Correspondence Between Temperature Classes and Ignition Temperatures of Media
When selecting explosion-proof electric heaters, the maximum surface temperature of the equipment must be lower than the ignition temperature of the medium being heated. Temperature classes T1 to T6 correspond to maximum surface temperatures of 450°C, 300°C, 200°C, 135°C, 100°C, and 85°C, respectively. If the ignition temperature of the medium is 200°C, the selected equipment must have a temperature class of T3 or higher; T2 or lower classes must not be used. The maximum surface temperature of Ex d IIB T4 Gb does not exceed 135°C, making it suitable for IIB gas environments with ignition temperatures above 135°C; the maximum surface temperature of Ex d IIC T6 Gb does not exceed 85°C, making it suitable for IIC gas environments with ignition temperatures above 85°C, covering more easily ignitable media such as hydrogen and acetylene.
Requirements of Flameproof Structure for Heater Terminal Compartments and Flanges
Ex d flameproof electric heaters rely on the enclosure to withstand internal explosions without damage and to prevent flame propagation to the outside. A flameproof joint surface is required between the terminal compartment and the heating chamber. Flange types are divided into circular flanges and square flanges (model suffix F). Heaters can use 220V or 380V voltage, and a temperature controller can be integrated into the terminal compartment. During design and selection, it is necessary to verify whether the gap, length, and surface roughness of the flameproof joint surface meet the corresponding explosion-proof rating, and to confirm that the flange sealing surface can adapt to the medium temperature and pressure cycles.
Power Matching and Protection Configuration of Temperature Control Cabinets
The load range of explosion-proof temperature control cabinets is typically 10 to 1000KW, with automatic instrument control or manual adjustment modes, programmable multi-segment temperature curves, segmented output power limiting, and time event output functions. They are suitable for precision temperature control applications such as heat treatment of metal materials, temperature rise control of electric heating furnaces, infrared heating drying rooms, and crystal growth. For overload or load short-circuit protection, semiconductor-grade fast fuses can be selected. During selection, it is necessary to match the thyristor voltage regulation or power regulation scheme according to the total heater power, starting current, and temperature control accuracy requirements, and to confirm that the explosion-proof rating of the control cabinet is consistent with that of the heater.
