combustion corner

Flame and Fire: History of the Industrial Gas Industry

/ BURNERS & COMBUSTION SYSTEMS TECHNICAL CONTENT, MANUFACTURING HEAT TREAT TECH, OP-ED

Jim Roberts of U.S. Ignition entertains readers in a Combustion Corner editorial about how the industrial gas industry evolved from its humble beginnings in the early 1900s into a precision-driven force that transformed combustion technology and modern manufacturing.

This editorial was first released in Heat Treat Today’s November 2025 Annual Vacuum Heat Treating print edition.

Let’s think about how young the industrial gas industry really is.

A Short Pipeline in Time

The first real industrial usage was way back in the 1800s somewhere. But there was no infrastructure, no supply other than bottled gas for industrial applications. The gas industry, as far as we recognize it, did not really take off until somewhere around the early 1920s when the first welded pipeline was installed. Then, as usage increased, it became apparent that safety was going to be a concern. The addition of mercaptan (rotten egg smell) was not until the late 1930s.

With the growth of commercial and residential usage, the demand for gaseous fuels grew by 50 times the original market size anticipated between 1910 and 1970! What does that demand look like? Today there are over 3 million miles of gas distribution lines connected to 300,000 miles of big transmission pipelines in the U.S. alone. All that growth in a span of 100 years, essentially. That means the transmission pipeline system in the U.S. could stretch around the planet 12 times!

USS coke gas pipeline in the foreground with the Conrail Port Perry Bridge spanning the Monongahela River, Port Perry, Allegheny County, PA (Lowe, 1994)
Source: Library of Congress Prints and Photographs Division

Most of that construction occurred during the post-war 1940s to 1960s timeline. That’s one busy industry! And it dragged all the thermally based markets and industries along with it. Now, we have come to accept the availability of natural gas as so commonplace that we cannot imagine life without it.

Responding with Precision

So, now you ask yourselves, “Why this history lesson, Jim?” Well, because we are supposed to be learning about combustion and the era of major combustion advancements — and if I would quit veering off into side topics we might actually get there. But it is all interconnected.

If you recall the story of the heat treater with the bedpost burners (October 2025 edition), he had no inspiration to improve efficiency or performance because those darn bedposts would burn gas just fine. So, what changed? Firstly, the world had been through a couple of military conflicts during this rise of the gas industry. And sadly, sometimes the best technological advances occur in times of conflict; engineering becomes more precise. All of a sudden, instead of hammering out horseshoes for the cavalry, we were heat treating gun barrels and crankshafts for airplanes. We needed to be more than precise — actually, we had to be perfect. So, we stepped away from the old heat treatment ways and developed systems that we could control to within a couple of degrees.

As a result, burners became specialized. Each process became unique and precise. Instead of pack carburizing components, a company called Surface Combustion developed a piece of equipment called an Endothermic generator. This device made carbon-based atmosphere out of natural gas or propane- and nickel-based catalysts. All of a sudden, we could do very precise non-scale covered heat treating. And the burners from companies like North American Combustion, Eclipse Combustion, Maxon, Hauck, Pyronics, Selas, W.B. Combustion, and on and on, all scrambled to develop the specific types of burners that the heat treaters and iron and steel makers needed.

Another important milestone hit around 1963: the Government got involved (gasp!). The Clean Air Act of 1963 essentially said we needed to burn our fuels cleanly and not spit smoke into the air. Those laws got reviewed again in 1970, 1977, and again in the updated Clean Air Act of 1990 with some of the biggest revisions.

With all of these changes, we had several drivers for innovation in the combustion world. Again, precision became a must. Heat treating became a very standards-driven industry. Metallurgists roamed the planet inventing both new materials and the processes to achieve them. Gas companies themselves became huge drivers of innovation and developed think tanks, like the GRI (Gas Research Institute), where people learned and laboratories hummed with development projects investigated in conjunction with burner and furnace companies. Academia became involved with industry in the form of organizations like The Center for Heat Treating Excellence (CHTE) and the Metal Treating Institute (MTI). Suddenly, the industry was more than just blacksmiths.

We’ll talk about how burner companies became design specialists and system efficiency experts and what that meant to various burner styles in next month’s offering.

References

Lowe, Jet. 1994. Panorama of Industry (Conrail Port Perry Bridge, Spanning Monongahela River, Port Perry, Allegheny County, PA). Historic American Engineering Record, HAER PA,2-POPER,1-2. Library of Congress Prints and Photographs Division.

About The Author:

Jim Roberts
President
US Ignition

Jim Roberts president at U.S. Ignition, began his 45-year career in the burner and heat recovery industry focused on heat treating specifically in 1979. He worked for and helped start up WB Combustion in Hales Corners, Wisconsin. In 1985 he joined Eclipse Engineering in Rockford, IL, specializing in heat treating-related combustion equipment/burners. Inducted into the American Gas Association’s Hall of Flame for service in training gas company field managers, Jim is a former president of MTI and has contributed to countless seminars on fuel reduction and combustion-related practices.

For more information: Contact Jim Roberts at jim@usignition.com.

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Flames and Fire: Straighten Up, Move Forward… Or Not?

/ BURNERS & COMBUSTION SYSTEMS TECHNICAL CONTENT, GUEST COLUMN

In this Technical Tuesday installment, Jim Roberts, president of U.S. Ignition, examines various flame profiles in heat treat operations. Today’s Combustion Corner compares gravitational lift, premix burners, fuel nozzle fixed air mixing burners, and nozzle mixing burners, while exploring design improvements to keep you well informed.

