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Daily Operation Precautions

1. For the first firing after the furnace has been rebuilt and re-sintered, the stainless steel probe must be tested using the grounding and leakage current probe testing device provided by the manufacturer to verify that it is properly grounded. Thereafter, periodic inspections should be conducted based on the condition of erosion at the bottom of the furnace lining. Kangda Electric Furnace The steel molds used in sintering furnaces must be inspected for outer diameter dimensions and concentricity. The steel molds should have evenly distributed vent holes, and prior to use, they must be blast-cleaned to remove rust. The concentricity tolerance must be strictly limited to within 5 mm; otherwise, the resulting furnace liners will vary in thickness, thereby affecting the service life of the furnace lining.

2. When starting up a cold furnace with a full charge, the low-power baking period must be strictly limited to 5 hours before commencing the heating and melting process. This is crucial for the healing of cracks in the furnace lining.

3. When removing slag from the furnace, be sure to set the power control dial to the zero position and turn off the inverter button. This is to prevent accidental electric leakage through the metal rod, which could lead to an electric shock accident. (This is critical for safety.) 4. If there is no shift change scheduled, it is strictly forbidden to allow any residual molten iron to cool in the furnace until the next shift begins. All molten iron must be completely tapped out or transferred into a holding mold before the end of the shift for later use. After the iron has been fully poured out, the empty furnace lining must be allowed to cool safely and effectively for at least 8 hours. During the cooling period, water supply and pump operation must not be interrupted under any circumstances; otherwise, the furnace lining may overheat, causing damage to the coil insulation. In the event of a power outage during the cooling period, immediately activate the emergency measures. During normal cooling, ensure that all molten iron is completely poured out and keep the furnace lid open to accelerate the cooling process. If the cooling rate is too slow, the cracks in the furnace lining will become deeper, and when the furnace is restarted after cooling, these cracks will be difficult to heal, increasing the risk of furnace breakthrough. If cold charge materials are added to accelerate cooling, ensure that the cooling period lasts at least 15 hours; generally, this practice is not recommended.

V. Tasks to be performed after each old lining is removed:

1. Inspect the coating layer on the coil surface. Any areas where the coating layer is damaged must be removed and repaired using coil coating material. The repaired areas must be thoroughly dried—after repair, the surface needs to air-dry naturally for at least 24 hours, or if assisted heating is used, it should be dried for at least 12 hours. Otherwise, during the firing process, moisture from the coating layer could penetrate into the coil, causing arcing in the new lining. The coil coating material, made of high-alumina composition, effectively prevents the coil from overheating. The thickness of the coating layer should be controlled according to the furnace size: approximately 6 mm thick at the upper section and about 25 mm thick at the lower section, forming an inverted conical shape.

2. Inspect the erosion condition of the old furnace lining from top to bottom. Near the coil side, there must be a uniformly distributed loose layer of furnace lining material—this is the most effective buffer protection layer that can prevent molten iron from directly damaging the coil by piercing through the furnace. Otherwise, when the furnace is pierced, a large amount of molten iron could instantly burn through the coil without sufficient time for the alarm system to activate.

6. Method for remelting solidified molten iron inside the electric furnace: First, tilt the furnace slightly, then apply power to the furnace at a very low wattage—typically 50-100 kW for a 300-kW, 8-ton furnace—for at least five hours or longer; the longer the duration, the safer it is. Monitor the ground leakage current readings continuously, and immediately shut down the furnace if any abnormalities are detected. If you notice any irregularities in the furnace lining, promptly remove the affected section—this is the most common scenario leading to furnace breakthrough.

7. Precautions when inspecting the power distribution cabinet, replacing circulating water, or disconnecting the isolating switch: (1) Set the power output to zero and disconnect the power supply. (2) Manually trip both air switches in the basement. (3) Press the “Stop” button on the panel.

Discharge the capacitor for 5 to 10 minutes, and only proceed with the above operation after observing on the operator panel that the busbar voltage has dropped to zero.

A major malfunction will result in immediate shutdown of the high voltage for inspection.

8. Every two weeks, routinely disconnect the power supply to the electric furnace water control cabinet in the distribution room to simulate a sudden power outage and verify whether the generator can automatically start up and whether the emergency pump for the furnace can operate. The generator should be able to run continuously for approximately 5 to 10 minutes. If the generator malfunctions, do not start the furnace.