down into the bag. So those are kind of the different ways that you can break the uh, the cake up is another way that you can categorize it. And then the last way is just what kind of filter does it actually use? Is it a top load bag system? Is it a bottom load bagging cage system? Does it use a pleated filter? Does it use a large diameter cartridge pleated filter? So there’s a lot of subcategories that go into it. And it really depends on your application on which one is going to be best for what you want to do.
Chris: [08:32] Yeah. Thank you for that breakdown. And I think you’ve just saved me probably, you know, hours of scratching my head when I’m talking to people because they, they, they may pick a different one of those different categories and talk about it. And then I got to figure out which one it is. So I’ll give a brief summary. You mentioned the systems. You have the hood, the duct work, the box or the bag hose where the filters sit and the exhaust system and a fan that would also be included in that. Then for the actual categorization, it can be done a couple ways, so you can do it based on when the bags are cleaned. If they’re clean, when they’re still in the Airstream, when they’re still processing dirty gas and turning into clean gas, or sections that go offline when they do the cleaning. So those online and offline, you can also divide them based on how they clean. So pulsejet reverse air shaker type pulsers plenum pulse plenum cleaners and rotary arms. And also the type of filter. So those sort of great great breakdowns. We didn’t talk about this before the episode. But do you find that some of these are more commonly used in combustible dust aspects versus sort of inert dust aspects, Or do you have any thoughts on that?
Matt: [09:43] Yeah. So within that I guess a little bit more background on myself. So most of my background has been processing engineering projects within cement, calcined lime, steel waste heat to power. And within those industries, the ones that are using pulverized fuel mostly in cement, they have all been pulsejet style systems and the reason is they do a very good job of cleaning the gas or, sorry, cleaning the the dust off of the filter bag, but they also do it with very little ambient air. So, you know, a reverse air system can use a lot of the process gas. But if you’ve got holes and things like that in there, you know, you can start bringing in a lot of air and leakage. And so within these pulverized coal systems or pulverized fuel systems that we’ll use in cement, for example you really want to minimize and have absolutely no air and leakage because you’re always using the low O2 combustion gases off of a different side of the plant that you’re using to come in and dry the material. But anyways, what I see more commonly are the high pressure or medium pressure pulse jet systems within those applications.
Chris: [10:56] Okay. Yeah. Thanks for sharing that. And the goal of this episode was actually really to focus more on just getting dust cleaned up. Because we covered combustible dust so much so we didn’t really prep for, for the combustible dust side. But I think it’s helpful just to give the listeners an overview, and it’s definitely helpful for me in terms of the kind of standard system we outline. Now, what do people need to know about the first couple pieces? So hoods and ductwork, what should people be aware of with regard to those subsystems if you will.
Matt: [11:28] Yeah. So the hoods are kind of interesting. And hoods and enclosures, sometimes those terms are used interchangeably to me. They’re, they’re different. But I can understand how they can be interchanged when you’re talking to somebody for the first time. So to me, is the enclosure or box or whatever you’re using to create a barrier between where the dust is being generated at that point and then the outside world, and then the hood is where you’re transitioning your pickup or your ventilation point from the enclosure to the transport duct. And it’s minor. That’s why I don’t mind when the terms are interchanged, because it’s not that big of a deal. But there is a reason to have that hood in place. And that’s so you have a smooth transition. You can create some physical distance between the transport duct and the enclosure. And the reason I say that is the general face velocity you want at your hood is going to be somewhere between about 200 to 300 ft per minute, which I believe. And don’t hold me to this metric, but I think it’s somewhere around like a meter per second, one, 1.2, something like that. At that point, that’s what you want because that’s how you can move the fine dust particulate. But if your enclosures are built properly, all of the heavy dust will drop back out or it will stay within that system. One of the analogies I give in my training classes is when my daughter is helping my wife or myself, you know, cook and stuff like that, I don’t get nervous when she grabs the flour in the jar until I notice there’s no lid on the jar, right? And so I don’t mind how much dust she generates effectively in the enclosure.
