The Glass Industry's Use of Infrared Thermometer
In the production process of the glass industry, temperature measurement and control is one of the very important and necessary means. Infrared temperature measurement has the advantages of simple operation, fast response, no aging, small drift, flexible configuration, and will not pollute the glass. Factors such as solutions are valued.
In the glass industry, it is necessary to measure the temperature of transparent and opaque objects. Opaque objects include molds, domes and side walls of glass melting furnaces. As the measured object of non-contact temperature measurement, glass is a transparent visible object, its spectrum is in the near-infrared spectrum range, and its emissivity is related to the wavelength and the thickness of the glass. When the spectral range is between 5 and 8 μm, its emissivity is the highest, so the temperature of the glass can be reliably measured in this range. The measured value corresponds to the surface temperature of the glass, independent of the thickness of the glass, in this range and basically no radiation occurs. In order to avoid the influence of the measurement by the surrounding air, the thermometer only uses a narrow infrared spectral band. High-quality thermometers only work in the spectral range of this so-called environmental window, because there is no absorption of infrared rays due to air humidity or carbon oxides, thus avoiding the measurement caused by changes in air humidity or measuring distance. temperature error. The narrow band range 5 (approximately 5 μm) is used to measure the temperature of the surface.
Infrared thermometers generally work in the spectral range of 5.14 μm, because the hot exhaust gas of the burning fire in this region will not affect the measured value. For other areas of application, it is necessary to measure the temperature inside the glass, since the glass layers close to the surface are strongly affected by convection. What needs to be measured here is the melted glass, so a thermometer in the near-infrared range is required. Since the depth of penetration achieved at different wavelengths is also different, the choice of pyrometer depends on the thickness of the glass layer. Non-contact temperature measurement technology for glass melting furnaces, tin baths and annealing furnaces is increasingly replacing traditional thermocouple temperature measurement in glass melting furnaces.
Compared with thermometers, thermocouples will age and drift quickly under high working temperature and aggressive environmental conditions. In order to protect thermocouples, platinum metal is required to be used as a protective shell in some places, which will increase the cost a lot . Specially used in this field, it can work even when the ambient temperature reaches 250°C without cooling system. By using the fiber optic pyrometer, the installation and operation costs can be significantly reduced. The optical fiber can be protected by a solid stainless steel casing, and the longest can 30 meters. Required installation accessories such as mounting brackets, air cleaners, peep tubes (usable up to 1200°C).
Measurement of Glass Drops
In principle, the temperature of the glass drop can only be obtained by non-contact temperature measurement technology. Due to the short cycle time, a pyrometer with a fast response time is required and must also be able to measure the internal temperature of the glass drop, which can be inaccurate because the surface temperature of the glass is strongly influenced by ambient conditions. The penetration depth of the glass is determined by the spectral range of the thermometer, and the selection should be based on the type of glass and the size of the droplet.
Normally the temperature is held and displayed for a short time by means of the maximum value memory. Digital infrared thermometer, it measures the internal temperature of dripping glass in the automatic glass bottle production line, and the response time is 10 milliseconds. Measurement of Glass Mold Temperature Measuring the temperature of the glass mold also requires a fast response time because the glass mold opens and closes at a rapid rate. Because the temperature of the metal object is to be measured here, the spectral sensitivity of the thermometer should be in the short-wave infrared range, and the response time should be between 1 and 2 milliseconds. In addition to the measured value output of 0–20mA or 4–20mA, a serial interface (RS232 or RS485) can also be selected, so that data processing can be carried out by a computer. The instrument can also choose a convenient mounting bracket and cooling cover.
Temperature measurement in flat glass production
For the temperature measurement of flat glass, we also have a suitable pyrometer with a spectral range of 5 μm, that is to say, only the surface temperature of the glass is measured. This measurement method is used in tin baths and lehrs in flat glass production lines. As mentioned above, the emissivity in this spectral range is very low, so that the radiation of heat rays has practically no influence on the measurement.
Glass further processing and light bulb production
Glass surface temperature is an interesting process parameter in light bulb production, bending and annealing of flat glass, and hot firing. The measurement of temperature here should also have nothing to do with the thickness of the glass, so a pyrometer with a spectral sensitivity of 5 μm should also be used.
