Below is everything you need to know about industrial ovens.
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Video courtesy of The Grieve Corporation.
Industrial ovens are equipment designed to reach elevated temperatures for processes such as heat treating, metal conditioning, and curing coatings. Generally, there are two primary categories of industrial ovens: batch and continuous. Batch ovens process multiple parts simultaneously, while continuous ovens are typically used in high-volume production environments and often feature integrated heating and cooling systems.
Industrial ovens can be powered by various sources depending on their usage, including gas, electricity, steam, hot water, microwaves, or fuel oil. These energy sources can be utilized in both batch and conveyor-style ovens.
Effective product loading and airflow patterns are essential for the optimal performance of an industrial oven. The airflow configuration, which depends on the product type and loading method, can vary in six different forms. Forced convection is used for heat distribution, as illustrated in the diagram below.
Industrial ovens come in three distinct types, each with its own construction, product handling methods, and adaptability. These types include:
Laboratory ovens are utilized for testing samples in product development or for light-duty production of small components.
Industrial batch ovens are designed to handle large volumes of products and are available in sizes that vary from a few cubic meters to numerous cubic feet.
Conveyor ovens are employed in automated production lines and are tailored to integrate seamlessly into specific manufacturing workflows.
The function and characteristics of an industrial oven are determined by its application. Curing ovens facilitate chemical reactions between powders and metal surfaces, while drying ovens eliminate moisture from raw materials. Additionally, some industrial ovens are used to prepare metals for further processing, melt metals, or remove impurities.
Listing every type of industrial oven is challenging due to the constant development of new models. Specialized ovens are created for specific production processes. Below is a summary of some common types of industrial ovens available from manufacturers.
Baking ovens release moisture, volatile compounds, or trapped gases from coatings on finished products. In powder coating, the baking process heats the powder to its melting point to adhere it to a metal piece. Manufacturers use baking and curing as interchangeable terms.
Baking ovens are thermal processing units that integrate curing and drying functions. They accelerate the drying of painted parts by removing moisture from the air, resulting in a smooth, flawless finish.
In the food and packaged food industries, batch and conveyor baking ovens are employed to enhance the efficiency and speed of food production.
Batch ovens are designed to heat large volumes of products and are available in various sizes and configurations based on their intended use. They can be either bench-top or walk-in models and are typically heated by electrical elements or direct/indirect burners. These ovens also expel trapped gases from products to avoid deterioration.
Conveyor or continuous ovens are designed for high-volume production and feature adjustable speed settings. They typically include a cooling zone, multiple heating zones, and an exhaust hood. These ovens are used for various processes such as drying, curing, annealing, stress relieving, bonding, tempering, preheating, and forming. Their conveyor belt system integrates seamlessly into production or assembly lines, offering high production capacity, automation, and flexibility.
Curing industrial ovens are used to bond powders or paints to metal surfaces and can also harden products made from rubber, plastics, and different metals. Available in various types with multiple applications, these ovens are constructed with insulated steel panels and frames and can be powered by electricity, UV light, hot oil, steam, or natural gas. While their temperature ranges may differ, most curing ovens can achieve temperatures up to 800°F (426°C).
Gas industrial ovens generally have a higher initial construction cost compared to electric ovens, but they are more economical to operate due to lower gas prices. They heat up faster and maintain temperature more effectively than electric or infrared ovens, contributing to reduced operating costs. These ovens use natural or propane gas and are used for various functions, including curing coatings on steel and aiding in the production of automotive components like brake pads and linings. Below is an example of a continuous conveyor gas-fired oven.
Drying ovens are designed to eliminate moisture, heat-treat metals for extrusion, and sterilize medical instruments. They operate using natural or forced convection and can also function as vacuum ovens for powders, granular materials, and electronic components. When used for moisture removal, the oven settings are adjusted based on the measured moisture content of the product.
Electrically heated ovens use electricity, offering rapid heat-up times, precise temperature control, and lower operational costs. They are particularly well-suited for handling combustible materials or metals like aluminum, which may discolor when heated with gas.
Infrared ovens use high intensity lighting to maximize production and minimize energy usage. Electromagnetic radiation instantly brings the oven to full power with consistent and precision heating. Infrared ovens are preferred for coating and curing processes and applications that require precision and speed. Their major drawback is their initial cost. Their main selling features are efficiency, precision, and reliability.
