In this episode, host Mike Abare talks with Max Griffiths, regional sales manager at Magnum Systems and an expert in conveying plastic resins and pellets. They dig into the complexities of pneumatic conveying systems, the impact of environmental conditions and the importance of a meticulous system design.
They also discuss the challenges in handling different types of plastics, the nuances of system components and the consideration of safety measures, particularly concerning dust collection and explosion protection. Max underscores the importance of relying on experts for optimal system design and performance.
Transcript
Mike Abare (intro):
Welcome to Magnum Systems Podcast, where we'll aim to dive deep into the world of A for automate, I for integrate, and M for manufacture. I'm your host, Mike Abare, and I'll be bringing you expert interviews, thought-provoking discussions, and real world case studies that shed light on the latest trends and developments in systems integration. Whether you're a seasoned professional who has seen it all, or just curious about manufacturers who are revolutionizing their operations, this podcast is your one source resource, so sit back and relax as we aim to cover all the challenges automation and integration are solving today. Let's do this.
Mike Abare:
Hello everyone. Today we have Max Griffiths with us. Max is a subject matter expert when we start talking about plastic resins and plastic pellets and the conveyance of those materials in pneumatic convey systems. Max, can you take a few moments to introduce yourself and just share a little bit more about your expertise in the conveying of plastic pellets and resins?
Max Griffiths:
Sure. Yeah. Max Griffiths here, new regional sales manager for the Northeast for Magnum Systems. I have about five years experience on the conveying and transfer of predominantly plastic pellets and flakes. A lot of time spent on the designing of systems and the handling of plastic pellets and flakes. Looking forward to the conversation.
Mike Abare:
When I hear about plastic flakes, plastic resins, I mean I can think of a lot of different plastics in our life, everything from a soda pop bottle to maybe even the plastic that's used on the dashboard of a car. What is the different types of plastic out there that our customers would be looking to convey in a pneumatic system?
Max Griffiths:
Yeah, so my experience personally comes from the conveying of the polyethylene pellets, polypropylene pellets and polycarbonate pellets. I would say predominantly a lot of my time has been spent on the PET recycling side. We're handling both flake from the incoming curbside recycling to the finished pellets after the extrusion and cutting. All these material characteristics need to be taken into account when designing your transfer system, whether that's pressure, vacuum, dilute phase conveying, dense phase conveying, which I'm sure we'll get more into the details of that in a few minutes.
Mike Abare:
You shared, I mean, predominantly in the recycling of plastic and you said curbside, so I'm thinking of everything from that water bottle to the soda pop bottle to anything else that might come into our plastic or recycling area. I mean, that gets obviously processed to the recycling center and then people are buying that scrap, and then what are they doing with that?
Max Griffiths:
Well, those bottles from your curbside are going to your MRFs, which are your mass recycling facilities. There, they're being ground and washed and then repackaged mostly in the bulk bag, super sacks or gaylords. From there, they're being purchased by your plastic recycling processors, who they're taking those plastic flakes conveying them into likely optical sorters where your PET is being separated from all your other plastics, like polypropylene caps on the bottles, you need to get rid of that before your PET can be properly recycled, re-extruded, pelletized and sent out to your bottle suppliers, whether it's Pepsi, Coke, Nestle, all those major players in the PET game. But yeah, a lot of my experience, it's there on that PET recycling side. A lot of knowledge from the upstream on the sorting, to the downstream of the, whether you're filling rail cars, bulk bags or pneumatic bulk trucks.
Mike Abare:
So there's a lot of handling that happens between the time the recycling truck shows up at our curb to it actually being put back into a pellet for the plastic extruder company, again, whether they're doing bottles or whatever with it? A lot of different opportunities there, depending which segment you're working with there, whether it's the recycler or the end user that's trying to pelletize the recycled material.
Max Griffiths:
All that's taken into account when designing the conditions of the convey system. On the flake side, you don't have to worry as much about the breakdown of the flake through the product transport, but when you get to that pellet side after your finished pellet, that really needs to be gently conveyed. A lot of people are doing that, whether it's an optimized dilute phase conveying or a dense phase conveying. This might be a good time to touch on the difference between the two. Your optimized dilute phase is a medium pressure, medium velocity. When I'm talking velocity, I'm really talking airflow, CFM.
Optimized dilute phase, you're staying in your PD blowers, positive displacement blowers or vacuum pumps. The dense phase conveying, which is your slow motion slug conveying, now you're getting into your compressors, you're getting into the high end economic impact, whether it's a large scale compressor network, where on the other side, on the PD blower, the initial investment isn't as high, but on that finished pellet, you really want to transfer that as gently as possible. A dense phase system is always considered, but if the distances are short, the bends are low, you can consider an optimized dilute phase conveying.
