In this installment of the Controls Corner, we are addressing inductance in a furnace heating system, and the critical role it plays in various industrial systems, including furnace load systems. Impedance acts as a measure of how much a circuit resists the flow of AC current. In this guest column, Brian Turner, sales applications engineer at RoMan Manufacturing, Inc., explains how impedance applies in electrical circuits.
Inductance is a fundamental concept in electrical engineering, and it plays a critical role in various industrial systems, including furnace load systems. In furnaces used for heating, inductance is a key factor influencing the system’s electrical performance, energy efficiency, and overall operational behavior.
To talk about inductance, let’s first address impedance and how it applies:
In electrical circuits, impedance refers to the total opposition to the flow of alternating current (AC), which is a combination of both resistance (from resistors) and reactance (from inductors), essentially acting as a measure of how much a circuit resists the flow of AC current, taking into account both the resistive component (like a resistor) and the reactive component (like an inductor at a specific frequency) within the circuit.
Load configuration, power source (IGBT, VRT, ERT) to the furnace feedthrough Source: RoMan Manufacturing Inc.
Inductance
Inductance is the property of an electrical conductor that opposes a change in the current flowing through it. It arises from the magnetic field generated around the conductor when an electric current passes through it. The unit of inductance is the Henry (H).
In an AC circuit, inductance creates a phenomenon known as inductive reactance, which resists the flow of current. Inductive reactance (XL) is given by the formula:
XL= 2πƒL
Where: • XL is the inductive reactance (in ohms) • f is the frequency of the AC supply (in hertz) • L is the inductance (in Henrys)
This reactance influences how the current behaves in the system, which is particularly important in furnace load systems where high current flows are common.
Resistance
Electrical resistance is the opposition that a material offers to the flow of electric current. It is measured in ohms (Ω) and depends on factors such as the material’s properties, its temperature, and the geometry of the conductor (length, cross-sectional area). In heating systems like vacuum furnaces, resistance is harnessed to convert electrical energy into heat through Joule heating (also known as resistive heating).
The relationship between electrical power, voltage, current, and resistance is governed by Ohm’s law:
V = IR
Where: • V is the voltage across the heating element(in volts) • I is the current through the element (inamperes) • R is the electrical resistance of theelement (in ohms)
The heat generated by the furnace’s heating elements is a function of the power dissipated in the resistance, given by the equation:
P = I2 x R
This shows that the heat produced is directly proportional to the resistance and the square of the current flowing through the heating elements
Close Couple
Reducing the material in the secondary* reduces resistance (HEAT = I2 x R)
Reducing the area in the secondary reduces inductive reactance increasing power factor
To be most efficient, use the shortest amount of conductor material from the electrical system secondary to the furnace feedthrough. Additionally, keep the distance between those conductors as small as possible.
Power Factor and Efficiency
Inductance in a furnace load system causes the current and voltage to be out of phase. This phase difference results in a lower power factor, which is a measure of how effectively the system converts electrical power into useful work. A lower power factor means that more apparent power (the combination of real power and reactive power) is required to achieve the same level of heating.
In practical terms, a furnace with a high inductive load will draw more current from the power supply for a given amount of heating, leading to increased energy losses and inefficiency.
In practical terms, a furnace with a high inductive load will draw more current from the power supply for a given amount of heating, leading to increased energy losses and inefficiency. Power factor correction techniques, such as the use of capacitors, are often employed to counteract the effects of inductance and improve system efficiency.
Conclusion
Inductance is a fundamental factor in the operation of furnace load systems, influencing everything from heating performance to energy efficiency and power quality. By understanding and managing inductance, furnace operators can optimize their systems for maximum performance while minimizing energy losses and operational costs. Controlling inductance is essential for ensuring that furnace load systems operate reliably and efficiently in demanding industrial environments.
*The connection from a vacuum power source to the furnace’s feedthroughs, this connection can be made using air-cooled cables, water-cooled cables, or copper bus.
About the Author:
Brian Turner Sales Applications Engineer RoMan Manufacturing, Inc.
Brian K. Turner has been with RoMan Manufacturing, Inc., for more than 12 years. Most of that time has been spent managing the R&D Lab. In recent years, he has taken on the role as applications engineer, working with customers and their applications.
Maintaining clear communication for high precision processing, critical with medical component heat treating, requires sophisticated operations. In today’s Technical Tuesday, Mike Grande, vice president of Sales at Wisconsin Oven Corporation, provides an overview of how the industrial internet of things (IIoT) advances heat treat performance capabilities and ensures accurate, repeatable results.
Today’s technology is evolving at an exponential rate. Over the last several years, digital technology has provided more and more connectivity between devices and processes. One of the most impactful is IoT technology. From smartphones to virtual assistants, touchscreen refrigerators to thermostats and interconnected home management systems, these products are quickly changing the way people interact and connect.
In addition to consumer products, the industrial world is also seeing increased reliance on this technology to improve throughput, decrease energy use, and increase equipment longevity by capturing and analyzing the data generated by their machines.
What Is IoT and IIoT Technology?
IoT (internet of things) refers to everyday items that have been equipped with sensors that transfer data over a network. Refrigerators, lights, thermostats, smart speakers, and entire homes are now available with IoT technology. Devices equipped with IoT options provide conveniences like remote monitoring, advanced programming, and smart learning, which make daily and household tasks easier. What seemed like science fiction just a few years ago has become reality.
This impressive technology does not only apply to the consumer world. The application of IoT to the manufacturing sector is even more impactful. Industrial internet of things (IIoT) is the term used to describe the application of connected IoT technology to industrial machinery. These systems collect and analyze data, learn from that data (“machine learning”), perform predictive maintenance, and then share that information with personnel, manufacturers, including manufacturers of the machines being monitored, and even other devices. This type of data collection and analysis gives valuable insight into the facilities, processes, and equipment to ensure that everything from energy usage in a facility to equipment performance for a process is optimized.
Figure 1. The IoT gateway collects the data from oven-mounted sensors and wirelessly transmits it to the cloud. Source: Wisconsin Oven Corporation
How Is IIoT Used in Industrial Ovens and Furnaces?
IIoT technology tracks the performance and health of the most critical components and conditions in the ovens and furnaces they are monitoring. The system utilizes an IoT gateway (Figure 1), which collects information from predictive maintenance sensors that gathers performance data and stores it over time. The gateway also wirelessly transmits the data to a cloud platform where it can be displayed in dashboards, designed for easy viewing and monitoring. Thresholds are set at warning or alarm conditions. When exceeded, the system alerts the user or the oven manufacturer that there is a problem. This type of system predicts component failures before they occur, allowing time to schedule maintenance and minimize unplanned downtime.
Figure 2: An example of a dashboard used on an oven IIoT system Source: Wisconsin Oven Corporation
The data is displayed in a dashboard format (Figure 2) which permits visual analysis of the information, and intuitive understanding of the process being performed in the oven. In the example of an oven used to process parts in an inert atmosphere, the x-axis represents the elapsed time, which can be expanded or collapsed by the user in order to provide a more (or less) detailed view of the process. The y-axis tracks variables such as temperature, pressure, oxygen level, nitrogen flow rate, and humidity level.
A few examples of the oven data gathered and analyzed by an IIoT system are as follows:
The output of the temperature controller is monitored. If, for example, the controller output is normally running at 30% for a specific oven (meaning the oven is using 30% of its full heat capacity), and for no apparent reason it increases to 60% output, this indicates either an exhaust damper is stuck open and causing the oven to exhaust too much of its heat, there is a heater failure, or a door is not closing fully, or something else.
Vibration sensors installed on recirculation blowers can monitor the health of the oven. Since blowers are rotating machines, they have a predictable vibration frequency and amplitude. As the blower bearings wear over time, these vibration parameters change. The IIoT system uses proprietary algorithms to determine acceptable vibration levels at different temperatures and RPMs. As the vibration values change over time, the system can predict when blower failure is likely, prior to it occurring. This allows replacement parts to be ordered before a “hair on fire” situation where the equipment suddenly stops working, interrupting production and workflow.
