Industrial float glass production

Versatile possible application of digital pyrometers in the float glass industry

Float glass is produced in the so called float glass process. It is the base for insulation glass, window glass, safety glass, mirror glass or automobile glass. During the process the glass melt is leaded continuously from the melting furnace on to a liquid tin bath where the glass spreads out. By means of DIAS pyrometers PYROSPOT the temperatures in the float glass process can be measured on liquid glass as well as on solid glass and so the quality of the glass can be monitored.

The digital DIAS pyrometers PYROSPOT can be used in many production processes . They measure the temperatures on glass without contact precisely there.
The digital DIAS pyrometers PYROSPOT can be used in many production processes . They measure the temperatures on glass without contact precisely there. Image source: ICAPlants/Wikimedia Commons/CC BY-SA 3.0

The image on the right side shows the production process of the float glass production:

(1) Tank
(2) Canal
(3) Tin bath
(4) Lehr
(5) Glass cutting zone

Schematic representation of the float glass production. Pyrometers can be used for the non-contact measurement here.
Schematic representation of the float glass production. Pyrometers can be used for the non-contact measurement here.

Pyrometer with fiber optic cable for the temperature measurement on liquid glass

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.

The pyrometers with fiber optic cable PYROSPOT 3s are equipped with a special air purge unit and a ceramic tube or sighting tube.
The pyrometers with fiber optic cable PYROSPOT 3s are equipped with a special air purge unit and a ceramic tube or sighting tube.
Float glass production: Because of very high ambient temperatures in the melting tank only pyrometers with fiber optic cable can be used for the non-contact temperature measurement.
Float glass production: Because of very high ambient temperatures in the melting tank only pyrometers with fiber optic cable can be used for the non-contact temperature measurement.

Solid float glass requires a special spectral range for a accurate temperature measurement

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.

Digital pyrometers with large temperature measurement ranges

Here the pyrometer models PYROSPOT DT 40G, DT 42G, DT 44G, DT 54G or DT 56G 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.

For a long maintenance-free operation the pyrometers of PYROSPOT Series 4x can be equipped additionally with a cooling jacket with air purge unit.
For a long maintenance-free operation the pyrometers of PYROSPOT Series 4x can be equipped additionally with a cooling jacket with air purge unit.
The high-accurate pyrometer PYROSPOT DT 54G and DT 56G are designed for the glass industry and have an integrated double laser
The high-accurate pyrometer PYROSPOT DT 54G and DT 56G are designed for the glass industry and have an integrated double laser. Image source: ICAPlants/Wikimedia Commons/CC BY-SA 3.0, DIAS Infrared GmbH

Measure solid float glass at lower temperatures

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.

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