Mike Abare:
When I think about pneumatic conveying of, I'll say most materials and plastic resins and pellets and flakes would fall into this, they're showing up at our customer site or any one of those processors. It might be in a rail car, it could be in a PD truck. I doubt at that size they're putting it in bulk bags. But you said there are scenarios where the end user who's going to melt that plastic down and extrude it again, may be buying it in bulk bags as well.
Max Griffiths:
Oh, absolutely. A lot of these end users do not have the rail hookups, so rail cars are off the map. Pneumatic bulk trucks availability, that's kind of a driving factor nowadays. I mean, they're not as readily available as they were, so bulk bags and gaylords, bulk bins, those unfortunately are some of the easiest ways to bring those pellets into the plant.
Mike Abare:
When we start thinking about pneumatic conveying, I'm going to put storage in there as well. Let's break that down a little bit because when I think about storage of plastic pellets or resins or flakes, is there anything there in storage that we need to take into consideration, the angle of the cone on the silo or the use bin or even treatment of that, do we need to put any type of dehumidified air across that? Is there temperature control? What are the things we need to think about in storage of these materials?
Max Griffiths:
They're not as troublesome as some other products. Obviously Magnum has a lot of experience on the food side, mineral industrial industry. On the plastic side, dehumidification and temperature in the storage silo isn't a major factor. Now, talking about the slope of the cone on the discharge of the silo, when you're dealing with a PET plastic flake, they are a light bulk density, they don't flow as easily as a finished pellet, so we would always recommend a 70 degree cone, which is a bit different from your standard 60 degree cone on a typical silo.
Mike Abare:
You just said it, and thank you for hitting on that. Products do behave differently. In my experience, pellets tend to flow more like water and just easily come out of a silo, and if not careful, it can flood a system out pretty quickly as well. When we get to the discharge of the silo, you talked about the cone, is there any other flow aids, whether that's a bin activator or Solimars or things we need to think about to help move that difficult product?
Max Griffiths:
Yeah, so on the flake side, we haven't had too much luck with any aeration, like a Solimar pad. Most of what we would recommend is a mechanical bin activator. There are other products on the market, whether it's a screw conveyor that then feeds your downstream rotary valve. All these need to be considered. We really wouldn't recommend no flow aid at all. Definitely upsize the discharge of the silo, whether it's your standard 10-inch on a pellet, we would maybe take that to a 14 or 16-inch, maybe even bigger, maybe a 20-inch on the flake side. Flakes definitely have the tendency to bridge, so flow aids, definitely on the mechanical side, need to be considered.
Mike Abare:
Now we're getting that product out of the silo, out of the use bin, we're putting it in a convey system, as we decide whether to go vacuum or pressure or dilute or dense. I mean, you've already kind of covered the dilute and dense phase side of it. Vacuum versus pressure, is there a favorable approach to conveying this or does that vary by product, whether it's pellet or flake or resins, or is that just a customer preference?
Max Griffiths:
The customer's typically looking on our expertise on that end, my experience personally comes on the pressure side. Flakes, like we've talked about from the beginning of the conversation here, they're a difficult product to handle. We would recommend a pressure conveying on that. That can be done depending on the distance. That could be done with a regen blower, if the distance and the bends are high, we would go with the PD blower, but that really comes to plant layout. Another point I'd like to touch on here is, the most direct route for that pellet or flake is the optimum conveying practice, so you want to limit distance and you want to limit bends because as your distance and bends grow, your pressure loss increases, which then your velocity increases, which leads to your product attrition, product aggregation. There's always factors where a bend is needed, distance is needed, and that's all taken into account in the initial design of the system.
Mike Abare:
We talk pressure applications. I know we start heating up the air when we start using a PD blower as our means to convey or produce that air. My experience is, for basically what every PSI you're raising that discharge temperature that blower roughly 15 degrees, so conveying it 10 PSI, that's 150 degrees at the discharge just for the rise across the blower plus whatever the inlet air is. We could be producing what? 250 degree, 240 degree air, depending what the ambient air is at that plant or where they're pulling their air from, because they may pull it from other sources than just ambient. How does temperature play into the conveying of these materials?
