The faster the refractory installation, maintenance or repair, the more efficient and, by extension, profitable it is to the company, as savings fall to the bottom line. In this Technical Tuesday installment, Roger Smith, director of technical services at Plibrico Company, LLC, examines the challenges of insulation systems, taking a closer look at ultra-lightweight refractory gunite as a fast, flexible solution to controlling heat.
Manufacturers that rely on industrial grade furnaces, boilers and incinerators to produce their quality products are always looking for ways to improve. It is how they stay relevant and, more importantly, profitable. But you don’t get better just by desiring it. You need to identify better ways to get things done and introduce risk-neutral change to current operational processes. By some estimates, inefficient processes can reduce a company’s profitability by as much as one third.
Given refractories’ importance in safeguarding an operation’s multimillion-dollar thermal-processing equipment, and to avoid unscheduled downtime, it is smart business to have a sustainable maintenance and repair process in place. When a refractory situation does arise, the more proficient the process solution the better.
Controlling the Heat
Click the image above to read Roger Smith’s column on extending the life of refractory linings.
Furnace design is largely about controlling heat to maximize energy efficiency. An energy source — whether that is gas, coal, wood or electricity — is used to heat the furnace, and the furnace lining is designed to keep that heat inside the furnace. There are other factors to be considered, such as the environment inside the furnace, whether there is any abrasion or chemical interactions, or whether the furnace maintains a steady state temperature or undergoes temperature cycles. Regardless of what considerations have to be made for the hot-face lining, an insulation package must be used to reduce fuel consumption and control the cold-face temperature.
There are a large variety of insulation packages and materials that can be used in furnace design. Insulation comes in the form of board, fiber, brick and castables. Each type of insulation comes with its own sets of considerations, such as insulation value, installation method and cost. When considering the insulation package for the vertical wall of a furnace, support must also be considered because the insulation is expected to stay where it is placed and not slump over time. There also must be a means of connecting the hot-face working lining to the furnace structure to provide support. This is accomplished with an anchoring system that connects to the furnace shell and penetrates some distance into the dense hot-face working lining.
Anchoring Systems Challenge Insulation Installations
Anchors are considered to be the bones of a refractory installation and have several functions. They hold the refractory to the wall to keep it from falling in. They also prevent wall buckling due to the internal thermal stresses created by high temperatures. And, to a lesser degree, anchors can also help support the load of the refractory weight.
The anchoring system, however, can present big challenges when installing or maintaining the insulation. In most furnace applications, anchors are first welded directly to the furnace shell. Next, the insulation package is installed and finally the working lining. With anchors sticking off the furnace shell, installing insulation can become a challenge.
Fiber insulation in the form of blanket can be pressed into the gaps between the anchors, but it is important that the insulation remains in place during the life of the furnace. Industrial furnaces tend to vibrate, either from use of combustion or exhaust blowers or other process equipment. This constant vibration can cause fiber insulation to slump and lead to hot spots in the furnace wall due to the lack of insulation.
Figure 1. Anchoring systems are installed before refractory insulation and can pose challenges.
Insulation board is rigid enough to support itself on its end and can be found in a variety of densities and thicknesses to obtain the required insulation value. However, insulation board typically comes in sheets that will have to be cut to fit around the anchors. This can result in a significant amount of manpower and a significant amount of time in a furnace installation. The downtime of an industrial furnace can be costly, which often results in tens of thousands of dollars per hour in lost profits. For this reason, companies try to minimize the time spent rebuilding a furnace. Fewer man hours on a rebuild also tends to reduce the overall cost of the project.
Ultra-lightweight refractory gunites offer a means of installing a large amount of insulation in a relatively short period of time. A gunite is a monolithic refractory castable that is pumped dry through a hose under pressure and is mixed with water at the nozzle. Once the wet castable impacts the surface, it stiffens quickly to avoid slumping and hardens as it dries. This means that the gunite could be installed over the anchors with minimal time. The installer only needs to wrap the end anchors with masking tape to keep them clean for the working lining.
Figure 2. Cold-face and heat storage/loss graph for a production furnace
Distinct Differences in Refractory Gunites
Ultra-lightweight castables are a sub-set of the lightweight castables category but with a very important difference: density. For example, the average lightweight castable with a maximum service limit of 2400°F typically has a density of about 80–90 pcf (pounds per cubic foot). By comparison, ultra-lightweight castables with a maximum service limit of 2400°F will have a density of about 25–30 pcf.
This important distinction comes into play when looking at insulation thickness and calculating cold-face temperature. At the stated densities in a furnace operating at 2000°F, it would take nearly three times more lightweight castable than an ultra lightweight castable to achieve the same cold-face temperature — making many ultra-lightweight castables perfect for insulation and most lightweight castable refractories impractical to use as part of the total insulation package.
Ultra-lightweight castables that achieve final densities of 25–30 pcf while offering service temperatures above 2400°F are available through various refractory manufacturers. One such product, Plicast Airlite 25 C/G (aka Liquid Board) from the Plibrico Company, is designed to be installed via casting or gunite using conventional gunite equipment. With low thermal conductivity and thermal-shock resistance, this material is durable and quick to install. It also has advantages over insulation board, which has a labor intensive installation process of cutting around all the welded anchors, and fiber insulation, which can experience frequent hot spots due to slumping insulation. With an ultra-lightweight, Liquid Board-type of castable, it is possible to attain required insulation values and extended lining life with the installation speed of a refractory gunite.
Working With, Not Against, the Anchoring System
Let’s consider a real-life production furnace operating at 2000°F with a simple 9-inch refractory lining consisting of six inches of dense refractory and three inches of insulation. For comparison, we will assume an ambient air temperature of 81°F and eliminate any effects of exterior wind velocity. The dense refractory working lining for these examples is Pligun Fast Track 50, a 50% alumina, 3000°F-rated refractory gunite.
As seen in Figure 2:
Using three inches of ceramic fiber blanket at a density of 6 pcf, a cold face temperature of 252°F can be achieved.
Using three inches of insulation board at a density of 26 pcf, a cold face temperature of 247°F can be achieved.
Using three inches of an ultra lightweight gunite such as Plicast Airlite 25 C/G with a maximum service temperature of 2500°F and assumed density of 25 pcf, a cold-face temperature of 262°F is expected.
The calculated difference in cold-face temperature between insulation board and the ultra-lightweight gunite is 15°F, but the difference in installation time savings could be multiple shifts.
Figure 3. Ultra-lightweight gunite is quickly applied over anchors with standard equipment.
The cost of downtime can be incredibly high for any manufacturer, especially since downtime can result in a series of costs and losses (both tangible and intangible), including production, labor, replacement costs, product losses and, if unexpected, reputation damage. Industry resources estimate downtime can cost thermal processing companies between $250,000 and $1 million per hour. When multiplied over several shifts, this could mean millions of dollars in downtime costs. Not to mention that labor is a major contributor to the overall cost of a refractory project. The quicker the refractory installation, the less downtime and the more profitable the company.
For example, in an approximately 750-square-foot round duct application (cylinder) with anchors already installed, on average, installation of four inches of the different insulation types can be estimated at:
Fiber Insulation — 137 total labor hours, or ~5.5 square feet/hour
Insulation board — 288 total labor hours, or ~2.6 square feet/hour
Ultra-light gunite/Liquid Board — 80 total labor hours, or ~9.4 square feet/hour
The quick and easy installation of the ultra-light gunite/Liquid Board represents an average estimated financial savings in downtime of between $35 million and $130 million — savings that drops directly to a company’s bottom line. The time compression of installing gunite also holds an added advantage for the insulation installer because labor hours can come with a premium price tag and can sometimes be in short supply. All of this makes the ultra-lightweight gunite solutions an excellent choice to minimize downtime and rebuild costs while meeting the furnace design criteria.
Conclusion
Manufacturers that rely on industrial-grade furnaces, boilers and incinerators to produce their quality products are constantly looking for ways to reduce costs, increase profits and improve efficiencies by looking at and introducing risk-neutral change to current processes. Maintaining efficiency and avoiding unscheduled shutdowns of heat processing equipment requires maintenance. Selecting quality materials and risk neutral installation processes that minimizes maintenance completion times can help companies become more efficient.
About the Author:
Roger M. Smith Director of Technical Services Plibrico Company, LLC
Roger M. Smith, a seasoned professional in the refractory industry, is the director of technical services at Plibrico Company, LLC. With a master’s degree in Ceramic Engineering from the University of Missouri — Rolla, Roger has over 15 years of experience in the processing, development and quality assurance of both traditional and advanced ceramics. He has a proven track record in developing innovative ceramic formulations, scaling up processes for commercial production, and optimizing manufacturing operations.
In this Heat TreatRadioepisode, Mark Rhoa, Jr. from Chiz Bros, a company specializing in ceramic fiber products, discusses insulation with host Doug Glenn. Mark focuses on the benefits of ceramic fiber in industrial applications. The conversation covers decarbonization, the importance of insulation and thermal shock resistance, the shift to electrically heated modules, and practical maintenance tips for ceramic fiber-insulated furnaces.
Below, you can watch the video, listen to the podcast by clicking on the audio play button, or read an edited transcript.
Doug Glenn:I want to welcome our guest today: Mark Rhoa Jr. from Elizabeth, Pennsylvania, near Pittsburgh. Mark’s been involved with the industry for quite a while with Chiz Bros, our sponsor for today. Mark is also aHeat TreatToday40 Under 40honoree from the Class of 2021. And, Mark, could you tell me who started your company — your dad or your dad and his brother? I don’t know the history that well.
Mark Rhoa: My dad actually joined the company in ‘97, but when he joined, Chiz Bros. had been around for a good 30 years or so. It was started by the Chiz brothers originally: Al, Ray, and John Chiz. As they got older and some of them moved on from the company to retire, my dad took over the company in 2014, and that’s when I came on board.
I’ve been here about ten years. And Ray Chiz Jr. just recently retired; he is one of the original owners’ sons who was working here running our warehouse. He’s the last with the Chiz name to work here. We say that the Chiz haircut is kind of what I’ve got going on. You can know by the haircut there’s a lot of Chiz’s still working here, and you might even be an honorary.
Doug Glenn: I can be an honorary, for sure. I don’t have enough on the side.
Chiz has been around for 50 some years doing specialty solutions for refractory applications in the metals, power, glass, and ceramics industries. And you guys deal with multinational companies as well as the small Ma and Pa shop furnace manufacturers or heat treaters/thermal processors, a pretty good mix. You’ve got great customer service, reasonable pricing, and quick delivery. And I know you and I have talked about how you guys pride yourselves on having a lot of stuff in stock. And finally, you guys have your Pittsburgh location and are also in Detroit, which is a relatively new addition, right?
Mark Rhoa: Yeah, about two years ago we opened up a Detroit warehouse. We’ve always had some good clients up that way. You’ve got to have some boots on the ground to be super effective. I say to get the easy orders you’ve got to have the stuff on the ground to get the hard orders, which are the phone calls at 5 o’clock on a Friday saying, “Hey, we need to pick this up because the furnace is down.” And we didn’t have that opportunity to improve our customer service up there before opening that location.
We try to punch above our weight to compete with the big guys on pricing. We make sure we’re always still answering the phone.
Doug Glenn: It makes a huge difference when you’ve actually got people answering the phone.
My understanding is that you provide castables, fibers, brick, etc. But today we want to hone in a little bit on ceramic fiber.
Mark Rhoa: Ceramic fiber is the big portion of our business. We’re one of the biggest Unifrax (Alkegen) ceramic fiber distributors in the country. So, a lot of what we do is being driven by ceramic fiber products we supply. We still can supply castables, bricks, and everything in between. But ceramic fiber drives the ship for us.
What Is Ceramic Fiber? (04:58)
Doug Glenn: Let’s talk about that. Most of our listeners are folks with their own in-house heat treat. But let’s assume we’ve got some people watching that don’t know some basics.
Tell us about ceramic fiber: What is it? How is it made? What are we using it for?
Mark Rhoa: I describe it to people who may not know much about it by comparing it to the Pink Panther insulation that people may recognize up in their roof or in their walls. Ceramic fiber is white, but picture that insulation for 2300°F. That’s what ceramic fiber is, and it’s a form that we sell the most of right now.
