Infrared Temperature Measurement | Combustion & Environmental Monitoring

Float Glass

Temperature measurement is critical for the glass making process. The relationship between weight and temperature of molten glass is very linear, making accurate temperature measurements very important for flat glass production with minimal stress.

Click on the different sections on the diagram to see which Land products are most suited for each step of the process.

Float-glass-schematic-v1 A-regenerator B-portarch-672a4331ff44407ef76686c6feb45bf9_(1) C-tankroof D-tankbottom E-tankexit F-canal G-tinbath H-tinbathexit I-lehr J-massairs
Regenerator Port Arch Melt Tank Melt Tank Base Melt Tank Exit Canal Tin Bath Tin Bath Exit Lehr Mass Airs


550-3000 °C (1022 to 5432 °F)

Accurate and reliable temperature measurement of the crown and packing is essential for this important and vulnerable area of the tank. Thermocouples, despite their lower initial cost, can rapidly deteriorate. Infrared thermometers provide a long-term, cost effective and more reliable measurement.

A-tank-diagram A-tank-spot

Port Arch

550-3000 °C (1022 to 5432 °F)

Measurement of the port arches, especially in cross-fired furnaces, can provide important information on basic firing conditions, giving early indication of an incorrrect or unbalanced firing situation.


Melt Tank

Thermocouples have been used for many years for this crucial measurement. However, at the high temperatures at which they operate deterioration can be rapid and often undetectable due to contamination of the element and migration of elementary materials from one wire to the other. With the NIR-B Glass it is possible to use the proven technology of the NIR Thermal Imager to accurately and continuously profile the temperature of the entire furnace, including glass, refractory walls and port arches and the crown/roof, with only a small opening in the wall.

Glasstank Spacer

Melt Tank Base

100-1000 °C (212 to 1832 °F)

The condition and safety of the furnace refractories are vitally important, especially as the end of a campaign approaches. An Arc radiometric thermal imager can continuously measure temperatures of the refractories and provide both warnings and alarms to minimize the possibility of glass break-out or refractory failure.

D-tankbottom-arc D-tankbottom-screenshot

Melt Tank Exit

The AMETEK Land Fibre-optic Model FG radiation thermometer is a 2-wire temperature sensor which has been specifically designed to solve measurement problems and improve control of process temperatures in the glass industry.


980-1300 °C (1800 to 2400 °F)

The choice of thermometers here is dependent on the construction and operation of the canal. Short wavelength thermometers will measure the bulk temperature of the glass.


Tin Bath

250-1100 °C (500 to 2000 °F)

A knowledge of the temperature profile is vital in this area for the production of consistently high quality glass. When glass is just a few millimetres thick, selected waveband thermometers operating in a narrow band around 5µm are used to accurately measure the surface temperature of the product.


Tin Bath Exit

150-750 °C (302 to 1382 °F)

Using a thermal scanner here can detect faults and uneven heat patterns in the glass.



150-750 °C (302 to 1382 °F)

As the rate of cooling in the lehr is so important, frequent accurate measurement of the temperature profile is critical. For temperatures above 300°C, 5µm thermometers are recommended, but as temperatures fall below 300°C the long wavelength thermometers should be used so extending the capability of measurement down to ambient levels.

I-lehr-photo I-lehr-screenshot

Mass Airs

20-250 °C (68 to 4820 °F)

Once the glass ribbon exits the lehr it is further cooled by banks of air nozzles above and below the glass.

After that it is cut and trimmed to size and then shipped.

The mass air nozzles must cool the glass in a uniform way across the entire width of the glass - if they don't residual stresses in the glass will negatively affect the glass. In the worst case it will have so much stress that it breaks at the cutting station. Stress can also negatively affect the visual properties of the glass causing distortions when looking through the glass. The use of Landscan after the mass airs shows the uniformity of cooling from edge to edge and also shows problems associated with clogged or inactive nozzles.

The image on the right shows a 12 1/2 foot wide ribbon after the mass airs - the horizontal stripes on the glass are the result of each air nozzle's impingement on the glass. In this image the ribbon has cracked due to stresses within the glass.