Is your combustion equipment truly compliant? In this guest column, Mesa Wentling, Marketing/Field Service at PSNERGY, explores two mandatory annual requirements introduced in the latest edition of NFPA 86: Standard for Ovens and Furnaces. The updates — Safety Train Verification and Radiant Tube Integrity Inspections — directly affects combustion-based heat treating equipment. Wentling breaks down what each requirement entails, how to achieve compliance, and the risks operators face if they don’t.
NFPA 86: Standard for Ovens and Furnaces establishes the minimum safety requirements for equipment that uses heat to process materials. The standard is designed to prevent fires, explosions, and hazardous operating conditions in industrial heating systems.
Although there are many updates in the most recent edition, these two mandatory annual requirements directly affect combustion equipment in use by most heat treating operations: Safety Train Verifications and Radiant Tube Integrity Inspections.
Safety Train Verification
The annual Safety Train Verification requirement focuses on confirming that each component of the fuel safety train is present and functioning correctly. Often in older furnace installations, components like gas line drip legs or wye strainers were omitted. Combustion systems rely on a sequence of valves, switches, regulators, and interlocks that must function in a precise way for safe furnace operation. These devices can drift out of adjustment, wear mechanically, or fail electrically over time.
Verifying the gas safety train annually ensures that all protective devices respond when necessary. This procedure confirms valve functionality, switch setpoints, regulator performance, and the integrity of wiring and interlocks. The goal is to identify any signs of degradation of the gas safety train before it becomes a safety hazard.
Radiant Tube Integrity Inspections
RTI Inspection | Image Credit: PSNERGY
Radiant Tube Integrity Inspections are now another required annual check. Radiant tubes operate in severe thermal environments that can lead to cracking, oxidation, warping, or weld deterioration. A tube that loses integrity can leak products of combustion into the furnace chamber, which can contaminate products, affect temperature uniformity, and create unsafe operating conditions. Loss of integrity can occur through thermal cycling, corrosion, or mechanical stress. The annual inspection ensures that any failing tubes are identified before they compromise safety or performance.
Three common ways to perform Radiant Tube inspections are with (a) digital combustion technology, (b) pressure testing, and (c) visual inspection. Digital combustion technology uses furnace atmosphere and O₂ data to identify failing tubes. This method significantly reduces downtime and manpower, improves safety, and increases accuracy. Pressure testing includes furnace shutdown, tube sealing and pressurization, pressure verification, and final seal removal and reassembly. Visual inspection requires furnace shutdown and multi-day cooling, confined space entry with elevated risk, and offers limited accuracy due to restricted access, typically identifying only major cracks in cold tubes.
Noncompliance Is a Liability
It has been observed through industry interactions that many heat treaters have not yet come into compliance with these updated NFPA 86 requirements because of the long-standing belief that their equipment was effectively grandfathered in. Historically, older furnaces and ovens were not always required to meet new verification or inspection criteria. That is no longer true. Due to the grandfather clause being eliminated, every furnace or oven, regardless of installation date, must comply with the current standard.
Failure to comply with the annual requirements can have significant consequences. Noncompliance increases exposure to safety incidents, unplanned outages, and equipment damage. Insurance carriers and auditors are placing greater emphasis on documented conformance to NFPA 86, and missing these verifications can affect coverage or lead to corrective actions.
In the event of an incident, lack of compliance presents substantial liability. Connect with industry experts in combustion like PSNERGY who can provide resources that help heat treaters and metal processors meet these requirements efficiently. You should expect detailed guidance, inspection procedures, and combustion technology for Safety Train Verifications and Radiant Tube Integrity Inspections, along with service options for facilities that need support. These resources assist operators in building compliant, safe, and reliable operations. For more information on the recent edition of NFPA 86, be sure to visit www.nfpa.org.
About The Author:
Mesa Wentling Marketing/Field Service PSNERGY
Mesa Wentling specializes in industrial marketing, with hands-on experience supporting furnace efficiency, combustion, and manufacturing-focused initiatives. She works with engineers and furnace specialists to help communicate complex combustion and performance data in a clear, accessible way.
Jim Roberts of U.S. Ignition engages readers in a Combustion Corner editorial about the hidden complexity of balancing furnace pressures —explaining how thermal expansion, gas velocity, and pressure fluctuation interact in modern burner systems, and how flue gas recirculation can push firing efficiency from 30% to 75% while cutting NOx emissions by more than half.
This editorial was first released in Heat Treat Today’sMarch 2026 Annual Aerospace Heat Treating print edition.
When I made the comment about the negative attitude in Part 1 of this series (Air & Atmosphere Heat Treating, February 2026), I was referring to the fact that most of these burner designs require a suction component (in this case, the eductor) to help pull the exhaust gases out over the heat exchanger portion of the burner. Also, if we just tried to pressurize the burners and force the exhaust gases out through the exchanger section, there would be a pressure buildup in the furnace. With that comes the destruction of door seals. Burner plates begin to leak, and when the doors open, the operators and furnace guys get greeted with a blast of 2000°F flue gas. I can honestly say, I have not, in all my years in this industry, met a furnace guy who likes a thermal haircut.
So, by balancing the pressures, we can save gas, reduce emissions, and probably even heat treat some products along the way.
A comment like, “just balancing the pressures,” seems like such an easy thing to accomplish. And, for all the experienced furnace guys out there, that is probably regarded as pretty simple stuff. But we have to give proper respect to the myriad of moving parts in today’s modern burners and heating systems. When I say moving parts, perhaps the better description is designing around the fluctuations in pressures, temperatures, and flows that these modern systems all perform to operate at these efficiencies.