Ceramic fiber
You can take that and cut gaskets out of it. You can form it into hard boards through a vacuum forming process. You can take it folded into what we call ceramic fiber modules; your furnace probably has modules in it if it’s a traditional gas-fired or electric furnace. Ceramic fiber products typically aren’t used on the vacuum side of things. People with all vacuum furnaces are probably not going to be using ceramic fiber. There are cloths that are ceramic fiber based as well. There’s a bunch of other ways it’s used.
Ceramic fiber is made of a blown, spun glass. Essentially what you’re doing is dropping the liquid aluminum silica mixture, and it gets blown or blown and spun at super high temperatures. I’m not going to get into the details of the differences there, but whether the stream is blown or is spun on wheels will determine the tensile strength of blanket.
In the grand scheme of things, what you’re doing is collecting all that fiber and getting it onto a mechanism that’s moving along a conveyor belt. Then it’s getting needled from each side to interlock the fibers to make a 26” wide blanket. It’s going to be trimmed off an inch when it goes through, and at the end you have a 24” wide x 1” thick, 8-pound density roll coming out.
Those densities can vary based on how much fiber is going into it. It’s pounds per cubic foot. But when you’re using a 1” thick piece, it’s divided by twelve from a weight standpoint. The fiber you’re needling in there determines the density.
And there are slightly different chemistries for 2300°F, 2600°F, and the most expensive would be 3000°F polycrystalline. The process to make that is a little bit different, too.
But most people are probably more interested in what we’re doing with it. What’s the Chris Farley line in Tommy Boy? We’ll keep it PG, but “take a butcher’s word for it” — take our word for it; it’s made the right way.
Now we can get into how it’s actually used.
Doug Glenn: It’s basically like insulation in your house, like you said. That’s probably the best description of it for people that need to know. But it can obviously go to a much higher temperature.
In an industrial setting, why would you use fiber versus a castable or brick?
Why Fiber? (08:28)
Mark Rhoa: Ceramic fiber is a great insulator. We’ll probably get into why a better insulator is important for decarbonization efforts and things like that.
It’s certainly a better insulator than castables, easy to install, and easy to use. The main reason it’s preferred is for its insulating value and ability to have varying temperature ranges, which you can certainly do with castables and brick.
But to put brick in a wall 12” thick, for argument’s sake, you will need four layers of 3” brick on there. With ceramic fiber, you can take one 12” x 12” module, shoot it onto the shell, attach it, and be good to go from there.
The main thing would be longevity and stuff like thermal shock value. One of the things you have to worry about with castables and brick — maybe not as much with IFB but standard brick — is the heat cycling. Heat treat furnaces are a great example of that.
That door is opening up a lot, so the air is coming in there. People probably see it in their furnaces. The castable is going to want to crack because it’s not designed for thermal shock like ceramic fiber is.
There are certainly applications that you wouldn’t want to use ceramic fiber for. If you’re looking at a traditional heat treat furnace, it depends on how the load is supported: If the floor is the refractory, it is actually supporting the load, and you’re going to want some sort of brick, some sort of castable. Fiber is going to be soft, compressed, and get beat up. You can’t necessarily put it everywhere, but there are areas where it may be up for debate on.
You can use a brick or you can use fiber in the wall. Traditionally, you’re going to use fiber for the insulated value, thermal shock value, installation, and weight; it’s a lot lighter.
A lot of heat treating furnaces are small compared to the massive furnaces in steel melting. They’re going to ship heat treating furnaces. With ceramic fiber, a 12” x 12” fiber module, 12” thick, weighing roughly 12–14 lbs. is 5–10x lighter than brick or castable.
Repairability (10:51)
Doug Glenn: How about addressing the repairability issues between castable and brick and fiber?
Mark Rhoa: Fiber, especially if you’re getting into higher temperatures, can have some shrinkage to it. But you’re able to repair fiber a lot easier. If you wreck a little bit of fiber, you can get in there and get it repaired quickly. With a brick or castable everything’s tied together as either a monolithic piece or a bunch of bricks that are connected, it can start to become a house of cards scenario where you pull and one goes down then everything goes down.
Doug Glenn: It’s like a Jenga game. You pull that brick out on the bottom and what happens?
Figure 2. “You don’t want to pull out the wrong brick.”
Mark Rhoa: Yeah, you don’t want to pull the wrong brick.
Doug Glenn: You already mentioned the temperature ranges we’re talking about. The standard bottom temperature is 2300°F; the fibers are good up to 2300°F. Then you’ve got 2600°F and then 3000°F. Is that roughly the breakdown when you’re looking at fibers?
Mark Rhoa: I don’t know why they ended up doing this, but for 2300°F ceramic fiber, realistically you only want to use it to 2150°F. That goes along with the shrinkage curve of it. I forget the exact number, but I think it’s like in 24 hours, you get less than 3% shrinkage. Typically, the rule of thumb is that you don’t want to use that full temperature range; you want to give yourself 150°F of cushion to be safe. It will still have shrinkage after that up to that temperature.
I don’t know who ever thought of that; it was probably some genius marketing guy to get a little extra.
Fiber Shrinkage (12:57)
Doug Glenn: You’ve mentioned shrinkage a couple different times. Why does that happen with ceramic fiber? And how does that impact installation?
Mark Rhoa: When ceramic fiber hits its operating temperatures, it shrinks up. On the chemistry side, I don’t have an answer there. But we factor in compression to help alleviate when something shrinks. It’s already pushing out against something. It still keeps its resiliency (it wants to pop back out), and that’s factored into every design.
If you’re doing 12” modules, you’ll have a batten strip between them. That makes up for some of the shrinkage that may come where there’s not compression. Any sort of design we would do, or probably anyone would do, is going to factor in shrinkage. You don’t want to just put something in there, and when it shrinks, it leaves a gap. You want to make sure you have something in there that’s going to fill that gap; and that’s typically for modules.
Now if you’re getting to a low temperature, we’re talking about a furnace at 1200°F, you’re not going to have to worry about shrinkage. Even in some of those furnaces, you’ll see designs we call wallpaper — a pin’s exposed and you’re layering on top of it. You’re just kind of overlapping gaps, but you’re not going to have any shrinkage there, so you don’t really have to worry.
Figure 3. Avoiding gaps when shrinkage occurs
Doug Glenn: There is one question I did want to ask you when we were talking about the different temperature ranges of 2300°F, 2600°F, and 3000°F. Are the chemistries between those different?
Mark Rhoa: They’re all alumina silica based. 2300°F is like 50% alumina and 40% silica. They’ll typically inject some zirconia in it, maybe around 15% zirconia. That gives it the extra boost. Alumina is what drops down.
We don’t want to get into every example, but it does have a lower aluminum content. Sometimes in aluminum melting you can get some flexing because there’s zirconia in there, so you need to know the exact application.
And then the polycrystalline, what people call the 3000°F, would be 72% alumina. And that’s made in a calcined process. The 72% alumina is the key factor.
You can also have super high aluminum blankets. Saffil® is the typical brand name. And that’s a 95% plus alumina. That’s for high hydrogen atmospheres, stuff where there’s bad attacking, bad off gassing. The alumina is usually more resilient to that. Some aerospace applications have that stuff spected in for effectiveness and also because they probably have government money. Why not pay for the highest quality, most expensive thing, right?
Electric Element Modules (18:32)
Doug Glenn: You mentioned modules before, but I want to take a little bit of a different angle. The modules you were talking about have no type of heating element in them. They’re just simply the insulating modules that you put on the side of the wall, side by side, maybe alternating the orientation. But what I want to talk about are electric element modules. Can you describe what those are and why you are using them? And maybe hit on the decarbonization or electrification element of those?
Mark Rhoa: Traditional fiber modules are used in a gas furnace, even an electric furnace that may be heated by glow bars or radiant tubes or something like that. That’s going to have a similar penetration there.
One of the systems we call our ELE system. I’d say in the last two years we’ve probably had as many inquiries or conversations about going to these electrically heated modules than we have in the past 5–10 years combined. A lot of that has to do with companies wanting to get away from gas, or they’ve got pressures for different environmental or cost saving reasons.
What we’re doing with that is hanging the elements on the ceramic fiber module. And when they show the pictures of this one, there’ll be one in there. But that allows us to do a modular system where they can get a lot of power on those walls, and it lets us keep a lot of the same insulating value from using modules without having to use brick or a super heavy element in the sidewalls for support.
Electric Element Modules
When someone says we’re putting this many BTUs of gas; here’s the load, size, weight. We do the electric calculations to see how many kilowatts of power we need to pump into this furnace and elements in order to heat something up just like you would do with gas.
And rest assured, someone a lot smarter than me does those calculations. I’m just a pretty face that gets to sell them. But this is something that we’re seeing a lot of. There’s a big push coming from the government and boards of directors.
Doug Glenn: It’s going to help companies reduce their carbon footprint if that is their desire.
I have a question for you about those and specifically about installation. If every module needs a power source, do you have to punch a hole in the furnace wall for every module, or can you interlink them and only have one power source at the end of the chain?
Mark Rhoa: Good question. I didn’t do a good job describing that, but the modules will still go in just like a regular module. They actually have an extra set of ceramic tubes in them. When we do our design, we know where the elements are going to be hung.
If you have a 10-foot wall, you’re not going to have ten 1-foot pieces of element. You’re going to have an eight foot string of elements along that wall, and they will be hooked into the loops. One end of the hook will go on a loop, the other end will go on the ceramic tube that’s inside the module.
If you have a 12’ x 12’ high wall, and you may have a 10’ element in there, you’re probably only going to have four penetrations, maybe more. It’s not going to look like Swiss cheese. They’re going to be linked together.
These are all based on the number of zones in a furnace, too. Some super high aerospace applications are going to have everything super fine tuned just like it is with burners. If you think about how certain applications require way more precision and control over burners, the same thing can be true for these elements, too. The more precision and control you need, the more complicated it’s going to be just like it is with burners.
Before you hang the elements, you could look in that furnace and it would look just the same as a regular gas-fired furnace without the burners. Then you start hooking the elements on the walls. And the pictures of it are helpful.
If anyone has seen Home Alone, he goes into his basement and his furnace is shooting out all the flames. If you walk into a plant and can see that, getting that to seal will prevent heat from leaving.
Mark Rhoa
Furnace Doors (23:52)
Doug Glenn: When I think about ceramic fiber (which you don’t often see it inside a furnace if the door is closed), but a lot of times you’ll see it jammed in around the doors. To me it doesn’t look like that’s the way it’s supposed to be. So, doors are an issue, right? Can ceramics help with that?
Mark Rhoa: In heat treating furnaces, the temperatures aren’t totally crazy like forging furnaces where there’s a lot of shrinkage so they’re replacing it all the time. In heat treat, the temperature is lower. The main wear and tear items we see when we’re working on a repair with a client are around the doors because they’re getting the mechanical abuse of constantly changing. In some of the decarbonization talks I’ve attended and given at trade shows, we’re really looking at ways to save heat. Just making sure your door is sealed properly can do wonders.
If anyone has seen Home Alone, he goes into his basement and his furnace is shooting out all the flames. If you walk into a plant and can see that, getting that to seal will prevent heat from leaving.
You hear all these decarbonization talks, you see all these millions of dollars being thrown around, and, really, you can make a huge difference on a shoestring budget by simply making sure your door is sealing the way it’s supposed to seal.
If you can see the heat coming out, it’s like dollars flying out of your furnace on a game show. You’d have people lined up for that every day of the week.
So you hit the nail right on the head there. A really small, easy way to make a calculated decarbonization effort is making sure you have a door plan or you’re changing it.
It’s the same thing with tuning burners. Little tunes to a burner can save tons of gas and tons of CO2.
Figure 5. Heat leakage from doors needing maintenance
Doug Glenn: Making sure you’re maintaining good flame curtains on a continuous furnace, all that stuff just keeps the heat from coming out.
Did I see correctly that you guys do door repairs?
Mark Rhoa: We’ll do door repairs in our own shop. If someone ships a door to us, we’ll do the realigns there. About 20 years ago, we stopped having our outside contracting arm. Now we’re not doing any of the fieldwork. But we do realign doors in our shop.