In order to monitor the burners on gas-fired ovens, the flame safety system is wired to the IIoT system. This allows remote evaluation of the flame sensor, purge timer, and other components that are critical to safe and proper burner operation. On older ovens, nuisance shutdowns can occur due to a dirty combustion blower, dirty flame rod, faulty airflow switch, or other reasons. An IIoT system allows the oven manufacturer to remotely diagnose this type of issue without ever sending a service technician to the job site, saving time and money.
An oven IIoT system is often used to measure the oven chamber pressure. Ovens can be intentionally operated at a neutral pressure, a slightly negative, or slightly positive pressure, for various process-related reasons. A pressure sensor measures this value and, via the IIoT gateway, delivers it to the dashboard in real time. If the chamber pressure strays outside of a predetermined range, this indicates a failure such as an improper damper setting or a malfunctioning exhaust blower.
The Benefits of IIoT Technology
Predictive maintenance is one of the most important benefits of IIoT. The ability to prevent potential equipment breakdowns and resulting process bottlenecks is invaluable. Not only does IIoT allow plant managers and operators to schedule maintenance ahead of time, it also reduces maintenance hours by knowing exactly what the issue is that needs to be serviced. This reduction in unplanned downtime increases productivity, which translates to higher profits.
The quantity of detailed, relevant data available (real time and retroactive) via the IIoT system exceeds the information a service technician can gather oven side, especially if the oven has stopped working. Using IIoT to remotely gain information to service the equipment, the problem can often be resolved the same day.
Perhaps the most impressive benefit of IIoT is remote diagnostics. Whether a furnace or oven is experiencing occasional unexplained shutdowns, or is completely out of commission, it typically takes days or weeks to schedule a service technician to inspect the equipment and diagnose the problem. However, if the oven is equipped with IIoT, a call can be made to the oven manufacturer who can remotely log into the system dashboard. They will be able to view and analyze the data gathered by all the sensors going back over time, without sending a service technician to the job site. Also, the quantity of detailed, relevant data available (real time and retroactive) via the IIoT system exceeds the information a service technician can gather oven-side, especially if the oven has stopped working. Using IIoT to remotely gain information to service the equipment, the problem can often be resolved the same day. Further, the IIoT system gathers and records the data going back in time for months, which is invaluable when trying to diagnose a chronic or intermittent failure.
Another use of IIoT technology is energy management. Through IIoT monitoring, facilities and equipment can be set to optimize energy efficiency. By ensuring the oven uses only the amount of heat energy necessary, and no more, its energy consumption is minimized. The system can reveal, for example, that a second shift oven operator opens the oven doors for five minutes to unload the parts and then load the next batch, while the first shift operator takes ten minutes to do the same process, wasting a great deal of energy as heated air spills out of the oven for an extra five minutes with every batch.
Data Security
IIoT devices use encryption to protect against unauthorized access to the oven operational data. Data transmitted between IIoT devices and the cloud is encrypted using protocols like Transport Layer Security (TLS). This provides confidence that only approved parties can access the information, safeguarding it from those with malicious intent. This ensures that even if data is intercepted, it will appear as jumbled information that cannot be read without the decryption key.
Because the data collected relates to the oven or furnace being monitored, and is not descriptive of the parts being processed, it would be of limited use to anyone who gained unauthorized access. If a malicious actor discovered, for example, the vibration levels, temperature controller output, or the status of the burner system while the oven is processing a load, it would be of limited proprietary value and would not directly reveal information about the parts being processed since no information about the load is included in the data.
In considering the security risk of an IIoT system collecting and transmitting data to the cloud, it must be compared to the alternative, which is bringing a service technician to the job site to perform the required maintenance or troubleshooting. When a service technician is invited on site, they have the opportunity to view the parts being processed, which temperature profiles apply to which parts, material handling methods, ancillary processes performed before or after heating, and even unrelated proprietary processes performed in the facility. This level of intrusion is much greater than simply sending the oven IIoT data to the cloud and avoiding the service technician entirely.
The Future of IIoT
Since the introduction of IIoT to the industrial oven market, it has gained acceptance by a wide range of manufacturers, and it is expected to continue to grow. Artificial intelligence (AI) is becoming a part of IIoT, as it can optimize the algorithms used in predictive maintenance. Also, IIoT can incorporate AI’s cognitive capabilities to better be able to learn at what thresholds of vibration, pressure, etc., to send alert notifications.
To Summarize
Consider purchasing an IIoT system with your next industrial oven. The successful implementation and use of IIoT provides a competitive advantage to the owner of the equipment. In today’s world of “doing more with less,” IIoT can increase productivity, reduce maintenance costs and unplanned downtime, and decrease energy use, all at minimal cost, and with no additional personnel required.
About the Author:
Mike Grande Vice President of Sales Wisconsin Oven Corporation
Mike Grande has a 30+ year background in the heat processing industry, including ovens, furnaces, and infrared equipment. He has a BS in Mechanical Engineering from University of Wisconsin-Milwaukee and received his certification as an Energy Manager (CEM) from the Association of Energy Engineers in 2009. Mike is the vice president of Sales at Wisconsin Oven Corporation.
In this installment of the Controls Corner, we are addressing load configurations in a furnace. An industrial furnace is made up of multiple zones for the heating of the load. These zones are strategically placed to minimize heat losses and to give the best heat profile for the application (minimize hot and cold spots in the vessel). In this Technical Tuesday installment, guest columnist Stanley Rutkowski III, senior applications engineer at RoMan Manufacturing, Inc., highlights the differences between power controls based on voltage and current.
The utility company transmits power to the electrical grid in terms of “voltage” and “current.” Voltage is the pressure to push the current through the wires. The amount of voltage required is a function of the losses in the system (resistance, reactance, and impedance). Utility companies transmit this via the highest voltage available to minimize the current. By minimizing the current, the cross section of the conductors to transmit gets smaller and less costly to run over long distances. At an industrial facility, a step down transformer (distribution type) is used to change the high voltage from the utility company to plant voltage (and by the same ratio increase the current from low to high).
In the operations of a furnace, the term commonly used is power, which is a multiplication of two variables, voltage and current.
In the operations of a furnace, the term commonly used is power, which is a multiplication of two variables, voltage and current. The utility company transmits power in a three-phase configuration with 120 degrees difference between phases (typically labeled A-B, B-C, and C-A). Let’s take a brief look at four major load configurations.
Single-Phase Load
A single-phase load uses one of the three legs of the system in operation. This type of system is best used in three zone applications to try to balance the power of each zone to the utility. A single-phase load allows for the most control of a zone in a furnace as it is individually controlled, but potentially causes the most disturbances to the utility company.
Two-Phase Load (Scott-T)
A Scott-T system is a way to balance load a three-phase system but allow for two loads in operation. In a five zone furnace, you could configure a three-phase system for the middle three zones and a Scott-T system for the first and last zones (front and back). A Scott-T system has a single point of control for the two zones to have the least disturbances to the utility company.
Three-Phase Load
A three-phase load can be in different configurations, the most common being Delta and Wye. The differences between them are the vectors of the voltage and current. A Wye system has less voltage and more current while a Delta system has less current and higher voltage. Care needs to be taken to minimize potential circulating currents that can be created by the vectors of three-phase systems. The three-phase system is a single point of control for the loads and causes less disturbances to the utility company. Mixing of three-phase systems inside a furnace (Delta and Wye) can help further minimize disturbances to the utility company.
IGBT (Insulated-Gate Bipolar Transistor)
An IGBT (Insulated-Gate Bipolar Transistor) system is a hybrid system that uses a three-phase primary to create a single-phase load. This allows for the highest level of control while minimizing the disturbances to the utility company. This system also allows the usage of higher frequencies to shrink the footprint of the transformers, allowing the use of rectification to minimize inductance and minimize the high current runs to the load(s).
About the Author:
Stanley F. Rutkowski III Senior Applications Engineer RoMan Manufacturing, Inc.