When Combustion Corner covered pressures and velocities in August and September 2025, you will recall that under these temperatures, everything starts moving around under the temperature growth and pressure increases. Velocity increases like crazy, and at heat treating temperatures, the very components expand significantly enough to affect the pressure and delivery of flue gases.
High temperatures cause flue gases to expand significantly because increased thermal energy boosts gas molecules’ kinetic energy, making them move faster and spread out. This principle, described by gas laws like Charles’s Law, leads to volume increases that necessitate expansion joints in equipment to prevent system damage and maintain integrity. This expansion can create immense stress on combustion systems, requiring specialized components like expansion joints to absorb thermal growth and maintain seals, while the high heat can also induce chemical changes and dissociation, influencing performance in other ways.
For example, can you begin to envision how furnace designers and burner design engineers have to pay attention to component growth while maintaining the critical pressures of the furnace and the burners and heat exchangers? It’s a dance, let me tell you! I believe I pointed out a while back that a 6-inch diameter radiant tube or burner combustor will grow almost an inch in length when running at 1400°F and above. If it’s growing in length, it is also trying to grow in diameter. It’s like trying to produce a constant flow of water at a constant spray rate on your garden hose, all the while the hose is changing dimensions. Not so easy is it?
To sum up, with heat recovery, and then with the addition of flue gas recirculation and high velocity burners, it is really quite remarkable how well many of these systems perform. The firing efficiency of a flue gas recirculation system over a conventional cold air burner can be the difference of 30% fuel efficiency and 75% fuel efficiency! We are talking about some serious fuel dollar savings when that all happens. And now, with recirculation, you are also cutting NOx by better than half as well.
Next time we will talk about how these systems do all of this.
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.
What do aerospace and industrial heating vessels have in common? Backups for essential systems. In this Technical Tuesday installment, Bruce Yates, president of Protection Controls Inc., explores how NFPA 86 Standard for Oven and Furnaces addresses redundant flame safety, compares common sensing approaches, and highlights recent advances in UV scanner technology that improve reliability and reduce maintenance risks.
This informative piece was first released in Heat Treat Today’sFebruary 2026 Air & Atmosphere Heat Treating print edition.
Introduction
Boeing Aircraft lost billions of dollars before realizing that the 737 MAX’s MCAS (Maneuvering Characteristics Augmentation System) needed a redundant angle-of-attack vane to prevent erroneous MCAS-induced drive commands. Lockheed Martin uses dual-redundant MIL-STD-1553 data bus (that is, a shared communication pathway for exchanging data between electronic systems) on its Apache Guardian attack helicopter for target acquisition and cueing for the helicopter’s fire-control radar system. Spacecraft internal Active Thermal Control Systems (ATCSs) can either be a fully redundant thermal-control loop or a single loop system that is equipped with a redundant accumulator to be activated if needed. The accumulator represents a single point of failure that can result in a loss of crew.
Aerospace is not the only industry where redundancy is an important aspect of safety. It is critical in the industrial heating industry. NFPA 86 Standard for Ovens and Furnaces has for many years required redundant pilot gas valves and redundant main gas valves.
Let’s discuss redundant flame safety.
Redundancy in Industrial Heating
There are two types of flame sensors generally used on industrial burners: flame rods and ultraviolet scanners. Flame rods are simply stainless steel rods that intersect the burner flame. A voltage potential from the combustion safeguard is applied to the flame rod. When a flame is present, an electrical current (measured in millionths of an amp) flows from the flame rod through the ionized gases of the flame to the burner, which is grounded. This current is amplified in the combustion safeguard and energizes a relay output to power the fuel valves (see Main Image).
Redundancy can be achieved by using a two-burner control with one flame rod. The flame signal from the flame rod goes to the sensor input of both positions of the two-burner control (Figure 1).
We will devote the rest of this article to UV scanners (Figure 3).
Figure 1. Redundant flame safety with a single burner flame safeguard with a flame rod sensor
Figure 2. Solar radiation begins at approximately 2,800 Å and is therefore not detectable by the flame rod sensor.Figure 3. Demonstration of two independent UV tubes producing UV rays out of sync with one another | Image Credit: Protection Controls
Redundant Flame Safety with UV Scanners
The tube of a UV scanner responds only to radiation in the spectrum of 1,900 to 2,300 Å (Figure 2). Peak response is at 2,100 Å (210 nm). Solar UV starts at about 2,800 Å, as shown in Figure 2, and is therefore not detectable by the device. Solar radiation, of course, extends into the visible spectrum (4,000 Å) and extends into the infra-red spectrum. A UV tube consists of a fused silica or UV glass envelope, two electrodes, and a gas contained in this envelope. This is called a cold-cathode gas-discharge tube.
This tube conducts or ignites when it is irradiated with ultraviolet light and when sufficient voltage potential exists across the two electrodes. The electrodes can be made of tungsten, molybdenum, or nickel. When a photon of sufficient energy is absorbed into the cathode electrode, electrons are emitted and are drawn to the anode. A larger cathode allows more electrons to avalanche, causing higher current flow and thus higher sensitivity to UV. There are high sensitivity UV scanners designed for special burners that will produce low UV, such as one designed by Protection Controls, Inc.
The gas in the tube is usually a helium-hydrogen ionizable mix. Electrons released by the cathode release electrons in the ionized gas, becoming a self-sustaining discharge much greater than that of the originally generated electrons and producing a very high current gain or avalanche effect. The sensitivity of a tube will very slowly decrease over a period of time. Replacement should be made after 8,000 hours of operation. The current produced by the photoelectrons is measured in millionths of an ampere, so this current is amplified in the combustion safeguard to energize a relay that can then energize the fuel valves.