While microwave ovens are widely known for home cooking, recent advancements have introduced their use in industrial processes. Microwave heating offers a quick and efficient way to heat-treat parts, often at a lower cost compared to traditional methods, and features reduced heating, processing, and cooling times.
Microwave heating generates energy directly within the component being heated, leaving the oven itself cool. This method cuts processing times by 50% and energy use by 70%, leading to significant cost savings in part processing and production. Additionally, high-frequency heating effectively processes non-metallic or non-conductive materials that are challenging to treat using conventional methods.
Tunnel ovens feature open-ended chambers linked by a metal belt with a baking surface. Products are either baked directly on the hearth or placed on a pan.
Tunnel ovens are classified into two types: direct gas-fired and indirect gas-fired. Direct gas-fired ovens use air turbulence to bake products more quickly. They feature thermocouple sensors for zone temperature control and even heating with flames positioned both above and below the chamber. Tunnel ovens operate continuously with minimal downtime between batches, making them ideal for industries such as food and automotive manufacturing.
Vacuum ovens regulate atmospheric pressure within the heating chamber to eliminate contaminants and enhance process control. By removing oxygen, they prevent oxidation and manage surface reactions. These ovens enable drying at lower temperatures, making them suitable for delicate materials.
To understand the operation of an industrial oven, the initial consideration is the type of fuel used for heating. This can include hot water, direct or indirect gas, ultraviolet light, steam, or electricity.
The next critical factor to consider is the airflow pattern of industrial ovens, which can include:
For consistent oven temperature, airflow must travel with minimal obstructions and at a steady rate.
The National Fire Protection Association (NFPA) categorizes industrial ovens into Class A and Class B. Class B ovens are not used for volatile materials or solvents, whereas Class A ovens are designed for such substances. Manufacturers must adhere to the NFPA guidelines specified in the NFPA 86 Code Book.
The type of fuel used in an industrial oven dictates its operational characteristics. Below is an overview of the most commonly used fuels.
Gas ovens fall under Class A and can transfer heat either directly or indirectly.
In a direct gas oven, a fan circulates heat from a gas burner, with temperatures potentially reaching up to 1000°F. Typically, these ovens operate between 180°F and 500°F. They use convection to distribute heat quickly, fueled by propane or natural gas. Although they have a higher initial cost compared to electric ovens, their operating costs are lower. Below is an image of a tunnel oven with direct gas heating.
Indirect gas ovens use a stainless steel heat exchanger heated by gas or propane. Air is circulated through the heat exchanger to radiation tubes that heat the product, as can be seen in the diagram below.
In the diagram, the gas burner is positioned to the right of the oven, with the circulating fan located further to the right. The fan directs air through the burner to the radiant tubes. Indirect gas industrial ovens keep the combustion process separate from the work area.
Steam ovens heat water to its boiling point to generate steam, which is then used to warm the oven. They are typically used in situations where speed and time are less critical. The temperature range of these ovens is limited to 212°F, which is the boiling point of water.
Hot water ovens function similarly to steam ovens but at a lower temperature range, typically 160°F or below. Heat is transferred through radiator coils via circulating hot water, warming the air that is then directed to the work area. Like steam ovens, hot water ovens operate slowly and are time-consuming.
Ultraviolet (UV) ovens utilize UV light to rapidly cure substances applied to various substrates. They employ mercury vapor, fluorescent, and LED lamps for this process. UV ovens are commonly used to cure coatings on automobiles, boats, aircraft, missiles, and skis. Below is an image of a UV industrial oven used for curing resins.
Electrical industrial ovens use Incoloy-sheathed heating elements and are classified as Class B. Temperature control is managed by regulating the flow of electrical current. These ovens are cost-effective, produce no pollutants or emissions, and heat up quickly. They have a long lifespan and radiate heat directly, eliminating the need for fans, blowers, or other moving components.
In a microwave system, microwaves penetrate directly into the material to heat it. This method does not need extra pressure and utilizes inertia-less heating, meaning the oven itself does not heat up significantly. Microwave heating offers a high rate of heating with minimal energy consumption.
The effectiveness of microwave heating depends on achieving uniformity, where microwaves are evenly distributed across the product being processed.