This informative piece was first released in Heat Treat Today’s August 2025 Automotive Heat Treating print edition.

A furnace guy walks into a bar and shouts, “Straighten UP!” The other furnace guys respond, “It won’t work!”

Thus begins another wander down combustion lane where we try to figure out what I’m talking about. We have discussed in other articles how various fuels and sources of air (and everything else) can affect the heating rates produced by our combustion equipment. We have talked about fire. We haven’t talked about what fire looks like.

So, in the following column and subsequent releases we are going to talk about flames and fire, and why there are a fairly substantial number of flame profiles available to heat treaters, steel makers, and all of you high-temp-type people. Why are there different flame shapes, and what does flame color do for you?

Burner Types

Figure 1. Nozzle-mixing burner ThermJet cutaway

Firstly, let’s start with the various types of burners commonly used in the art of high-temp processing work.

  1. Gravitational lift: This type of burner is exactly what it sounds like; it works just like a candle. The fuel/air mix is naturally rising with the thermal current of the flame and combusting as the flame rises, climbing the heat column.
  2. Premix burners: This is where the fuel and air are mixed together and then ignited. By controlling the percentages of fuel and air in the mixture, we control the characteristics of this flame.
  3. Fuel nozzle fixed air mixing burners: This is where a steady stream of oxidant (air) is flowing, and the fuel is throttled up and down to affect ignition and capacity of fuel.
  4. Nozzle mixing burner: Finally, and by far the most used in our industry, this is where the fuel and oxidant mix internally in the burner, and a flame configuration is determined by the burner outlet or the mixing nozzle. (See Figures 1 and 2.) You may hear burner nozzles referred to as a cup, a spinner, flame retainer, just about any type of reference. You may also hear them referred to as a danged hot thing — an accurate description as well — so don’t touch.

Design Improvements

With development of the nozzle mixing burner 60+ years ago, design improvements began in earnest. One of the first patents for nozzle mixing industrial burners was issued to Eclipse Fuel Engineering in 1967. Pretty soon there were all sorts of designs and patents, as burner companies raced to improve reliability, performance, and heat delivery characteristics.

Figure 2. Nozzle-mixing burner Eclipse Thermair

Some of the concepts that came along in the subsequent years were “air staged” burners. In this design feature, the fuel is delivered in the center of the flame nozzle. Progressively changing air holes in the nozzle stages the combustion of the fuel as it makes contact with the air. As the gas burns and the exhaust gas expands, it will often increase volumetrically by up to seven to eight times its cold state condition. That’s a lot of expansion, and it forces the pressure in the burner body to increase at an amazing rate. As the flame progresses through the burner and seeks the exit point (the part we see, you know, the fire), it can be moving along at — get this — flame speeds up to 400 feet per second!

That’s enough for today. We’ll pick this conversation back up next month.

Jim Roberts
President
US Ignition
For more information: 
Contact Jim Roberts at jim@usignition.com

Find heat treating products and services when you search on Heat Treat Buyers Guide.Com

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Step Back from the Fire, Caveman, and Think

/ BURNERS COMBUSTION SYSTEM NEWS, HEAT TREAT NEWS, MANUFACTURING HEAT TREAT NEWS, OP-ED

Heat treatment is a hands-on science and it can be easy to forget about continuing education. In today’s edition of Combustion Corner, Jim Roberts, president of U.S. Ignition, encourages readers to continue cultivating their own heat treat learning and offers specific and practical educational resources to do just that.

This informative piece was first released in Heat Treat Today’s June 2025 Buyers Guide print edition.

So, a furnace guy walks into a heat treating facility and says, “What’s that?”

The Flame and Man

Since the invention of fire, we as upright, walking, opposing-thumb-equipped critters have been learning to control it. We have learned at the elemental level that we can change the properties of just about anything on the planet simply by exposing that item or material to the flames. Certainly, we hold fire as one of our most fascinating benefits of our existence.

Yet, in the grand scheme of things, we are just now really learning to control at levels that our Neanderthal cousins would never have conceived, and they didn’t! Conceive the possibilities, that is. I mean, for the first 400,000 years of our human existence, (that’s a mindblower, isn’t it?), fire had four basic purposes: warmth, light to see in the dark, protection from predators/enemies, and to cook our food. Later, we discovered that by heating up the tip of certain sticks, you could make the stick useful over a longer time. It didn’t wear out as fast. And from there we figured out ways to change other materials at our behest by using the flame. Weapons and tools followed.

In the bigger picture, we only have figured out the really cool uses in the last 5,000 years — and the really, really cool stuff in the last 300 years. So, the learning curve for us has been relatively late when it comes to the heat and the flame and the ability to understand it — to really control it.

Furthering the Science of Heat

How did we get to this stage of significant control over temperatures and systems that would melt a Cro-Magnon’s noodle right there in his big ol’ skull? We used our ever-developing brains. We used intelligence to advance the art of using the flame. Others before us thought their way into our present-day future. Shouldn’t we keep the ball rolling? Isn’t this ever-evolving commitment to responsible use of the flame what we need to do? We accept the gift of those before us and strive to improve on it for the upcoming iterations of humankind. Idealistic? I think not.

The premise of temperature is basically fixed. We can put it in a furnace, we can put it in a vacuum, we can melt the very rocks our planet is made from. So, let’s use the very latest available knowledge to further the science of heat. Let’s improve the situation, both at work and personally, by using our brains and by learning about what is going on with the furnaces, the parts, the fuels, and all the methods of heating. Let’s keep learning about the latest technologies. Let’s actually control this wondrous element.