Critical Maintenance to Avoid Tube Gas Contamination
While UV scanners are very reliable, tube gas contamination may occur with large temperature shock (ΔTEMP/ΔTime) or large physical shock (a 2-inch drop may cause 100G shock), causing the electrode to UV glass envelope seal integrity to be compromised. Because of this, it is possible for a UV tube to conduct current when no UV is incident upon it. This would normally be detected during the flame safeguard safe start check. When an indicated flame on condition exists prior to purge or ignition, the safe start check relay prevents ignition and gas valve energization.
In addition to safe start check before every heating cycle, a monthly preventative maintenance schedule should be in place if the burner is used daily. This consists of closing a manual gas valve. The electrically powered gas valves should close in two to four seconds as the UV scanner and combustion safeguard respond to loss of flame.
If a burner is in continuous service, we recommend that this maintenance schedule be performed weekly. An alternative to this is to use a self-checking ultraviolet scanner and control. In the past, this type of scanner involved an electrically operated shutter, which alternately would block and allow UV to the tube. However, having a mechanical device operating close to the burner heat and vibration is a recipe for frequent and premature failures; it is typically rated for only 140°F to 175°F maximum and is quite expensive.
Going Shutterless
Figure 4. Note how each amplifier has its own flame relay | Image Credit: Protection Controls
Newer designs are available that completely avoid using a mechanical operating device to moderate the UV, increasing reliability and durability. For example, the Dual/Redundant Self Check UltraViolet Flame Sensor and Combustion Safeguard Control from Protection Controls includes two UV tubes in one ultraviolet sensor to monitor one burner flame. UV tubes respond to welding sparks, ignition sparks, lightning, bright incandescent or fluorescent light, solar radiation, gamma rays, and x-rays.
Since UV tubes produce UV rays when they conduct, two UV tubes in one sensor would not normally be suitable for sensing a burner flame, as one UV tube could be responding to the other tube and not the flame. But in the case of this safety control, two voltage supplies to the UV tubes are out of phase with each other. When one UV tube is powered and may respond to UV rays, the other UV tube is off. Additionally, the two UV tubes are powered through two rectifier circuits from two transformers that are out of phase with each other. The two UV tubes are powered and sense UV from the flame on alternating half cycles (Figure 3).
Each UV tube and rectifier circuit provides input to its amplifier. Each amplifier provides input to its own flame relay (Figure 4). Upon burner startup, before burner ignition, if either UV tube is in conduction, the safe start check circuit does not permit powering the fuel valve.
During the burner run cycle, if either UV tube fails in the conduction state, the cycle will safely continue with the other UV tube sensing the burner flame. See Figure 5.
Regardless of which sensor option you choose, accounting for flame redundancy and ensuring your maintenance plan is proactive enough for the method chosen is key to a safe manufacturing environment.
Figure 5. Redundant flame safety for single- and multi-burner flame safeguards: (a) redundant flame safety with a single burner flame safeguard with an ultraviolet sensor and (b) redundant flame safeguard (2-burner shown) with an ultraviolet sensor. | Image Credit: Protection Controls
About The Author:
Bruce Yates President Protection Controls, Inc.
Bruce Yates is the president of Protection Controls and is involved with management, sales, and engineering responsibilities. He graduated from the University of Illinois with a Bachelor of Science in Electrical Engineering in 1968. He works with his brother Douglas in the family-owned flame safeguard control manufacturing company, started by his father, James, and uncle, Robert, in 1953.
Jim Roberts of U.S. Ignition engages readers in a Combustion Corner editorial about the double-edged sword of heat recovery technology —explaining how efforts to reduce fuel consumption inadvertently drove up NOx emissions, and how flue gas recirculation (FGR) emerged as the design solution capable of cutting both fuel use and emissions by up to 50%.
This editorial was first released inHeat Treat Today’sFebruary 2026 Annual Air & Atmosphere Heat Treating print edition.
A furnace guy walks into the heat treating plant and says to the operators standing nearby, “This exhaust system and these burners all have a negative attitude.” The other furnace guys say, “They better be negative, or they would not work well!” As if we don’t have enough negativity swirling around in our world as it is, now we are happy about it?
In the Annual People of Heat Treat (September 2025) we talked about the types of burners that were developed as heat treating and furnace sciences and combustion designs evolved. We also chatted about how the advent of new fuels and government regulations was going to take a chunk of our attention in the coming years — for example, pollution laws coming to the forefront of our industry in the late ‘70s and onwards. Interesting new burner designs sprung up, primarily, as you recall, to address the usage of gas. In other words, how can we reduce fuel usage?
But First, NOx
The cost of gas skyrocketed for a stretch and it led us first to energy reduction plans. But with heat recovery sciences came the phenomenon of higher flame temperatures. When you get higher flame temperatures, you can sometimes (okay… all the time) generate NOx. One of the primary constituents of atmospheric pollution is NOx, and it became a prime target for reduction by the EPA and other governing air quality folks. As it should be.
Just a quick step back to the “remind me again, Jim” world. What do we breathe? Air, right? We have to have oxygen. But what we tend to forget is that air is roughly 79% nitrogen. So, what we breathe is actually nitrogen spiked with oxygen, and the fuel that we generally burn, natural gas, has some nitrogen in it too.
Natural gas can have as much as 5% nitrogen in it, although membrane filtering usually controls pipeline gas content at around 1%. The point is that nitrogen is the dominant gas in our combustible portfolio, and when we make it really hot, it makes NOx. And that is considered bad for all of us. So, NOx from fuel-borne nitrogen can be released at temperatures as low as 1400°F. Sometimes that is referred to as “sudden NOx” because it releases quickly. All of us Furnace Guys know that 1400°F ain’t nothing in our world.