Stanley F. Rutkowski III is the senior applications engineer at RoMan Manufacturing, Inc., working on electrical energy savings in resistance heating applications. Stanley has worked at the company for 33 years with experience in welding, glass and furnace industries from R&D, design, and application standpoints. For more than 15 years, his focus has been on energy savings applications in industrial heating applications.
Like most power systems, power control dates back to vacuum tube technology. Like radios, amplifiers, and other industrial equipment, the furnace market started using transistors as the technology evolved. Vacuum tubes were not generally balanced and contained poisonous elements and were phased out of usage in almost all industries. In this Technical Tuesday installment, guest columnist Stanley Rutkowski III, senior applications engineer at RoMan Manufacturing, Inc., distinguishes the different methods used to regulate power input to furnaces.
An ERT/SCR power control Source: RoMan Manufacturing, Inc.
In today’s furnace market, there are generally three primary types of control systems: VRT, SCR, and IGBT. Each of these control technologies employs different methods to regulate the power input to the furnace, which in turn generates the required heat. These control systems transfer the power from the plant power system to a transformer in line with the load (heating elements). Power is delivered to a plant in a three-phase system from the utility company. The least costly and highest power factor systems have a balanced load across the three phases during the operation of any furnace.
VRT (Variable Reactance Transformer)
A VRT incorporates a feedback mechanism to either increase or decrease the amount of DC injected into the controlling reactor in the system. This increases or decreases the amount of current in the system to control the heat in the furnace by comparing it to the scheduled setpoint. A VRT system can have the following configurations:
Single-phase power controller for single load applications
Scott-T three-phase power controller (this is a system that allows all three phases of the incoming power system to be utilized in a two-phase load application)
Three-phase power controller (in either a Delta or Wye configuration) for three zone load applications
SCR (Silicon Controlled Rectifier)
An SCR control system uses a pair of thyristors (gated diodes) to control the amount of power applied to the primary of a transformer. The SCR control delays the start of the waveform, and the control point is reset when the waveform crosses the zero line. An SCR system can have the following configurations:
Single-phase, phase-angle controlled for single load applications
Single-phase, zero-cross controlled for single load applications
Single-phase, on-load, tap-changing controlled (this incorporates multiple pairs of the thyristors together to lessen the losses of the SCR system)
Scott-T three-phase power controlled (this is a system that allows all three phases of the incoming power system to be utilized in a two-phase load application)
Three-phase, phase-angle controlled (in either a Delta or Wye configuration) for three zone load applications
Three-phase, zero-cross controlled (in either a Delta or Wye configuration) for three zone load applications
IGBT (Insulated-Gate Bipolar Transistor)
An IGBT power control Source: RoMan Manufacturing, Inc.
An IGBT uses a diode bridge, capacitor, and switching transistors to control the amount of power applied to the primary of a transformer. The input frequency to the transformer is controlled by the switching transistors. The diode bridge is connected to the three-phase system allowing single, Scott-T (two zone), or three zone systems all to pull a balanced load across the three phases of the plant power system. A line reactor is incorporated to maximize the power factor in the system, minimizing the total power usage of the furnace. The IGBT system also uses a square wave into the transformer and a rectifier after the transformer to remove inductance out of the power delivery system to reduce costs of cables, breakers, and other components in the total package.
About the Author:
Stanley F. Rutkowski III Senior Applications Engineer RoMan Manufacturing, Inc.
Stanley F. Rutkowski III is the senior applications engineer at RoMan Manufacturing, Inc., working on electrical energy savings in resistance heating applications. Stanley has worked at the company for 33 years with experience in welding, glass and furnace industries from R&D, design, and application standpoints. For more than 15 years, his focus has been on energy savings applications in industrial heating applications.
What are advanced management systems and how does deep integrative system management software help automotive heat treaters improve processes while saving on time and unnecessary expenses? Explore the future of software technology for the management of heat treating operations in this Technical Tuesday by Sefi Grossman, founder and CEO of CombustionOS.
The heat treating industry is on the brink of a technological transformation. Just as the momentous adoption of websites and emails transformed the nature of work for manufacturers, the advanced software systems are thrusting us into a new era of simplicity, automation, and deep integrations.
This article explores how advanced systems — an application of ERP (enterprise resource planning) and MES (manufacturing execution systems) combined with the power of AI — is revolutionizing facility operations, enhancing quality, efficiency, and profitability.
What Are Advanced Systems?
Advanced systems simplify, streamline, and automate operations by lifting the data burden off of plant personnel. While most existing systems focus on the part inventory workflow, more advanced systems go beyond by directly integrating into the heat treat process to track at bin/tray/tree level.
This requires real-time scheduling control, barcode scanning, digitizing recipe and process (no more paper), and direct sensor/PLC integration. Because of its critical nature, an advanced system is most likely an on-premise and cloud “hybrid solution” that is not crippled by internet connectivity issues. This allows it to still utilize rapidly evolving cloud systems that provide external services like messaging, big data storage, and AI to name a few.
Precise Processing
Figure 1. CombustionOS developers spend extensive time with operators and plant managers to create interfaces that are intuitive and easy to use. Pictured is access to job data stats from a mobile device being used outside of the manufacturing plant.
Repeatable, accurate methods to ensure optimal time, temperature, and atmosphere of the decided heat treatment processes are possible with advanced systems.
Utilizing existing sensors and hardware interfaces, data is collected in short intervals, transformed into meaningful data formats, and stored in a database. Network technologies such as HTTP, Modbus, and other analog to AI technologies make this possible with minimum additional hardware. The data is managed locally on the facility network, and synchronized with cloud services for further processing, analysis, and long-term history storage.
With a close monitoring of all these variables, facilities can tighten acceptable specification ranges. Deep integration with equipment ensures that data flows seamlessly from sensors and devices to the central system.
This real-time data collection and processing enables facilities to monitor operations continuously and make informed decisions quickly. For example, integrating data from temperature sensors, pressure gauges, and other monitoring devices ensures that all critical parameters are tracked and managed effectively. Additionally, if a temperature reading deviates from the acceptable range, the system can immediately alert the relevant personnel, allowing them to take corrective action before it becomes a critical issue.
In addition to quality assurance, integrated artificial intelligence tools optimize job scheduling. Unlike traditional date/time calendar methods, AI systems predict job completion times based on real-time process data. This is particularly useful for roller furnace setups, where continuous processing occurs, but it is also beneficial for batch furnaces. Optimized scheduling improves resource allocation and operational efficiency, ensuring that jobs are completed on time and to the required specifications. The difference between a “calculation algorithm” and AI is that, with AI, you do not have to pre-program it. It automatically learns and adjusts for known variability in your hardware and even the personnel that are operating the equipment.
Finally, the automation of these systems captures and records all necessary information accurately. This reduces the risk of non-compliance, improving the overall quality of the final product. For example, a Detroit-based heat treating facility reported that accessing real time data to ensure compliance with industry standards has allowed them to spend 40% less time on documentation tasks.
Figure 2. Having increased control over the process gives more peace of mind to operators that components perform as needed.
Alleviating Burden on Maintenance and Inventory
Predictive maintenance is one of the most significant applications of AI in the heat treating industry. Traditional maintenance schedules are often based on fixed intervals, which can lead to unnecessary downtime or unexpected failures. AI driven predictive maintenance, on the other hand, uses real-time data to determine the optimal times for maintenance activities. This approach not only reduces downtime but also extends the lifespan of equipment.
A Detroit-based heat treating facility implemented an AI-driven predictive maintenance system (PMs) and saw a 25% reduction in equipment downtime. By analyzing data from critical parts, inventory, process tracking history, and various sensors, the AI system could predict when components were likely to fail, allowing the maintenance team to inspect and address issues proactively beyond their standard PMs. This not only improved operational efficiency, but also saved significant costs associated with emergency repairs and unplanned downtime.
Additionally, the integration of QR codes for inventory and process tracking enables quick and accurate data entry compared to manual logging. For instance, when racking parts out of bins, operators can simply scan QR codes, which automatically update the system with the relevant information. This not only speeds up the process but also minimizes the chances of human error.