To do that, we must embrace the knowledge, we have to know what we are looking at. We need to know the history and have a vision for the future. We need to teach and be taught.

Learning the Industry

If you or your reports need to get up to speed with our industry, indeed our very science — GO TO SCHOOL! The fact you are even reading this publication shows that you are open to learning. Let’s ace the test!

Heat Treat Today runs a drink-from-the-firehose learning experience called Heat Treat Boot Camp. You can learn the latest and greatest technologies and new technologies on the horizon in heat treating. Send yourself, send your people.

The Metal Treating Institute (MTI) runs an online certification school that teaches the ins and outs of the heat treating industry. The Industrial Heating Equipment Association (IHEA) runs an annual Combustion Seminar. Almost all the major furnace and equipment suppliers offer seminars on their specialty niche.

Educational Opportunities Include:

  • Ipsen Global has “Ipsen U”
  • Surface Combustion offers Virtual Learning Applications
  • SECO/WARWICK produces a Global Training Seminar on continuous improvement and heat treating
  • Can-Eng offers analysis of specific inquiries
  • Ajax Tocco will come to your facility to conduct the latest schooling on your equipment

All you must do is decide that you are going to continue to learn more. How can you not with these kinds of services around you?

Don’t forget Safety. National Fire Protection Agency (NFPA) seminars are available from NFPA themselves. Industry experts who have certified trainers, like Rockford Combustion, also offer multi-day seminars on equipment safety.

I can attest to the effectiveness of these kinds of learning commitments. I have been both a student and a teacher at some of the aforementioned seminars. The scope of learning can be broad or focused. It’s up to us to keep mentally expanding, so that the lessons learned don’t get lost, and the future technologies get a fair review.

I have been watching with interest how over the last 25 or so years precise control over combustion has been evolving. The major controls and process monitoring companies have been striving to gain precise control and safety on furnace equipment for years. I might add, they have been successful in varying degrees, and safety and maintenance have improved greatly.

I just spoke recently with a company in Erie, Pennsylvania. They have developed a program that monitors each individual burner. Not only does it tell if the burner is running, but if there has been a component failure, if the burner is out of tune, it can self-correct, and if there is a failure, they shut it off. Oh, and they do that for you, from THEIR office. The technology just grows and grows, doesn’t it?

So, I know some of you were wondering where I was going with the Caveman intro, and some of you probably would have preferred that I kept going up to the point where we were cooking mammoth steaks on sizzling rocks with our Cro-Magnon buddy. But we are better than him, and we need to keep proving that. Don’t you think?

Besides, this is the final month before school is out for the summer. Let’s give education a nod here.

I am sorry if I did not mention your company, no slight intended. If so, contact your customer base to alert them to any learning experiences that may be available.

Keep learning. Until next time…

About the Author

Jim Roberts
President
US Ignition

For More Information: Contact Jim Roberts at jim@usignition.com.

Find heat treating products and services when you search on Heat Treat Buyers Guide.Com

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The Future Is Coming Three Times Faster Than You Think

/ BURNERS & COMBUSTION SYSTEMS TECHNICAL CONTENT, GUEST COLUMN, MANUFACTURING HEAT TREAT TECH, OP-ED

In this Technical Tuesday installment featuring Combustion Corner by Jim Roberts, president of U.S. Ignition, readers are enlightened about how upcoming policies might impact their burner systems, fuel mixtures, and equipment. Could certain policies impact technical requirements of heat treating? Find out more below.

This informative piece was first released in Heat Treat Today’s July 2025 Super Brands print edition.

A furnace guy goes into a bar and says, “This looks like a fast crowd… and all the players nod in agreement.”

Where are we? It’s the future! And in heat treating and combustion circles, the changes that will occur in the next several years will be very impactful to our industry. We’ve all heard these things, and we have some of the very best experts in the world working for us in this industry to make sure that we continue to grow and to be a leader in the legislation and rules that could cripple the wonderful world of heat treating and metals.

We are lucky to have industry associates at the Metal Treating Institute (MTI) who understand the impact of some of these new regulations. In this year’s Air & Atmosphere issue of Heat Treat Today magazine, Michael Mouilleseaux (Erie Steel LTD) provided updates on the proposed decarbonization initiatives. I have seen presentations by Michael and his committee composed of Heather Falcone (Cook Induction Heating Company) and Ben Gasbarre (Gasbarre Thermal Processing Systems). This is critical knowledge for us all, and we should be staying as vigilant and supportive as we can. Michael’s interview is a must-read in that February issue – if you missed it, go back and read it. Please.

And then you say, “What’s this got to do with combustion equipment and the stuff that this Roberts guy is normally talking about?”

Well, not only does the decarbonization mandate mean the possibility of costs through government burdens and penalties, but the equipment and process change requirements are going to be staggering if we don’t prepare.

As long as I’m in a name-dropping mood, I’m going to mention Brian Kelly of Honeywell. Brian is a degreed aerospace engineer, and yet he decided to come play in the mud with us furnace guys for a career. Brian has several detailed presentations online about some of the prime initiatives for all the combustion equipment companies — hydrogen Combustion. Yep, the “H” word. The holy grail of zero pollution. One of those presentations includes fascinating detailed data on hydrogen and other emission initiatives, given by Brian Kelly and Todd Ellerton on YouTube regarding future combustion technology requirements.

“So, what does the “three times faster” thing mean, Jim?”

