In the daily operation of industrial electric heating furnaces, the maintenance of resistance wire heating elements is often overlooked by procurement personnel, yet it directly affects equipment lifespan and temperature stability. Resistance heating relies on current passing through nickel-chromium alloy or iron-chromium-aluminum alloy resistance wires to generate heat, which is then transferred to the furnace chamber materials by radiation, conduction, or convection; compared with electromagnetic induction heating, it has greater thermal inertia and slightly slower response, but its structure is simple and the maintenance threshold is low. During procurement, it must be clarified that resistance wires are prone to oxidation at high temperatures, and after long-term use, the resistance value will drift, causing changes in power output. Compared with non-metallic heating elements such as silicon carbide rods and silicon molybdenum rods, resistance wires are suitable for medium- and low-temperature zones and have lower cost, but their lifespan is significantly shortened under working conditions above 1200°C. The matching heating element type should be selected according to the furnace chamber working temperature.
The temperature in the furnace chamber is monitored in real time by a thermocouple, and a PID controller adjusts the input power to achieve temperature control. Procurement personnel should pay attention to the installation position of the thermocouple and the matching of compensation wires to avoid long-term overload of the resistance wire caused by temperature measurement deviation. Unlike arc heating, a high-temperature solution used for metal melting, the temperature control accuracy of resistance heating furnaces depends more on PID parameter tuning. During maintenance, if a decrease in heating rate or current fluctuation is found, first check whether the resistance wire is locally oxidized and thinned, and whether the terminal connections are loose, rather than directly adjusting the PID parameters. When manually fine-tuning, change only one parameter at a time, observe for two complete cycles, and then adjust the next one. This practice can avoid temperature control oscillation caused by multi-parameter coupling.
The furnace chamber lining mostly uses high-purity alumina or mullite fiber and other high-temperature resistant materials, and its insulation performance affects the heat loss of the resistance wire. Compared with electromagnetic induction heating, which generates heat directly inside the workpiece, the heat of a resistance heating furnace must be transferred through the furnace chamber space, so damage to the lining or pulverization of the fiber will significantly increase energy consumption. During acceptance, procurement personnel can check the matching between the lining material grade and the furnace chamber size to avoid frequent on-off operation of the resistance wire caused by thinning of the insulation layer. In daily maintenance, oxide debris in the furnace chamber should be cleaned regularly to prevent it from accumulating on the surface of the resistance wire and causing local short circuits. The replacement cycle of heating elements is related to the furnace atmosphere. Under working conditions containing corrosive gases, even if the temperature does not exceed the limit, the resistance wire may fail prematurely, so a spare parts plan should be formulated based on usage records.