Matt: [13:08] I only care about the dust that’s generated that’s close to where it can get out of that enclosure. And so that’s why the hood is always going to be situated at a point to where it can capture the really fine dust. But again, the reason you want that physical distance is that you may only be, you know, 250 ft per minute at the inlet to the hood, but in the transport duct I have to be significantly faster. I’m talking 3500, 4000 ft per minute. Some materials have to be closer to 4500 or 5000 ft per minute. So if you do not create that transition, you increase the amount of resistance in the system. You can also create this kind of vacuum cleaner nozzle that’s pulling in a lot of extra material into the baghouse, which you don’t want. So that’s one of the things that I’ll see is that I’ll see a good enclosure, but I won’t see a hood, and that’s where people will overload their baghouse. And that’s because they’re picking up a lot of extra material that isn’t in quotes dust, but it’s just getting pulled into the bag house.
Chris: [14:09] So I can picture what the hood design looks like. And I have some kind of some feedback on that from a previous episode, but the enclosure is that is that like a big thing that the workers are working in, or is that a smaller like, can you just kind of give us an example of what what the enclosure and hood system looks like just for the, the audience?
Matt: [14:27] Yeah. So, you know, if we talk about, you know, like a paint booth, you know, so the booth itself could be considered part of the enclosure and then, you know, like the slots behind it would be the hood section itself. Another one would be on belt conveyors. So something different. So this isn’t where a person’s working, but you’ve got a transfer point from a chute down to a belt conveyor that’s moving, you know, a rock material or something like that around. So now you’re going to create a box that that chute will enter into that sets above, it sets above and right on the belt itself. So then the dust that’s generated from that transfer, most of it stays in the enclosure. And then I’m using the hood to pick up and direct the fine dust up to the baghouse itself.
Chris: [15:14] Okay. Perfect. That’s a good way to explain it. And I didn’t I didn’t think of the two different parts there. So the enclosures really do to minimize the dust escaping the, the dust collection system to kind of hold it there, let the large particles settle out while the small ones can get sucked up the hood. I think one of the ways that Diane mentioned it in, episode 18 of the podcast, was that with the duct work you can only pick up dust. That’s about half the diameter of the duct work. So I have a really small duct Duckworth tubing. Then you have to be really close to the dust. You need to have high velocities, and you’re going to pick up a lot of extra stuff then. And you’re going to miss the dust. It’s not close enough. I think what you’re saying with the hood design is that it allows you to get farther away. You can kind of taper that down and get a larger area with a smaller velocity. You can pick up the dust. Does that make sense?
Matt: [16:06] Yeah, that’s completely in line with one of the reasons to, you know, have a smooth transition. You’re right. If you have just a pipe and you’re pulling air through it, you’re actually going to end up. If you look at the velocity contours around it, you’re going to pull air in from behind the face of the duct itself, you know? So the first way you get around that is you put a flat flange on it, but then that’s not the most efficient way to transition air from low velocity to high velocity. And so that’s when you go to the next step of putting in a tapered design. Think of a pyramid style kind of hood that gives you a much granular increase in speed. And that’s just another way to make the system more efficient by reducing the system resistance at that point.
Chris: [16:50] Okay. Thanks. Thanks for sharing that. That’s a I think that helps to kind of lay out the different pieces. So.
Matt: [16:55] Well, one of the things is not sorry. So with ductwork, just the one, the one point I make to people about that, it’s really in three areas is one, minimize the total amount of ducting you’re going to run when you can. So sometimes when looking at a project, moving the bag house sometimes will make more sense than trying to do like a 200, you know, 200 foot long run, you know, to connect to the back house because you’ve got a whole lot of extra ducting. It’s going to be harder to balance. You know, the other one with ducting is remember, every time you change direction you want to have so many, you want to have about 5 to 7 diameters of straight run before and after that. And that’s really like if you think of a river when it goes around a bend, you know, it’s going to widen out. And then it kind of consolidates itself back down. The air is going to do the same thing. And the more times you change direction, if you don’t allow it to consolidate itself back down, it takes more energy to make it change direction again. So that’s another one. And then the last one is kind of a Goldilocks rule, right? If you can’t be too big and you can’t be too small in diameter of the ducting that you’re running, if you’re too big, then your velocity is too low and material is going to drop out if you’re much too small, then your velocity is going to be really high, assuming the same volume, and you’re going to have abrasion issues and things like that within your within your system.
Chris: [18:13] Yeah, those are some good points. And I, I know, made a couple notes here. One is what kind there actually is. I think there’s multiple parts to this. But what kind of percentage of material should we be picking up with, with a well functioning dust collection system.