The second form of NOx is referred to as “thermal NOx” and that is the major source of NOx in our world. That is when we heat the air we are combusting in a burner, burning off most of the 21% oxygen. Then, flame temperature climbs, and continues to now superheat and try to burn that remaining 79% of nitrogen. As temperatures approach 2300°F, the magic happens.
Thermal NOx forms significantly at high combustion temperatures, typically starting above 1300°C (2372°F), with formation increasing exponentially as temperatures rise, especially above 2800°F (1538°C), due to atmospheric nitrogen and oxygen reacting at peak flame temperatures. Does anybody remember what happens to flame temperatures when we preheat the combustion air (recuperation, recirculation, etc.)? Flame temp and heat transfer increase and we go up to theoretical flame temperatures of 3200°F without even working at it.
Solving Energy Efficiency Through Design
So, let’s return to the original question: What happened when we tried to only save gas with heat recovery? Answer: We installed energy efficient burners but increased the emissions footprint in doing so. We cut down on energy expenditure but made exhaust an issue with the higher temps.
For most industrial and commercial applications, the optimal range for flue gas recirculation (FGR) is between 10% and 25% as this range offers significant NOx reduction without compromising combustion stability or efficiency. By adjusting the pressures coming into the burner and then balancing the exhaust outlet pressures over the heat exchanger body, normally with an extraction device called an “eductor,” we can dial in the percentage of recirculation the burners are operating under.
Figure 1. Flow diagrams depicting the basic design for both direct fired and radiant tube style burners | Image Credit: Honeywell
With this design, I have seen fuel and emission reductions of 50% when compared to the existing conventional combustion systems. It really is a testament to what design and research can produce for us (Figure 1).
We’ll look more closely at these designs 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.
Jim Roberts of U.S. Ignition engages readers in a Combustion Corner editorial about how rising fuel costs have driven dramatic improvements in furnace efficiency and combustion technology over the past 60 years, transforming heat treat processes from 20% to 70% fuel efficiency.
This editorial was first released inHeat Treat Today’sJanuary 2026 Annual Technologies to Watch print edition.
A furnace guy walks into the shop and sees the cost of gasoline. “This keeps going up, what gives?”
My first car got about 10 MPG — we will not even go near to discussing when that was. Gasoline costs have since driven cars to become more efficient with 30+ MPG vehicles.
Last month’s article highlighted how there are five qualities in our heat treat processes: Quality and Accuracy, the necessary attributes; Efficiency and Performance, the variables; and Profit, which comes whenever we improve the two variables. We have discussed government regulation on emissions and technological breakthroughs that improved combustion technology in earlier articles, but now we turn to the connection of combustion and cost: how gasoline costs drove improvement of the two variable qualities of heat treat processing for combustion, Efficiency and Performance.
Gasoline Costs: A Timeline
Up until about 1960, the world of heat processing was pretty much a level playing field with Efficiency and Performance. We had tons of fuel at our disposal. Pollution was known but not yet a criterion to manage processes. So, burner efficiency and design were very low end. Nobody cared. Fuel was almost free. In doing research for this story, I found records of natural gas being less than $0.50 per million BTUs. Electricity was on par with delivered BTU costs. But then the cost of fuel started to fluctuate. The furnace guys started to notice; if nothing else changed, our friend Profit would weaken.
From 1930 to 1980, electricity pricing went up 500%. Natural gas started to bounce around in price. It was less than a $1.00/thm in the ’60s and ’70s, peaking during times of fuel shortage at $16.00/thm. Ten years later, in 2016, it hit $2.30/thm again. Some pretty wild fluctuations. In fact, it should be noted that the industry overseas had already begun to shift technologies — several years ahead of the U.S. — because they had been suffering with high fuel costs in Great Britain, Germany, Western Europe, and in Asian markets.
Furnace guy and the suppliers had to improve the efficiency and performance.
Troubleshooting and Combustion Design Changes
At first, you look at easy fixes to improve Efficiency and Performance. An example would be that insulation and refractory science really improved. If you can keep the heat in the furnace, you need less fuel to hold it at these high temperatures, right? So, improve the insulation.
Next, let’s get the burners from just being the opening in the furnace that you pour gas into, and make the burner more like a carburetor on an engine. Let’s get control of the air and gas ratios.
Next, let’s recover some of the flue gases and pre-heat the air coming into the burner. When you do that, the flame temp goes up, sometimes by as much as 400-500°F. That means higher heat transfer rates to the parts inside a now well-insulated furnace. Huge efficiency gains started happening.
Efficiency and Performance got a huge boost when the burners started to have high velocity discharge rates. In other words, we now had flames that were hotter and going into the furnace at several hundred miles an hour more than before. With that comes circulation improvement inside the furnace. And much like pudding in a blender, the faster the beaters, the smoother the mix. To give you an idea of the scope of these improvements, form 1960 to 1990, a matter of only 30 years, furnace and burner technology improvements went from 20% fuel utilization to estimated 60-70% fuel efficiencies, even higher in some instances. And there it was, super efficiency driven to occur by fuel cost and flucturation of supply.
To really hit home what that meant, let’s look at a 1,000-lb load of steel. Our process temp is 1750°F. Our furnace and combustion efficiency used to be 20%. That would require 1,370,000 BTU to heat up in an hour. Now, with 75% furnace and burner efficiency, that’s 352,000 BTU. You just saved approximately 1,000 ft3 of gas per hour! If we use the average industrial gas price today at $3.80/1,000 ft3, the difference of all this is $24,000/year, and that’s just a 1,000-lb load. Real world, the numbers are significantly higher, as all you furnace guys know. Imagine the dollar savings when fuel was at $16.00/thm?
And so, there it is. The well-known realization that in most markets, the dollar cost of the energy triggers improvement of technology.