Fiber is pretty easy to work with. Door perimeters are something that can easily be done by someone’s own maintenance crew. Maybe they’ll need one of our sales guys there making sure they do it right the first couple times. But it’s not a hard thing to do. If you have a 12 inch module perimeter, switch those 40 modules out once a year and you’ve got fresh gas savings.
Ceramic Maintenance (27:07)
Doug Glenn: Let’s shift gears a bit and talk about typical maintenance of ceramic-insulated furnace. What do we need to be careful about? Any tips you can offer?
Mark Rhoa: There’s another really affordable thing you can do. You can probably sometimes see this if you have a hot spot where paint’s chipping off or melting or if you have a temperature gun you can find those hot spots. If you see heat on the outside, then you’re typically going to see some sort of crack or gap on the inside. Make sure you have scheduled maintenance downtime with your furnace and stuff in any of those cracks.
If you’ve got a really big furnace or a continuous furnace, roller hearth, furnace type thing, the roll seals are some of the areas where you’re going to end up losing a lot of heat because there’s more wear and tear there. There’s just more opportunity for expansion and contraction.
We do have ceramic pumpable products. We call it liquid ceramic fiber for when there’s a hot spot on a furnace, it’s a big one, and you can’t get in there, you can drill a little hole on it, pump it in from the backside, and fill that up. You don’t want to start making your furnace Swiss cheese and poking holes.
It can be a quick stopgap. If you can’t get inside the furnace, fill it in from the backside, too. Because you don’t want those hot spots to grow and cause problems. You don’t want them to get to the hardware.
Then you may have a module where the hardware gets too hot in the backside and the module ends up falling in. That’s one scenario. You can get out ahead of it by filling some of those gaps.
For a refractory on the hearth, too, if you don’t want to replace a hearth you can find a refractory contractor to come in and (if you have a big furnace) spray gunite over the hearth to fix any gaps or cracks.
Doug Glenn: That’s more for castable, though?
Mark Rhoa: Yeah. On the fiber side of things, you’re looking for hot spots.
Doug Glenn: The takeaway is to make sure you’re taking regular thermal imaging of your shell of the furnace. If you’re noticing some hot spots, it’s time to investigate.
Mark Rhoa: If you have a lot of furnaces, you can get a thermal imaging gun for a couple hundred bucks and really [keep an eye out].
An even bigger deal are the doors. It will blow your mind if you look at the temperatures on a fresh door seal versus an old one. Have a temperature gun to justify to your bosses. “Hey, we realigned this, and it is 150°F. This time last year it was 250°F–350°F degrees.” Common sense can tell you we’re losing more heat when it’s like that.
Concerns with Free Floating Fiber (30:20)
Doug Glenn: Can you address the concern that some furnace users have regarding free floating fiber, especially in furnaces where there’s high velocity airflow?
Mark Rhoa: Talking about the benefits of fiber versus brick and castable, one of the benefits of the hard refractory is it does better with high velocities. Patriot furnaces may have a fan in there. Typically, they’re not getting high enough where we need to worry. You can put coatings on the fiber or rigid dyes or things like that to harden them.
But from a health and safety perspective, anytime you’re working with fiber you want to make sure you’re wearing a mask. They have warning labels on them. It’s not like it was back in the day. I’m not allowed to say the “a” word [asbestos]. So there are not worries like that anymore, either. But refractory ceramic fiber still does have a warning label on it.
We do have body size soluble fiber. Alkaline earth silica (AES), non RCF fiber, a bunch of fancy names, are more prevalent in Europe because of their rules. California’s got a lot of rules, too….
But we do supply that as well. It doesn’t have any sort of warning labels on it.
Obviously, when you’re working with it, you want to wear a mask because dust in general isn’t good. But it’s naturally soluble for your body.
It’s not quite as strong. It can have more shrinkage at lower temperatures. But it’s best to talk with somebody and understand what the right product is to use. Things can be a little worse, but there is a slight move in the direction of body soluble fiber because there are no warning labels on it. But it’s not drastic.
Some of the similar concerns foundries have is with sand and airborne silica now. Technically, I guess going to the beach we’d have airborne silica, too. There’s justification to taking those precautions, but it’s certainly not all doom and gloom.
The ceramic fiber is essentially little glass beads, like a tadpole head and then there’s a fiber tail that interlocks.
Mark Rhoa
Doug Glenn: What I heard wasn’t so much a human safety issue. It was the use of ceramic blankets inside of an aluminum annealing furnace: If the fibers got airborne, they would come to rest on the coils and mess up the strip going through. And then you have contaminated coil or it’s marked.
Mark Rhoa: The issue with that is the shot on the fibers. The ceramic fiber is essentially little glass beads, like a tadpole head and then there’s a fiber tail that interlocks.
Fiber has come a long way. The shot content is way lower than it used to be. But it’s certainly a concern if that gets on a coil and then it goes through the rolling mill and you make a small dent in all the glass … yeah.
A lot of different things can be done for that. People put up cladding; people rigidize it to lock the fiber in.
There are definitely concerns for all the applications. Big aluminum homogenizing furnaces may have that. Traditional, smaller batch annealing furnaces may not.
It would be the same thing if a little piece of brick chipped off onto [indiscernible]. The worry with some of the fiber stuff is it’s obviously a lot smaller so you don’t get to see it.
Doug Glenn: It’s a lot more conducive. You can imagine the difference between a brick being hit with high velocity air and a fiber, you would just see the degradation of the fiber. A fiber ceramic blanket would go down quicker.
Induction at Chiz (35:20)
I have one other question for you about Chiz. Your company was one of our sponsors at our recent Heat TreatBoot Camp, and I was surprised when you had an induction coil on your table. If you don’t mind, address what it is Chiz is doing in the induction area?
Mark Rhoa: We were using the company down the road from us, Advanced Materials Science (AMS), to machine some of our fiber boards and bricks that were a little too complicated for what we had in-house at the time. They have some really good CNC equipment up there. The guy who owned AMS was looking to sell off that branch of his business. We had been one of his bigger clients, and we came to an agreement to it; it’s still out of the same building, same equipment, same guys that are doing all the good work.
We started getting in there and saw a lot of the induction heating equipment on the client list — a lot of those electrical plastics, high temperature plastics, electrical marinite and transite boards, which we got into a little bit in the Chiz Brothers world but didn’t fully dive into it because the temperatures are a little bit lower than what we’re dealing with on the ceramic fiber side of things.
It’s been really good for us. They’ve got great machining capabilities down there to machine some of these complex parts out of NEMA G10 and marinite and transite and all these terms that were relatively new to me when we bought them.
It’s really helped us at some of these trade shows because three types of furnace guys walk by: the gas-fired guy, he’s my best friend; the induction guy used to be like, “There’s not that much we can do with you.” Now, we can do a lot with them.
And then I’m still trying to figure out how I can be happy when the vacuum furnace guy walks by. That will be a different battle for a different day. I’m not trying to get into the graphite felt world. I probably just can’t be friends with everybody.
But it’s been good to get into the induction industry. It’s something that we’ve been growing over the last year or two because we hadn’t been engaged with people quite as much as we had.
Doug Glenn: Well, we’ll look for opportunities for you to be friends with the vacuum people. One thing I know from experience, Mark, you could be friends with anybody. I’m sure you can work it.
Mark Rhoa: I’ll try my best.
Doug Glenn: You’re doing good.
Thanks so much. I appreciate your time and appreciate you being here.
Mark Rhoa: Look forward to seeing you at the next event. For anyone watching, Heat TreatBoot Campwas great. Whether you’re a supplier or heat treater, it’s a good group of people bouncing ideas. It’s a crash course on a hundred different things in two days. I was there to sell stuff, but I learned stuff, too, which was an added bonus. I’d recommend it to anyone watching. It’s a good way to force yourself to get out of the office. I will definitely be back.
Attendees of the 2024 Heat Treat Boot Camp with the Heat Treat Today team Heat Treat Boot Camp Completion Ceremony: (L to R) Doug Glenn, Mark Rhoa, Thomas Wingens
About The Guest
Mark Rhoa Vice President Chiz Bros Eleanor Rhoa, daughter
In the heat treat industry, Mark handles Chiz Bros‘ relationships with various end-use customers as well as furnace manufacturers. Given the critical need for energy efficiency and uniform temperature throughout the heating process, Mark has been able to develop custom refractory and insulation solutions for customers to meet their complex needs. Through participation in the ASM’s Heat Treat Show, MTI’s Furnaces North America,Heat TreatToday’sHeat TreatBoot Camp, and IHEA’s Decarbonization SUMMIT, Mark has been supportive of the industry, but more importantly, has helped countless customers improve their thermal efficiency and profitability. Mark was recognized inHeat TreatToday40 Under 40 Class of 2021.
Understanding abrasion can be the key to extending the life of your refractory lining. The following article provided by Plibrico Company examines abrasion resistance, its role in choosing a refractory solution, and what factors to take into consideration when assessing counter-measures.
Refractory material is designed to be very durable, withstand extreme service conditions and defy mechanical abuse in many different types of thermal-processing operations. However, severe conditions that cause abrasion in the form of high levels of mechanical scraping and airborne particulate matter can challenge refractories, shortening their service lives.
Abrasion resistance is one of the most critical and possibly the most misunderstood considerations when choosing a refractory solution. A clear understanding of what abrasion is and, perhaps more importantly, what it is not can prevent needless repair costs and lead to significant savings. This is especially important when evaluating refractory designs for a new application or when considering upgrades for an existing one.
What Abrasion Is
Abrasion is the destructive process that causes a material to wear away through mechanical scraping or scratching. Anyone who has ever grated cheese or sanded wood has experienced the abrasion encountered in everyday life. As abrasion continues, thin layers of the abraded material are removed, leaving the object thinner and usually making its surface smoother.
The same process can be observed in the refractory world. Refractory linings are abraded by high-velocity airborne particulate, cleaning tools and fuel/process materials that pass through the unit and come into contact with the lining. The telltale sign of abrasion is a refractory lining that has steadily become thinner while its surface has become smoother. The surface may even shine as if it had just been polished, which is not surprising when we consider that polishing is another common form of abrasion.
Fig. 1. Abrasion damage to the refractory bottom of a choke ring of a thermal-oxidizer unit
What Abrasion is Not
Abrasion is considered a type of mechanical abuse, but it is not the only type of mechanical abuse to which refractory linings are subjected. Equally common is impact: the sudden, forceful collision between the refractory lining and a moving object. Impact can come from a variety of sources. The moving object may be a cleaning tool, a piece of process material, a chunk of fuel or a dislodged mass of refractory or slag, depending on the application. Impact with such objects typically results in chips and cracks in the refractory lining.
Refractory materials designed for abrasion resistance tend to have increased strength and hardness compared to those found in traditional refractories, and these abrasion-resistant materials may provide some resistance to impact. Abrasion-resistant properties can also lead to increased brittleness. This is because if the impact exceeds the strength of the material, chipping and cracking could potentially be worse than in traditional refractories.
Compression and tension are also forms of mechanical abuse and can be caused by changes in the shape of the refractory lining as it is heated or cooled or by movements of the furnace shell itself – by intentional design or otherwise. Here again the increased strength and corresponding brittleness of the material could potentially result in a negative effect on the refractory lining.
All types of mechanical abuse can cause thinning of the refractory lining, so it is important to conduct a detailed investigation into the destructive mechanism before drawing any conclusions. Refractory solutions designed to resist abrasion may not be helpful against damage caused by impact, compression or tension.
Similarly, solutions designed to address other types of mechanical abuse may be ineffective against abrasion. For example, stainless steel needles are commonly incorporated into refractory linings to extend service life when impact resistance is required. The needles bridge cracks formed as a result of the impact, making it more difficult for these cracks to grow and connect. This helps the refractory lining hold together longer. The bridging provided by needles has no effect in an abrasion situation, however, since crack growth is not caused by the abrasion process.
Meeting Abrasion-Resistance Demands
Once abrasion is identified as the main mode of failure, there are several options to counter it. Selecting a refractory material based on a raw material hard enough to resist the abrasion is a common technique. For one material to abrade another it must be harder than the material being abraded. For instance, a diamond can be used to scratch glass, but glass cannot be used to scratch a diamond.