Matt: [18:29] Ooh. Good one. It really depends. So it’s going to depend on, you know, like the density of dust, the fineness. So I was just working in part of a quarry earlier this week, and the material that goes through the primary and secondary crusher, I mean, the top end size on that stuff is still, you know, three and four inches, you know, so So yes, there’s a fine fraction to it, but it also has some surface moisture, you know. So I’m not expecting to collect a whole lot of dust off of that system. Just kind of what’s being fractured within the crushers themselves. Move over to another area and a cement plant in like the finished milling building and effectively most of the dust collectors there are kind of at times considered product capture systems. And so they may actually be capturing the majority of the finished product. Going through that system is all being collected in a baghouse. And at that point, your grain loading is considerably higher because it was designed to actually capture all that fine material. So it really depends. So I don’t have a good rule of thumb, except for the fact I would say less is more if your system can handle it, you know. So if you can get away with theoretically between, you know, just the two of us at the water cooler, you know, if you if you’re thinking 30% is what you need to collect, but for some reason you can keep your ventilation points dust free by collecting only, let’s say, 20% of the total, then I would do that. You know, you really want to figure out what’s the minimum effective dose that I can maintain a dust free environment at those points.
Chris: [20:07] Okay, that’s an interesting way to think about it. And it wasn’t quite the way I had in my head. I was picturing a lot of facilities running dust collection systems, and maybe not running them correctly or running them optimized. And my, my kind of expected answer might have been, you know, a lot more than you’re currently collecting or something like that, at least in the combustible dust world where not having that collected means that you kind of have a hazard that’s building up. But I mean, I’m sure that’s part and parcel with what you’re saying as well, that you have improved that system. You’re going to be able to pick up more of it. And you know, the hood design, the enclosure, those are all different ways that you can improve that.
Matt: [20:47] Yeah. And even if you step back one, one step farther into the process, you know, the first thing you want to ask is, well, what am I actually collecting dust off of? You know, what is this hood and enclosure going on? The amount of volume I need for a 48 inch wide duct is going to be considerably different than if you’re looking at, like, a screw or maybe a bin that’s taking on grain or something of that nature, you know, so you really want to back up one step further and go, okay, well, how much ventilation do I need at this point in order to properly maintain the dust inside of it based on best practices, and then look to other industries and like what you’re doing yourself. Okay. Where have people actually had problems with this? What were they doing? What can I learn from that and implement that within my system as well?
Chris: [21:34] Yeah, that makes a lot of sense. And it ties right back into your duct design because the follow-on question to the how much should you pick up was actually going to lead right into what you’re saying that you need to not have too big of a doctor, too small of a duck. You have too big of a duct, it’s going to settle in your duct work, and then you just have the dust sitting there overhead, which is a hazard. Or if it’s going too fast, then you’re going to have an abrasion in your duct line, like you said. And then you’re just going to be having smaller and smaller particle size, which is an additional hazard that you wouldn’t need to be wouldn’t need to be involved if you had the correct airflow velocity through there. Yeah. So it’s interesting how the process still, you know, holds true and comes back to combustible dust hazards as well I think so. So we have hoods and ductwork now we have some ideas there. What do people need to know about baghouses and bags?
Matt: [22:24] So since you limited me to only 30 minutes, I’ll see if I can put this out there. Sorry. If anybody I.
Chris: [22:30] Know this is your favorite part, so…
Matt: [22:32] I know it’s, you know, hopefully nobody feels like they’re trying to drink from a fire hose here. But if there’s one item and I’ve kind of been alluding to this as we’ve been talking, but if there’s one item that people will take away on what a baghouse or dust collector should be, and that’s it should be a dust collection system and not a vacuum cleaner. Okay. It shouldn’t be used as a part of your material handling system or a material handling device within the system. It’s meant only to collect the dust that is not going to settle out or maintain itself, or stay within the enclosure itself. That’s pretty much it. Everything else goes into, you know, what’s the process gas made out of? Do I need to make it out of stainless? Can I use a coating? Should I use a medium pressure system to clean down? You know, do I go with long bag technology with a bottom and high side inlet, etc., etc., etc. and that’s where you can dig really into the minutia of the idea. But the point being is that I should only be collecting as much dust as is necessary to make the whole process efficient.
Chris: [23:37] Right? Okay. And I have to give you a chance here on the filters as well, because I know that’s what BWF, you know, focuses on originally. But what are the different things that you need to be aware of if you’re, I don’t know, picking materials and I’m sure thicknesses and, you know we’ve how tightly it’s woven in that is there are there considerations with the actual filter material that are important to think of.