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.
What if your furnace could run faster, cheaper, and cleaner — without major capital investment?Carl Nicolia, president at PSNERGY, LLC, discusses how using waste heat recovery and smart combustion monitoring can cut cycle times in half, reducing gas consumption, and eliminating zone temperature variations.
This informative piece was first released inHeat Treat Today’sOctober 2025 Ferrous & Nonferrous Heat Treatments/Mill Processing print edition.
Optimizing combustion and reclaiming waste heat can dramatically improve furnace performance. A real-world bar and coil annealing case study shows how simple retrofits reduced ramp cycle time, cut gas consumption, and eliminated zone temperature variation. The results demonstrate how heat treaters can boost throughput, lower costs, and improve quality without major capital investment.
The Challenge of Industrial Furnace Efficiency
Industrial furnaces are the backbone of metals processing, enabling heat treatment, annealing, forging, and countless other applications. Despite their importance, these furnaces are inherently inefficient. In most cases, less than half of the energy generated by burning natural gas actually reaches the load. Energy is continuously lost through exhaust gases, radiant losses, opening losses, and the heating of fixtures and refractory walls.
On top of this inefficiency, combustion ratios drift over time. Burners fall out of tune, air-to-fuel ratios shift, and temperature distributions across zones become imbalanced. Even with regular maintenance, most furnaces run well below their optimal performance for a significant portion of their operating lives. See figures 1a and 1b, which illustrate how quickly furnaces drift out of tune. Therefore, regular monitoring and adjustment are essential to avoid energy losses and reoccurring performance issues.
This raises a critical question for heat treaters and metal processors: how much efficiency is being left on the table? And more importantly, what would it mean for throughput, energy costs, and product quality if some of that efficiency could be reclaimed?
The following case study of a bar and coil annealing furnace provides a compelling answer.
Figure 1a, 1b. A demonstration of temperature drift that happened in a furnace that was serviced in August 2018 and then again in May 2019. The red points represent oxygen levels measured at each burner when the PSNERGY team arrived on site, while the blue points show oxygen levels immediately after tuning. Although the furnace was optimized during the August 2018 service, the system had already shifted far from optimal conditions within a few months (May 2019). This highlights the inherent inefficiency and constant variability of combustion systems. Source: PSNERGY, LCC
The Application
The facility in this example operates a batch furnace dedicated to bar and coil annealing. The furnace is equipped with 14 non-recuperated U-tube burners across two heating zones.
While reliable, the furnace faced two persistent challenges: long cycle times and inconsistent temperature uniformity across the two zones. Both issues reduced throughput and posed risks to product quality and delivery while also driving up energy costs.
The Problem
The problems facing this manufacturer were not unusual. Long cycle times limited furnace productivity, creating bottlenecks in meeting customer demand. At the same time, uneven zone temperatures made it difficult to maintain uniform metallurgical properties in the product.
With natural gas prices trending upward, energy costs compounded the problem. Every additional hour in the cycle not only resulted in lost throughput, but also higher gas consumption.
The Objective
The project set out with three clear objectives:
Reduce total cycle time: By shortening ramp-up time, the furnace could complete more loads per month, increasing throughput.
Improve zone uniformity: Temperature variation between zones not only affected quality but also required longer soak times to ensure the coldest parts of the load met specifications. Eliminating this variation would allow for both higher quality and shorter cycles.
Lower gas consumption: With energy representing a major portion of operating costs, reducing fuel usage was essential to improving competitiveness and profitability.
The Solution
This improvement method went beyond the traditional practice of tuning a furnace every six to twelve months. Instead, it involved a broader approach utilizing waste heat recovery and digital monitoring tools to achieve optimal combustion at every burner.
The process involved:
Installing ceramic radiant tube insert assemblies into the U-tubes
Utilizing a combustion monitoring and alerting system to measure air-to-fuel ratio at all burners on the furnace
Adjusting all burners to operate within an optimal excess oxygen window (typically between 2.8% and 3.2%) and maintaining those settings over time
Ensuring balance between zones allowing the furnace to deliver uniform heating to the load
Figure 2. Before vs. after RIT installation. Source: PSNERGY, LLC
The project began with installing waste heat recovery on all 14 of the non-recuperated U-tubes. In this case, ceramic radiant tube inserts (RTIs) were used because they are quickly and easily installed and capture waste heat normally lost out the exhaust, keeping the energy inside the furnace. Additionally, the RTIs improve temperature uniformity, and reduce gas consumption (see Figure 2).
Installing combustion monitoring at each burner is key to keeping the improvements in place. Instead of waiting for issues to show up in product quality, operators can see what is happening at the burners in real time. When a burner starts drifting out of balance or tune, they have the data to correct it immediately. Constant visibility helps the furnace stay efficient and consistent.
Precision is important when considering the physics of combustion. Measuring excess oxygen at less than 1% (running rich) indicates incomplete combustion is occurring, leading to carbon monoxide and soot formation. At the other extreme, running with too much excess air (running lean) wastes energy. Even 5% excess oxygen results in roughly 13% less energy to the load, while 7% excess oxygen increases those losses to 21%, all while burning the same amount of natural gas.
The Results
The outcomes of this project were dramatic.
Ramp cycle reduced by 53%. Prior to any improvements, the furnace cycle time was 30 hours, with ramp-up time accounting for a major portion of the overall cycle. After optimization, ramp-up time was reduced by 8 hours, enabling faster turnaround and greater throughput.
Gas consumption reduced by 59% per load. Improved combustion efficiency means that less fuel is required to reach the same metallurgical results. This reduction directly lowers operating costs and CO2 emissions per ton.