Well, all major combustion equipment companies, like Honeywell, understand that hydrogen requires three times the amount of fuel to generate the same amount of available heat as natural gas. Hydrogen also burns with seven to eight times the “flame speed” of natural gas. It burns, on average, about 400 degrees hotter (F) than natural gas. And so, from an engineering standpoint, there are a fantastic number of variations that must be considered as we look forward, especially when addressing CO₂ and other emissions. Add propane, butane, methane, producer gas, landfill gas, and anything else that is presently being utilized in the heat treat circles, and that provides a lot of possible variations!

Now, it needs to be said that a good many burners can burn hydrogen already. The anticipation of this level of scientific and ecological requirements was seen a long time ago. Conversely, many cannot. Brian Kelly explains that 17% of the present pre-mix/blended fuel systems cannot utilize this fuel. It also bears mentioning that there are three different grades of hydrogen production levels.

So, let’s start doing the math on how many iterations it will take. But here is the biggest tidbit of hydrogen science in the combustion world – hydrogen is the smallest molecule and the lightest in a molecular sense. Helium is smaller and lighter, for fact-checker purposes, but we aren’t trying to burn helium, are we? So, as we blend hydrogen with our other fuels (i.e., the most practical way to maintain some of the infrastructure and equipment), we need to have our combination equipment suppliers test and verify that which exists will work.

Obviously, if it takes three times the fuel volume, existing gas delivery lines will be an issue. At the molecular level, smaller and lighter means that many existing seals, connections, and control valves may no longer be gas-tight and may leak. That’s not good! If the flame speed of these fuels is five to eight times that of existing fuels, temperature profiles within the process will need to be reviewed and re-calibrated. And if it burns 400 to 500 degrees hotter, certainly that will require a review of the former materials of construction.

So, how does this tie into the original theme of “The future is coming fast?” Well, we have just touched briefly on one possible fuel transition that is on the horizon. Carbon points/credits are already being taxed in Europe. We can bet that these global decarbonization efforts will be moving ahead. We will need a review so that a “head in the sand” mentality does not catch any of us in the thermal processing community flatfooted and ill-prepared.

It’s easy to think that it won’t affect you. When I mentioned “three times as fast,” of course, I was alluding to the fuel references, and the best way to be prepared for the future is to see it coming. Be alert and stay current, and we will adapt as an industry, as we have so many times before. Until next time …

About The Author:

Jim Roberts
President
US Ignition

Jim Roberts president at U.S. Ignition, began his 45-year career in the burner and heat recovery industry focused on heat treating specifically in 1979. He worked for and helped start up WB Combustion in Hales Corners, Wisconsin. In 1985 he joined Eclipse Engineering in Rockford, IL, specializing in heat treating-related combustion equipment/burners. Inducted into the American Gas Association’s Hall of Flame for service in training gas company field managers, Jim is a former president of MTI and has contributed to countless seminars on fuel reduction and combustion-related practices.

For more information: Contact Jim Roberts at jim@usignition.com.

Find heat treating products and services when you search on Heat Treat Buyers Guide.Com

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Is It Stuffy in Here? Exhaust Systems

/ ATMOSPHERE AIR FURNACES TECHNICAL CONTENT, BURNERS & COMBUSTION SYSTEMS TECHNICAL CONTENT, GUEST COLUMN, Manufacturing Heat Treat Technical Content, OP-ED

In each installment of Combustion Corner, Jim Roberts, president of U.S. Ignition, reinforces the goal of the series: providing informative content to “furnace guys” about the world of combustion. The previous column examined the air supply inlet — the inhale, and this month, Jim is examining the exhaust system — the exhale, and how to inspect it, maintain it, and manage it.

This informative piece was first released in Heat Treat Today’s March 2025 Aerospace print edition.

A guy walks into a room full of furnace guys and says, “Is it just me, or is it a tad stuffy in here?”

We have all been able to imagine that it is hard to focus and do your job in an environment where it seems like it’s hard to breathe. Well, our hard workin’ buddy, the furnace, is continually stuck in a cycle of trying to breathe in, breathe out — and then somewhere in between, the magic of combustion and heat happens! We talked last month about the “breathe in” part of the combustion process. This month, we are going to remind you that if you take a really good, productive, inhaled, life giving breath, you are probably going to want to exhale at some point, too!

Tip 2: Ensure Exhaust Systems Are Properly Functioning and Clean

Inhale, exhale. It makes sense that if we were earlier having issues with the air supply inlet, the exhaust should also be checked. Today’s combustion equipment is sophisticated and sensitive to pressure fluctuations. If the exhaust is restricted, the burners will struggle to get the proper input to the process. I used to use the example of trying to spit into a soda bottle. Try it. It’s tough to do and invariably will not leave you happy. Clean exhaust also minimizes any chance of fire. Read on for three examples.

A. Check the Flues and Exhausts for Soot

If you are responsible for burners that are delivering indirect heat (in other words, radiant tubes), you have a relatively easy task ahead to check the flues/exhausts. Each burner usually has its own exhaust, and one can see if the burners are running with fuel-rich condition (soot/carbon). Soot is not a sign of properly running burners and will signal trouble ahead. Soot can degrade the alloys at a chemical level. Soot can catch fire and create a hot spot in the tubes. Soot obviously signals you are using more fuel than needed (or your combustion blower is blocked, see the first column in this series).

As a furnace operator or floor person, it should be normal operating procedure to look for leakage around door seals.