Matt: [00:24:06] Yeah, for sure. I mean, if you can yeah, there’s a lot of ways that you can pick a filter bag wrong. And there’s a lot of ways you can pick a filter bag that is effectively more than what’s actually needed for the process, and it really comes into a hand and glove idea. You know, we need to understand the process that it’s going to be operating within from not just the gas composition and temperature, but you know, what does the dust look like? Is the dust normally very dry and free flowing? What’s its particle size or is it sticky and agglomerating? And you know, this rings true with yourself, but you know, it’s combustion in issue, you know, do I need to put a stainless steel mesh material in here to make sure the whole bag is grounded out? Do I need to use a grounding wire to make sure that happens, so that the bag is conductive to the tube sheet and the tube sheet is grounded to the, you know, the bag house. And the bag house is actually grounded to the ground. You know, all of those things. So it really comes back to I need to understand your process and what the bag House is supposed to do for the process. And then we can really start looking at what kind of fabric do you need? What kind of fabric finish do you need? What kind of cage do you need? Can you get away with mild steel? Do you need something that’s galvanized because of the gases you have? Is stainless an option? You know, it all comes back to what is the operating environment for the filter okay.
Chris: [25:33] So that’s we’ve got through the hood now or our dust is traveling up through the hood. It went through the ductwork. It’s gotten into the baghouse. What do we need to know about exhaust systems? And well, maybe we’ll do exhaust systems alone and then we’ll talk about fans at the end. So what do we need to know about, you know, exhaust systems for dust collection.
Matt: [25:49] So the same principles for your inlet ducting will apply for the exhaust system. The only difference is that everything in the exhaust system is supposed to be clean air. Right? You know, all the dust was supposed to be captured within the baghouse. And so the requirements of that minimum velocity actually get relaxed. So you don’t have to have that gas traveling so fast on the clean side. So you can go a little bit larger in diameter, which will give you less resistance. That would be one. Where are you going to exhaust the system, you know, is this going to exhaust back into a building. Is it in a large warehouse where it’s not a big deal? Is it going to go through the roof, through the side of the building, you know, things of that nature. And the last one is, I know you said we were going to talk about fans separately, but I’ve seen a lot of good systems. And then what they’ll do is they’ll have the fan on the roof and they will put a really hard 90 degree elbow coming right off of it. And to me, that’s like the perfect routine at the Olympics on the balance beam. And then you just don’t stick the landing. It’s. Everything was right up until that point. And I think people forget that you can create a significant amount of back pressure, but at the discharge of the fan itself, that will impact the operation of the whole upstream system itself.
Chris: [27:10] Yeah, I’ve heard that before, where the fans are really a critical part in it, it changes with time too. Right? So your system during start up in the first couple of months and years, there are different operating parameters. Then, you know, once it’s an older system, or if you add more duct lines or all that sort needs to be accounted for, have you come across cases where fans become, you know, undersized over time or the system needs to be upgraded to larger fans?
Matt: [27:33] Yeah, absolutely. This is definitely one of those items where when either modifications are done after design or the installation does not match design, then the fan sometimes has to be adjusted to make up for that. So for instance, let’s say you had a system that was designed that was supposed to have, let’s say, 200ft of total ducting and ten elbows, and you end up with a system that now has 350 ft of ducting and 15 elbows. You know the fan you bought for the first system, the one you wanted, is not going to work anywhere close to as well on the system that you actually installed and have. And so that’s where I’ve seen issues. Is that what it was designed for isn’t the way it was installed, or it was designed and installed properly. And then as you said, you know, now we add 3 or 4 more pickup points to it and the fan just doesn’t have the extra capacity to handle it.
Chris: [28:33] Yeah, that makes sense. And Diane brought that up quite a bit on her podcast episode I think I think on Engineered Modifications was like the top the top challenge with companies if you change that system, then you can end up with things like combustible dust settling out in your ducts and that sort of thing.
Matt: [28:50] Yeah, absolutely. Absolutely. If you don’t do that, you know, tap and tapers, right. Bring it in branches to the main trunk line. Yeah. And you know, like you and I talked about before, I mean, the fan is the arbiter of truth. I mean, you can do whatever you want to that system, but the fan is going to know and it’s going to basically call you out on any changes that you make on that system.