Zone temperature variation eliminated. By balancing combustion across zones, the furnace achieves uniform heating, reducing the risk of quality issues and minimizing the need for extended soak times.
Figure 3. Graph shows Zone 1 and Zone 2 uniformity (identical curves depicted by yellow and green lines) after the combustion monitoring improvements. Source: PSNERGY, LLC
For the manufacturer, these results translated into both immediate savings and long-term operational advantages. Throughput increased while emissions and quality risks were reduced (see Figure 3).
Broader Implications for Industry
While this case study focuses on a single bar and coil annealing furnace, its implications extend across the heat treat and metals industries.
Most industrial furnaces, regardless of size or application, experience similar inefficiencies. Over time, combustion drifts away from optimal conditions, often unnoticed until performance or quality issues arise. Standard practice, tuning once or twice a year, is rarely enough to maintain proper function.
Capturing waste heat and utilizing technology to monitor and maintain combustion represent major opportunities for manufacturers. By reclaiming even a portion of the 10–30% efficiency losses that occur between tunings, facilities can realize double-digit improvements in throughput and energy consumption.
The return on investment can be substantial. In most cases for these improvements, it’s months. Additional throughput alone will often justify the investment. In many locations, natural gas providers have incentives in place for these projects as they are proven to make substantial reductions in energy use. Just as important, optimizing combustion extends the life of burners and tubes, reduces maintenance emergencies, and stabilizes furnace operation; again, reducing cost and improving efficiency.
Conclusion
Industrial furnaces are indispensable, but they do not have to be inefficient. This bar and coil annealing case study demonstrates that even established furnace systems can achieve impactful performance gains through retrofit combustion optimization.
By focusing on cycle time, energy use, and zone uniformity, manufacturers can unlock faster throughput, lower costs, and higher product quality, while also reducing emissions and operating stress.
The lesson for heat treaters is clear: combustion is not just a background process, it is the heartbeat of the operation. Maintaining combustion properly through the use of easily implemented technology can turn a productivity drain into a competitive advantage.
About The Author:
Carl Nicolia President PSNERGY, LLC
Carl Nicolia is president of PSNERGY, LLC, which provides modern solutions to combustion problems, improving equipment life, enhancing productivity, and reducing emissions through smart application of proprietary products, services, and technology.
Jim Roberts of U.S. Ignition engages readers in a Combustion Corner editorial about how focusing on the right priorities in the right order naturally leads to profitability in heat treating.
This editorial was first released inHeat Treat Today’sDecember 2025 Annual Medical & Energy Heat Treat print edition.
It’s a crisp winter day, and a furnace guy walks into the heat treat plant and says, “Something has changed here, it feels…more modern.” The rest of the furnace guys shrug and continue with the tasks at hand. But the furnace guy is right — something has been changing all along and will continue to do so in the foreseeable future, I’ll wager.
We’ve talked about how certain trends and needs have driven the growth in the industry. My ramblings have included bed posts and pipelines and the flavors of different fuels, and what it all boils down to is change. These changes are attempts to get the following qualities into our processes in the heat treating world:
Quality
Accuracy
Efficiency
Performance
Profit
“But Jim, you listed profit as the last measuring stick! What is wrong with you?” It would be pretty easy to invert this list; turn these guideposts upside down and the world you are in would still work. But if we add longevity in business as an additional goal, then it will not be too long before you begin to realize that the order is listed correctly here. For the most part, in my experience, the heat treating industry has kept the order intact. It is an honorable path, I think.
Quality and Accuracy are the new givens. We do not have to spend time on this. As long as we have been wielding control over metal, those properties are the constant. From hammering out the very first horseshoes, if they did not fit the horse or cracked and broke after a couple of steps, you were not in the horseshoe business very long. These days, standards clearly map out the goal: a client tells us what is demanded, maps it out for us in a specification, and we meet it.
Items 3 and 4 are where we focus today. If we can improve Efficiency and Performance after meeting the Quality and Accuracy targets, then good old item 5 happens — Profit. It just happens. What a concept! Now you may think this is a re-run of every BUS-101 class or seminar you have seen. Maybe you are right, but this is where I veer off as a furnace guy and get back to the business of combustion as it applies to our industry.
We talked earlier about how the natural gas industry expanded and built this fantastic infrastructure to provide fuel to all of us. Electric providers did and are still doing the same thing.
At the end of the transmission line, whether gas pipe or electrical cable, sit the furnaces and ovens that heat treating needs. The buck stops here. Speaking of bucks, in order to get to profit, what must we do? If we really only have Efficiency and Performance in our control (Quality and Accuracy are presumed to be met), then let’s look at how that changed, in furnace guy world…next year [in 2026].
All the best to everyone in the Holiday seasons. May you be blessed with good health and happiness.
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.
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 inHeat Treat Today’sNovember 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.
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 inHeat Treat Today’sOctober 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 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.
Maintaining precise temperature uniformity is a cornerstone of pyrometry compliance and part quality in heat treating. Yet, traditional manual tuning of multi-burner furnaces is slow, labor-intensive, and prone to inefficiencies due to nonlinear system responses.
In this Technical Tuesday installment, Ben Witoff, manager of Information Systems and Data Strategy for Fives North American Combustion, Inc, outlines a new linearization-based approach to combustion tuning. This approach offers a data-driven method to shorten uniformity adjustments, improve survey outcomes, and elevate furnace performance to higher AMS2750H classes with greater repeatability and less operator intervention.
This informative piece was first released inHeat Treat Today’sOctober 2025 Ferrous & NonFerrous Heat Treatments and Mill Processing print edition.
