US Ignition

In this Technical Tuesday installment, Jim Roberts of U.S. Ignition entertains readers in a Combustion Corner editorial about how fuel sources became more affordable over time and aspects of combustion burner design. Stick around for his side story on the “innovative” use of bedposts.

This editorial was first released in Heat Treat Today’s October 2025 Ferrous/Nonferrous print edition.

A furnace guy walks into a heat treat facility and sees burners everywhere. Furnace guy says to the faces in the room, “Why did you pick those types of burners?” Thinking this is a trick question, the heat treaters respond, cautiously, “To make things hot?” Of course, they are correct, because making fire and heat is the name of the game, right?

But as we have considered burner styles, designs, flame shapes, and air delivery types with our last couple of Combustion Corner columns, I suspect there was a good deal more analysis given to the selection of burners.

To appreciate the history of burner design, “furnace guy” should realize why burners evolved in the first place: fuel source. When the first burners were starting to be used on box furnaces, they used oil, kerosene, and fuel that had to be pumped. Over the years, many different fuels have been used. Yet, we have a tendency to think of gaseous fuels as the only option for burner performance.

Bedpost Burners

I recall the first time I got called into a facility to try and improve the performance of the furnaces (yep, I truly am a furnace/burner guy). It was a big box furnace that could handle 3-ton quench and temper loads. At that point, I was unaware of the multiple types of burners that were out in the market.

The owner of the shop opened the furnace door for me to see the combustion system. I stared. Sticking into the walls of this big box furnace were bedposts. These “burners” were purchased at 50¢ a post from some hotel auction, and they had about 50 spare posts to boot.

Grinder slots had been cut into the top of these posts. Refractory had been mudded into the mounting blocks to protect the fuel feed, which was being forced, or should I say blown, in through the bed posts and atomized by the pressure of being squeezed through these slots in the knob at the top of the posts!

The fuel? Diesel fuel. Regular, old, out-of-the-pump diesel fuel. Or kerosene, for that matter. I was told the system could also use fire pulverized coal, sucked into the bedpost by pitot feeds of compressed air. They lit the burners with burning oily rags tossed into the chamber and quickly opened the valves controlling the fuel.

I was there to sell new modern high-efficiency gas burners.

I declared that this was antiquated, unsafe, archaic, dirty, and said about a thousand other denigrating comments.

The owner of this heat treat said, “Yep, it’s all those things, and more!” He continued, “It’s also reliable, simple, and predictable.” He mused, “I suppose that that thing hasn’t really broken down or shut off in the 25 years since we built it!”

I’m a fairly quick study and surmised that I was not going to make this sale. Duh! This furnace had everything they needed. And the gas system I was going to propose was going to be expensive.

A Burgeoning Gas Industry and Our Next Column

That furnace was still running when I made a move to another city some 10 or so years later.

Eventually, the gas industry that cropped up made fuel cheap…and I mean cheap. I thought, “I bet that guy and his accursed bedpost burners will talk to me now!” So, I went back, and that fella said, “Yeah, we got out of the business that used that old process and moved on. We’d be glad to talk about modernization.” And we did.

That same outfit that operated bedposts for burners for 50 years became a vanguard for modern efficiency and process improvement.

Natural gas as a fuel source is quite modern. Nowadays, that is essentially the truth: natural gas and sometimes other gaseous equivalents tend to be the most widely used fuels in the industrial world.

When looking at the rapid developments of burner configurations and why they developed, it is best first to understand some of the history of these developments. See you in the next installment to talk about the history of the industrial gas industry.

About The Author:

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.

In this Technical Tuesday installment of Combustion Corner, Jim Roberts, president of U.S. Ignition, examines various burner nozzle shapes, sizes, and effects. Use this helpful resource to evaluate whether your own in-house heat treat burners are the right choice for your applications.

This informative piece was first released in Heat Treat Today’s September 2025 Annual People of Heat Treat print edition.

A furnace guy walks into a bar and shouts “Straighten UP!” The other furnace guys turn to furnace guy #1: “It won’t work!” Just like last month. Let’s continue this topic.

What would you say if I asked you, “What does fire look like?” How would you describe fire to me — color, size, smell, temperature? It’s kind of a weird thing to try and do.

Last month, we ended by talking about how “air staged” burner design can make the flame exit the nozzle at a whopping 270 mph. There’s a reason that trade names for some of these burners are “Therm-Jet” and “Tempest” and “Hot Shot.” In these instances, velocity and turbulence are the game. The flame appearance is almost always a pinpoint tip, not dissimilar to what we have all seen spitting out of the tail of a fighter jet aircraft.

And, as an interesting aside, these high-velocity industrial burners can be victims of the same phenomena as a jet engine: flameouts. A tremendous amount of design time and testing has been dedicated to keeping the flame “retained” on the nozzle. If the flame lifts off the nozzle, cup, etc., it risks being blown out by the high-velocity stream of gases being produced in the guts of the burner. At these speeds, you cannot count on the burner backlighting, so a flame failure is imminent.

More Burner Types

The other types of nozzle-mixing burners are flat flame burners. These are sometimes called wall huggers or radiant wall burners. In these designs the idea is to have as little forward momentum to the flame as possible and to run the burners in a fuel-rich or highly luminous state. The design features are such that the whole wall of the furnace will be glowing radiantly and using radiation from the glowing walls to heat the product.

There are also infrared burners, where the burners are like a porous foam or screen grid and flame just glows on these surfaces. Again, the intent is radiant heat as opposed to velocity gases. These are very prevalent continuous production processes where radiant, consistent heat is required.

There are also radiant tube burners, where the flames are fired through an alloy or ceramic tube, and the flame is isolated from the process completely. The idea here is that the tube does not allow the products of combustion to make contact with the parts. Also, in most radiant tube furnaces, some sort of process atmospheres — comprised of a variety of gases to protect the products in the furnace from oxidation or to impart a metallurgic property to those parts — have been introduced to the chamber and the process.

As such, burner design engineers have to figure out how to give a very uniform heat delivery to the tube they are firing into. Many times, a burner will need to mix the air and gas very slowly (compared to direct fired furnace burners) to ensure the flame releases its radiation at a very uniform rate, so as to not distort the radiant tube itself. And the users of these variety of burners range from flame hardening to direct fired to indirect fired atmosphere processes and many more.

We will continue this discussion point in subsequent columns because understanding these burners is critical to using them correctly. As for the original idea that flame shapes can affect all sorts of process performance, we will revisit this topic and others, because it’s all important. Different flame shapes can significantly impact combustion performance by influencing factors like flame speed, stability, heat release, and certainly one of the big design goals now, emissions reductions. We’ll tackle these topics in future columns.

Until then, I would suggest that you take a walk into the plant and check out the variety of burners that you may have. Let’s endeavor to find more about them and consider, “What would make this burner the right choice for this application?” Then, discover what you can learn about them and their history. We will tie that all together when we discuss the next installment.