Industrial ovens serve a range of applications, from applying coatings to small electronic components to curing finish coatings on parts for airplanes and trucks. In cleanroom environments, they help remove moisture to control and contain contaminants.
Industrial ovens have a wide range of applications and are crucial in nearly every manufacturing process to enhance product performance and reliability. Below are some of the more common uses of these versatile machines.
Industrial ovens are employed to sterilize medical devices and instruments, as illustrated by the dry heat sterilizer shown below. The medical industry demands equipment with exact temperature control to effectively eliminate bacteria, microbes, and viruses. The precise temperature regulation provided by industrial ovens meets these stringent requirements.
Industrial ovens are utilized to bake coatings onto pills and to function as oxidizers for eliminating excess chemicals and waste from these coatings.
Industrial ovens are used for static and dynamic burn-in testing of integrated circuits and electronic devices, including laser diodes. They create extreme conditions to identify potential issues in products, particularly in electrical circuits. Below is an image of a burn-in testing industrial oven and a burn-in board.
Industrial ovens compact and bond materials below their melting point, a process that is used in injection molding and metallurgy. The sintering process increases a material's strength and density. Pictured below is a sintering oven for a heat treatment of Teflon coated pipes and pipe fittings.
Heat treating processes, such as tempering, aging, stress relief, and annealing, involve heating metals to specific temperatures. Tempering reduces brittleness, while stress relief alleviates structural, residual, and thermal stresses. Aging accelerates the effects of usage, and annealing enhances ductility. Below is an image of a heat treatment oven from Wisconsin Oven.
While industrial ovens are highly productive and valuable, several factors must be considered when deciding to use or purchase one. Key considerations include:
Each of these factors is detailed further below.
Regardless of whether an industrial oven uses gas or electricity, it needs energy to operate. Electric ovens heat up rapidly and produce no emissions, but they have a lower initial cost compared to gas ovens. However, their operational costs can be higher due to energy consumption.
Gas industrial ovens typically have a higher initial cost compared to electric ones, but they are more cost-effective to operate due to lower gas prices. As Class A ovens, gas models require explosion relief mechanisms due to their direct or indirect firing methods. This requirement increases both the installation time and costs.
Another important consideration for gas ovens is accessibility, as gas service may not be available in all locations, unlike electricity. When opting for an electric industrial oven, it's crucial to assess the facility's power capacity, as not all buildings can support the necessary amp draw. Upgrading the power supply may incur additional costs.
Industrial oven manufacturers provide a list of recommended daily maintenance tasks to ensure the equipment operates correctly. This includes checking safety systems, controls, and gauges, and carefully following the prescribed startup procedures.
The heat generated by industrial ovens can lead to the accumulation of dirt and grime on their components. It is essential to regularly inspect fans, heating elements, and ducts for debris. For gas industrial ovens, it is also important to check the burners for proper flame length and even gas distribution.
The NFPA offers inspection teams that can be scheduled to perform regular maintenance checks on ovens.
To ensure the safe operation of an industrial oven, adherence to NFPA 86 standards is essential. Proper training, routine maintenance, and correct usage are key to preventing serious injuries and accidents.
Manufacturers provide detailed guides outlining required protective clothing, product transport methods, and cleaning procedures. Different materials, especially those that are flammable, combustible, or volatile, have specific safety requirements. Legal regulations govern the handling of each material type.
Safety requirements may encompass:
Pressure relief is crucial to handle potential explosions in an oven. The relief area should be one-fifteenth of the oven’s interior volume, achieving a venting area ratio of 15 to 1.
An exhaust fan must be distinct from the recirculation fan.
The oven will not function unless the exhaust fan motor is activated and airflow is established.
Flammable vapors and gases must be cleared out before the heating element is turned on.
Most industrial ovens have a safety label attached that specifies the types of materials being heated, along with details such as quantities, operating temperatures, and exhaust rates.
These settings are set above the oven’s maximum temperature. If the heat exceeds the limit, a switch will trip to automatically shut down the oven.
Contactors serve as an additional fail-safe but can become fouled over time. Backup systems are in place to ensure the oven shuts down in case of overheating.
Explosion-proof ovens are more costly than Class A or Class B ovens. They are subject to detailed guidelines outlined in NFPA 70.