Max Griffiths:
That also needs to be taken into consideration during the initial design. From my experience, if we could keep that discharge temperature around 150 degree F, we're okay. But like you said, when we're creeping up north of 250, we could bring in a low cost air-to-air cooler. If there's chilled water on site, that's also a more efficient way to cool down that conveyor, so we could do an air to water cooler. The temperature of the pellet traveling through that convey system, every bend that takes, it's creating friction along the backside of that bend, which also creates heat. Those two temperatures play into the product attrition. As those pellets are ripping around those bends, they're pulling off what we call in the industry, angel hairs and streamers. They're generating fine dust. That kind of gets back to the most ideal and efficient routing of the transfer system. Anytime you can limit those bends and distance is an ideal during the transfer of the pellets and flake.
Mike Abare:
I think you alluded to it a little bit earlier about velocities, dense phase versus dilutes. Again, it sounds like what you're recommending or suggesting is that the lowest velocity you can have to carry that product, whatever that distance is, whether it's short, 40 feet, two elbows or 500 feet and six elbows, whatever that distance is, velocities are going to play a big factor in how we look at that system and certainly ultimately what the degradation, and like you said, attrition is on that product.
Max Griffiths:
Pneumatic transfer is all about keeping the relationship between your pressure and airflow. Again, when I'm talking airflow, you can think of it as velocity. As you move down that convey line, your pressure is going to drop, which means your velocity is going to increase, and at the end of the convey line, whether you're feeding a silo or a rail car, your velocity is going to be the highest. You also have your minimum velocity needed at your pickup point, so that's our pickup velocity. We need to get that product moving above the saltation. That minimum pickup velocity is an indicator of what your terminal velocity is going to be at the end.
Mike Abare:
Let's talk a little bit about environmental conditions because I could sit here and say, okay, I'm designing a system that has a silo on it, we're conveying 200 feet to whatever the end process is feeding an extruder. I should be able to take that system that's designed for Pennsylvania and drop it into Texas or drop it into Colorado. Is it that simple? Can one system cover all geographical areas or are there considerations there we got to think through?
Max Griffiths:
Unfortunately not. Like I said, I mean designing of the pneumatic convey system, there's so many factors that need to be considered, and environmentals are one of them. Ambient temperature, outside air needs to be considered. Elevation, dew point, all these play a significant role into how the material reacts inside the system. I keep saying system because that's how this is all designed. Everything plays a role into the performance of the overall transfer.
Mike Abare:
Tell me a little bit about the technology that you see going into these systems. Can you speak to how even using technology today and designing systems really can help them overcome inefficiencies that they had in the past and just haven't wanted to change thought process or thinking or take the next step into modern system design?
Max Griffiths:
Really, anybody can move a product down a pipeline. It's just a matter of how efficiently you do it. What I've had experienced in the past is, you rely on that real time feedback, which is given by your temperature transmitters, your pressure transmitters, your flow meters, all that feedback is telling you that you're meeting the transfer performance and the reliability of the system because that's really what it comes down to is, a plant doesn't want to have plug lines or extreme degradation of the product at the bulk bag loadout or rail car loadout because that's just money lost on their end. Given that reliable pressure and flow feedback, we're giving you the top performance on that system.
Mike Abare:
I sit here, I know certainly conveying a pellet and a flake versus a powder or a resin, that filter receiver, that dust collector, I mean those designs have to be different depending on the material. Can you kind of expand, I mean a pellet that virtually might have little or no dust versus a resin, which obviously has fine particulate low micron, right?
Max Griffiths:
On the dust collection side, I've dealt with your typical bag dust collectors, your cartridge filters. There's the low cost receiving cyclone to an inline filter or hanging bags, but how often do you want your operators maintaining that dust collection? In my experience, I would always rule out that low cost hanging bag or just simple inline filter. We would definitely recommend the cartridge style or bag filter design. That really comes down to material characteristics and dust loads.
Mike Abare:
As I'm kind of getting down into the component level of a system, right? An airlock is different for a pellet than it is for a flake, than it is for a powder resin. Can you expand on airlock construction design?
Max Griffiths:
For your pellets, the airlocks are relatively simple. They're sized off of a higher fill efficiency when handling a flake, and they're typically a lot smaller than your flake handling valves. On the flake side, your fill efficiency drops due to the range and particle size and the much lighter bulk density. On the flake side, you're typically oversizing your valve. That increases your fill efficiency, which is likely you're pushing that 50, 60% fill, but there's also different designs in the valve technology to reduce the chopping and jamming, whether that's in the rotor or the recommended purge kits, endplate purges, body purges that keeps your seals and bearings clean to prove the reliability and lifetime of that valve. Flakes are just tricky, so a larger valve when handling flake is always recommended, but that also needs to be considered downstream on the convey side as well, because as your valve increases, so does the leakage up through that valve, so that needs to be taken into account when doing the initial design.
