In the aerospace industry, industrial ovens are a vital part in the process of parts manufacturing and refurbishing. Whether it’s annealing metal to strengthen the part and relieve stress, drying paint and curing composites, or part de-embrittlement to soften and rehabilitate components in maintenance and repair, asking the right questions can be the key to efficient, low cost operation of aerospace industrial ovens.
1. What do I need to know about industrial oven energy use?
For about 100 years, natural gas has been used to heat industrial ovens. Traditionally, air was put into a burner and blown to the other end of the oven with fans or blowers. The hot air surrounded the product whatever its size or shape, which was eventually heated to the average oven temperature. In general, industrial ovens can heat product up to about 1,000 F, with typical operating temperatures in the range of about 180 F, 450 F, and 500 F.
Gas with heated, circulated air, known as convection, is good for heating a whole oven fast and for heating irregularly shaped product, particularly in batches, since the air gets into its nooks and crannies. But much energy is lost via heating the entire oven, from heated air exiting the front or back of the oven, and from powering its fans or blowers. Even with modulating burners heating with gas is essentially an all-on or all-off process, which is inefficient since heating the entire oven is required for even small parts.
2. What’s the most efficient form of industrial oven heat?
While people assume gas powered industrial ovens cost less than electric, electric can actually be cheaper and more efficient. Today one of the most efficient ways to heat an industrial oven is with invisible electric, infrared energy, which does not require heating the entire oven, and has no fans, blowers, or moving parts so it is totally silent. Infrared energy occurs within the electromagnetic spectrum imparting heat when the product absorbs the light, which is invisible as it is below the visible light spectrum.
“Gas is like a fire breathing dragon; it gets hot right now but lacks the energy efficiency, finesse, and control of electric infrared,” says Jesse Stricker, president of Intek Corp., a Union, MO-based designer and manufacturer of industrial ovens, heaters, heating elements, process controls systems, and material handling equipment. “Electric infrared is particularly effective on exposed surfaces such as drying paint and curing composites, and for continuous, industrial inline heat process systems such as belt or monorail conveyors.”
Because of electric infrared’s energy efficiency, it has also been adopted for space heating applications. For instance, some of our electric infrared space heaters can run on only 700 watts, but provide the same usable heat as a 1500 watt conventional unit that uses a fan, blower, and heating coils. 700 watts is about half the required power of a standard hair dryer. Since the low wattage draws less current, plugging in multiple heaters is less likely to trip electrical circuit breakers, which is a common problem with less efficient heaters.
One of the easiest ways to reduce industrial oven energy requirements, focus heat, and optimize performance is with zoned, modular electric infrared heaters. Like Lego blocks, these electric infrared heater modules, typically in 12” x 24”, 12” x 36”, or 12” x 48” sizes, become structural members of the oven. Because some include integrated hangers, mounting brackets, and wire connections, they can be designed to work individually for small areas, ganged together for larger areas, and may be ceiling hung or wall mounted for effective heating.
The belt conveyor ovens or monorail conveyor ovens often used in aerospace can also provide another element of control. Individual heat zones can be provided with separate controls, enabling greater, more consistent heating of product on an automated, hands-free basis.
“If an aerospace company is heating a smaller component, it isn’t necessary to heat the entire oven,” says Stricker. “Instead, it is more efficient to heat just the necessary heat zones of the oven.”
“For the greatest oven efficiency and flexibility, electric infrared heaters can provide nearly unlimited heating zones that can be turned on or off as needed,” he explains. “Top to bottom, front to back, every foot in a conveyor oven path can be zoned for maximum, continuous process heating efficiency, monitored by a thermocouple in each zone. To adapt to individual parts running through the oven hour by hour, smart controllers can be used to ensure temperature tolerance and consistency as well.”
Another advantage of electric infrared heating is that it is very precise and adjustable, which can help provide the tight temperature tolerances often required in aerospace. Since infrared wavelength correlates with temperature and energy absorbs into each product at certain wavelengths, manufacturers can adjust the heat to match the wavelength of a substrate in the oven for greater energy efficiency and oven performance.
3. How can I optimize oven design for my industrial process?
Buyers often look at “standard” industrial ovens, but most end up with some sort of custom solution to fit their specific requirements, whether for higher or wider coverage, or heating elements with special voltage or wattage ratings. Fortunately, such design enhancements can often be achieved with electric infrared for little or no added cost.
Custom heating elements can be used to enhance industrial oven performance. For instance, glass or ceramic faced heating elements can be used for high-heat applications, flexible silicone rubber for lower temperatures, housing depth increased to allow for additional insulation, or double wall housing insulation used for in-wall installation.
In the aerospace industry, some custom oven designers and builders can even combine oven types, such as gas convection and electric infrared to good effect. Because heat rises, typical ovens are hotter at the top than the bottom, which can be a concern in the aerospace industry where consistently tight tolerances are required.
“While many aerospace companies still specify gas convection ovens, more are adding electric infrared to control their oven’s temperature zones independently,” says Stricker. “To temperature balance all areas of the oven within a degree or two, for instance, they may be used to heat the oven’s bottom more than its top.”
4. Do I have to buy a new oven if mine is inefficient or underperforming?
Once an industrial oven goes past its useful life, it loses efficiency which can raise cost, delay production, or compromise product quality. But before replacing the entire oven with a new unit, first consider whether an oven retrofit or upgrade will work.
Sometimes repairs can be as simple as installing required replacement parts such as high-temperature insulation, porcelain terminal blocks, heat controls, or heating elements.
Even when the repair is more extensive, the solution can be considerably less expensive than buying a new oven.
“Updating industrial oven heaters or heating elements can often boost oven performance to its original specs or even improve them,” says Stricker. “Some oven manufacturers engineer modules that will fix a performance problem, yet are easy enough for self-installation. Upgrading from an older technology like gas convection to a modern one like electric infrared is also possible.”
When repairing, retrofitting, or updating an industrial oven is no longer a cost effective way to improve its performance, it is time to buy a new oven.
Intek Corp. is based in Union, MO. For more information visi www.intekcorp.com.
Del Williams is a technical writer based in Torrance, CA.
