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Glass Stream & Glass Gob

Glass, like honey, changes viscosity dramatically with a small change in temperature. Glass that is too cold will flow more slowly and will solidify too soon. Glass that is too hot will flow too quickly and will solidify more slowly. Effective control of glass stream flow and glass gob weight is therefore highly sensitive to glass temperature, and the glass industry typically wishes to control glass stream and gob temperature within a fraction of a degree.

Application Overview

A single-wavelength sensor is not appropriate for most glass applications because the glass is highly transparent at short wavelengths. The sensor reading will vary with changes in glass color, size, and composition, as these factors will determine the transparency of the glass. A long-wavelength single-wavelength sensor is not appropriate for most glass applications, even though the glass is opaque at these wavelengths because these sensors measure only the surface of the glass and are very sensitive to optical obstruction and misalignment. Varying with air currents, the temperature of the surface of the glass is significantly cooler than the bulk glass temperature and a single fingerprint on the lens of a long-wavelength sensor will result in an error of tens of degrees. For a reliable and accurate measure of glass stream or gob temperature, a dual-wavelength sensor is usually required because only a dual-wavelength sensor will automatically compensate for changes in glass color, size, and composition.

Glass gob actively being processed into glass bottles
Williamson Wavelength Advantage

The transparency of glass changes dramatically with wavelength. For a dual-wavelength sensor to produce an accurate and reliable reading, it is essential that the glass be equally transparent at both measured wavelengths. For this reason, wavelength selection is a critical criterion.​ Two-color sensors offered by others are filtered at wavelengths that do not view equally well through most types of glasses and are therefore not appropriate for measurement of most streams or gobs. For this reason, the Williamson dual-wavelength sensors are uniquely qualified for use in these challenging applications.

Pyrometer Benefits
  • Consistent gob weight and stream flow.
  • Consistent glass distribution within the mold produces consistent and uniform mechanical dimensions and reduces optical distortion.
  • Optimum temperature control reduces demand for lubrication.
Wavelength Technology
  • Dual-Wavelength technology automatically compensates for misalignment and dirty optics.
  • Williamson’s unique wavelength set permits accurate and reliable temperature measurement of glass streams and gobs regardless of color, size or composition.

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