Infrared Application of the Month:
Drying Solvent-based Paint on Metals
An OEM of metal components required a more efficient means of drying solvent-based paint on parts in production. Their previous method -- a conventional oven -- required long drying times to prevent the paint forming "skin" which can cause blistering. The existing method caused production bottlenecks. Working with the applications experts at Heraeus Noblelight, the plant installed a shortwave infrared system, to dry the paint. Because infrared radiation passes through the outside surface, the paint dries from the inside out, resulting in a better-looking, more durable surface, produced in less time.
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Infrared Application of the Month:
Booster for Convection Oven
An automobile production line wanted to increase throughput, but had little floor space to add. The manufacturer installed an infrared oven using fast mediumwave infrared lamps at the front end of their existing convention oven; this process rapidly heated the paint and set the topcoat on the body paint. The frames continue on to a forced-air convection oven where less-critical paint drying (underparts and components) can take place. The rapid topcoat drying of high-profile vehicle surfaces eliminates the possibility of dust damage drying the convention phase. Conveyor speed is increased with only minimal additional use of plant floor space.
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Tech Center Spotlight: Digital Controllers
Single-Loop PID Temperature Process Controllers
Temperature process controllers offers easy to use, accurate, reliable PID control. These single loop panel mount controls include auto-tuning, a universal sensor input and PID control output. Available in standard 1/4 DIN size, these auto-tuning temperature controllers automatically set PID control parameters for optimal system performance. Manual settings also permit on-off, P, PI or PID control modes.
- User-defined menu system allows the user to assign up to 20 paramaters in the operations menu.
- Dual display provides better recognition of process changes, including current process value and set value.
- Ramp to set point feature controls temperature rise.
- Includes a single alarm output as standard.
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Stock Designs:
Nano XP Infrared Heater
Nano XP Heaters feature extremely high linear power combined with a Nano diffusion layer as a primary reflector, giving this new infrared source a significant edge in many heat processing industries that need to operate under extreme process conditions. The Nano XP is the latest in a long line of significant technology advancements at Heraeus Noblelight. The heater provides extremely high linear power combined with a Nano diffusion layer as a primary reflector. The new Nano XP reflector is not made of gold or metal oxides but of a unique layer of nano synthetic glass. This material is extremely heat-resistant (up to 1000°C), as well as being resistant to attacks from acids, lye and other aggressive substances.
Learn more about the Nano XP Stock Infrared Heaters from Heraeus Noblelight.
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Technical Learning: Drying of Water-based Coatings
continued from last issue
Figure 3
Figure 3 (above) then shows the efficiencies for the individual heaters increasing with decreasing heater temperatures. It is to be noted that with falling heater temperature (below 1200°K) the convection losses of the radiation sources rise significantly and can no longer be ignored. However, with optimum process control, this disadvantage can be compensated for, and consequently is not taken into consideration in Figure 3 above.
The theoretical comparison of the different radiation sources shows that the efficiency is high using medium wave radiation and that with decreasing wavelength the part of the radiation absorbed in the water film decreases. Comparing the efficiency of a 2600°K radiation source with a 1500°CK source, it can be seen that the efficiency rises from ~ 13 percent (2600°K) to 28 percent (1500°K). This theoretical result indicates a leap in efficiency (a doubling).
Series of Experiments
The proof of the increase in efficiency has been established in two independent series of experiments. Tests were carried out at a test plant and on a printing machine.
- Printing machine experiment: Here also different IR heaters were fitted in a dryer on a printing machine (sheet-fed offset) and compared. Energy input and print quality were recorded and compared at different speeds. The comparison of the test results showed that, at the same speed and the same degree of drying the energy consumption was by 30 to 50 percent lower with medium wave IR heaters. See Figure 3 above.
This practical test runs proved the theoretical conclusion and the question of which is the best IR heater in practice was answered.
The medium wave carbon heater is the most efficient radiation source and achieves energy savings of up to 50%. With the demands of today's printing industry, naturally one should ask the question of how easily all this can be converted into practice. High operating speeds demand high power densities with fast response times as well as an easy integration with existing dryers.
The carbon heater offers high performance and today's construction principles allow high power intensities (up to 80 kW/m2) with response times in terms of seconds.
Results and Summary
Practical comparative drying tests show that a carbon heater at 1500°K requires only half of the energy for the drying process compared with a short wave IR heater.
Carbon heater technology can be fitted in today's dryers. As a result of the fast response time and the high power density, this technology is now used in applications which have hitherto been purely the province of short wave IR heaters. Furthermore the low starting current of the Carbon heater eliminates the need for expensive soft start facilities required for short wave systems.
In further tests, it has been shown that the efficiency leap described in this article is just the start of energy saving in the drying of water-based dispersion lacquers. The laboratory experiments and analysis indicate an energy-saving potential greater than 50%. In addition, higher power densities are technically achievable.
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That's it for this month's issue of Application Notes for IR Heating. Feel free to encourage your colleagues to subscribe. Just click HERE to send them an invitation to subscribe. It's quick, easy, FREE, and no-obligation.
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