It follows that refractory materials based on very hard raw materials, like silicon carbide, can be used to resist abrasion and extend the life of the lining. It should be remembered, however, that a refractory lining is made up of many different materials, not just the main constituent raw materials. Clay, cement, silica and other softer components will still be exposed and abraded even if abrasion of the main aggregate is stopped completely.
Another option is to investigate the source of the abrasion and make adjustments to the process. Can a less-abrasive cleaning tool be used? Is there a way to limit the contact of the abrading process materials with the refractory lining? Is it possible to adjust the angle between the refractory lining and the incoming airborne particulate?
A seemingly minor change in the process, with minimal cost and no downsides to the operation, can save in refractory replacement costs. When changes to the process are not an option, it is best to consider the abrasion resistance of the lining as a whole and select a specifically designed abrasion-resistant solution. A qualified, knowledgeable refractory solution expert with genuine experience will help you make the best decision for your specific application, taking into consideration the following:
Speed of installation
Service life
All-in price
Fig. 2. Airborne particle matter has contributed to the abrasion damage seen in the refractory of a thermal-oxidizer choke ring. Notice on the left side of the photo how the abrading of the refractory lining becomes worse.
Abrasion-Resistance Testing
The most common measure of holistic abrasion resistance used to compare refractory solutions is the ASTM 704 test. This test exposes refractory lining materials to a stream of abrasive particulate that cause a portion of the sample to be abraded over time. By keeping sample size and shape constant – along with particle velocity, particle material and test duration – various refractory materials can be compared on an apples-to-apples basis.
This testing can be performed by any qualified refractory testing lab and most reputable refractory manufacturers. Test results are recorded based on the volume of material lost from the sample during the test and are reported in cubic centimeters. Products with excellent abrasion resistance consistently test at 5 cc of loss or less, while elite materials can score less than 3 cc of loss.
Products designed specifically for abrasion resistance will report ASTM 704 results on their material technical data sheets. It is important to remember that the abrasion-loss numbers reported on material technical data sheets are based on samples prepared in a lab under controlled conditions. Achieving these same properties in the field under real-world, job-site conditions would require a high-quality refractory installer partnered with a world-class refractory manufacturer.
Fig. 3. Severe conditions lead to abrasion damage in the refractory lining of this dry-ash hopper. Notice the abrasion damage goes past the anchor line, leaving the bottom-left anchors exposed.
Conclusion
The thinning of a refractory lining due to abrasion is a source of frustration for many thermal-processing operations and is one of the most common modes of failure encountered in the refractory world. But, by taking the time to understand the failure mechanism and learn about the options available, you can realize significant savings by avoiding needless costs in the future.
Heat TreatToday publisher Doug Glenn wraps up this three-part series with Pelican Wire experts by talking with John Niggle from Pelican Wire about thermocouple insulation types and considerations.
The first two episodes cover the history, types, vocabulary, standards, and other basics of understanding how thermocouples work. Listen to the previous episodes of the series here.
Below, you can either listen to the podcast by clicking on the audio play button, or you can read an edited transcript.
The following transcript has been edited for your reading enjoyment.
Doug Glenn (DG): Welcome to Heat TreatRadio!
John Niggle (JN): Yes, it's good to see you again, Doug. I know we've run into each other a couple of times out there in the field. I'm looking forward to having the opportunity to do all of this stuff in person again.
DG: It will be nice. Before we hit the record button, we were talking about shows this fall and hoping that they happen because you, like I, are ready to get out and go.
You are the business development manager for Pelican Wire. If you don't mind, give us just a little bit of background about you and about your experience in the whole thermocouple world.
Pelican Wire headquarters
JN: Sure, absolutely. As you said, I am the business development manager at Pelican Wire. I've been at Pelican since 2013 so we're working out my eighth year here. I'm a career industrial sales representative. I do have previous experience also, actually, in the process instrumentation industry. Way back when, before I even knew how to spell thermocouples, I was selling that stuff when I first got out of college. My career has, sort of, gone full circle, let's say.
DG: Very nice. Well, you've got plenty of years of experience, which is great. We've had two previous episodes with your colleague, Ed Valykeo, and we covered a good bit of stuff. We covered a lot of basics in the first episode. We covered standardization, and things of that sort, in the second episode. I want to encourage any listeners who haven't listened to those episodes, feel free to go back, Google “Heat TreatRadio” and search for “Pelican Wire” and listen to episodes 1 and 2.
John, you and I want to move forward. I'm always kind of curious about this question: From your perspective, with your experience, why do we use thermocouples? Let's talk about what they are and why we use them.
JN: First of all, we have to assume that somebody is trying to measure the temperature of some sort of a process- a process or an event of some kind. That's basically what they're trying to do. Compared to other devices like RTDs, bimetal thermometers, liquid expansion state change devices and so forth, thermocouples are robust, they're inexpensive; they're repeatability, they're ease of use and size -- all of those factors lead them to be more widely used than another sort of thermal measurement device of any kind. It is the preferred method.
On top of that, I mentioned the expense part. Because they're relatively inexpensive, there are certain industries, the heat treat industry and smelting industry, for example, consider these as, actually, consumable or disposable. So, the cost factors in significantly in the industry that we're talking about here.
DG: I live in western Pennsylvania and the town where my wife grew up, there was an old Leeds and Northrup manufacturing plant. I believe they made the consumable thermocouples for melt shops. You would, basically, throw the thermocouple in and it would melt quickly but it would give you a response during that time.
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JN: Right. And, as I mentioned earlier, the response factor is important, or that's one of the factors considered, when people are looking at thermocouple wire. And, you're correct, Ed Valykeo, as you mentioned, has 40 years of experience in the industry and has seen exactly the same sort of thing that you're talking about where people will just tack weld it onto something that gets thrown into a furnace or it gets thrown into a melting pot or something like that, and they're looking for that instantaneous temperature.
If you don't mind, I'll tell you that we've done some work, actually, in the aerospace industry and we had a customer that we sold significant, literally miles, of thermocouple wire to (when I say aerospace, it was specifically for space exploration) and this was because of whatever we had done with the insulation. I can't tell you, because it was before my time, but this is what was relayed to me- they were able to get another 3 - 4 seconds of temperature measurement out of that wire. That critical, extra data for them made all the difference in the world.
DG: We're going to get to the insulation part which should be interesting. You won't have to tell us any trade secrets, but we are headed in that direction anyhow.
So, different types of thermocouples. Again, just a review question for us. Why use them? Why the different types and why are we using different types?
JN: Forgive me, Doug, and the rest of the audience, for that matter, if I end of repeating some of the things that came out in the previous episode. Basically, when you're talking about thermocouples, there are the two chemistries; for lack of a better term, you have “base” and “noble” metals. The base metals are really the metals that we focus on at Pelican. The noble metals are the more expensive ones- rare earth metals, tungsten, titanium, platinum and all those sorts of things that people spend exorbitant amounts of money on. There are purposes for those, but, typically, what you're going to see in the heat treat industry, in particular, you're going to see a lot of the base metals.
I like to say that, truly, the 20 gauge K, in particular, is the 800 pound gorilla in the room. It's almost considered, and I think it would be by people in the industry, a commodity. There are untold miles of that wire that are used in the heat treating and smelting industry. K is used, really, because of the temperature range. It fits in well with what people do in the heat treating industry. It is good for temperatures from zero up to around 1260 C. It's inexpensive, it covers the ranges that those people are looking for, and, again, it's the 800 pound gorilla in the room when it comes to temperature measurement in the heat treating industry.
Click to read the Heat Treat Today Original Content article on thermocouples.
The other types such as J comes up periodically, particularly if you're looking at lower temperature ranges. You won't see it quite as often in the heat treating industry. You will see it somewhat, but not to the degree that you would K. The J thermocouple wire has an iron leg so it does oxidize and you need to be careful about that sort of thing. Type T thermocouple wire has a narrower range. It has very good response times in cryogenic and cold temperature applications. The higher, upper end of type T thermocouple wire, typically, wouldn't be of terrible interest to the audience that we're involved with here, for the most part, because the upper ends around 370 to 400 C degrees, in lab environments; that's where it's going to be the most popular.
There is also type E. It's a higher temperature, as well. Response time. Broader range is a little bit better than K at lower temperature ranges. An interesting one is type N that you will see fairly often in the heat treating industry. For those people not familiar with type N, it is different alloys than type K. It covers virtually the same temperature range that type K does and will, actually, have less drift than type K. It is more expensive because of the alloys that it is made of, but, again, if you're interested in less drift, then type N is worth looking at. It hasn't quite caught on in the US the way it has in, say, Europe, in particular, and that really has to do with the infrastructure of the instrumentation. People have instrumentation that is either calibrated for K or J or something like that. Now, there is instrumentation out there, now, that would use K and N both, so we may see more, particularly, in the aerospace industry I would think it would become more and more popular.
DG: That's helpful. It's always good to hear those things over again.
How about the parameters and/or the factors that need to be considered when you're constructing the wire to start with? What do we need to be worried about in that area?
JN: I don't know if I like the word “worried” exactly, Doug. It's more, what do we need to think about? What do we need to be concerned about? Besides the metallurgy that we just talked about, we need to think in terms of what the sensor is actually going to look like. Is it just the wire? Thermocouple wire, by itself, can be a thermocouple; that's it, without any protection or anything like that.
As I mentioned earlier, you can tack weld it to an ingot, or something like that, and there you go. You don't have any probe, there is no thermal well to protect it or anything like that. But, what we do need to think about, then, is the process that it's going to be involved in. Where is it going to be used? Is it going to see an environment where there is a flow. Is it going to see an environment where somehow the thermocouple wire can become damaged? In that case, then, we're headed in the direction of talking about what our customers are interested in. And for a customer for Pelican Wire, we're mainly talking about people who actually assemble thermocouples – they make the connections, they have the molds and all that sort of thing.
To be clear, Pelican Wire just makes wire. And, again, the thermocouple wire can be used as a thermocouple, but a tremendous amount of wire is actually connected to some sort of a sensor or a probe, as I said, and is protected in a thermal well or something along those lines.
"But, what we do need to think about, then, is the process that it's going to be involved in. Where is it going to be used? Is it going to see an environment where there is a flow. Is it going to see an environment where somehow the thermocouple wire can become damaged? In that case, then, we're headed in the direction of talking about what our customers are interested in."
John Niggle
DG: Do we also have to be concerned with oxidizing, carburizing atmospheres, corrosive atmospheres? Is that, also, something that we need to be aware of?
JN: Absolutely. And that is one of the reasons you will see a probe thermocouple is because the wire is protected from that atmosphere. Nearly all of the wires that we talked about would be affected, particularly, in say, like a sulfurous environment; it would be subject to corrosion, oxidation and something along those lines.
Other factors, of course, are the accuracy and how much space we have. Believe it or not, if it's going to go into a small orifice, then we need to think about what the age size is going to look like. And then the environment: Is it going to be abrasive? Is there movement? Is there some sort of braiding motion that could wear a hole in the wire in the insulation and so forth? There are a lot of things to think about.
DG: And, it would probably be a good idea, especially if our heat treat people are running anything outside of the norm, regardless of what it is, whether it be atmosphere, configuration, fixturing, if there is anything outside the norm, they would probably be wise to mention it to the thermocouple wire and/or thermocouple probe manufacturer and make sure that they know so that you guys can get help get the right thing on there in their furnace.
JN: Yes, absolutely. At the end of the day, we work with this every day. We have design engineers on staff who can assist with technical questions and so forth and, of course, our customers, and the actual thermal wire assembly people, this is what they do every day of the week.
“I'll tell you that we've done some work, actually, in the aerospace industry and we had a customer that we sold significant, literally miles, of thermocouple wire to (when I say aerospace, it was specifically for space exploration) and this was because of whatever we had done with the insulation.”
DG: Let's talk about something a little bit new, I guess, to our conversation here in this 3-part series, and that is the insulation that's going to go around these wires. Can you tell us what are the different types of insulations and what are the advantages and/or disadvantages of each, and why would we be using them?
JN: I'll break it down into, what I would call, the four basic categories. That would be an extruded insulation, insulations that are tapes, fiberglass insulations that are routinely worked with and then, of course, high temp textiles. High temp textiles, in particular, would be of interest to the audience here in the heat treat metallurgy world.