The Manual Uniformity Tuning Model
Heat treat furnaces require precise combustion system tuning to produce high-end parts for aerospace, automotive, and construction industries. Temperature uniformity surveys (TUS) are the accepted industry standard for verifying the quality of these metal processing furnaces. Current standards such as AMS2750H specify a temperature uniformity that must be maintained inside the furnace work zone. End users, like Boeing, GE, and Pratt & Whitney, have mandated these temperature uniformity quality standards for their suppliers who heat treat components for their products.
Today’s furnace and combustion system TUS tuning methods are slow, inefficient, and outdated. These methods require skilled technicians to make precise, manual adjustments to single components in an iterative fashion. Adjustments require this recursive approach because the system of equations governing an industrial furnace’s heat distribution is nonlinear — an adjustment in one part of the furnace system will require tweaking the set up in other area(s).
In the typical case of a multi-burner furnace which has more than one temperature measurement point, the temperature distribution across a measurement array is not directly proportional to the change in a single burner’s firing rate. Due to the system’s nonlinearity, each independent tuning adjustment has incidental, cascading downstream effects on the rest of the system. Every attempt to resolve temperature disparity in one area of the furnace can consequently bring another area out of compliance.
Reinvention of the Tuning Process
Fives North American Combustion, Inc. (FivesNA) has developed a solution that shortens the time of the temperature uniformity tuning process when used before each TUS and optimizes the furnace temperature uniformity. The North American CertiFire panel implements a patented (Robertson and Dzik 2024) temperature mapping algorithm that creates a linear approximation of any furnace’s system of equations, regardless of its geometry or complexity. Once linearized, the temperature distribution can be resolved through simultaneous adjustments.
The temperature mapping algorithm creates a response matrix that correlates changes to the furnace’s heat inputs with changes in the steady-state distribution of heat throughout the furnace’s work zone. A thermocouple array is used to measure the work zone’s three-dimensional temperature distribution while the furnace’s burners are modulated. It is critical to the accuracy of this response matrix that the burner modulations are precise and repeatable. To accomplish this, actuated gas valves are inserted in the gas line to individual burners taking the place of a manually adjusted limiting orifice valve.
Each individual burner modulation has its own characteristic effect on the entire work zone’s temperature distribution. Figure 1 shows two different burner modulations and Figure 2 shows the resulting furnace temperature distribution over the same period. Nine thermocouples were placed on a rack within a furnace in accordance with the AMS2750H standard for this furnace volume and class, with eight thermocouples at each of the cubic work zone’s vertices and one in its center (SAE International 2022, p 44, Table 17).
Figure 1. Two different burner modulations (Source: FivesNA)Figure 2. Temperature response to two different burner modulations (Source: FivesNA)
The firing rate of each burner was increased to a fixed amount for a set number of minutes. The second burner was not adjusted until the work zone’s bulk temperature returned to the baseline average temperature. The two burners noted in Figure 1 were firing in the same plane, several feet from one another. Despite the burners’ close proximity and similar adjustments, their effects on the temperature distribution shown in Figure 2 are uniquely different. Not only does the overall rate of temperature change differ between the curves, but so do the individual thermocouple reactions. Thermocouple 5 (shown in orange), for example, shows the largest change in temperature for the first burner’s modulation, but experiences a much weaker response during the second burner’s modulation.
Mathematical Approach
The linear approximation of the furnace’s system of equations can be written as shown in Figure 3. Where vector T represents the temperatures of q thermocouples, vector B represents the bleed valve modulations of r burners, and response matrix K represents their relationship. By compiling each of these burner modulations and their resulting temperature effects, the furnace’s unique response matrix can be calculated using the formula shown in Figure 3.
Figure 3. Linearized furnace equation and response matrix creation
Once the response matrix is known, the linearized furnace equation can be reversed. By dividing a vector of thermocouple temperatures T by the response matrix K, the equation yields a vector of automated burner gas valve positions B. In a steady state furnace, starting with a vector ΔT representing the required changes in temperature for each thermocouple to reach the survey temperature, this equation can solve for ΔB, the necessary burner gas valve adjustments to achieve temperature uniformity.
The process of training entails the CertiFire map out the general valve positions needed to bring the furnace close to uniformity. Metaphorically, it is writing the manual of the furnace’s behavior which takes time to develop (a few hours). The tuning operation, which is the next and final step after the training, is like reading the manual and applying the guidelines set by the training. This process takes only a few minutes to dial in the valve positions for improved uniformity, as discussed below in the case study.
Case Study: SIFCO Industries, Inc. – Cleveland, Ohio
SIFCO furnace 8001 is a single zone box furnace with four high velocity burners firing above the load on the left wall of the furnace and four high velocity burners firing through piers below the load on the right side of the furnace. All burners were configured with a cross-connected variable ratio regulator. The combustion air was fixed for fuel-only turndown, and furnace control was achieved through a single impulse air bleed valve, which affected all regulators equally.
Adding the linearizing technology to furnace 8001 required the installation of eight actuated gas valves, replacing the existing manually adjusted limiting orifice gas valves, and a PLC subpanel. This added subpanel controls each motorized actuator independently. To drive the actuators, the subpanel was wired with two inputs from the existing panel: the tuner control variable (CV) over a 4-20mA signal, and the controller set point (SP) over ModbusTCP. The existing control panel was left in-place and is still the primary furnace control interface.
Pyrometry
Furnace 8001 is certified according to the AMS2750H pyrometry standard at the following three temperature SPs: 900°F, 1500°F, and 2100°F. Additionally, the survey process requires first holding the furnace 100°F colder than each SP (800°F, 1400°F, and 2000°F) before increasing the temperature to the desired production SP to prevent overshoot.