Here’s a sub tip: If you cannot see the exhaust outlets directly, look around the floor and on the roof of the furnace up by the exhaust outlets. Light chunks of black stuff is what is being ejected into the room when it breaks free from the burner guts (if it can). That will tell you it’s time to tune those burners. If you do not have a good oxygen/flue gas analyzer, get one. It can be pricey, but it will pay for itself in a matter of months in both maintenance and fuel savings.

B. Seriously … Check the Flues and Leakage Around Door Seals

If you are running direct-fired furnace equipment, or furnaces that have the flue gases mixed from multiple burners, it gets a little trickier. All the same rules apply for not wanting soot. Only now, it can actually get exposure to your product, it can saturate your refractory, and it can clog a flue to the point that furnace pressure is affected. An increase in furnace pressure can test the integrity of your door seals. It can back up into the burners and put undue and untimely wear and tear on burner nozzles, ignitors, flame safety equipment, etc. As a furnace operator or floor person, it should be normal operating procedure to look for leakage around door seals.

C. Utilize Combustion Service Companies

Ask the wizards. Combustion service companies can usually help you diagnose and verify flue issues if you suspect they exist. It’s always a great idea to set a baseline for your combustion settings. Service companies can help you establish the optimum running conditions. Again, money well spent to optimize the performance of your furnaces. I’m sure you already have a combustion service team; some are listed in this publication. Otherwise, consult the trade groups like MTI and IHEA for recommended suppliers of that valuable service.

Check flues monthly. It should be a regular walk around maintenance check.

Don’t let the next headline be your plant. See you next issue.

About The Author:

Jim Roberts
President
US Ignition

Jim Roberts, president at US Ignition, began his 45-year career in the burner and heat recovery industry directed for heat treating specifically in 1979. He worked for and helped start up WB Combustion in Hales Corners, Wisconsin. In 1985 he joined Eclipse Engineering in Rockford, IL, specializing in heat treating-related combustion equipment/burners. Inducted into the American Gas Association’s Hall of Flame for service in training gas company field managers, Jim is a former president of MTI and has contributed to countless seminars on fuel reduction and combustion-related practices.

Contact Jim Roberts at jim@usignition.com.

Find heat treating products and services when you search on Heat Treat Buyers Guide.Com

Is It Stuffy in Here? Exhaust Systems Read More »

‘Furnace Guys’ and Filtration Systems

/ ATMOSPHERE AIR FURNACES TECHNICAL CONTENT, BURNERS & COMBUSTION SYSTEMS TECHNICAL CONTENT, Manufacturing Heat Treat Technical Content, OP-ED

Jim Roberts, president of U.S. Ignition, joins us in the renewal of the Combustion Corner column. In this installment, Jim establishes that the goal of the series is to provide informative content to “furnace guys” about the world of combustion, furthering the spirit of the Heat Treat Today motto: “We believe people are happier and make better decisions when they are well informed.”

This informative piece was first released in Heat Treat Today’s February 2025 Air/Atmosphere Furnace Systems print edition.

Contact us with your Reader Feedback!

So … A guy walks into a room full of furnace guys …

And the story (or joke) begins again. I used to be one of the furnace guys. It’s a really niche group of strange, unique, and sometimes knowing people, who, by the way, are not gender specific. To me, “a guy” is a moniker as specific as saying that person over there is a swimmer.

But as furnace guys, those same individuals have a peek at the stuff that normal planet walkers don’t. They — or rather WE — know how to almost tame the beast. We have learned what it means to control temperatures that can crack stone. We can bend metal and make it do what we want at temperatures that the human eye cannot gaze upon without safety filters between us and the beast.

And what is this beast? It’s called combustion. It’s a phenomenon that allows the very air around us and anciently sourced resources to burn like hellfire and yet still do our bidding. But there are fewer and fewer guys who manage the beast these days. And that is how a column like this takes launch.

This publication, and its talented editorial staff, have always been driven to provide information that, in their own words, will allow the greater masses this privilege: “We believe people are happier and make better decisions when they are well informed.”

It was not lost on the staff that with dwindling numbers of longtime combustion people some of the benefits of being “well informed” were needed. They felt information could be presented in such a fashion that old-timers like me could share some of the tried-and-true techniques that we have used over the years. The hope is to not only make the workplace safer, but also to increase efficiency and performance in the processes that utilize combustion.

When we walk into almost any facility and go over to the underperforming furnaces, we can bet part of the problem will be inlet air source or exhaust outlet issues.

To some, this will seem like remedial information. That is GREAT. Because that means that you already understand a fair portion of the pathway to combustion performance. You can be the lead in your facility on combustion safety and understanding. Yay!

We are going to start with a visit to an article I wrote some time ago that then later became a pamphlet called “10 Combustion Tips.” It was written with plant maintenance guys in mind as they traveled the factories and facilities that they had responsibility for. We’ll turn this into a series of tips that are really intended for those less experienced to start. We’ll continue in upcoming editions of Heat Treat Today, and hopefully, everyone will feel like this was beneficial when cruising the aisles of your factories.

Tip 1: Keep the Process Air Filters Clean

I know, this seems so obvious, doesn’t it? Utilities tell us over and over to keep your home furnace filters clean. But I would be willing to bet that almost 30% of all furnace issues that we see in the field start at the blower supplying our combustion air. It’s the lungs for your burners! Any filter blockage will result in serious problems. As the system impedes under a clogged filter, your process may not get the required input. Clogged filters put undue strain on the combustion air blowers over time, so your electrical and motor maintenance costs may escalate. Additionally, the burners may go fuel rich. This wastes fuel and can create carbon, which at its best is an insulator. At its worst, it is a fire hazard.