For an oven to be rated as explosion-proof, its enclosure must contain any explosion and prevent the ignition of vapors, gases, dust, or fibers. According to NEC, ANSI, and NFPA standards, "explosion-proof" means the enclosure can contain a blast and minimize damage.
Operating temperatures must adhere to the specified guidelines for the oven and must not exceed the combustion temperature of any gases or dust present inside the oven.
All industrial ovens must comply with the guidelines set by the NFPA, which provides a comprehensive list of stipulations, requirements, and regulations for both industrial and commercial equipment.
Typically, manufacturers opt for batch or conveyor ovens due to their high capacity and durability. While laboratory ovens also meet the standards of industrial ovens, they are generally designed for smaller-scale testing or treatment of parts.
Despite the differences among the three types of industrial ovens, it's important to understand each type, particularly when choosing the best oven to meet your production requirements.
When considering a heating solution for production, it is crucial to understand the distinction between an industrial oven and an industrial furnace, as they are often confused with one another.
Laboratory ovens are designed for applications requiring forced air convection to ensure even temperatures. They are used for processes such as annealing, die-bond curing, drying, Polyimide baking, and sterilization. These ovens typically range from one to 32 cubic feet in size and can achieve temperatures exceeding 350°C.
Laboratory ovens are built for various thermal treatments, including drying, heating, thermal testing, and aging. Their versatility makes them common in testing labs, academic institutions, and industrial material testing facilities.
In contrast to industrial batch ovens, laboratory ovens feature latched doors, pressure release panels, stainless steel interiors, solid-state controllers and contactors, as well as chemical-resistant exterior coatings.
Batch ovens operate at temperatures exceeding 1250°F (676°C). They come in walk-in or cabinet styles, with capacities ranging from a few to several cubic feet. These ovens typically feature an aluminized steel interior, adjustable ductwork, a painted exterior, and a digital controller with a control panel. As illustrated in the image below, batch ovens are designed to process large single batches at high temperatures, offering significantly greater capacity and size compared to laboratory ovens.
Conveyor ovens come in various configurations, such as flat conveyor belts, chain systems, Ferris wheels, carousels, overhead trolleys, serpentine setups, spindles, and slat designs. Unlike batch ovens, conveyor ovens eliminate the need for manual loading and unloading as well as separate heating and cooling phases, leading to reduced labor and energy costs. These ovens are commonly used for processes including tempering, annealing, curing, preheating, drying, heat-shrinking, and heat-forming.
Conveyor ovens offer less flexibility compared to batch ovens, as they are integrated into specific production processes. Despite having similar temperature capabilities to batch ovens, conveyor ovens are designed for continuous or indexed feeding through heat zones. They are automated to handle large volumes of small to medium-sized products. The image below shows a chain-driven conveyor oven.
Many times people get confused regarding the difference between industrial ovens and industrial furnaces and tend to use the terms interchangeably. In essence, both devices are methods of creating extremely high temperatures in fireproof enclosures for heat treatment purposes. There are key differences, which are outlined below.
The most significant difference between ovens and furnaces is their operating temperatures. The industrial oven shown below is used for aerospace curing and aluminum aging, functioning at temperatures ranging from 450°F to 850°F. In contrast, the industrial furnace depicted operates at much higher temperatures, between 2000°F and 2250°F.
In an industrial oven, the air is heated in a separate chamber from the product and then circulated. As illustrated in the diagram, high air circulation is essential for effectively heating the product.
In a furnace, heat comes into direct contact with the product being processed. The heat source can be arranged in various configurations to ensure even heating, as demonstrated in the image of the box furnace below.
Industrial furnaces and ovens function in either an air or inert gas atmosphere. Unlike ovens, furnaces can also operate in combustible environments, such as those containing hydrogen or endo- and exothermic gases.
Air circulation and precise temperature control enable industrial ovens to carry out processes like cooking, baking, curing, and other low-temperature tasks. In contrast, the high temperatures of industrial furnaces allow them to handle more intensive operations such as tempering, annealing, and carburizing.
Engineers designing industrial ovens must consider several key factors. Foremost among these is the choice of construction materials, including both interior and exterior metals, insulation, and the strategic placement of ductwork to ensure optimal airflow.
