The Glass Industry's Use of Infrared Thermometer
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 a cooling system. By using an optical fiber 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 reach 30 meters. Required installation accessories such as mounting brackets, air cleaners, peep tubes (usable up to 1200°C).