Tip Solutions

A. Check the filters monthly: It is pretty easy to see if a filter is dirty. Your production folks may have even told you the furnace is slowing down. Less air, less heat. Take a peek … you will know. If it’s a fiber-based filter, replace it. Better yet, make it a habit to check filters every month.

B. Clean the screen: If not a replaceable filter, clean the metallic/plastic screen type with some solvent that will cut the machine/quench oil that’s probably the clog culprit. DO NOT put the filter back on dripping wet with solvent. I apologize to furnace guys out there for having to explain that, but it’s the new world, right? If you didn’t understand why, please refer to the movie “Back Draft.”

C. Get outside: Consider ducting an outside air source to the combustion air blower. Fresh air delivered at a stable temp will always help with furnace and burner performance.

So there, was that so hard? Nope, almost simple. And yet when we walk into almost any facility and go over to the underperforming furnaces, we can bet part of the problem will be inlet air source or exhaust outlet issues.

Don’t let it be your plant. See you next issue.

About the Author

Jim Roberts
President
US Ignition

Jim Roberts, president at US Ignition, began his 45-year career in the burner and heat recovery industry directed for heat treating specifically in 1979. He worked for and helped start up WB Combustion in Hales Corners, Wisconsin. In 1985 he joined Eclipse Engineering in Rockford, IL, specializing in heat treating-related combustion equipment/burners. Inducted into the American Gas Association’s Hall of Flame for service in training gas company field managers, Jim is a former president of MTI and has contributed to countless seminars on fuel reduction and combustion-related practices.

For more information: Contact Jim at jim@usignition.com.

Find Heat Treating Products And Services When You Search On Heat Treat Buyers Guide.Com

‘Furnace Guys’ and Filtration Systems Read More »

Improving Your Use of Radiant Tubes, Part 4

/ BURNERS & COMBUSTION SYSTEMS TECHNICAL CONTENT, FEATURED NEWS, MANUFACTURING HEAT TREAT, OP-ED

op-ed

In previous months, this series has explored the geometry of a tube, why radiant tubes matter, what happens inside the tube, and radiant tube control systems. For the first three installments, check out Heat Treat Today’s digital editions in November 2022, December 2022, and February 2023. For the month of May, we will continue our discussion of different modes of control for radiant tube burners.

This column is a Combustion Corner feature written by John Clarke, technical director at Helios Electric Corporation, and appeared in Heat Treat Today’s May 2023 Sustainable Heat Treat Technologies print edition.

If you have suggestions for radiant tube topics you’d like John to explore for future Technical Tuesdays, please email Bethany@heattreattoday.com.

John B. Clarke
Technical Director
Helios Electric Corporation
Source: Helios Electric Corporation

High/low and on/off controls require different control strategies from a proportional mode of control. In all cases, we assume the temperature control will be provided by a proportional-integral-derivative loop (PID loop). The function can be provided by a stand-alone instrument or a PID function in a programmable or process controller. The PID algorithm looks not only at the temperature of the process as indicated by the control element (thermocouple or RTD) and compares it to the setpoint — but it also considers the offset and rate of change as well. When properly tuned, a PID control loop can provide control accurate enough to match the process (actual) temperature to the setpoint within a degree or two.

For the lay person, another way of describing a PID loop is to consider how a driver regulates the speed of his automobile. Assume you are driving and want to catch up with and follow the car ahead of you — to do so, you need to match that car’s speed and maintain a safe distance. What you don’t do is floor the automobile until you get to the desired following distance and then hit the brakes. What you do is first accelerate to a speed faster than the target car to close the gap, then you instinctively take your foot off the accelerator when you get close, slowing gradually until your speed and position are as you desire. In this example, you have considered your speed, how close you are to the car you are attempting to follow, and the rate at which you are closing the gap. A PID loop is nothing more than a mathematical model of these actions.

The PID control loop provides an output — the format can vary, but it is in essence a percent output. It is a percent of the maximum firing rate the system needs to provide to achieve and maintain the desired furnace temperature. This percent output can be translated directly into a proportional output for proportional control — where the firing rate is proportional to the loop’s output.

On/off or high/low controls require a different approach where a time proportioning output is provided in which the burner fires on and off on a fixed time cycle. In this mode of control, the PID loop’s output is multiplied by the cycle time to determine the on or high fire period and the on or high fire time is subtracted from the cycle time to determine the off or low fire period. Cycle times can run from as little as 30 seconds to as much as a few minutes. Obviously, the shorter the cycle time, the more responsive the control, but also the more wear on the control components. The cycle time should be as long as possible but still meet the needs of the process control.

Don’t confuse these pulses with other control methods that are marketed as pulse firing. When people speak of pulse firing, they often mean a pattern with alternate burners firing to provide greater temperature uniformity and heat transfer. This is a very interesting subject and the topic for another day.

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Improving Your Use of Radiant Tubes, Part 4 Read More »

Improving Your Use of Radiant Tubes, Part 3

/ BURNERS & COMBUSTION SYSTEMS TECHNICAL CONTENT, FEATURED NEWS, MANUFACTURING HEAT TREAT, OP-ED

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Over the last several months, the Combustion Corner series has challenged readers to spend some time researching opportunities to improve their use of radiant tubes — their performance, efficiency, and uniformity. So far, the series has explored the geometry of a tube, why radiant tubes matter, and what happens inside the tube. When it comes to radiant tube systems controls, what are your options? Read on to learn about the three modes of control.