Reducing Operational Costs
The adoption of advanced ERP and MES systems has led to substantial cost savings for many facilities. These systems reduce operational costs through the implicit automated integrations that technologies like CombustionOS bring. Here are just a few ways that operational costs have been cut:
Decreasing shipping and receiving management from three to just one employee
Minimizing rework costs by timely process alerts
Reducing personnel by replacing constant manual oversight with accurate, digital tracking systems
Lowering administrative costs by utilizing a more efficient and accurate invoice automation platform
Case Study: A client reported comprehensive cost savings, including a 20% reduction in shipping and receiving time, fewer logistics and furnace operators needed, a 33% decrease in rework costs, a 15% savings in maintenance costs, and a 25% reduction in accounting overhead. These efficiencies translate into substantial payroll savings and improved profitability.
How To Implement
Figure 3. When racking parts out of bins, operators can simply scan QR codes, which automatically update the system with the relevant information.
One of the most significant advancements in heat treating technology is the deep integration with various equipment types. Unlike traditional ERP systems, which often lack true integration, advanced systems work backwards from equipment data, building ERP functionalities around this integration to ensure seamless and accurate data flow.
First, there are advanced systems that can handle data from both digital and analog sensors. So, for heat treaters who are juggling a variety of sensors and systems, looking for an integrative advanced system that has adaptability will ensure compatibility with existing equipment while keeping an eye on cost. Facilities can continue using their current equipment while benefiting from advanced monitoring and control capabilities.
Second, advanced ERP/MES systems can take collaboration with multiple vendors. Rather than uproot current systems and relationships, work with an advanced systems provider who is able to collaborate with other software and systems. Advanced ERP/MES systems provide comprehensive solutions that include deep equipment integration and full ERP functionalities. This approach reduces the complexity and cost of integration, ensuring that all components work together seamlessly.
Key Applications
Most operations in a heat treat department will benefit from advanced systems due to the time-saving automations that the system integrates. But many heat treaters are looking to adapt and integrate older systems and often more complex designs, like roller hearth furnaces. Here are some steps that experts will take to guide you through to make the digital integration smooth and effective:
First, it is important to understand you don’t need to boil the ocean. Starting with a more advanced inventory tracking system that employs barcodes can set the underpinnings for a more integrated system while providing immediate benefits to your logistics.
Then, it is also key to get a deep understanding of your current process and map out your operational workflow. Using a flowchart program helps visualize the process to make sure all stakeholders are on the same page.
Some aspects of your current process are probably outdated (perhaps created by someone who is no longer at the company), while others are key to the core of how you operate. Understanding the difference is crucial to make sure you unlock potential automation without disturbing your core process and flow.
You’ll then need to prepare every required form, document, chart etc. that you use in the operation. For process control, recipes, and lab testing, provide many parts/iterations to capture the complexity.
Finally, take inventory of any existing digital systems you have adopted, like inventory tracking, spreadsheets, or custom software. The existing system network, including servers, Wi-Fi setup, and hardware (PCs, printers, scanners, etc.) will be utilized as much as possible in the transition to reduce the need to purchase and set up different equipment.
The future will require constant innovations and thoughtful leveraging of increasingly advanced systems. Unlike static, homegrown, or “pieced together” solutions, the most advanced systems are constantly updated with new features, ensuring they remain at the cutting edge of technology. Engaging directly with plant personnel to understand their needs and challenges allows systems like CombustionOS to evolve and improve continuously.
The heat treating industry is on the cusp of a technological transformation, driven by advancements in ERP, MES, and AI. These technologies offer the potential to enhance quality, efficiency, and profitability, making them essential for the future of manufacturing. By embracing automation, integrating advanced AI capabilities, and committing to continuous innovation, the industry can achieve new levels of operational excellence.
About the Author:
Sefi Grossman Founder & CEO CombustionOS Source: Author
Sefi Grossman has been at the forefront of technology revolutions for the past two decades and has been leading the technology company CombustionOS for nearly seven years.
Ever wish you had a map to follow when navigating your power source? In the following Technical Tuesday article, Brian Turner, sales applications engineer at RoMan Manufacturing, Inc., charts the route that power takes from the source to the load and back again in a vacuum furnace.
In a vacuum furnace, the journey from the load (the material being heat treated) to the incoming power involves a complex arrangement of components that deliver, control, and monitor electrical energy. Here’s a breakdown of the path from the source to the load and back to the source of incoming power of a vacuum furnace:
Load
The material — either an item or batch of items — that is undergoing heat treatment; can be metals, ceramics, or composites.
Heating Elements
Common materials for heating elements include graphite, molybdenum, or tungsten, depending on the temperature range and application.
Electrical Feedthrough
These are used to transmit electrical power or signals through the vacuum chamber wall. They often contain insulated conductors and connectors to ensure safe transmission without leaking air into the vacuum environment.
Conductors
The most common methods to connect power from a vacuum power source to the furnace’s feedthrough include air-cooled cables, water-cooled cables, and copper bus bar. Power efficiency can be improved when selecting the length, size, and area between conductors. This can be achieved by close coupling the power system to the electrical feedthroughs, reducing resistance and inductive reactance, and improving the power factor.
Machined Copper Bar Source: RoMan Manufacturing, Inc.
Controlled Power Distribution Systems
The furnace market today generally relies on three primary types of control power distribution systems: VRT, SCR, and IGBT. Each of these technologies employs different methods to regulate the power input to the furnace, which in turn generates the required heat.
VRT (Variable Reactance Transformer)
The VRT controls AC voltage to the load, this is accomplished by a DC power controller that injects DC current into the reactor within the transformer.
The SCR controls the AC output voltage and can be paired with a transformer to step the voltage up or down and close couple to the furnace feedthroughs.
IGBT (Insulated-Gate Bipolar Transistor)
Balanced three-phase voltage is rectified through a bridge circuit to charge a capacitor in the DC bus. The IGBT network switches the DC bus at 1000Hz to control the AC output voltage to a Medium Frequency Direct Current (MFDC) power supply.
MFDC power supply transforms the AC voltage to a practical level and rectifies the secondary voltage (DC) to the heating circuit.
A line reactor on the incoming three-phase line mitigates harmonic content.
Control Systems
These systems manage the furnace’s operation, including driving the setpoint of the power system, temperature control, vacuum levels, and timing. They often consist of programmable logic controllers (PLCs), human-machine interfaces (HMIs), sensors, and other automation components.
Incoming Power
This is the origin of the furnace’s electrical energy, typically from a utility grid. It provides alternating current (AC), which is distributed and transformed within the furnace system to power all necessary components. In industrial settings, power companies usually charge for electricity based on several factors that reflect both the amount of electricity used and how it’s used. Some common charges/penalties are energy consumption (kWh), demand charges (kW), power factor penalties, and time-of-use (TOU) reactive power.
Conclusion
The careful arrangement of heating elements, electrical feedthroughs, conductors, and controlled power distribution systems allows for precise temperature control, ultimately impacting the quality of the processed material. Understanding the role of various control systems, such as VRT, SCR, IGBTs, and transformers is crucial for optimizing furnace performance and managing energy costs
About the Author:
Brian Turner Sales Applications Engineer RoMan Manufacturing, Inc. Source: RoMan Manufacturing, Inc.
Brian K. Turner has been with RoMan Manufacturing, Inc., for more than 12 years. Most of that time has been spent managing the R&D Lab. In recent years, he has taken on the role as applications engineer, working with customers and their applications.
What is the path forward for thermal loop systems, and how is “sustainability” at the forefront of this technology? The following article is co-authored by Peter Sherwin, global business development manager of Heat Treatment, and Thomas Ruecker, senior development manager, at Watlow. They examine four scopes to take into consideration when assessing thermal loop systems in the context of greenhouse gas emissions and their environmental impact.