Extruded insulations can be a variety of thermoplastics. A term that, I think, Ed has probably mentioned before and we've talked about before is extension grade wire. That typically has a PVC insulation on it and the reason PVC works for that is that it's cheap and extension grade wire, typically, does not see the sorts of high temp environments that you're going to see in processes. It's really a signal wire that takes the signal from the probe or from the sensor to the process control device.
DG: So what kind of temperature tolerances can the extruded wire handle? Are we talking 300, 400 degrees? I guess you talk C, I talk F.
Teflon frying pan
JN: We talk whatever language our customer likes to talk, but we do talk C quite a bit. So, PVC is quite low, it's in the 200s F. But, when you're looking at fluoropolymer insulations (and Pelican is really a high temp house, so we focus on the higher temp insulations) you have FEP and PFA, those are in the 200s. PFA actually goes up to 260. So, you can see, it's probably not suitable for heat treating applications, smelting and that sort of thing. The advantages to those compounds would be that you're going to have abrasion resistance. Think about your Teflon frying pan: it's slick, it's smooth. So, if you're in an environment where there is some movement, it will be good for that. And, of course, it will have excellent moisture resistance and chemical resistance. Those would be the advantages to the extruded wire. The other advantage would be, because you'll have a thinner wall than you will with the other insulations, you'll have some more flexibility. So, if you have a type N radius, you can go around a corner easily.
The next step up, in terms of temperature resistance, would be the tapes. Basically, in that area, you're looking at PTFE tape, mica take and capped-on tape or polyamide tape. Those will give you slightly higher heat resistances. The mica, in particular, would give you more. (Mica, as a matter of fact, is used as a supplement to the PTFE to give it even higher heat resistance.) Mica will go up to 500 C, PTFE and the polyamides match, in terms of heat resistance, the extruder products around 260. What they do give you, again if you use the tapes, is the heat resistance you're looking for, some abrasion resistance and the moisture resistance. You'll have less flexibility because those products are stiffer, but they're also going to be a little bit lighter weight unless you incorporate the mica into it. Then, when you do that, you're going to end up with an even stiffer wire and it will be a little bit heavier, and all those will be larger in diameter than an extruded wire. If you look at an environment where you need to poke the wire through a hole and that hole is an eighth of an inch, you need to think really hard if what you're doing is going to work.
DG: So you've got extruded and you've got tapes.
JN: The next step after that would be fiberglass. In the case of fiberglass, you have E glass and S glass. Of the two, E glass would have the lower temperature resistance and you're looking at 482 C on the high end. For S glass, you're up to 704 C. Now you're starting to talk about insulations that you will see in the heat treat environment; it's quite common, especially on the S glass side where you're looking at the 704, you'll see a lot of people that need 500 C for whatever reason. The advantage, obviously, to the glass, as I mentioned, is the higher heat resistance.
There are disadvantages. Think about fiberglass for a minute. We actually have to saturate the wire to keep it from fraying without it ever really experiencing any abuse. If we don't saturate it, then the wire can fray, and you can get fiberglass in your fingers even, which is unpleasant. So, fiberglass has some disadvantages like that. If you put it in an environment where there is some movement, abrasion, vibration or something like that, it can be problematic. Also, it's going to be stiffer because it's saturated, typically. Sometimes you'll even see those saturants even cause problems in a heat treat environment where, if it gets too hot, the saturant can leave an ash behind. You're going to lose flexibility, as I said. You're not going to have the abrasion resistance, the chemical resistance or the moisture resistance that you're going to get from an extruded product.
The other one that we see, again, literally miles and miles and miles of, in the heat treat world would be what's called Refrosil and Nextel, (those are both, actually, trade names). We're talking about vitreous silica and ceramic. Again, those are, what we call, high temp textiles. Now, you're looking at products that are in the 1200 C range. Ceramic goes up to 1204, vitreous silica is in the 870's. Again, there are some of the same disadvantages with those that you're going to have with glass. It's going to be somewhat fragile. We don't saturate those because the saturants are not going to hold up in the environments that they're going to be placed into, so you would have that ash residue left.
Again, it will be stiff, it will be even larger in diameter than the fiberglass, which is larger than tape which is larger than the extruder products. Of course, you're not going to have the abrasion resistance, the moisture resistance or the chemical resistance. But it does protect the wire in those elevated temperature environments that are critical for the heat treating industry.
DG: Let's back up a bit. I want to understand something you said. You said, in the fiberglass, it is saturated and in the textiles it's not. I want to know what you mean by saturated.
JN: It's either a solvent-based or a water-based saturant that is applied to the wire to protect it. Think in terms of a varnish. It would be like a protective coating. Again, it just keeps the exterior of the wire, the bare wire, from being exposed. It's a coating, but we call it a saturant.
DG: High temperature textiles tend to be the stuff we're using, in the heat treat industry, probably most.
JN: Yes. Again, when I mentioned the 800 pound gorilla in the room, the 20-gauge K with the vitreous silica or the Refrosil would be an extremely popular product in the heat treating industry, absolutely.
DG: Let me ask you a very, very fundamental question. I'm curious of your answer to this. Why do we insulate wires at all? Is it done to protect from temperature or is it done simply to protect them from crossing with each other and grounding or shorting out? Why do we insulate?
"I'll go back to something that I know Ed talked about: the Seebeck effect. You have this loop; if you don't have that loop, then you don't have anything. You don't have the EMF, the electromotive force, that you're looking for."
John Niggle
JN: It is the second part. When you look at any wire construction, the two singles have to be insulated from each other. I'll go back to something that I know Ed talked about: the Seebeck effect. You have this loop; if you don't have that loop, then you don't have anything. You don't have the EMF, the electromotive force, that you're looking for. We do make a wire that is not duplex, but, typically, what you're going to see is a wire that has two singles and then it's duplexed with an insulation over the top. We do make a wire that the two singles are jacketed in parallel and then no jacket is placed over the top but that is for an application that wouldn't be suitable for the heat treat industry.
DG: I asked that question, because for those who are unbaptized in this conversation, it's kind of interesting. So, we're talking about insulation and we're doing a lot of conversation about temperature ranges and, for someone who wouldn't think so, they would say, "Well, that means you're insulating because of temperature." But, really, the reason you're insulating wire is for electrical. It's to keep them apart. It's just how high of temperatures those insulations can handle, not that you're insulating the wire to keep them cool. Right?
JN: Absolutely not.
DG: That may sound very basic, but there may be people that think that, so I want to get that on the table.
JN: Most of the people in the audience are probably familiar with this already. Typically, what happens is the wire is stripped so we have exposed ends. And then those ends, as we mentioned earlier, can be tack welded onto something or they can just be out there. The thermocouple world, by the way, is an incestuous world where we have customers, we kind of compete with those customers, some of our customers compete with others of our customers but then they buy supplies from each other. You probably already know that from talking with other people in this industry. At any rate, the wire is stripped and then it's either tack welded or it's connected to some sort of sensor or probe of some kind.
DG: It's a tangled web, the whole thermocouple world. You've got customers, yet you sell to certain suppliers who also sell to those customers. It can be complicated! But that's OK, we'll let you guys worry about that; we just want to make sure the thermocouples are good and we'll be in good shape.
Another question for you: We talked about the process and a lot of different environments about what type of thermocouple you should use, but does the process being monitored influence the type of insulation that should be used? Obviously, temperature is going to have an impact, but is there anything else?
JN: Yes. Let's circle back to what we talked about earlier just a little bit. When you look at the process, you need to think of what is going to happen to that wire? Is it going to see, first of all as you mentioned, the temperatures? That is certainly important so that comes into play with the insulation. But, we need to think about, Is there movement? Is there going to be some abrasion? Is there some sort of activity that could damage the wire somehow? Then, we need to look at the chemicals, like we talked about. Do we need some chemical resistance? Do we need water resistance? Is it going to be submersed in something? Those things all need to be considered.
Again, as I mentioned earlier, the actual placement of the wire. Does it need to be inserted in a hole? At Pelican, we produce wire down to 40 and actually 44 gauge which, I think, will probably be stunning to most of the people in your audience because, again, 20-gauge K is what these people think about. In the heat treating industry, what you see is they need a robust wire, something that's going to be able to handle those temperatures and a large conductor like that.
Another thing to think about, actually, is a bend radius. Are you going to put the wire somewhere where it needs to go around a corner, around a bend? Then, are you better off using a stranded wire? A stranded wire is going to have more flexibility. You can buy a 20-gauge stranded wire, you can buy 24-gauge, 28-gauge, 36-gauge.
DG: Now, what do you mean by stranded?
JN: Stranded wire would be instead of just one solid 20-gauge conductor, you have multiple strands that make up that 20-gauge. But, if you think about it, multiple strands of wire will actually be more flexible. You'll still get the same results, but it will be more flexible if you need to go around a corner or if you need to insert it into something.
DG: It's almost like a braided wire as opposed to a solid.
JN: Yes. Now braiding is a little bit of a different process. When we're talking about stranded wire, it's, basically, just spiral. Braided is more crossed into each other, which, coincidentally, is the way that the fiberglass and the high temp textile insulations are made – those are actually braided. And, by the way, I'll just toss this out, it's made on equipment that really hasn't changed since the ‘20s. I'm not talking about the 2020s, I'm talking about the 1920s! Rumor has it, some of that braiding equipment was, actually, designed by Thomas Edison. I'm not sure if that's really true. But that is the process used to apply the fiberglass and high temp textiles.
DG: So, anything else as far as any other considerations we need to take into consideration when we're talking about choosing insulation? If not, that's fine.
JN: I think I covered them, Doug.
DG: At Pelican Wire, your company, I know you guys deal with a broad number of markets, I'm sure, one of them being heat treat. What do you see as any special demands or special concerns that are, maybe, unique or, at least, inherent in the heat treat market?
". . . what you see is insulations that are higher in temperature resistance, as well. In some cases, as I mentioned earlier, in ovens where there is a saturant involved, we could see ash. Some people ask that saturant not be applied to the fiberglass and that's certainly something that can be done."
John Niggle
JN: For the heat treat market, again, I'll go back to what I said earlier, we see a lot of 20-gauge K used. It's because of the higher heat requirements, the higher heat that is involved with the processes of heat treating. Secondly, what you see is insulations that are higher in temperature resistance, as well. In some cases, as I mentioned earlier, in ovens where there is a saturant involved, we could see ash. Some people ask that saturant not be applied to the fiberglass and that's certainly something that can be done.
Sometimes we're even asked to not put tracers. We go back to what we talked about earlier with the metallurgy- you have two legs, a positive and a negative leg. Well, how do those end users tell those legs apart if they look similar, if they're an alloy of some kind? So, we put a tracer wire in there so you have a red leg and a yellow leg, in the case of type K, or sometimes you just have a red leg depending on what they ask for. Those tracers can, actually, cause problems, too, if the ovens are hot enough and they are in there for long enough times. We even have customers who ask us not to put tracers in their wire, for that matter.
Accuracy, of course, is extremely important. I know that Ed, in a previous episode, talked about standard limits, special limits and all that sort of thing. Typically, you're going to see special limits used in the heat treat industry and, in some cases, we're asked even for special calibration points. In previous podcasts, I've heard you talk with other people about AMS2750 and how that comes into play. It is extremely critical for the folks in the heat treating industry and something that clearly a thermocouple wire producer has to understand.
Episode 1 of 3 of AMS2750 series
DG: Let's say you've got a customer that calls you and wants to talk about their thermocouple needs, let's say there is some sort of special need. What would you suggest they have, in hand, when they call you? What do you need to know from them to help you do a better job with their thermocouple needs?
JN: Honestly, the first question we do ask is: What temperature are you going to be running this at? How hot are we going to be? We, absolutely, need to know that. That helps us narrow down the alloy that we might be looking at, whether it's type K, type J, type E, or whatever. And then, of course, it's a natural thing to dial in the insulation after that. Quite honestly, one of the things that frustrates me is when people say, "I need Teflon." Well, OK. Do you need FEP or do you need PFA? Those are both fluoropolymers like Teflon is. We need to talk about temperature resistance, so don't tell me you just need Teflon. We do need some specifics when it comes to that sort of thing. Again, we talked earlier about stranding and stranded wire. Do you need some flexibility? What gauge size do you think you need? How robust does this wire need to be? Those are some of the key factors we need to know about.
