Improving Glass Furnace Operations
A technical glass component manufacturer is reaping multiple benefits by accurately measuring temperature within its glass melt tank.
For nearly a century, Les Andelys, France-based Holophane has produced and transformed glass for technical applications, specifically optical glass components for automotive lighting. It has set itself apart by its understanding of both pressed glass and optics, as well as its ability to combine these two skills.
When it rebuilt the 33-sq-m, 85-ton, end-fired regenerative furnace in 2014 at its Les Andelys plant in Northern France, Holophane looked to replace its existing visual camera system with thermal imaging technology to provide continuous “on line” temperature measurement. AMETEK Land recommended its Near Infrared Borescope (NIR-B) Glass with an auto-retraction system, which can operate effectively at the extremely high ambient temperatures adjacent to the glass melt tank, while providing real-time, high-quality thermal images and temperature data from inside the tank.
At the Les Andelys plant, the NIR-B Glass was installed above the throat of the tank in a location with a high ambient temperature of over 60°C. For this installation, AMETEK Land recommended a heat shield below the borescope to reduce the heat coming directly from the throat. The solution also incorporated an auto-retract mechanism that provides the instrument with additional protection. The mechanism enables instantaneous automatic retraction from the furnace wall in the event of failure of air purge, water cooling, and mains power, or if an over-temperature condition is detected at the borescope tip.
Developed specifically to operate in the demanding environment of a glass melt furnace, the NIR-B Glass is designed to withstand the high ambient temperatures. It features an integral cooling system, plus a specially designed air purge that keeps the 90° lens clear of contaminants to provide 24/7 data to the plant. Even at very high furnace temperatures, it delivers high-definition (656 x 494 pixel) thermal images to generate highly accurate traceable temperature measurements in the 1,000-1,800°C (1,832-3,272°F) range. The system is suitable for float, container, borosilicate, fiber glass and specialty glass furnaces.
Capabilities and Benefits
Among the borescope’s benefits to Holophane is its ability to provide a 90° wide angle thermal image with clear “visual” definition, combined with a continuous temperature readout. This helps the operators maintain furnace control and therefore optimize productivity.
The NIR-B Glass has been used to continuously monitor the optical profile (temperature profile) along the furnace walls to optimize the location of “hotspots” and to monitor areas of the crown for high temperature with alarms to prevent overheating. AMETEK Land’s Cyclops optical pyrometer was used as the basis for the technology incorporated into the NIR-B Glass.
With over 324,000 available temperature measurement points in the field of view, the borescope can also be used to monitor for drift in crown roof thermocouples by assigning emissivity values for a specific or range of data points. The clear, wide angle thermal image provided by the NIR-B Glass has helped Holophane operators monitor the glass batch line and batch flow from the charging end up to the throat. With configurable outputs, it is possible to create an alarm if the batch crosses the desired melt line. By using an area function in the advanced LAND image processing software (LIPS), Holophane is also able to monitor foam.
The NIR-B Glass alerts the operator to any air leakage or ratholes/cracks in the melt tank, as well as corrosion areas near the chargers or burners. The instrument allows an operator the option to see the difference in temperature gradients when the burners are not operating correctly, which may be an indication that the burner needs to be cleaned or re-aligned, or that the air-to-gas ratio requires adjustment.
“The borescope helps greatly to maintain the right quality flames with good turbulence and shape, therefore optimizing the quality of our end products along with our energy usage,” said Emmanuel Declerck, Holophane’s industrial director. “The images provided by the instrument are particularly important at the exit, near the throat, where temperature profiles are routinely monitored by operators. We are confident that as a direct result of implementing AMETEK Land’s solution, we are achieving significant savings in energy usage.”
A Clear Picture
Combing clear “video” images with continuous real-time temperature data has allowed the NIR-B Glass to replace Holophane’s traditional CCTV cameras and provide a full optical profile every reversal. The NIR-B Glass solution offers Holophane’s plant operators the ability to clearly “see” cold spots from air leaks in the structural refractory, making it easier to detect cracks and enable prompt repair. In addition, its operators can visualize flames to optimize the flame patterns and thermal efficiency, as well as overlay thermal profiles across the crown and along the melt for more accurate batch line control, production throughput optimization, and batch transit time recording.