Heat treatment thermal loop solutions provide several sustainability benefits, including reduced energy consumption and waste. The power controller regulates the power output to minimize energy waste, and the possible integration with renewable energy sources and circular economy principles provides a complete power solution that spans from element design to recycling and renewables. The thermal loop solutions, in combination with insulation design and materials, provide energy-efficient solutions that contribute to sustainability and reduce the environmental impact of heat treatment processes.
When discussing these systems in the context of greenhouse gas emissions and their environmental impact, it is essential to consider Scopes 1, 2, and 3, as well as the less common Scope 4:
Scope 1 (Direct Emissions): Heat treatment processes often involve the combustion of fossil fuels like natural gas, propane, or oil to generate heat. These direct emissions are attributed to the equipment used in the heat treatment process, such as furnaces and ovens. Efforts to reduce Scope 1 emissions include upgrading to more efficient equipment or adopting alternative heating technologies, like induction or electric heating systems.
Scope 2 (Indirect Emissions from Energy): In heat treatment processes and thermal loop systems, electricity is often used to power various components, such as pumps, fans, and control systems. The emissions associated with generating this electricity are considered Scope 2 emissions. To reduce Scope 2 emissions, companies can improve energy efficiency, invest in renewable energy sources, or purchase green energy from their utility provider.
Scope 3 (Other Indirect Emissions): These emissions are associated with activities throughout the value chain of heat treatment applications and thermal loop systems, such as the manufacturing and transporting of raw materials, equipment, and waste management. Companies can work to reduce Scope 3 emissions by collaborating with suppliers to improve the environmental performance of their products and services, optimizing transportation and logistics, and implementing waste reduction strategies.
Scope 4 (Avoided Emissions): In heat treatment applications and thermal loop systems, avoided emissions may come from implementing energy-efficient technologies, waste heat recovery systems, or other innovative solutions that reduce overall energy consumption and associated emissions. By quantifying these avoided emissions, companies can showcase the positive impact of their sustainability efforts on reducing their carbon footprint. Avoided emissions can also be highlighted when subcontracting heat treatment requirements to a more energy-efficient source rather than running an in-house operation. In this approach, the heat treatment process is outsourced to an external, specialized heat treatment service provider, especially if the in-house equipment is due to be lightly utilized. These service providers operate independent heat treatment facilities and offer services to multiple clients across various industries and generally run 24/7 with high utilization.
At the component level, energy savings can be realized using current technology. Advanced SCRs provide predictive load management functions and hybrid firing algorithms and contribute to sustainability by optimizing the energy usage of heat treatment processes. These SCRs offer real-time monitoring and control of energy consumption, while predictive load management systems use specific algorithms to manage peak power loads and adjust to optimize for local conditions (load shedding or load sharing). Hybrid firing systems use a combination of firing methods to control power factors and reduce the negative impact on the electrical infrastructure.
Heater design is also essential. Switching time impacts heater life with fast, modern switching modes (hybrid firing) significantly extending heater life compared to slower switching from conventional mechanical contactors.
Systems can be rapidly tested, simulated, and modeled through computational engineering. Several thermal loop systems today have improved temperature uniformity due to these methods.
Adaptive thermal system (ATS) solutions are the next frontier of thermal loop solutions. Rather than selecting the best-of-breed components — sometimes with overlapping functionality and kitting a complete solution — ATS provides a merged design between heater and control systems. ATS is already in place in several semiconductor applications, and this type of technology is looking to scale into heat treatment applications shortly.
Figure 2. Watlow Adaptive Thermal Systems ATSTM Source: Watlow
Challenges and Limitations
The initial investment in heat treatment thermal loop solutions can sometimes be higher than in traditional methods. However, this investment often leads to a significantly lower total cost of ownership and improved return on investment due to the thermal loop solutions’ increased efficiency, improved quality control, and extended life.
Ensuring regulatory compliance is complex and time-consuming, requiring organizations to have the right people, processes, and equipment.
Future Trends
As Industry 4.0 and digital transformation continue to gain momentum and Industry 5.0 practices are implemented, heat treatment thermal loop solutions will become increasingly important. Integrating digital technology and machine learning algorithms will provide even greater control, traceability, and transparency, enabling organizations to make informed decisions based on real-time data and predictive analytics. In addition, as new materials and manufacturing processes are developed, adaptive and flexible heat treatment thermal loop solutions will need to evolve to meet these challenges and provide the necessary level of control and efficiency for these new applications.
Conclusion
Heat treatment thermal loop solutions provide several benefits over traditional heat treatment methods, including improved temperature control, increased efficiency, and improved sustainability outcomes. The integration with Industry 4.0 and data management systems, as well as the use of FMEA and OEE metrics, further help enhance the performance of heat treatment processes. As Industry 4.0 digital transformation and Industry 5.0 practices continue to evolve, heat treatment thermal loop solutions will play an increasingly important role in the future of heat treatment.
About the Authors:
Peter Sherwin Global Business Development Manager of Heat Treatment WatlowThomas Ruecker Senior Business Development Manager of Heat Treatment Eurotherm, a Watlow company
Peter Sherwin, global business development manager of Heat Treatment at Watlow, is passionate about offering best-in-class solutions to the heat treatment industry. He is a chartered engineer and a recognized expert in heat treatment control and data solutions.
Thomas Ruecker is the business development manager of Heat Treatment at Eurotherm Germany, a Watlow company. His expertise includes concept development for the automation of heat treatment plants, with a focus on aerospace and automotive industry according to existing regulations (AMS2750, CQI-9).
“Communication is key.” As heat treating equipment and processes evolve, it becomes critical that the accompanying control systems also develop to maintain “communication.” In this Technical Tuesday installment, guest columnist Stanley Rutkowski III, senior applications engineer at RoMan Manufacturing, Inc., discusses how digital control system communications have improved to increase energy efficiency for manufacturers with in-house heat treat operations.
This informative piece was first released inHeat Treat Today’sMay 2024 Sustainability Heat Treat print edition.
Industrial furnace applications that rely on resistive heating will consume large amounts of electrical energy when processing their loads. Utilizing digital controls technologies to maximize this type of heating allows for a cleaner-and thus greener-approach to energy demands.
Typically, heat treat processes have a long duration (hours to days in length), and each load can have its own unique recipe in the amount of power required. With unique recipes, there tends to be a ramp-up phase (getting the vessel to temperature), followed by a soak phase (which demands more control over the power system), and then a cool-down phase (an even more controlled state). As the power is controlled through the furnace system, disturbances occur with different technologies. This starts with “tube technology,” then variable reactance transformer (VRT) technology, then silicon controlled rectifier (SCR) technology, and finally IGBT (insulated-gate bipolar transistor) technology. As these technologies have evolved, their ability to communicate information digitally has allowed for less disturbance in the power system and allowing both a less expensive energy bill and a cleaner energy usage for the process.
Definitions
Electrical Power
Power losses in an electrical system are defined by five aspects (Figure 1):
Resistance (R): a function of the material cross section and the length of an electrical conductor.
Reactance (XL): a function of the area in a circuit and is a vector 90 degrees offset from resistance.
Capacitance (XC): a vector 180 degrees offset from reactance. In inductive circuits, capacitance can be added for power factor correction.
Impedance (Z): the vector sum of resistance, reactance, and capacitance.
Power Factor [cos(F)]: the ratio of resistance to impedance. In industrial applications, displacement power factor (DPF), the offset of the current to voltage waveforms, is used in the billing of electrical power.
There are five unique aspects that define electrical power usage (Figure 2):
Real power (kW): the amount of power that is generated.
Reactive power (kVAR): the amount of power that is wasted.
Total power (kVA): the rate at which power is consumed. This is also referred to as apparent power.
Power factor (cos(F)): the ratio of real power to total power. In industrial applications, the displacement power factor (DPF) is the offset of the current to voltage waveforms and is used to bill for electrical power.
Peak demand: the capacity required when the power grid experiences the highest power demand in a specified period of time.
3 Most Popular Types of Control Systems
For the most part, today’s furnace manufacturers use three main types of control systems: VRT, SCR, and IGBT. Each operates with slightly different methods to control how power goes into the heat treat furnace and creates heat.