DG: Let's say, for example, somebody does want to get a hold of you or Ed, your colleague who was on the first two episodes, how is best to do that? How can we get a hold of Pelican Wire?
JN: Our web address is www.pelicanwire.com, about a simple as it possibly gets. Our email addresses are, actually, quite simple, as well. If anybody wants to email me, it's jniggle@pelicanwire.com. You can contact me directly, if you want to, or we have a sales inbox and that is simply sales@pelicanwire.com. We do have a phone number, but it seems a lot of people don't care about phone numbers as much these days. But the number is 239-597-8555.
DG: I have one, unrelated, question for you that I know the world is wanting to know: How is it having a company in Naples, Florida, that's what I want to know?
JN: I'll tell you what, Doug, the answer today will be different than the answer in October or December. It's actually quite nice. We moved down here 8 years ago in 2013. I moved from the Midwest and didn't really feature myself owning palm trees, but I own palm trees, which is pretty darn cool. We are, as the crow flies, about 3 miles from the water, where I live anyhow, 20 minutes by car. Our office and manufacturing facility are, actually, on the very edge of the everglades. You can see the picture in the background behind me. That's our building. That's actually facing east. That is a sunrise over the everglades. We're on the very edge of the everglades. There is a lake right next to our building and then, after that, it's everglades all the way over to Miami. And, real quick, our weather pattern comes from the east. It doesn't come from the Gulf. This time of year, in the summer at about 3:00 in the afternoon, about the time that we're doing this call right now, a thunderstorm blows up and it comes from the east over the everglades and it moves to the west. The trees blow that direction, you can see it coming. It's interesting. During the wintertime, I have to tell everyone, you'd probably be jealous, but it is truly paradise.
DG: Yes! I've been to Naples, ate at a nice restaurant down there, years ago, but it was very nice.
You guys are also employee-owned, right?
JN: That's correct, yes. The company is over 50 years old. The founder of the company passed away in 2008 and, before he passed away, he converted the company to an employee-owned operation. So, we've been employee-owned since 2008. We've purchased a couple other companies since then that folded into, what we call, the Wire Experts Group. Pelican Wire is part of that. We have a sister company out in Colorado. We bought another facility in Chicago and folded that into our company in Colorado. So, yes, we're employee-owned and it works out really well for the employee owners, I'll tell you that much.
DG: That's great. John, it's been a pleasure talking with you. Thanks for taking the time. I appreciate your expertise. Hopefully, we will see you out on the pavement somewhere in the real world.
JN: I'll, actually, be seeing you at the heat treat show in about 3 weeks.
DG: That's about right, yes.
JN: Hopefully, some of the people that are listening we will see, as well.
Doug Glenn
Publisher Heat TreatToday
To find other Heat Treat Radio episodes, go to www.heattreattoday.com/radio and look in the list of Heat Treat Radio episodes listed.
Dan Szynal, VP of Engineering and Technical Service, the Plibrico Company
A significant number of refractory lining failures can be traced to either faulty design or improper installation of the anchor system. The tips of anchors in particular need special consideration due to their exposure to the highest temperatures.
In this Technical Tuesday feature for Heat Treat Today, Dan Szynal, Vice President of Engineering and Technical Service for the Plibrico Company, a manufacturer of monolithic refractories, gives 3 important tips for refractory engineers and managers to use in achieving an improved anchor design.
It is estimated that up to 40% of refractory lining failures can be attributed to a problem with the design of the anchor system or improper installation. This is a significant number. When designing a refractory lining for an industrial application, anchor design becomes one of the most important factors in creating an improved lining that is supported properly. In particular, the tips of the anchors experience the highest temperatures because they are closest to the hot face and thus become an important consideration.
Anchors have several functions. They hold the refractory to the wall to keep it from falling in. They also prevent wall buckling due to the internal thermal stresses created by high temperatures. And, to a lesser degree, anchors can also help support the load of the refractory weight.
To create a monolithic refractory lining that is properly supported and maximizes service life, here are three important metallic anchor tips you need to know.
Anchor Types and Service Temperatures
Figure 1.0: Recommended anchor tip temperature limits for various common alloys
For refractory linings using metallic anchor systems, refractory engineers and designers almost always use Class III austenitic stainless-steel anchors of various qualities. The typical grades of stainless steel used are AISI 304, 309, and 310. These contain chromium and nickel to provide the best corrosion resistance and ductility at high temperatures. For some applications in which temperatures are more extreme and the use of ceramic tile anchors is not practical for various reasons, AISI 330 and even Inconel 601 is sometimes used. These anchors have higher nickel content for superior oxidation resistance and tensile strength at temperatures of 2000°F or higher. Inconel 601 gives the added advantage of good resistance to both carburization and sulfidation in extreme applications.
Industry Best Anchor Practices
Anchor sizing for a refractory lining depends on the refractory thickness and number of components. Some designers use the practice of sizing the anchor height to be 75-85% through the main dense castable or gunned lining. Other rules of thumb used in the industry dictate that the anchor tip should be no more than two inches from the hot face of the refractory for thicker lining designs greater than 6-7″.
For refractory applications, it is useful to know the temperature gradient through the refractory lining–from the hot face to the cold face–to choose the proper anchor size so that one doesn’t exceed the temperature limit of the alloy being used. To help calculate the correct temperatures at different points in the refractory lining, many industry professionals will use a heat loss calculator/estimator. By using a heat loss calculator/estimator, one can choose the proper anchor height by determining the anchor tip temperature it will experience. There are numerous heat loss applications that can estimate the cold face of a furnace lining given the input conditions of a thermal unit. As part of its value-added service as a refractory solutions provider, Plibrico Company, LLC, has a web-based heat loss application that gives a good estimation of the thermal gradient of the refractory lining from hot face to cold face to maximize anchor thermal performance.
For example, look at figure 2.0. You can see a 9″ side wall of refractory lining using 6″ of a typical 60% alumina low-cement castable and 3″ of 2300°F lightweight insulating castable for an application operating at 2000°F with an ambient temperature of 80°F. For this application, we would select 309 SS or 310 SS metallic anchors because the intermediate temperature at about 80% of the main lining thickness is at about 1900°F. Although 304 SS anchors would be more cost effective and are most commonly used in the industry, the anchor tips would oxidize at this temperature and would essentially burn out.
A Word on Anchor Tips
Standard practice for several years now has been to allow for expansion of the anchor tines by covering the anchor tips with plastic caps, dipping them in a wax, or putting tape on them. Metallic anchors expand at about three times the rate of alumino-silicate refractories. The expansion material affixed to the anchor tips burns out at low temperature and allows the anchor space to expand without causing cracks in the refractory.
Best practices in metallic anchor design also must include anchor spacing. Greatly a function of the specific equipment and geometry size, refractory engineers must consider the specific installation area. For example, anchor spacing patterns will be different in a flat wall or roof as compared to a section that has a transition of geometry or a less critical area of a vessel.
Anchor spacing should be based on the features of each specific project, such as mechanical properties of the anchor, and the refractory lining as a function of the temperature. Refractory engineers will use these properties in mathematical models to help create the optimal anchor spacing pattern and plan.
Often, failures commonly attributed to the refractory component can, in fact, be caused by deficiencies in the anchoring system. A strong anchoring system is key to maintaining monolithic refractory lining integrity, even when it is cracked, to prevent a total structural collapse.
To prevent vessel lining failures, increase service life, and maximize refractory performance, incorporate these metallic anchor tips. With these tips, it is possible to design and optimize an anchoring system that will work well with the demanding needs of refractory linings today.
For more information about metallic anchors and refractory anchoring systems, contact the Plibrico Company at contact@plibrico.com
CMC stands for Ceramic Matrix Composite, and these materials are considered a subgroup of both ceramics and composite materials. CMC components are used in the energy and power, defense, aerospace, electrical, and electronics industries. In this Best of the Web Technical Tuesday feature, L&L Special Furnace Co., Inc. delves into the composition, applications, fabricating process, and uniqueness of CMCs.
An excerpt:
“CMCs are able to retain a relatively high mechanical strength even at very elevated temperatures. They offer excellent stiffness and very good stability, both mechanical, thermal, dimensional, and chemical.”
Dan Szynal, VP of Engineering & Technical Services, Plibrico
Installing new refractory materials is a necessary furnace maintenance practice which needs to be done periodically. But extended downtime and installation errors can be a major financial and operational headache. In this article, Dan Szynal, VP of Engineering & Technical Services, Plibrico, gives 12 factors which will ensure that the refractory installation is successful.
At 700°F, steam can exert 3,000 psi pressure.
During an initial dry-out, the powerful effects of superheated steam can cause explosive, devastating consequences to freshly cured refractory material. To that end, removing moisture from castable and precast shapes is a serious pursuit. The production pressures to minimize downtime can lead to shortcuts and rushed dry-out procedures. Usually, these sidesteps have the opposite effect, quickly compounding delays and costs by causing thermal damage to the linings and potentially incurring personal injury.
Dry-outs fail due to imprecise management of water extraction from refractories. At the boiling point of water, the pressure of steam is less than 1 psi. However, at 700°F, saturated steam reaches 3,000 psi, and possesses enough energy to disintegrate the most resilient refractories. Too much heat, rapid ramp-ups, vapor lock, poor curing, and surplus water can contribute to potentially hazardous situations.
Here are the 12 preventive factors to manage for dry-out safety and success:
1. Hot spots and flame impingement. Ensure that your burner flame is centered accurately. The direction of flame in the vessel must promote equal heating of all the refractory surfaces. A flame that impinges on a single area of the surface will quickly create a hot spot, forcing an unequal expansion of water vapor in that area and resulting in thermal spalling.
Thermocouples need to be monitored at both hot and cold areas to measure temperature consistency.
2. Temperature spikes. Insulation is ill-advised. Attempting to cover green castable with an insulating blanket can lead to destructive temperature spiking when the blanket is removed, breaks, or falls off. At a wall surface temperature of only 550°F, the removal of insulation exposes the surface to an extreme temperature shift which will activate unequal steam expansion and pressure.
3. Thermocouple placement and monitoring. Pay attention to the locations and readings of your TCs. Watching only the coldest location will allow the hottest area of your vessel to heat too quickly in the dry-out schedule. Conversely, monitoring only the hottest area will allow the colder area to retain more water than specified. This will lead to failure later in the schedule or during hold periods. At 700°F, steam can exert 3,000 psi pressure.
4. Air temperature vs. surface temperature. Thermocouples should report surface temperature. Air temperatures are typically 50°F to 100°F hotter, thus misreporting schedule impact. The initial hold period is typically designed to melt burn-out fibers. That creates important permeability. If the actual load temperature is lower than specified, permeability is not created, leading to failure in the next ramp-up period.
Pre-cast refractory requires longer bake-out schedules to release all water vapor.
5. Field vs. precast dry-out schedule. A field dry-out schedule is specified for single-sided heating. It precipitates a dual water migration, first (stage 1) towards the heat as the path of least resistance, but then reversing course (stage 2) and moving away from the heat, escaping towards the furnace shell. Field dry-outs are faster schedules than precast, where the pieces are heated from all sides simultaneously. The precast water migrates to the center of the piece, and that takes longer to escape. By misapplying the faster field dry-out to precast, there is a greater risk of water retention, which will ultimately lead to spalling, even at temperatures of 550°F or less.
6. Venting and air circulation. Proper venting is required to rid the furnace of water vapor during dry-out. Without vents and free air circulation, the steam is forced to exit via the furnace shell, which takes longer than the schedule would provide. Water will be retained closer to the shell side, increasing the likelihood for disintegration as temperature and steam pressure rise.
7. Surface coating. An impermeable coating on the refractory surface will prevent the stage 1 escape of water. Slowly, this water will be forced to move to its second exit, the furnace shell. This delay prepares the still-saturated refractory for failure at the next heat ramp-up.
8. Clear obstruction from weep holes. As stage 2 water migration occurs, it will escape to the furnace shell. There should be adequate weep hole capacity, cleared of obstructions which will allow the water to exit the furnace shell. These provide a release valve for buildup of steam pressure. Thermocouples need to be monitored at both hot and cold areas to measure temperature consistency. Pre-cast refractory requires longer bake-out schedules to release all water vapor.
