Glass production processes cover a wide range of temperatures, from room temperature to over 1600°C. Non-contact thermal imaging is well suited to gather temperature information about these processes, especially where contact temperature methods will disturb the process or will not survive the harsh environment. For a given process, the type of information gathered depends strongly on the infrared wavelengths used in the detector. With hot glass, shorter IR wavelengths (NIR and SWIR) typically reveal information about the interior temperatures of the glass, while longer wavelengths (MWIR and LWIR) reveal information about the surface temperatures. For molds, plungers, and other glass-forming equipment, shorter wavelengths reveal surface temperatures, while longer wavelengths tell more about reflectivity and wear of the surfaces. Combining information from different parts of the IR spectrum gives us a more complete picture of heat transfer during glass production. This, in turn, allows us to understand and solve more complex production problems.
Over the last 55 years, direct-view televisions have evolved from small black-and-white models to large, color models. Screen area has increased thirty-fold, requiring thicker glass to support the high vacuum load in the picture tube. The largest tubes now require more than 140 lbs. (65 kg) of glass, and are more than 1 inch (2.5 cm) thick in the screen area. These newer, larger televisions must support high- resolution digital signals, with much tighter requirements for screen inside contour and image quality. Manufacturing these large, thick, high-quality screens on old production lines is very challenging. This paper describes some of the ways that thermal imaging is used to meet these challenges. Some uses are simple, such as predictive maintenance inspections common in many factories. Other uses are more complex, such as evaluating metal wear in press equipment and providing data to validate complex models of glass forming. This paper also explores some of the special requirements placed on thermal imaging equipment in a television glass plant. Among other things, these include high operating and ambient temperatures (greater than 1000 degrees C) and the ability to measure temperatures in both highly reflective and semi-transparent materials.
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