VRT Control System
One traditional resistance heating setup uses a VRT control system that incorporates a saturable reactor, which controls the power applied to the transformer in the system (Figure 3). The control transformer on the output side of the transformer feeds back to the reactor to set the limit on the input power to the transformer.
Figure 3. VRT Control and Transformer Schematic (CT=control transformer); Source: RoMan Manufacturing, Inc.
SCR Control System
Figure 4. SCR Control and Transformer Schematic; Source: RoMan Manufacturing, Inc.
Another traditional resistance heating setup uses an SCR control system that includes dual thyristors (gated diodes) to control the amount of power applied to the primary of a transformer.
The SCR control delays the start of the waveform, and the control point is reset when the waveform crosses the zero line.
Figure 5. Comparison of Sine Waves; Source: RoMan Manufacturing, Inc.
IGBT Control System
Finally, an IGBT control system uses a diode bridge, capacitor, and switching transistors to control the amount of power applied to the primary (i.e., main power input of a transformer). The input frequency to the transformer is controlled by the switching transistors. Since the IGBT control system utilizes all three phases of the power system, the IGBT control can be set to a particular phase for the zero cross (for phase orientation in the application, synchronous mode) or left floating (non-synchronous mode), as is demonstrated in Figure 6. The input voltage to the transformer is increased by the operation of the IGBT control. As such, potential energy savings may be had with these types of controls as compared to tradition controls (such as on-off contractors, time proportioning controls, or other types of current proportioning control systems).
Figure 6. IGBT Control and Transformer Schematic; Source: RoMan Manufacturing, Inc.
Synchronization with the IGBT can be to the incoming lines (A, B, or C phase) and can be offset from each of the phases. The ability to offset from a phase allows for traditional arrangements (Single Phase, Scott-T, Delta and Wye) as well as unique offsets allowing for additional vector heating in the application with AC outputs. The unique arrangements beyond the traditional systems could allow for more uniform heating of the part and less energy being consumed during the process.
Advantages of Utilizing Communications
As technology for controlling heating systems has evolved, and with an emphasis on clean energy sources, the ability to communicate with the control system has increased as well. This communication allows for more precise control of the run for the load, improved power usage (better power factors and less peak power usage as well as less total power usage), and inputs into a preventive maintenance program.
Table A. Analog vs. Digital IGBT Systems
With an IGBT system, both analogue and digital control communications are available today. See Table A for a comparison on how each control option works.
In addition to the EIP defined pieces, there is the ability to access the FPGA system for graphical outputs that can be downloaded into another system in your process for storage, comparisons, or general record keeping for a part run. The FPGA is an internal processor in the control that allows for more data, charting, and diagnostics to be captured and used by the system for both energy consumption and possible preventative maintenance purposes.
Why does this matter? Let’s turn to some possible ways of using the data generated from digital controls systems:
Evaluate average, minimum, and maximum DC bus voltages to plan for the best time and day to run heat treat jobs. For high power draw jobs, planning ahead can minimize power costs; similarly, knowing power trends can be helpful to plan jobs requiring sensitive control of the heating.
Evaluate transformer output voltage to allow the system to detect any shorts in the process. If the controller output and transformer output diverge from the known turns ratio, a change has occurred in the system. This could be corroborated if controller on time and output power do not trend.
Track furnace run records with EIP communications and FPGA data. This will be most helpful in processing lots of data, as is the case for Milspec records.
Evaluate changes in power factor to monitor any loose cables, and so avoid reactive power losses.
Evaluate the current versus the voltage to monitor the resistance of the system. If there is an increase in the resistance, you could project the trends in wear of the heating elements, therefore predicting future required maintenance.
Evaluate the critical control temperatures of the system to know if it is being run close to, or above, its ratings or if there is a disturbance in the cooling systems.
Use knowledge of power usages and power stability to update recipes for load runs so they use less power over the total run; this allows for a less costly power-savings solution. With less power usage, more output of the total facility can be had as each station contributes less to energy consumption
Even more benefits can be realized when users and builders of furnace systems and component manufacturers collaborate in the design of the total system. Such dialogues lead to the creation of more interactive and intuitive solutions that minimize power consumption, minimize downtime, and maximize outputs. These practical benefits are the foundation of a greener system.
About the Author:
Stanley F. Rutkowski III Senior Applications Engineer RoMan Manufacturing, Inc.
Stanley F. Rutkowski III is the senior applications engineer at RoMan Manufacturing, Inc., working on electrical energy savings in resistance heating applications. Stanley has worked at the company for 33 years with experience in welding, glass and furnace industries from R&D, design, and application standpoints. For more than 15 years, his focus has been on energy savings applications in industrial heating applications.
The future of heat treating requires new manufacturing solutions like robotics that can work with modular design. Yet so also does temperature monitoring need to be seamless to know how effectively your components are being heat treated — especially through being quenched.In this Technical Tuesday,learn more abouttemperature monitoring through the quench process.
Gas Carburization
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Carburizing has rapidly become one of the most critical heat treatment processes employed in the manufacture of automotive components. Also referred to as case hardening, it provides necessary surface resistance to wear, while maintaining toughness and core strength essential for hardworking automotive parts.
Figure 1. Typical carburizing heat treat temperature profile showing the critical temperature/time steps: (i) carburization, (ii) quench, and (iii) temper. (Source: PhoenixTM)
The carburizing process is achieved by heat treating the product in a carbon rich environment (Figure 1), typically at a temperature of 1562°F–1922°F (850°C–1050°C). The temperature and process time significantly influence the depth of carbon diffusion and other related surface characteristics. Critical to the process is a rapid quenching of the product following the diffusion in which the temperature is rapidly decreased to generate the microstructure, giving the enhanced surface hardness while maintaining a soft and tough product core.
The outer surface becomes hard via the transformation from austenite to martensite while the core remains soft and tough as a ferritic and/or pearlitic microstructure. Normally, carburized microstructures following quench are further tempered at temperatures of about 356°F (180°C) to transform some of the brittle martensite into tempered martensite to enhance ductility and grindability.
Critical Process Temperature Control
As discussed, the success of carburization is dependent on accurate, repeatable control of the product temperature and time at that temperature through the complete heat treatment process. Important to the whole operation is the quench, in which the rate of cooling (product temperature change) is critical to achieve the desired changes in microstructure, creating the surface hardness. It is interesting that the success of the whole heat treat process can rest on a process step which is so short (minutes), in terms of the complete heat teat process (hours). Getting the quench correct is not only essential to achieve the desired metal microstructure, but also to ensure that the physical dimensions and shape of the product are maintained (no distortion/warping) and issues such as quench cracking are eliminated.
Obviously, as the quench is so critical to the whole heat treat process, the correct quench selection needs to be made to achieve the optimum properties with acceptable levels of dimensional change. Many different quenchants can be applied with differing quenching performances. The rate of heat transfer (quench rate) of quench media in general follows this order from slowest to quickest: air, salt, polymer, oil, caustic, and water.
Technology Challenges for Temperature Monitoring
When considering carburization from an industry standpoint, furnace heat treat technology generally falls into one of two camps, embracing either air quench (low pressure carburization) or oil quench (sealed gas carburization/LPC with integral or vacuum oil quench). Although each achieves the same end goal, the heat treat mechanisms and technologies employed are very different, as are the temperature monitoring challenges.
To achieve the desired carburized product, it is necessary to control and hence monitor the product temperature through the three phases of the heat treat process. Conventionally, product temperature monitoring would be attempted using the traditional trailing thermocouple method. For many modern heat treat processes including carburization, the trailing thermocouple method is difficult and often practically impossible.1 The movement of the product or product basket from stage to stage, often from one independent sealed chamber to another (lateral or vertical movement), makes the monitoring of the complete process a significant challenge.