According to the AMS2750H standard, the furnace’s internal volume requires nine type-K thermocouples placed at each vertex of the cubic work zone and one at the geometric center for temperature measurements during certification. Furnace 8001 had historically been certified as a Class-III furnace (±15°F). The client’s goal was to reduce the overall temperature span at each of the six SPs to move furnace 8001 to AMS7250 Class-II (±10°F).
Installation Overview
The solution was deployed on furnace 8001 the week of March 31, 2025. Six SPs across four calendar-days (April 4–7) were trained and tuned. The training and tuning algorithms run unattended, so the estimated labor hours to set up and run the process at all six SPs was approximately two hours.
Example Training Experience – 800°F
Training at 800°F ran from 7:52 a.m. to 10:16 a.m. on April 5, 2025, for a total of 2 hours and 24 minutes. The furnace PID tuner was disabled for this training, and each burner’s actuated gas valve was locked in place at its last position. One at a time, each automated burner gas valve was opened by 50% to allow more fuel to flow for three minutes before lowering back to its initial position for 15 minutes. An adjustment amount of 50% was arbitrarily chosen to elicit a strong temperature response.
As each burner’s firing rate was adjusted, a unique temperature characteristic was measured across all 12 thermocouples (SIFCO requires three additional thermocouples for its TUS). The difference in each thermocouple’s temperature rate of change and amplitude is the foundation for the training algorithm’s furnace map.
Example Tuning Experience – 800°F
After the 800°F training was completed, three tuning iterations spaced eight minutes apart at 10:40 a.m., 10:48 a.m., and 10:56 a.m. on April 5, 2025, were conducted. The result of the tuning iterations was a reduction in the temperature span (hottest minus coldest) from 20.2°F to 5.3°F, and a reduction from +4.7°F, -15.5°F to +1.3°F, -4.0°F with respect to the SP, well within the range of an AMS2750H Class-I furnace.
Figure 4. Thermocouple temperatures during 800°F tuning (Source: FivesNA)
The temperature range, shown in Figure 4, illustrates the initial span on the left half of the chart. A clear reduction in span can be noted at the inception of the first tuning iteration around the 10:40 a.m. mark. Note how not only are the coldest and hottest thermocouples brought in towards center, but the overall spread is also closer centered on SP. The same process was done for five additional SPs yielding the data in Table 1.
SP [°F]
Operating Time
Temperature Span [°F]
SP Variation [°F]
Effective AMS2750 Class
Training
Tuning
Initial Span
Tuned Span
Initial SPV
Tuned SPV
800
2.4h
15m
20.2
5.3
+4.7, -15.5
+1.3, -4.0
Class-I
900
–
10m
6.3
5.7
+1.9, -4.4
+1.5, -4.2
Class-I
1400
2h
1h
42.9
9.7
+22.7, -20.2
+4.6, -5.1
Class-II
1500
–
10m
11.9
11.0
+9.0, -2.9
+7.2, -3.8
Class-II
2000
2.4h
25m
21.3
11.5
+13.9, -7.4**
+3.4, -8.1**
Class-II
2100
–
8.5h*
28.6
9.0
+20.1, -8.5**
+4.8, -4.2**
Class-I
* Tuning at 2100°F was left to run overnight to test the effectiveness of longer hold times. ** Bulk furnace temperature read on average 20°F hotter at 2000°F and 2100°F than the controller SP. Reported SP variations are referenced to the median thermocouple instead of controller SP.
Note that the training was only needed for three temperatures. Since this initial data was captured, SIFCO has conducted three monthly TUS surveys. Prior to each survey, only tuning by the Certifire at the required temperatures was performed. The simplicity, efficiency, and accuracy of the linearizing technology ensures the subsequent client TUS will easily pass and maintain Class II uniformity.
Operating this linearizing technology does not violate furnaces with multiple temperature survey temperatures per AMS2750H because the valve positions are repeatable and maintain the original settings and pressures from the tuning prior to the TUS and will remain in that position until the next tuning (SAE International 2022, Section 3.5.4.1.1k).
Conclusion
Figure 5. Nick Klusty of SIFCO Forge
The adoption of linearization-based combustion tuning represents a significant step forward for the heat treat industry. SIFCO’s Facilities & Maintenance Manager Nick Klusty reflected on their new capabilities, saying, “We had been struggling to maintain Class III on this 8001 furnace for years. It took days to tune the furnace in preparation for every monthly TUS. Now it literally takes minutes. The North American CertiFire tunes so much better than we could ever achieve by hand. So good that we now have a second furnace available for Class II work, which opens up a new channel for production saving us the time and money of using outside services to heat treat Class II products.”
By replacing manual, iterative adjustments with a data-driven, repeatable process, furnace operators can achieve tighter temperature uniformity in less time, reduce the risk of failed surveys, and expand furnace capabilities to higher AMS2750H classifications. Beyond compliance, this approach enhances process stability and operational efficiency, ensuring that heat treaters are better equipped to meet the increasingly stringent demands of aerospace, automotive, and other critical industries.
References
Robertson, T., B. Witoff, and J. Dzik. 2024. Method and Apparatus for Improving Furnace Temperature Uniformity. U.S. Patent 12,104,788, filed October 1, 2024.
Ben Witoff Manager, Information Systems and Data Strategy Fives North American Combustion Inc.
Ben Witoff is the manager of Information Systems and Data Strategy at Fives North American Combustion Inc. After founding the company’s data engineering department in 2019, his work focuses on the development of IIoT-enabled combustion technologies and integrating data connectivity and advanced analytics into industrial processes. A Class of 2023 Heat TreatToday 40 Under 40honoree, Ben has also been a guest on Heat TreatRadio Episode #77: Algorithmic Combustion Tuning with Justin Dzik and Ben Witoff at Fives.
For more information: Contact Ben Witoff at ben.witoff@fivesgroup.com.