Chris: [29:09] I write that down. The fan is the arbiter of truth, I like that, okay. So that’s great. I mean, that’s that that is probably about as quick as you could describe a dust collection system and the different components. I would think we just kind of go through an overview. We talked about BWF Envirotec, your role there. We talked about the different components of a dust collection system, the hood ductwork, the box or the bag hose, the exhaust system and the fan. We talked about different categorizations, categorizing by when the filter bags are cleaned, if they’re cleaned in the airstream that’s online or if they’re, they’re cleaned when, you know, the Airstream is deactive in that part that’s offline. We talked about how the cake is cleaned off the bags, and we talked about different types of filters themselves. We went through hoods and enclosures. We went through ductwork, baghouses and fans and just kind of talked about what people need to know. And there are a couple of key things like fitting your process parameters, your dust or your material, or rather, your process conditions, your moisture levels, size and shape of what you’re picking up.
Chris: [30:19] Need to pick it up. You know, if you only need to pick up so much, that’s one thing. If you need to pick up everything, that’s another thing. And that all really needs to go into your, your dust design or your design of the whole dust collection system, that’s really what you need to know your stuff in order to do this and then still know your stuff afterwards. Because if you start making modifications to the system, then you know you’re going to end up with a not well functioning system at the end of the day. And as Matt said, you know, the fan is the arbiter of truth. It’s going to find out if you did something without telling. So with that, I just want to give you, you know, one more chance. Is there anything else that you think people need to know about dust collection systems? Maybe tying into combustible dust, but even just just things that you see out there in the industries every day that you’re working in.
Matt: [31:03] Yeah. I think the two items that come to mind real quickly. So the one is just general TLC on the piece of equipment, you know, like you talked about. As things run, they’ll change. The dynamics change. This is true with, you know, ducting. I mean ducting will not last forever. If it starts to get holes in it, then that’s going to take away the capacity. If the, you know, the hood for some reason starts to, you know, again, get holes in it for whatever reason or isn’t sealed properly, you know. So just general TLC on the overall system is definitely needed. The other one that I would bring up is more towards the combustible dust side, and that is instrumentation on a Baghouse is usually not as robust as I would like to see in some of those systems. So like for example, hopper level indicators, I don’t see them out in industry nearly as much as I would like to. And if you think about combustible dust, and for me, a lot of that history I have with them is pulverized fuels. So if they sit for a while and they start to smolder, these are all bad things to happen in a hopper. And if you don’t have the instrumentation to let you know, hey, my hopper is now at a high level and now it’s at a high, high level. I have no good way of looking into that bag house to get an idea of what materials coming out of the airlocks, or the double dump valves or whatever you have. So, you know, looking at it as a bag house as a way of enhancing the overall process. And sometimes you have to do that by putting some more instrumentation into it.
Chris: [32:31] Yeah, I like that. And that’s probably the next level discussion on all this is what instrumentation do we need to be able to, you know, analyze our system and understand when it’s, when it’s gone, when things are going towards, you know, a hazardous situation. So I think that’s a you know, that’s probably a great ending point for this episode. So yeah, we’ve been talking about a dust collector training mini session. We’ve been talking with Matt Devitt of BWF Envirotec. If you want to connect with Matt, we’ll have his contact information in the show notes at dustsafetyscience.com/32. I would certainly recommend people check out the Dust Collector Training Academy. It’s from September 16th to 19th of this year in Hebron, Kentucky. This is something that I really was hoping to get to last year. I didn’t make it, and this year I have it on my list to try to get to as well, because I know that there’s a lot more that we can learn over a three day period, and kind of getting your hands dirty then, and you can do it in a 25 minute podcast. So I would encourage people to check that out. We’ll have in the show notes. It’s also in the events calendar at dustsafetyscience.com.events. If you have any other events that you’re aware of that’s not there, you can definitely send those through. Make sure they get included. It’s getting a little bit busy there right now because we include every webinar, every in-person event around the world. So we need to come up with a filter system for that. But for right now, just keep sending it through and we’ll add them and we’ll, we’ll put the filters on later. And that’s it for this, this episode of the podcast. So as always, I just want to thank you for listening to the Dust Safety Science Podcast. Hope you have a safe and productive week ahead. I really appreciate everything that each of you are doing to make facilities handling combustible dust safer every day.