With the industry driving toward fully automated manufacturing, furnace manufacturers are now offering the complete package with full robotic product loading that includes shuttle transfer systems and modular heat treat phases to process both complete product baskets and single piece operations. Although trailing thermocouples may allow individual stages in the process to be measured, they cannot provide monitoring of the complete heat treat journey. Testing is therefore not under true normal production conditions, and therefore is not an accurate record of what happens in normal day to day operation.
Figure 2 shows schematic diagrams of two typical carburizing furnace configurations that would not be possible to monitor using trailing thermocouples. The first shows a modular batch furnace system where the product basket is transferred between each static heat treat operation (preheat, carburizing furnace, cooling station, quench, quench wash, temper furnace) via a charge transfer cart. The second shows the same heat treat operation but performed in a continuous indexed pusher furnace configuration where the product basket moves sequentially through each heat treat operation in a semi-continuous flow.
Thru-process temperature monitoring as a technique overcomes such technical restrictions. The data logger is protected by a specially designed thermal barrier, therefore, can travel with the product through each stage of the process measuring the product/process temperature with short, localized thermocouples that will not hinder travel. The careful design and construction of the monitoring system is important to address the specific challenges that different heat treat technology brings including modular batch and continuous pusher furnace designs (Figure 2).2
The following section will focus specifically on monitoring challenges of the sealed gas carburizing process with integral oil quench. Technical challenges of the alternative low pressure carburizing technology with high pressure gas quench have previously been discussed in an earlier publication.3
Monitoring Challenges of Sealed Gas Carburization — Oil Quench
Figure 3. “Thru-process” temperature monitoring system for use in a sealed carburizing furnace with integral oil quench — (3.1) Monitoring system entering furnace with thermocouple fixed to automotive gears, product test pieces (3.2) System exiting oil quench tank (3.3) System inserted into wash tank with product basket (Source: PhoenixTM)
Presently, the most common traditional method of gas carburizing for automotive steels is often referred to as sealed gas carburizing. In this method, the parts are surrounded by an endothermic gas atmosphere. Carbon is generated by the Boudouard reaction during the carburization process, typically at 1562°F–1832°F (850°C –1000°C). Despite the dramatic appearance of a sealed gas carburizing furnace, with its characteristic belching flames (Figure 3), from a monitoring perspective, the most challenging aspect of the process is not the heating, but the oil quench cooling. For such furnace technology, the historic limitation of “thru-process” temperature profiling has been the need to bypass the oil quench and wash stations, missing a critical process step from the monitoring operation. Obviously, passing a conventional hot barrier through an oil quench creates potential risk of both system damage from oil ingress and barrier distortion, as well as general process safety. However, the need to bypass the quench in certain furnace configurations by removing the hot system from the confined furnace space could create significant operational challenges, from an access and safety perspective.
Monitoring of the quench is important as ageing of the oil results in decomposition (thermal cracking), oxidation, and contamination (e.g. water) of the oil, all of which degrade the viscosity, heat transfer characteristics, and quench efficiency. Control of physical oil temperature and agitation rates is also key to oil quench performance. Quench monitoring allows economic oil replacement schedules to be set, without risk to process performance and product quality.
Figure 4. “Thru-process” temperature monitoring system oil quench compatible thermal barrier design: (1) Robust outer structural frame keeping insulation and inner barrier secure; (2) Internal thermal barrier — completely sealed with integral microporous insulation protecting data logger; (3) Mineral insulated thermocouples sealed in internal thermal barrier with oil tight compression fitting; (4) Multi-channel high temperature data logger; and (5) Sacrificial insulation blocks replaced after each run.
(Source: PhoenixTM)
To address the process challenges, a unique thermal barrier design has been developed that both protects the data logger in the furnace (typically three hours at 1697°F/925°C) and also protects during transfer through the oil quench (typically 15 mins) and final wash station (Figure 3). The key to the barrier design is the encasement of a sealed inner barrier with its own thermal protection with blocks of high-grade sacrificial insulation contained in a robust outer structural frame (Figure 4).
Quench Cooling Phases
Monitoring the oil quench in carburization gives the operator a unique insight into the product’s specific cooling characteristics, which can be critical to allow optimal product loading and process understanding and optimization. From a scientific perspective, the quench temperature profile trace, although only a couple of minutes in duration, is complex and unique. From a zoomed in quench trace (Figure 5) taken from a complete carburizing profile run, the three unique heat transfer phases making up the oil quench cool curve can be clearly identified:
Figure 5. Oil quench temperature profile for different locations on an automotive gear test piece shows the three distinct heat transfer phases: (1) film boiling “vapor blanket”, (2) nucleate boiling, and (3) convective heat transfer. (Source: PhoenixTM)
Film boiling “vapor Blanket”: The oil quenchant creates a layer of vapor (Leidenfrost phenomenon) covering the metal surface. Cooling in this stage is a function of conduction through the vapor envelope. Slow cool rate since the vapor blanket acts as an insulator.
Nucleate boiling: As the part cools, the vapor blanket collapses and nucleate boiling results. Heat transfer is fastest during this phase, typically two orders of magnitude higher than in film boiling.
Convective heat transfer: When the part temperature drops below the oil boiling point. the cooling rate slows significantly. The cooling rate is exponentially dependent on the oil’s viscosity.
From a heat treat perspective, the quench step relative to the whole process (hours) is quick (seconds), but it is probably the most critical to the performance of the metallurgical phase transitions and achieving the desired core microstructure of the product without risk of distortion. By being able to monitor the quench step, the process can be validated for different products with differing size, form, and thermal mass. As shown in Figure 6, the quench curve profile over the three heat transfer phases is very different for two different automotive gear sizes.
Figure 6. Oil quench temperature profile for different automotive gear sizes (20MnCr5 case hardening steel) with different thermal masses: Passenger Car Gear (2.2 lbs) and Commercial Vehicle Gear (17.6 lbs) (Source: PhoenixTM)
Summary
As discussed in this article, one of the key process performance factors associated with gas carburization is the control and monitoring of the product quench step. Employing an oil quench, the measurement of such operation is now very feasible as part of heat treat monitoring. Innovations in thru-process temperature profiling technology offer specific system designs to meet the respective application challenges.
References
[1] Dr. Steve Offley, “The light at the end of the tunnel – Monitoring Mesh Belt Furnaces,” Heat Treat Today, February 2022, https://www.heattreattoday.com/processes/brazing/brazing-technical-content/the-light-at-the-end-of-the-tunnel-monitoring-mesh-belt-furnaces/.
[2] Michael Mouilleseaux, “Heat Treat Radio #102: Lunch & Learn, Batch IQ Vs. Continuous Pusher, Part 1,” interviewed by Doug Glenn, Heat Treat Radio, October 26, 2023, audio, https://www.heattreattoday.com/media-category/heat-treat-radio/heat-treat-radio-102-102-lunch-learn-batch-iq-vs-continuous-pusher-part-1/.
[3] Dr. Steve Offley, “Discover the DNA of Automotive Heat Treat: Thru-process Temperature Monitoring,” Heat Treat Today, August 2023, https://www.heattreattoday.com/discover-the-dna-of-automotive-heat-treat-thru-process-temperature-monitoring/.
About the Author
Dr Steve Offley (“Dr O”), Product Marketing Manager, PhoenixTM
Dr. Steve Offley, “Dr. O,” has been the product marketing manager at PhoenixTM for the last five years after a career of over 25 years in temperature monitoring focusing on the heat treatment, paint, and general manufacturing industries. A key aspect of his role is the product management of the innovative PhoenixTM range of thru-process temperature and optical profiling and TUS monitoring system solutions.
How often do you think about the intelligent designs controlling the thermal loop system behind your heat treat operations? With ever-advancing abilities to integrate and manage data for temperature measurement and power usage, the ability of heat treat operations to make practical, efficient, and energy-conscious change is stronger than ever. In part 1, understand several benefits of thermal loop systems and how they are leveraged to comply with industry regulations, like Nadcap.
This Technical Tuesday article by Peter Sherwin, global business development manager – Heat Treatment, and Thomas Ruecker, senior business development manager, at Watlowwas originally published inHeat Treat Today’sJanuary/February 2024 Air & Atmosphere Heat Treat print edition.