This column is a Combustion Corner feature written by John Clarke, technical director at Helios Electric Corporation, and appeared in Heat Treat Today’s February 2023 Air & Atmosphere Furnace Systems print edition.

If you have suggestions for savings opportunities you’d like John to explore for future columns, please email Karen@heattreattoday.com.

John B. Clarke
Technical Director
Helios Electric Corporation
Source: Helios Electric Corporation

This month we will discuss the various modes of control that can be applied to radiant tube systems. We will consider three typical modes of control: on/off, high/low, and proportional control.

When a radiant tube is operated in an on/off mode, the burner is fired full on or completely off. Using this mode of control, the burner must be relit at the start of each cycle. The advantage of this mode of control is that the on firing rate can be optimized to provide optimum heat transfer, and when the burner cycle is off, the tube will idle. If the pulses are rapid enough, there is very little cyclical variation in temperature. The heat capacity (stored heat) of the radiant tube provides a flywheel effect to smooth out the temperature swings between on and off periods. The drawback of this mode of control is that the ignition system, most commonly a spark plug, is energized frequently, loading the transformer and wearing material off the spark plug and the valves that control the air and fuel are cycled frequently. If the cycle time is one minute — the burner must relight, and the valves must cycle over 500,000 times a year. Care must be taken to ensure the components used in this system are rated to survive this demand.

Another mode of control is high/low firing. With this mode of control, the burner cycles between the high firing rate and low firing rate, but instead of shutting down completely, the burners are returned to a low firing condition. In this mode of control, care must be taken to ensure the low firing rate does not overheat the firing leg of the radiant tube. Other than that, this mode of control is very similar to on/off control.

The last mode of control is fully proportional. In this mode of control, the burner fires between 0 and 100 percent of the maximum output depending on the burner demand. The air can be adjusted using a proportional valve or by varying the combustion air blower speed using a variable frequency drive, or in some cases, both. The fuel gas is regulated by a proportional valve or a regulator that matches the output pressure to an impulse or control  pressure. Using this mode, the burner fires more or less on ratio (with a consistent level of excess air), or some systems will increase the excess air at low fire to ensure clean combustion and to reduce the available heat at low fire. When a burner has higher levels of excess air, more energy is used to heat the air not used to burn the gas; therefore, less energy is available to heat the furnace chamber. This provides greater turndown (the difference between high and low firing).

Which method is best for a given furnace? That is impossible to say without considering the burner type and geometry of the radiant tube used in the furnace. All three methods can provide good uniformity and efficiency, provided it is appropriate for the equipment in question. In fact, there are applications that blend proportional with high/low firing to meet very specific needs. These systems simply alter the maximum — or high — firing rate to better meet the systems’ requirements.

Again, the control approach is a function of the burner, the radiant tube, and the application. There is really no one-size-its-all; each application must be approached with an open mind. The next column will address the role of heat recovery to efficiency in greater detail.

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Improving Your Use of Radiant Tubes, Part 3 Read More »

Improving Your Use of Radiant Tubes, Part 2

/ FEATURED NEWS, MANUFACTURING HEAT TREAT, OP-ED

op-edLast month, we introduced the importance of radiant tubes in the heat treat industry. We explored the “why” of radiant tubes and skimmed the surface, exploring materials, sizing, shapes, longevity, and installation — all topics we’ll deep dive into in future posts. This month, let’s explore what typically occurs inside a radiant tube.

This column is a Combustion Corner feature written by John Clarke, technical director at Helios Electric Corporation, and appeared in Heat Treat Today's December 2022 Medical and Energy print edition.

If you have suggestions for topics you’d like John to explore in future columns, please email Karen@heattreattoday.com.

John B. Clarke
Technical Director
Helios Electric Corporation
Source: Helios Electrical Corporation

The radiant tube burner combines fuel and an oxidizer (commonly air) in the presence of a source of ignition. Radiant tube burners differ from burners that are fired into an open furnace. They function to distribute heat as uniformly as possible within the interior of the tube to maximize its temperature and heat transfer uniformity. In some applications, a low rate of heat transfer is acceptable (for example, in the holding zone of a continuous furnace). In that same furnace, a much higher heat transfer rate may be required in the front of the furnace. In all cases, higher heat  transfer rates result in higher internal tube temperatures. In most cases, the higher the temperature, the greater the stress on the material.

Within the radiant tube in the visual flame region, the energy is transferred to the inner surface of the tube by convection and radiation. The rate of convective transfer has much to do with the mixing characteristics of the burner in question. Once combustion is complete, the heated products of combustion — CO2 , O2 , H2O, and N2 — continue to flow through the radiant tube. They impart heat to the interior surface of the radiant tube through convections and — in the case of the CO2 and H2 — radiation. The non-polar gases (O2 and N2) are effectively transparent to radiation: neither absorbing nor radiating heat. This transparency poses a problem for the performance of radiant tubes because the combustion process is ideally complete some distance before the end of the radiant tube.

There are a few ways to make use of the heat stored in the O2 and N2 . One way is to stir the mixtures to ensure these gases meet the inside walls of the tube and can convectively transfer their energy. Another way is to insert a “core buster” or other device into the exit end of the radiant tube. This device must be able to withstand the peak temperature of the products of combustion at this point, so it is typically constructed of some ceramic material or a composite of ceramics. As the heated gases pass over this “core buster,” the resistance forces higher flows around the perimeter of the tube, increasing convective transfer. The “core buster” also is convectively heated and can then radiate heat to the inner surface of the tube and, finally, the “core buster” increases mixing of the gases to ensure all remaining hydrocarbons and carbon monoxide are brought into contact with oxygen to complete the oxidation process.