9. Cold weather curing. In the curing process, simple hydrates form needle-like morphology. These structures promote permeability, and water/steam can more easily migrate through the refractory to escape. Curing in below-freezing temperatures alters the hydrates to be less permeable, thus trapping the water, even during dry-out and creating an inherent risk. As well, cold weather curing slows the required strengthening process, leading to a weaker refractory and likely spall. We have had a thermal operator tell us about a below-freezing cure that went badly: The water in the castable actually froze in place. When the dry-out was initiated, the castable melted and fell to the floor, where it subsequently cured and dried.
10. Cutting short cure time. Recommended dry-out schedules always assume a 24-hour equivalent curing time at moderate temperatures. By cutting short the cure time, water is retained, and strength is reduced. For example, a conventional castable requires 24 hours cure time; high cement/low moisture castable needs at least 16 hours. Adherence to product cure time specifications ensures optimum strength and a successful dry-out.
11. Free water removal without consideration. The goal of curing and dry-out is to create permeability in the refractory at lower temperatures (300°F) to enable water to escape. By quickly ramping up dry-out temperatures for the sake of time, permeability is diminished. At higher temperatures, (+500°F) steam pressure rises aggressively. Again, refractory composition drives curing and dry-out schedules, and as a rule, the faster temperatures rise beyond specification, the higher the risk of failure.
Pre-cast shapes spall at 550°F.
12. Refractory strength as a function of water content. A simple 1% excess of water will reduce refractory strength by as much as 20%. Overwatering by 1.5% cuts strength 25% to 40%. The implications are profound: the refractory will not withstand the steam pressures in dry-out, and worse yet, there is more water that must be extracted. A successful dry-out can be jeopardized by the slightest variance in water composition.
Conclusion
Meticulous care in refractory installation is the foundation to successful furnace operation. While no one looks forward to non-productive downtime, close adherence to product specifications, cure times, and dry-out schedules will ensure a more profitable return to operations. Managing the water issues in refractory composition is job one.
Welcome to another episode of Heat Treat Radio, a periodic podcast where Heat Treat Radio host, Doug Glenn, discusses cutting-edge topics with industry-leading personalities. Below, you can either listen to the podcast by clicking on the audio play button, or you can read an edited version of the transcript. To see a complete list of other Heat Treat Radio episodes, click here.
Audio: George Smith and Dan Graham
In this conversation, Heat Treat Radio host, Doug Glenn, speaks with George Smith and Dan Graham from SBS Corporation, based in Sarasota, Florida. SBS designs and engineers high-performing heat treatment solutions, including heat exchangers, filtration systems, and monitors. This episode will be especially interesting to companies who are wanting to dip their big toe into the Industry 4.0 or Internet-of-Things swimming pool but have been afraid to do so because of their cost or lack of organizational expertise. This episode introduces a relatively new product on the market that is specifically designed for entry-level applications.
Click the play button below to listen.
Transcript: George Smith and Dan Graham
The following transcript has been edited for your reading enjoyment.
“If your maintenance had the ability to monitor everything in your shop — 24 hours a day, 7 days a week, didn’t eat, sleep, or take a break — how much would that guy be worth to you? Probably quite a bit! Now, if you could also simultaneously record every data point from each sensor in your shop by the minute and then call, text, or email you date, time, and set-point readings, I think he’d be worth a lot more.” ~ George Smith of SBS Corporation
Thanks for joining us. I’m your Heat TreatRadiohost, Doug Glenn, also the publisher of Heat TreatToday, which you can find on the web at www.heattreattoday.com. The above was George Smith. George is one of two people we will talk to on this episode from SBS Corporation about their new entry-level and fully expandable monitoring system.
We’ll get back to George and our other SBS guest, Dan Graham, in just a few moments. But first, let me remind you that Heat TreatTodayis ready to help you do heat treating better. Our editorial content is targeted at manufacturers with in-house heat treat shops, especially in the aerospace, automotive, medical and energy sectors as well as general manufacturing. Heat TreatTodaybelieves that people are happier and make better decisions when they are well informed. And it is our passion to help you be well informed. We also like to inform you in ways that are current, like podcasts and targeted e-newsletters. You can subscribe to any of these services on our website. Take some time and check out the information we are providing and feel free to subscribe to any of the services we are offering. Go to www.heattreattoday.com/subscribe.
Doug Glenn (DG): Now let’s get back to our guest. Here is George Smith again, followed by Dan Graham, introducing themselves. Both of these guys were members of Heat TreatToday‘s inaugural class of 40 Under 40. First, here is George Smith.
George Smith, general manager at SBS Corporation
George Smith (GS): I am George Smith, and I am the general manager at SBS Corporation. I have been with the company for 6 years, and it is owned by my family.
Dan Graham (DGr): My name is Daniel Graham, and I have been with SBS Corporation since 2015, and I am the director of technology. I joined SBS as an intern at the tail end of my college career at Rollins College where I studied international business.
DG: Here now is George Smith expanding on his earlier description of the product SBS calls Watchdogg.
GS: [recording] “If you could also simultaneously record every data point from each sensor in your shop by the minute and then call, text, or email you date, time, and set-point readings, I think you’d be worth a lot more.” With Watchdogg, that’s exactly what you’re doing. The Watchdogg’s monitoring system monitors, records, and alerts the appropriate employee when a problem is going to happen before it actually becomes a problem. This can really apply to anything, whether that’s humidity in quench oil, low flow going to a heat exchanger or an over-temperature situation. Any place that you have a 4-20 mA signal available or a place to put a transmitter, you can monitor in real-time and predict what is going to go wrong.
Daniel Graham, director of technology, SBS Corporation
Just a quick example: In the middle of the winter in the Midwest, you’ve got a cooling fan up on your roof. Nobody is going to go check on that fan, but if it’s vibrating too much or pulling too many amps, that can be a sign that the bearing is going bad, so that fan is going to go soon. Watchdogg would text, call, or email you before that breakdown occurs based on those two things. So, if there is anything in your shop that can break down and cause a complete shutdown in production, the Watchdogg is perfect for you.
From the Beginning: SBS Corporation
DG: I have not typically associated SBS Corporation with this type of equipment, so if you don’t mind, give us a brief history of SBS, and what I think most people would typically associate you with, and then tell us about how you transitioned into something like Watchdogg.
DGr: SBS typically provides heating, cooling, filtering, monitoring, and safety equipment for the heat treat industry and we have been since 1974. Our flagship product is the Quench Air which is a quench oil cooler. It can be seen in nearly every major heat treat [shop] in the U.S., and we regularly sell our equipment in 38 countries worldwide. We started in Rochester, Michigan, and recently moved our manufacturing facility to Sarasota, Florida.
So, why text? We thought this was where the world was heading. Trying to find useful data to protect potential problems. Right now we have a product called the Aqua-Sense. This system detects humidity in oil and alerts via strobe and light when humidity is at unsafe levels in quench oil, so it is a local alarm. So, we kind of dipped our toes into technology, but as we looked at that product, we thought, “Wouldn’t it be cool if you could get a text instead? Why do you need to be in the same room as the Aqua-Sense to get the alert?” In our research, we could not find any supplementing systems that could simply alert by text that was industrial, inexpensive, and reliable, so we just developed our own system.
DG: How long has the Aqua-Sense product been on the market?
DGr: Maybe 7 years.
DG: So basically, the Aqua-Sense was kind of the springboard that at least provided the impetus and the idea to go from an Aqua-Sense, where you’re basically monitoring one or just a couple of specific items, to be able to monitor a lot more and be able to send out text, or I suppose, you can communicate in whatever fashion you want, whether it be text, emails, or whatever, correct?
DGr: Correct. All of that is customizable. You can say – this person gets a text, this person gets a text and an email, and maybe the maintenance manager would get a text, an email, and a phone call.
DG: George, you mentioned this is a family business. Tell us a little bit more about you, and especially since both of you guys were in the inaugural class of Heat Treat Today’s 40 Under 40, it would be interesting to know how you got involved with the industry.
GS: I grew up building our product so I’d come in and spend my summers putting together heat exchangers, and became real familiar with the industry at a really young age, so it was kind of just a natural mesh when my dad called me one day and said, “Hey, will you come in and work for the family business?” I was actually working as a wetlands biologist at the time, and I was in a swamp, pretty close to an alligator when he called, and I thought, “You know what? Sure!”
DG: How about you, Dan? What’s your quick history?
DGr: George and I actually went to the same college and that’s how I got to know him. I finished a couple of years after he did, and in order to finish my degree, I needed to complete an internship. I was having trouble finding internships that I was interested in, and so I gave him a call and he had an opening for me. So I started working ay SBS, finished my degree, and haven’t left.
In-House Heat Treat Shops and Watchdogg
DG: So let’s try to dig in a little deeper. I know you guys have mentioned how companies, to a certain extent, might use Watchdogg. Most of the people who are reading this are going to be manufacturers who have their own in-house heat treat. So, they’ve got dedicated furnaces and things of that sort. How might they best use this? What is typical?
GS: This is a way they can bring their old pusher furnace, vacuum furnace, or whatever they’re using, and bring them right up into the 21st century. This is a really easy system to install on any existing equipment, and then you can monitor everything from your cellphone—like temperatures, vibrations, methane levels, I mean really anything that you can send a 4-20 mA signal with, and there are thousands of applications for that. If something is starting to go wrong anywhere on that furnace, you’re going to get a text message, and it’s going to tell you exactly where something is going wrong.
We have a customer in Tennessee that has rotary furnaces and if those rotary furnaces stop spinning, they basically “banana” and that is a $120,000 shop breakdown. If you can’t get a guy in there with a hand crank right away to get that furnace turning, [then] to save a power outage or for whatever reason a belt breaks, we can send a message out to all those guys that need to grab those hand cranks and get over there. You’re going to avert a very expensive breakdown.
DG: Because people may not be thinking along these lines, let’s give people a sense of what the different types of things that you can monitor. George, you’ve already mentioned some. You’re talking obviously quench oil humidity as one and about flow of liquids, etc. Give us some examples of the more common ones.
GS: Temperature, pressure, methanol levels, proximity sensors, level sensors—there are kind of endless possibilities for it. What we’re doing right now at our shop is using one to weigh our bins so that we know when we’re getting low on certain long-lead items. When we get down to 45 pounds of ¼“-20 bolt, we know to order that, and we get a text message that reminds us to.
DG: That is very interesting and a cool way to do that. So it’s almost inventory control as opposed to process control.
GS: Right!
DG: So how many inputs can Watchdogg take? How many things can you monitor with one unit, or are these units serial? Can you connect them?
GS: You can connect them, but each actual bay station has twelve inputs available. For example, on our filters, we do pressure, temperature, humidity, and then you can get basically a scheduling of when you’re going to need to change all your quench oil filters in your shop. We can send a warning saying these are the ones that are coming up next.
Entry-Level Connectivity to the Internet of Things
DG: There are other companies that are coming out with stuff like this, right? Remote monitoring type of stuff, and we won’t mention names here because we’re not talking about them. But I’m sure a lot of our readers would know who those companies are. How does the Watchdogg differ from those products?
GS: The Watchdogg is industrial, but it is also a low-cost monitoring system. We’re going for people who are just getting into the industrial internet of things. We found in our research that typical systems of our competitors were much more expensive, or the home monitoring systems that would be lower cost couldn’t handle the transmitters that we would require in these facilities.
DG: It is safe to say it’s really a nice entry-level product for someone who might want to get started in this area?
GS: It’s one that you can grow with. The more that you add, you can work towards having your entire shop connected. You can start out with 12 different points; we call them failure points, which are basically those points in your shop where if something goes wrong there, it’s going to shut down production. The question is, what are the most important things that can go wrong, and then what transmitters can we use to predict a problem there? From there you can expand out to doing your filter maintenance or dissolve solids in quench oil.
DG: So basically anything you can measure that has a sensor that is going to put out a 4-20 mA signal.
GS: Yes, it’s going to capture that signal if it’s out of the normal range and it’s going to send you a message. But it’s also going to data log all of that, which brings us into Nadcap. You don’t have to have the guy with a clipboard. There is an unlimited amount of data that it can store and it’s also going to grab it when you want it, whether you want it grabbed once every minute or once every hour. It’s all adjustable. It also gives you a very friendly to read graph.