Mike Abare:
When I think about pellets, I mean they're different sizes. Is there a chance that the airlock is going to shear that pellet, and is that a concern for the customer?
Max Griffiths:
On the pellet side, it's not too much of a concern for the shearing, it's more on the flake side. There are some valve technologies out there where they have inlet plows to kind of direct the pellet into the open space inside the rotor. Those are available. We would recommend a convey stackup with a vent hopper to disperse that leakage air from the incoming product, so then you're maximizing your fill efficiency again and getting the most out of that valve before feeding the system.
Mike Abare:
I have one more thing, and it's always top of mind these days, is safety. I know certainly Magnum designs inherently systems so they're safe, however, as we talk plastics and pellets and all that, is there any other things we need to think about in just safety of design or things customers say, I wish you guys would've done this, or, hey, here's my concerns around safety?
Max Griffiths:
In my experience, it comes on the dust collection side, whether we put explosion panels on there, suppression valves upstream and downstream, or even the mode of transfer or the gas that you're using. I mean, you could go to a closed loop nitrogen if the product you're conveying is highly explosive. I've seen this on the PTA powder conveying, nitrogen needs to be not in an open loop, we'll do that in a closed loop to keep your nitrogen consumption down, but it also minimizes your risk of explosion.
Mike Abare:
In the United States, we obviously have this body, NFPH, National Fire and Protection Agency that publishes guidelines. They're not laws, right? They're guidelines, and then certainly there's what they call the AHJ, Authority Having Jurisdiction that tells us or tells the consumer what they need to do to protect their systems. When we start getting into explosion conversations, that's really important in the design of a system. I share that from my own experience. When we start thinking through that, it's important to know where the equipment is going to be located, because if that filter receiver, that dust collector is in the middle of the plant and there's no exterior wall, then that starts limiting our options because we can't vent into the inside of a building. I know that all comes into play. Have you had any tricky scenarios there about design around explosion protection that's had to think outside the box?
Max Griffiths:
Not too much. A lot of times our dust collectors are placed outside, not too many indoor plant dust collection. Keeps the plant maintenance down as well. I mean, those dust collectors really can become a housekeeping hazard as well. Our recommendation would be, keep the dust collection outside and rupture panels facing not towards the building.
Mike Abare:
The other thing, and we talked earlier about discharge temperatures on blowers, and so I got to imagine if we're coming out of a blower, whether it's 240 or 150, that pipe at the discharge of that blower is going to get some heat transferred to it as well. I shouldn't say I'm sure, I know it will dissipate as it goes down that line. Have you had customers concerned about that for a safety standpoint of how do we protect our employees, our maintenance people from getting burned on even just a convey pipe?
Max Griffiths:
Yeah, that just comes down to the education of your operators. Obviously you need to let them know that those temperatures can reach unsafe conditions, unsafe levels. You could sleeve them with some sort of insulation sleeve, but a lot of times I'm not really seeing that or haven't seen that, but definitely something to consider. Yes.
Mike Abare:
Yeah, I know I've had a few customers that wrap caution tape around it or paint around it. Caution, this area is hot, but just curious if you had seen anything else out there. Yeah, I think insulation becomes another thing. Shrouding it if you will. I've seen that out there as well. As we wrap this up today, what advice would you give to companies that are trying to optimize their conveying of plastic resin and pellets?
Max Griffiths:
Leave it to the experts. We're here to support you and provide the best solutions for your transfer system. We've touched on quite a bit in this conversation. Every transfer system is different. There's multiple conditions that need to be taken into consideration, and we have the experience, the know-how and the in-house capabilities to design these systems to the highest performance and reliability.
Mike Abare:
Leave it to the experts-
Max Griffiths:
Leave it to the experts.
Mike Abare:
I love that advice.
Max Griffiths:
If you run into the issues on your convey system that you tried to do in-house yourselves, we're here to provide the support to debottleneck that system too. That can just be maybe a change in pipe size, a change in blower. Those are the resources that we could provide.
Mike Abare:
Max, thank you for coming today, it's been a pleasure learning more about conveying of plastic pellets and resins. I really appreciate you being here.
Max Griffiths:
Yeah, I appreciate it. Good conversation.
Mike Abare:
That's a wrap for this episode of AIM. Thanks for listening and thanks for joining us today. If you have any questions or you would like to learn more about the topic we discussed today, feel free to reach out to us on our website or social media channels so you never miss an episode packed with valuable insights. Please join us next time as we continue to explore the ever-evolving landscape of systems integration. Until then, keep aiming for success. This is Mike Abare signing off. Good day.