The transfer of heat to the inner surface is dependent on the effective surface area. A tube with a nominal inside diameter of four inches may have a much greater effective surface area due to roughness, which resemble very small peaks and valleys. Anyone who has attempted to walk around a small Caribbean island can attest — it takes a lot longer than you would think by looking at the map and really scares your shipmates when they cannot find you. Cast and composite radiant tubes can be fabricated to increase this effective internal surface area. Tubing can also be equipped with internal fins.[blocktext align="left"]No matter what the construction, ultimately it does no good to transfer heat to the interior of the radiant tube if the tube cannot transfer the same quantity of heat through the exterior to the furnace and work being heated.[/blocktext]

Which mode of control is better? High/Low, proportional, or pulsed? Any method can achieve a uniform tube heat release given the correct burner radiant tube combination. The important thing is that the vigor of the mixing is matched to the length and roughness of the radiant tube. Burner X may be perfectly suited to a short radiant tube but lead to non-uniform heating as the tube length is extended. On the other hand, Burner Y, with a relatively lazy flame, may work perfectly on long tubes with lower heat transfer demands but be unsuitable for short tubes where high heat transfer rates are desired.

In the coming months, we will examine many of these areas in greater detail, and this author can make use of his experience of many failures to inform the readers of what not to do. Then, by extension, we’ll learn how to get more from the furnaces by thinking systematically about their radiant tubes, burners, and controls.

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Improving Your Use of Radiant Tubes, Part 2 Read More »

Improving Your Use of Radiant Tubes, Part 1

/ FEATURED NEWS, MANUFACTURING HEAT TREAT, OP-ED

op-edRadiant tubes are prevalent in heat treating applications. They are very simple devices: basically, a pipe that enters and exits the work chamber. Geometrically simple — but the considerations of how they should be applied, the optimal materials for their construction, and the best burner to use present a myriad of challenges and opportunities for improvement. As all heat treaters know, radiant tubes represent a significant expense as well as an opportunity to save on maintenance costs and improve furnace performance.

This column is a Combustion Corner feature written by John Clarke, technical director at Helios Electric Corporation, and appeared in Heat Treat Today's November 2022 Vacuum print edition.

If you have suggestions for topics you’d like John to explore in future columns, please email Karen@heattreattoday.com.

John B. Clarke
Technical Director
Helios Electric Corporation
Source: Helios Electrical Corporation

In the coming months, I hope to challenge the reader to spend some time researching opportunities to improve their use of radiant tubes — that is to improve their performance, both heating rates and efficiency, as well as to extend their life and perhaps improve the uniformity of the furnace being heated.

I apologize in advance if I sound like an economist — “It is this way, but on the other hand . . .” There are a lot of factors to consider when planning to upgrade your radiant tubes, their associated burners, recuperators, mountings, and supports.

To start, let’s answer a simple question: Why do we use radiant tubes? Two reasons come to mind: to protect the furnace atmosphere from the products of combustion and/or to diffuse the release of heat within the furnace or oven chamber to maximize temperature uniformity. In many heat treating applications, even a very small leak will contaminate the furnace atmosphere, damaging the work being processed.

How do we size radiant tubes? Again, it is obvious that we need to have sufficient heated external surface area to transfer the heat to the furnace chamber. This heat transfer will occur through convection and radiation, with the latter mode being more significant as the furnace temperature rises. The rate of convective heat transfer will depend on mass and velocity of air or atmosphere passing over the tubes. The radiant heat transfer rate is a function of the difference between the tubes’ surface temperature and the temperature of the furnace and work being heated. The good news with radiant heat transfer in closed furnaces is that all surfaces in the furnace participate to a degree with the transfer of heat to the work.

There are many shapes for radiant tubes: U-shaped, W-shaped, three legged, as well as systems where the firing and exhaust occur at the same opening, including P-tubes and single-ended tubes. Each has its advantages and disadvantages, which we’ll discuss in future articles.

How about materials? Again, we have a lot of choices. The tubes can be centrifugally cast, fabricated from sheet, or made of some ceramic or composite material. [blocktext align="center"]The formulation of each material varies greatly, and it is important that the material is suitable for the use temperature and chemical composition of the furnace atmosphere as well as always being compatible with the common products of combustion.[/blocktext]

How are the radiant tubes installed? Are the ends welded to a mounting plate, or perhaps a packing gland is employed to seal the tube while allowing some expansion or contraction? Both methods are commonly applied successfully. Composite tubes may have a flange that is clamped at the mounting location, or they may use a packing gland. The tubes may have internal supports within the furnace to prevent sagging. The tubes can be hung vertically, located to the side of, or placed under and over the work being heated.

How long should my radiant tubes last? Simply answered, for as long as practical. As a young person, I was mortified when I dropped a hammer in a customer’s pusher carburizing furnace, and it broke an alloy tube. When I confessed to the plant metallurgist, he laughed and told me the tube I broke was over twenty years old. Other customers may be satisfied if their tubes last 18 months, so there is no simple answer. That said, there may well be opportunities to extend the life of the radiant tubes in your specific application.

We will revisit many of these discussions in later articles, but hopefully this column has whetted your appetite for the next discussion in December: What typically occurs inside the radiant tube? After all, this is the Combustion Corner.

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Improving Your Use of Radiant Tubes, Part 1 Read More »

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