You can also cross-reference. Let’s say there is a correlation between the humidity in your oil and the temperature of your oil. You go onto the site, you click your temperature, you click your humidity, you pick your date range and it graphs them right together for you. So you can go back 2 years and ask, What temperature was my oil at 1:00 in the afternoon on December 24, 2017? You can go right to that day and figure out what each transmitter was reading.
Storage, Users, and Support
DG: So you said that it’s unlimited storage of data?
GS: Yes, it is unlimited storage.
DG: Now that tells me that it is cloud-based.
GS: It is cloud-based. It is stored on a local server in a secure facility which is protected by an SSL, multiple firewalls, and it is off-site from SBS.
DG: How about the number of users that can be on this?
DGr: Also unlimited. 15 or 1500. The idea is that it’s a safety device. You ought to be able to reach out to as many people as possible if something bad is going to happen.
GS: Let’s say, for example, that you’re reading all of a sudden that you’ve got a bunch of water in the bottom of your quench tank. Well, why don’t you let everybody in that building know to get out of there?
DG: Yes, right. I assume that you can customize. In other words, you’re not going to be sending one message to everybody all the time.
GS: No, you set up each transmitter individually. You put in a list that can call in sequential order or it can do a blast call where it just calls the entire list at the same time or texts and emails at the same time. When you do the sequential delivery, someone can actually acknowledge it as “I’m going to fix that problem,” and it will stop calling the rest of the list. And it also records who said, “I’m going to fix that problem”, who acknowledged that alarm.
DG: You guys are selling this domestically, North America, internationally? What’s the market area?
GS: We’re selling the cellular data-based one just in the USA. The Ethernet-based we’re selling internationally.
DG: What’s the difference between those two?
GS: The cellular has a cellular card in it that works like your cellphone, so you don’t need an internet connection. If you don’t want to run internet out in your heat treat, you can use a cellular-based one, which is dollars a month for the cellular subscription. The Ethernet has to have an Ethernet cable run to it.
DG: And you’re able to support this, I assume, remotely?
DGr: Correct. We have our site, which grabs all these points. You see your heat treat, you see all your sensors, you see where you’re at and a very easy to use website. That’s where you go to set up all your transmitters. So basically you connect power and the 4-20 mA signal to the Watchdogg box, and then you go online and you say, for example, this is going to be humidity, so it will be 0 – 100%. You put in 0 – 100%, 4-20 mA signal, and you want this to alarm when it hits 50% relative humidity—that’s halfway to having liquid water in your oil. Then you hit “Apply” and that sensor is up and running. These things take a matter of minutes to set up.
Let’s talk about difficulty of use. This is such an easy-to-use system. I think people tend to be intimidated by the Internet of Things or having web-based monitoring. It can be a scary word to a lot of people. This is a really simple system. My 70-year-old father went ahead and set his own up, and he is not a “techy” by any means. It takes minutes to set up. It arrives basically as plug in and play. You plug it into the wall, you plug your sensors in, and then we walk you through set-up online. With the customer’s permission, we can access their pages and walk them through setting up transmitters. The website itself really walks you through that on its own. It is very intuitive. Each transmitter takes about 3 minutes to set up, so if you sat down for a half hour, you could have your Watchdogg up and running.
Where Watchdogg Is Headed
DG: What are you planning for the future? What’s in the offing here?
DGr: We’ve talked about keeping the data storage on site, so having a dedicated server in the customer’s facility. Some people just don’t want that information to leave, no matter what. That’s something we see in the future that we’re working on currently. Something else that we have been working on is really meshing this Watchdogg with a customer’s current control panel. This is something that we see pretty soon in development. Basically, we would create like a middle man almost that would split the 4-20 mA signal so that you could use the Watchdogg and your control panel at the same time, using your existing 4-20 mA signals that are coming back to your main control panel on your furnace.
GS: We’re also working to improve our products, integrating Watchdogg into all of the equipment that we’ve already built—our Quench Air heat exchangers, filters, sand separators, scale removal systems.
We hate just having a light on the wall. We were at a heat treat a couple of years ago and they had one of our filter systems and somebody had put a rag over the alarm horn on it because it was annoying. Nobody knows when that filter is full because they can’t hear it go off. So instead, let’s text the maintenance manager and give him a heads up when he’s got 2 days before he needs to change out that filter bag and then we’ll send him another note when he needs to change it. That way he can schedule it ahead of time.
This is all about avoiding breakdowns for our customers. The most costly thing that can happen is having a breakdown. That was our whole focus in designing this—How can we stop breakdowns from occurring?
DG: Are you enjoying the development of it, and are you happy with how it’s rolled out so far?
GS: We’re having a lot of fun with it. We’re constantly wondering what else we can do with it as it has so many applications—in our own shop, much less customers calling saying, “You know, I’ve got this in place and it’s got two more slots open on it, can I do this . . . ?” Then we get to figure out how do they do that, and then in 99% of the cases, our answer is, “Yes, you can do that!”
We had a customer that wanted to monitor his methanol. He called us and said, “Can I do that? I’ve got a methanol transmitter.” We said, “Absolutely!” So he plugged it in and now he’s monitoring his methanol.
DG: Do you tend to find people that will buy it, plug in a couple of things, and then find other things to plug into it because they like it so much?
GS: Yes, exactly. Anything you can think of. Like I was saying with our 4-20 mA scales that we’re using, that wasn’t the intended, original use for this, but we’re not running out of parts that we need!
DG: That’s a relatively innovative approach to it, I think—even inventory control! That’s pretty cool!
So if you’re in a company that is interested in moving into the 21st century and are looking for a fully expandable monitoring system to introduce you to the internet of things, this Watchdogg system from SBS Corporation might be just the ticket. For more information, you should go to www.sbscorporation.com or contact me directly at doug@heattreattoday.com and I’ll introduce you to George Smith or Dan Graham.
You can find more Heat TreatRadio episodes by googling Heat TreatRadio. Believe it or not, we’ll be the first nonpaid thing that pops up. You can also subscribe to Heat TreatRadio on iTunes or SoundCloud. Don’t forget to visit our website frequently. We post one new piece of heat treat information every weekday. You can subscribe to our daily e-newsletter or you can subscribe to our growing number of industry-specific heat treat e-newsletters like our Leaders in Aerospace heat treat monthly e-newsletter, which will debut soon, if not already. We’ll also be introducing a similar version for our automotive industry heat treaters as well as our medical and energy heat treat readers. Watch for them in the near future. Also, since we know that you can’t solve all of your own heat treat problems, feel free to reference our list of heat treat consultants on our website or by googling heat treat consultants. We should be one of the top 2 or 3 results that pop up. Or you can simply type www.heattreattoday.com/consultant into your browser.
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This episode was produced by the recently engaged Jonathan Lloyd of Butler, Pennsylvania. Congratulations, Jonathan! I’m your host, Doug Glenn. Thanks for listening.
Doug Glenn, Heat Treat Today publisher and Heat Treat Radio host.
To find other Heat Treat Radio episodes, go to www.heattreattoday.com/radio and look in the list of Heat Treat Radio episodes listed.
This is the third in a 4-part series by Dr. Steve Offley (“Dr. O”) on the technical challenges of monitoring low-pressure carburizing (LPC) furnaces. The previous articles explained the LPC process and explored general monitoring needs and challenges (part 1) and the use of data loggers in thru-process temperature monitoring (part 2). In this segment, Dr. O discusses the thermal barrier with a detailed overview of the thermal barrier design for both LPC with gas or oil quench. You can find Part 1 here and Part 2 here.
Low-Pressure Carburizing (LPC) with High-Pressure Gas Quench – the Design Challenge
A range of thermal barriers is available to cover the different carburizing process specifications. As shown in Figure 1 the performance needs to be matched to temperature, pressure and obviously space limitations in the LPC chamber.
Fig 1: Thermal Barrier Designed Specifically for LPC with Gas Quench.
(i) TS02-130 low height barrier designed for space limiting LPC furnaces with low-performance gas quenches (<1 bar). Only 130 mm/5.1-inch high so ideal for small parts. Available with Quench Deflector kit. (0.9 hours at 1740°F/950°C).
(ii) Open barrier showing PTM1220 logger installed within phase change heatsink.
(iii) TS02-350 High-Performance LPC barrier fitted with quench deflector capable of withstanding 20 bar N2 quench. (350 mm/13.8-inch WOQD 4.5 hours at 1740°F /950°C).
(iv) Quench Deflect Kit showing that lid supported on its own support legs so pressure not applied to barrier lid.
The barrier design is made to allow robust operation run after run, where conditions are demanding in terms of material warpage.
Some of the key design features are listed below.
I. Barrier – Reinforced 310 SS strengthened and reinforced at critical points to minimize distortion (>1000°C / 1832°F HT or ultra HT microporous insulation to reduce shrinkage issues)
III. High-temperature heavy duty robust and distortion resistant catches. No thread seizure issue.
IV. Barrier lid expansion plate reduces distortion from rapid temperature changes.
V. Phase change heat sink providing additional thermal protection in barrier cavity.
VI. Dual probe exits for 20 probes with replaceable wear strips. (low-cost maintenance)
LPC or Continuous Carburizing with Oil Quench – the Design Challenge
Although commonly used in carburizing, oil quenches have historically been impossible to monitor. In most situations, monitoring equipment has been necessarily removed from the process between carburizing and quenching steps to prevent equipment damage and potential process safety issues. As the quench is a critical part of the complete carburizing process, many companies have longed for a means by which they can monitor and control their quench hardening process. Such information is critical to avoid part distortion and allow full optimization of hardening operation.
When designing a quench system (thermal barrier) the following important considerations need to be taken into account.
Data logger must be safe working temperature and dry (oil-free) throughout the process.
The internal pressure of the sealed system needs to be minimized.
The complexity of the operation and any distortion needs to be minimized.
Cost per trial has to be realistic to make it a viable proposition.
To address the challenges of the oil quench, PhoenixTM developed a radical new barrier design concept summarized in Figure 2 below. This design has successfully been applied to many different oil quench processes providing protection through the complete carburizing furnace, oil quench and part wash cycles.
(i) Sacrificial replaceable insulation block replaced each run.
(ii) Robust outer structural frame keeping insulation and inner barrier secure.
(iii) Internal completely sealed thermal barrier.
(iv) Thermocouples exit through water/oil tight compression fittings.
In the next and final installment in this series, Dr. O will address AMS2750E and CQI-9 Temperature Uniformity Surveys, which often prove to be challenging for many heat treaters. "To achieve this accreditation, Furnace Temperature Uniformity Surveys (TUS) must be performed at regular intervals to prove that the furnace set-point temperatures are both accurate and stable over the working volume of the furnace. Historically the furnace survey has been performed with great difficulty trailing thermocouples into the heat zone. Although possible in a batch process when considering a semi-batch or continuous process this is a significant technical challenge with considerable compromises." Stay tuned for the next article in the series of Temperature Monitoring and Surveying Solutions for Carburizing Auto Components.
With electricity costs increasing, heat treat facilities are looking for ways to harness energy and minimize heat loss through a variety of insulating methods and applications. Heat Treat Today‘s Technical Tuesday feature comes from Reál J. Fradette of Solar Atmospheres Inc of Souderton, PA (with Nicholas R. Cordisco of Solar Manufacturing Inc. contributing), analyzing the different types of furnace hot zone insulation materials with the following points taken into consideration:
A) Hot Zone Designs
All-Metal Designs
Ceramic Fiber Included Designs
Graphite Type Insulated Hot Zones
B) Defining Hot Zone Losses For Different Hot Zone Configurations
Calculating Power Losses For A Given Size Furnace
Effect Of Hot Zone Losses On Heating Rates and Peak Power
C) Effect on Power Losses With Various Insulation Layers and Thicknesses
Projecting Relative Losses Versus Felt Thicknesses
D) Equating Insulation Designs To Actual Power Usage
Projecting Cycle Costs For Different Areas Of Operation
Impact of Hot Zone Type on Total Cycle Cost
E) Summary And Conclusions
An excerpt:
The heating rate of a load will dictate the total energy required to heat that load at that heating rate. Heating as fast as possible is not often the best solution to the application.
