Glass Industry Applications

The importance of temperature measurement for the glass industry.

Temperature measurement is imperative to the glass industry as it comes down to the high energy process which is involved with manufacturing glass. Efficiency is enhanced with temperature measurement through preserving homogeneous quality as well as decreasing the amount of scrap from the glass plant. To have improved process control, temperature measurement actions are taken throughout multiple stages of production, including manufacturing of various glass such as float glass, fibre glass and technical glass. 

Advantages of Infrared Pyrometers.

• No need for physical contact, as remote measurement is available
• Pyrometers come in different spectral ranges according to application needs
• Tough equipment and fully digital interface with compact electronic components
• Little to no maintenance needed as they do not suffer wear and tear which would be due to high temperatures and exposed environments
• Speedy response times given within milliseconds
• Effortless handling and operation
• Cost-effective with outstanding delivery
• Able to measure a large range and variety of temperatures
• Highly accurate
• Remote mounting possible from hot target
• Moving target temperatures are easily detectable
• Able to be used in inaccessible or hazardous areas
• No effect of electromagnetic fields on the infrared pyrometer
• Does not interfere, damage or contaminate the process

Role of wavelength or spectral range in pyrometer selection

Glass behaviour changes according to wavelength changes, which makes wavelength selection imperative to the glass application.

• In the near and visible wavelengths of infrared region, glass is transparent. In spectral range of 5…5.14 μm temperature of the glass surface can be measured accurately as emissions are very high with almost zero reflections. AL 514 Infrared pyrometer is the product recommended for this spectral range and is more suited to float glass temperature measurement.
• At 8-14 μm there is no light penetration, which means that the glass is fully opaque. Reflection is approximately at 20% so the 8-14 μm range can be used with emissivity settings of e=0.8 (1.0-0.2) when reflectivity is 0.2. This range is particularly useful for measuring temperatures of bottles and thin glass sheets. However, if the glass has surrounding flames or hot objects, this may interfere with the reading of the pyrometer in this range.
• Spectral range 1 μm is recommended for molten glass temperatures. This is because the light can penetrate certain centimetres below which helps in measuring the glass temperature somewhat under the surface in the Melting tank, Feeder and Fore hearth. 

The table summarises the glass application and our recommended products for the same.

Float Glass Application

Melting temperature of the furnace is 1500°C where raw materials are fed into it. Molten glass is then moved to the tin bath via a canal. The glass then floats on the surface. As the glass runs through the tin bath, the temperature drops from 1100°C to 600°C. After the glass has exited the tin bath, it travels to the annealing lehr, it cools down so as to make the glass strain resistant, as well as not cracking and significantly cut ability of the glass is good. After the glass has been has been annealed, it departs the lehr where thereby glass is cut and transported.

Float glass temperature measurement is crucial in the working tank, canal, tin bath and annealing lehr. 

1- Application: Working Tank

Process temperature: 1500°C

Recommended pyrometer: 450 G-2 Glass pyrometer

2- Application: Canal

Process temperature: temperature must be minimum 1100°C before entering the bath

Recommended pyrometer: 450 G-2 Glass pyrometer

3- Application: Tin bath

Process temperature: starting at 1100°C and leaving the float bath as a solid ribbon at 600°C. As the glass flows down the tin bath temperature reduces down to 600°C

Installation of the infrared pyrometer: infrared sensors should be mounted above the tin bath

Recommended infrared pyrometer: AL 390 Infrared pyrometer

4- Application: Annealing lehr

Process temperature: 100°C-800°C

Installation of the infrared pyrometer: infrared sensors will be mounted at the top across the lehr at equal locations

Recommended infrared pyrometer: AL 514 Infrared pyrometer

Container glass applications

Typically bottles, jars, bowls and glass items designed to hold contents are considered container glass. The process of manufacture involves transferring molten metal from the working tank to one or more hearths/feeders. Molten glass then flows into the gob from the position it is dropped, into the moulds ready to form.

It is critical that temperature is precisely managed in the Fore hearth/Feeder. Managing the temperature will ensure that the molten glass reaches the gob in a homogeneous state. Temperature change is critical to glass viscosity and only a minor change in temperature can influence viscosity.

1- Application- Working Tank

Recommended Product: 450 G-2 Glass pyrometer

Temperature measurement is critical to maintain homogeneous condition of the molten glass within the tank.

 2- Application- Feeder/Fore hearth

Recommended Product: 450 G-2 Glass pyrometer
The 450 G-2 is the most suitable infrared pyrometer for measuring temperature in the Fore hearth. Fast response time allows changes in temperature range can be monitored easily. The Pyrometer has a small optical head, which allows it access to the most difficult to reach locations. The fibre optic cable can withstand heat up to 250°. Accessories can also be useful, particularly an air purge unit, to help keep the optical lens clean.

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3- Application- Glass Gob

Recommended Product: A 450 C

In order to get the desired wall thickness of the glass container, temperature management is imperative. An infrared pyrometer can ensure the correct gob temperature is achieved before moving onto the next stage. Container glass manufacture requires quick response devices. The response time of the two colour pyrometer is 20msec, making it a suitable choice for container glass manufacturing. A pyrometer with a water cooling jacket is the best choice for this application.

4- Application- Glass Mould

Recommended Product: A 250 Infrared pyrometer

The A 250 single wave infrared digital pyrometer with peak picker and software for continuous data storage is the best choice for this application.

Technical Specifications of Products