Like all contemporary production equipment, industrial ovens require specific technical setups for electronic settings, monitoring, and computerized control. These computerized systems ensure precise temperature regulation and consistent heating levels.
The following discussion explores various factors involved in the construction of industrial ovens.
When selecting metals for industrial ovens, temperature tolerance and corrosion resistance are primary considerations. Coated aluminized steel, capable of withstanding temperatures up to 1100°F, is often preferred due to its high resistance to moisture and heat-related corrosion, and it requires no maintenance for flaking or peeling. For processes involving acids or other corrosive materials, stainless steel interiors are commonly used.
Ductwork in industrial ovens is often louvered or slotted to ensure unobstructed airflow and consistent temperature distribution. For impinging ovens, which heat parts with grooves or crevices, specialized ductwork is necessary to increase airflow rates. The image below illustrates the ductwork used in a walk-in industrial oven.
Insulation in industrial ovens is crucial for achieving and maintaining the desired temperature. Despite operating at temperatures up to 1250°F, the exterior of the oven should remain cool to the touch. High-quality insulation, with the right density and properly compressed into the oven panels, minimizes heat leakage and ensures the outer surface stays cool.
The durability of an industrial oven relies on its wall panels and frame, which help to minimize heat transfer to the exterior. The side view of the industrial oven panel shown below demonstrates how insulation is installed between the aluminized metal sheets.
Temperature control is crucial for the operation of an industrial oven and is available in several types, including analog, microprocessor, and programmable proportional integral derivative (PID) controllers. Analog controllers, the simplest form, are suited for basic heating tasks that don't need precise temperature regulation. The image below illustrates an analog industrial oven controller.
Proportional Integral Derivative (PID) controllers offer a more advanced approach to managing industrial oven temperatures. These controllers precisely adjust the heat output based on the specific needs of each process and automatically adjust for changes in the system.
Successful airflow design in industrial ovens depends on three key factors: uniformity, airflow pattern, and nozzle or impingement design. Typically, industrial ovens maintain an air temperature tolerance of ±10°F, but this can be improved to ±1°F with enhanced air volume and better uniformity.
The choice of airflow pattern for an industrial oven depends on its design, whether it features shelves, hanging products, or carts. Airflow patterns can be vertical, horizontal, or a mix of both, as illustrated in the diagram below.
Impingement enhances air volume and accelerates heating by using slotted nozzles, cones, or louvers. The choice of nozzle depends on the product's texture, shape, and material. For items with grooves, folds, or ridges, nozzles with increased impingement are necessary.
Industrial ovens must meet certification standards set by numerous national and international bodies. Key organizations involved include the International Organization for Standardization (ISO), the Occupational Safety and Health Administration (OSHA) of the United States, Underwriters Laboratories (UL), and the National Fire Protection Association (NFPA).
While each certifying body has its own set of standards, there is often significant overlap in their requirements. Reputable manufacturers ensure compliance with the regulations of all relevant agencies to guarantee the safety of their products and customers.
Here is a brief overview of the requirements set forth by the most prominent regulatory agencies.
ISO/TC 244 specifies the criteria for industrial furnaces and related processing equipment. These standards cover safety measures, energy efficiency, design, construction, operation, processes, and quality control. The ISO/TC 244 regulations apply to all types of heated enclosures, including furnaces, ovens, kilns, lehrs, dryers, and other related devices. The various sections of these ISO standards are detailed below.
OSHA Code 3567: This regulation addresses industrial process furnaces and ovens, including those that utilize induction and dielectric heating devices, as well as related equipment. Additionally, large ovens used in bakeries fall under OSHA Code 3556.
NFPA 86-2019: The Standards for Ovens and Furnaces are designed to reduce fire and explosion risks associated with ovens and furnaces used in commercial and industrial material processing. This standard addresses Classes A, B, C, and D for dryers, furnaces, and thermal oxidizers. It outlines safety protocols for equipment operation and establishes criteria to mitigate hazardous conditions that could endanger individuals, machinery, or structures.
Underwriters Laboratories certify the electronic components, circuits, and controllers used in industrial ovens as specified in UL 508A. This standard details the design, control, and application of industrial control panels for general industrial purposes. According to UL 508A, control panels can be installed either within an enclosed cabinet or mounted on an open panel, as defined by the standard.
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