Styles and Characteristics of Explosion-Proof Electric Heater Radiant Tubes
Explosion-proof electric heater radiant tube inner core consists of U-shaped radially arranged end-welded heating wires and ceramic fixing brackets. There is no shielding between the inner core and the outer protective tube, ensuring good heat dissipation. For radiant tubes with a rated operating temperature of 1000°C, the heating wire material is Cr20Ni80 or 0Cr21Al6Nb, with a surface working temperature reaching 1200°C. The operating temperature of radiant tubes made of this material reaches 1000°C, and the fixing brackets are high-alumina ceramic components. The outer protective tube is a cold-drawn seamless thin-walled heat-resistant steel tube, made of 1Cr25Ni20Si2 or 1Cr25Ni35Si2. This material has excellent high-temperature heat resistance, high creep strength at high temperatures, and certain anti-carburizing properties. The design and material selection of this radiant tube have a large safety factor.
Styles of explosion-proof electric heater radiant tubes:
1. Wire-wound spiral radiant tubes: This type of radiant tube consists of a heat-resistant alloy steel tube and an explosion-proof electric heater. The explosion-proof electric heater is usually made of φ3-5mm heating wire wound around a heat-resistant insulating ceramic core with spiral grooves. The working voltage is 220V, and the power is typically 5-7 kW.
2. Strip-wound spiral radiant tubes: The structural characteristics of this type of explosion-proof electric heater are mostly the same as the first type, except that the heating element uses resistance strips wound around the core. The resistance strips are usually 1-3 mm thick and 12-30 mm wide. The core is often composed of multiple segmented cores. Under the same surface load, the heat radiation area is larger, and the material can be reduced. Typically, high-power point heating radiant tubes use this method.
3. Radial zigzag cage-type radiant tubes (also known as squirrel-cage type): The structural feature is that the heating wire (strip) of the heating element is bent into a "U" shape and inserted into several insulating and heat-resistant ceramic support plates, fixed in the middle with a heat-resistant rod. Typical effective dimensions: 800～3200; typical tube diameter: φ90～φ290. Single power: 2 kW～50 kW; single voltage: 30V～220V. This type of radiant tube has a longer service life.
Characteristics of explosion-proof electric heater radiant tubes:
1. Manufactured using high-quality raw materials to produce seamless cold-drawn heat-resistant steel tubes (maximum temperature 1200°C)
2. The inner core uses U-shaped radially arranged end-welded heating wire method
3. There is almost no shielding between the heating wire and the ceramic frame, and the temperature difference between the heating wire and the furnace is small
4. Operating temperature of 1000°C or 1200°C
5. The biggest advantage of the radiant tube is the use of seamless cold-drawn, thin-walled heat-resistant steel tubes (1Cr25Ni20Si2 or 0Cr25Ni20Si2), whose heat radiation is 12% higher than that of the same industry
6. After about 9000 hours of use, the electric heating alloy material used in the radiant tube should have high electrical conductivity and high electric heating conversion efficiency. Because the radiant tube is placed inside the sleeve, the heat transfer process is different from that of ordinary exposed heating elements. The heat shielding is large, and the temperature of the element must be controlled during the heating process to avoid overheating. When the radiant tube is heated in a closed state, the surface temperature of the heating element is about 100°C-130°C higher than the furnace temperature. Therefore, when selecting materials, it is necessary to analyze the furnace temperature and atmosphere and choose the appropriate heating material.
