Flawless float glass by high process stability – manufacturers of glass rely on pyrometers of DIAS Infrared GmbH

17. Oct 2014

The process control concerning the high-precision temperature measurement is an essential quality factor in industrial float glass production, glass hardening and glass forms as well as in conglutination of multilayer glass. Cracks, thickenings, thin spots or blisters appear as clear temperature differences and can disable the complete charge. So the temperatures of the liquid glass as well as from the solid glass have to be detected to intervene in the process and to change parameters as needed. For it DIAS Infrared has created a continuous solution with its pyrometers.

Specific spectral ranges for a precise measurement have to be considered for different states of glass. The following image illustrates schematically the manufacturing:


In the zones 1 and 2 (tank and canal) special fibre optic pyrometers are used for the measurement of the molten glass as there are very high ambient temperatures up to 200 °C. Here the models PYROSPOT DSF 30NG or DSF 34NG are mounted in combination with a special quick release mounting angle equipped with an air purge and sighting tube. The fibre optic cable and optic head withstand ambient temperatures up to 250 °C without cooling.

In the zones 3 and 4 (tin bath and lehr) the pyrometers have to measure solid glass. For this application pyrometers with a spectral range of 5 µm are necessary so that only the glass surface will be detected. At each position 3 pyrometers are placed in a row, left and right edge of the glass plate and the middle. This gives a rough temperature profile of the glass plate. Here the pyrometer models PYROSPOT DT 40G, DT 42G or DT 44G are used. As these pyrometers have very long temperature ranges the same model can be used in the different temperature zones. Caused by the high ambient temperatures in these zones the pyrometers will be mounted with a water cooling jacket and an air purge unit. This guarantees a long maintenance free operation.

In zone 5 (exit of lehr, cutting zone) the solid glass has to be measured at lower temperatures. For this reason the pyrometer models PYROSPOT DT 40L, DT 42L and DT 44L are used. As also the ambient temperature is lower only a solid adjustable mounting angle for easy alignment and strong mounting of the pyrometers and an air purge unit is required to keep the lens clean of contamination for a long term maintenance free operation.

Overview: Technical facts


  • Mono fiber optic cable with fixed optics
  • Temperature measurement range: 600 °C to 1800 °C
  • Spectral range: 0.8 µm to 1.1 µm
  • USB or RS-485 interface

PYROSPOT DT 40G, DT 42L and DT 44L

  • Spectral range: around 5 µm
  • Temperature measurement range: 100 °C to 2500 °C
  • Stainless steel housing with IP65 protection class

PYROSPOT DT 40L, DT 42L and DT 44L

  • Spectral range: 8 µm to 14 µm
  • Temperature measurement range: –40 °C to 1000 °C
  • Aiming: LED aiming light or laser aiming light adapter