Introduction
Heat treatment processes are a crucial component of many manufacturing industries, and thermal loop solutions have become increasingly popular for achieving improved temperature control and consistent outcomes.
A thermal loop solution is a closed loop system with several essential components, including an electrical power supply, power controller, heating element, temperature sensor, and process controller. The electrical power supply provides the energy needed for heating, the power controller regulates the power output to the heating element, the heating element heats the material, and the temperature sensor measures the temperature. Finally, the process controller adjusts the power output to maintain the desired temperature for the specified duration, providing better temperature control and consistent outcomes.
Performance Benefits
Heat treatment thermal loop solutions offer several advantages over traditional heat treatment methods, including improved temperature control and increased efficiency. The thermal loop system provides precise temperature control, enabling faster heating and cooling and optimized soak times. In addition, the complete design of modern thermal loop solutions includes energy-efficient heating and overall ease of use.
Figure 1. Watlow Industry 4.0 solution (Source: Watlow)
Heat treatment thermal loop solutions are integrated with Industry 4.0 frameworks and data management systems to provide real-time information on performance. Combining artificial intelligence and machine learning algorithms can also provide additional performance benefits, such as the ability to analyze data and identify patterns for further optimization. Ongoing performance losses in a heat treatment system typically come from process drift s. Industry 4.0 solutions can explore these drift s and provide opportunities to minimize these deviations.
Heat treatment thermal loop solutions can be optimized using Failure Mode and Effects Analysis (FMEA). FMEA is a proactive approach to identifying potential failure modes and their effects, allowing organizations to minimize the risk of process disruptions and improve the overall efficiency of their heat treatment processes. Historically, this was a tabletop exercise conducted once per year with a diverse team from across the organization. Updates to this static document were infrequent and were primarily based on organization memory rather than being automatically populated in real time with actual data. There is a potential to produce “live” FMEAs utilizing today’s technology and leveraging insights for continuous improvement.
Th e effectiveness of heat treatment thermal loop solutions can be measured using metrics such as overall equipment effectiveness (OEE). OEE combines metrics for availability, performance, and quality to provide a comprehensive view of the efficiency of a manufacturing process. By tracking OEE and contextual data, organizations can evaluate the effectiveness of their heat treatment thermal loop solutions and make informed decisions about optimizing their operations.
Regulatory Compliance
Nadcap (National Aerospace and Defense Contractors Accreditation Program) is an industry-driven program that provides accreditation for special processes in the aerospace and defense industries. Heat treatment is considered a “special process” under Nadcap because it has specific characteristics crucial to aerospace and defense components’ quality, safety, and performance. Th ese characteristics include:
Process sensitivity: Heat treatment processes involve precise control of temperature, time, and atmosphere to achieve the desired material properties. Minor variations in these parameters can significantly change the mechanical and metallurgical properties of the treated components. This sensitivity makes heat treatment a critical process in the aerospace and defense industries.
Limited traceability: Heat treatment processes typically result in changes to the material’s microstructure, which are not easily detectable through visual inspection or non-destructive testing methods. Th is limited traceability makes it crucial to have strict process controls to ensure the desired outcome is achieved consistently.
Critical performance requirements: Aerospace and defense components often have strict performance requirements due to the extreme conditions in which they operate, such as high temperatures, high loads, or corrosive environments. The heat treatment process ensures that these components meet the specifications and can withstand these demanding conditions.
High risk: The failure of a critical component in the aerospace or defense sector can result in catastrophic consequences, including loss of life, significant financial loss, and reputational damage. Ensuring that heat treatment processes meet stringent quality and safety standards is essential to mitigate these risks.
Nadcap heat treatment accreditation ensures suppliers meet industry standards January/February and best practices for heat treatment processes. The accreditation process includes rigorous audits, thorough documentation, and ongoing process control monitoring to maintain high quality, safety, and performance levels.
The aerospace industry’s AMS2750G pyrometry specification and the automotive industry’s CQI-9 4th Edition regulations are crucial for ensuring consistent and high-quality heat treated components. Adherence to these regulations is essential for meeting the stringent quality requirements of the aerospace and automotive industries and other industries with demanding specifications.
Temperature uniformity is a crucial requirement of both AMS2750G and CQI-9 4th Edition, mandating specific temperature uniformity requirements for heat treating furnaces to ensure the desired mechanical properties are achieved throughout the treated components. AMS2750G class 1 furnaces with strict uniformity requirements +/-5°F (+/-3°C) provide both quality output and predictable energy use. However, maintaining this uniformity requires significant maintenance oversight due to all the components involved in the thermal loop.
Calibration and testing procedures are specified in the standards to help ensure the accuracy and reliability of the temperature control systems used in heat treat processes.
Detailed process documentation is required by AMS2750G and CQI-9 4th Edition, including temperature uniformity surveys, calibration records, and furnace classifications. This documentation ensures traceability, enabling manufacturers to verify that the heat treat process is consistently controlled and meets the required specifications.
Figure 2. Eurotherm data reviewer (Source: Watlow)
Modern data platforms enable the efficient collection of secure raw data (tamper-evident) and provide the replay and reporting necessary to meet the standards.
Th e newer platforms also off er the latest industry communication protocols – like MQTT and OPC UA (Open Platform Communications Unifi ed Architecture) – to ease data transfer across enterprise systems.
MQTT is a lightweight, publish-subscribe- based messaging protocol for resource-constrained devices and low-bandwidth, high-latency, or unreliable networks. IBM developed it in the late 1990s, and it has become a popular choice for IoT applications due to its simplicity and efficiency. MQTT uses a central broker to manage the communication between devices, which publish data to “topics,” and subscribe to topics that they want to receive updates on.
OPC UA is a platform-independent, service-oriented architecture (SOA) developed by the OPC Foundation. It provides a unified framework for industrial automation and facilitates secure, reliable, and efficient communication between devices, controllers, and software applications. OPC UA is designed to be interoperable across multiple platforms and operating systems, allowing for seamless integration of devices and systems from different vendors.
The importance of personnel and training is emphasized by CQI-9 4th Edition, which requires manufacturers to establish training programs and maintain records of personnel qualifications to ensure that individuals responsible for heat treat processes are knowledgeable and competent. With touchscreen and mobile integration, a significant development in process controls has occurred over the
last decade.
Figure 3. Watlow F4T® touchscreen and Watlow PM PLUS™ EZ-LINK®
mobile application
By integrating these regulations into a precision control loop, heat treatment thermal loop solutions can provide the necessary level of control and ensure compliance with AMS2750G and CQI-9 4th Edition, leading to the production of high-quality heat treated components that meet performance requirements and safety standards.
Continuous improvement is also emphasized by both AMS2750G and CQI-9 4th Edition, requiring manufacturers to establish a system for monitoring, measuring, and analyzing the performance of their heat treatment systems. This development enables manufacturers to identify areas for improvement and implement corrective actions, ensuring that heat treat processes are continuously improving and meeting the necessary performance and safety standards.
To Be Continued in Part 2
In part 2 of this article, we’ll consider the improved sustainability outcomes, potential challenges and limitations, and the promising future this technology offers to the heat treat industry.
About the Authors
Peter Sherwin, Global Business Development Manager – Heat Treatment, WatlowThomas Ruecker, Senior Business Development Manager, Watlow
Peter Sherwin is a global business development manager of Heat Treatment for Watlow and is passionate about offering best-in-class solutions to the heat treatment industry. He is a chartered engineer and a recognized expert in heat treatment control and data solutions.
Thomas Ruecker is the business development manager of Heat Treatment at Eurotherm Germany, a Watlow company. His expertise includes concept development for the automation of heat treatment plants, with a focus on aerospace and automotive industry according to existing regulations (AMS2750, CQI-9).
For more information: Contact peter.sherwin@watlow.com or thomas.ruecker@watlow.com.
This article content is used with the permission of heat processing, which published this article in 2023.
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