Summary of Standard Operating Procedures and Safety Precautions for Smelting Furnaces
Smelting furnaces are one of the core pieces of equipment in the metal processing industry. The standardization of their operation directly affects product quality, production efficiency, and personnel safety. The following is a summary of standard operating procedures, safety precautions, and emergency response measures to provide practical guidance for practitioners.
I. Standard Operating Procedures for Smelting Furnaces
1. Pre-shift Preparation and Inspection
Equipment Inspection:
- Inspect the furnace body and lining for cracks, peeling, or corrosion. Repair any defects promptly.
- Confirm that there are no leaks in the gas/oil pipelines and valves, and that the combustion air system (fans, ducts) is operating normally.
- Verify the accuracy of temperature instruments (thermocouples, thermometers), pressure gauges, and safety valves, ensuring they are within their expiration dates.
- Check that the electrical system grounding is good, cables are undamaged, and control switches are sensitive.
Material and Tool Preparation:
- Raw materials require pretreatment: remove oil, mud, sand, and flammable and explosive impurities (such as plastics and paint). Damp raw materials must be dried (moisture content ≤ 0.5%).
- Preheat crucibles, ladles, stirring rods, and other tools to prevent uneven heating that could cause cracking or molten metal splattering.
- Prepare protective equipment (flame-retardant clothing, safety glasses, high-temperature resistant gloves, safety helmet) and emergency tools (dry sand, fire extinguisher).
Personnel Preparation:
- Operators must be trained and qualified, and familiar with equipment performance and safety procedures.
- Wear full protective gear, tie long hair tightly, and do not wear synthetic fiber clothing (which is flammable).
2. Ignition and Heating
- Ignition Sequence: First, turn on the combustion fan to purge the furnace cavity with cold air for 1-2 minutes (to remove residual combustion gases). Then, ignite the ignition rod and slowly open the fuel valve. Once the flame stabilizes, adjust the air-fuel ratio (to ensure complete combustion and reduce harmful gas emissions).
- Heating Control: Heate at the rate specified for the furnace type (e.g., ≤100℃/h for medium-frequency furnaces) to avoid rapid heating that could cause lining cracking. Closely monitor the temperature instruments during the heating process to prevent overheating.
3. Smelting Operation
- Charging: Add raw materials in batches and evenly to avoid overloading and causing furnace overflow; large pieces of raw material should be crushed before addition to prevent clogging of the furnace opening;
- Temperature and Composition Control: Monitor the temperature of the molten metal in real time during smelting (e.g., control the melting temperature of aluminum alloys at 720-750℃), take samples regularly for composition analysis, and add alloying elements as needed;
- Stirring: Use a preheated stirring rod to stir evenly to ensure uniform composition, avoiding contact with the furnace lining during stirring;
- Slag Removal: Remove slag promptly using specialized slag removal tools to avoid introducing impurities.
4. Shutdown and Cooling
- Shutdown Procedure: First, stop charging. After all molten metal has been discharged from the furnace (or kept at a constant temperature), reduce fuel supply, gradually close fuel valves, and stop the combustion blower.
- Cooling Requirements: Allow the furnace to cool naturally until the furnace temperature ≤200℃ before opening the furnace door. Forced cooling with water is prohibited (as it can easily cause the furnace lining to crack).
- Cleaning and Maintenance: After cooling, clean any residual slag and metal clumps from the furnace. Inspect the furnace lining for wear, repair any local defects, and clean and lubricate the equipment.
II. Safety Precautions
1. Personnel Safety
- Smoking, eating, or storing flammable or explosive materials near the furnace is prohibited.
- Maintain a safe distance from the furnace (≥1.5 meters) during operation and avoid directly facing the furnace opening.
- When pouring molten metal from the furnace, ensure the ladle is stable and avoid tilting or collisions.
- Never touch high-temperature tools or molten metal directly with your hands. After use, place tools in designated areas.
2. Equipment Safety
- Regularly check the furnace lining thickness; replace when wear exceeds 1/3 of the original thickness.
- Gas furnaces must be equipped with leak alarm devices, and pipeline sealing must be checked regularly.
- Medium-frequency furnaces must be protected from short circuits in the induction coil to prevent overcurrent damage.
- Safety valves and pressure gauges should be calibrated every six months to ensure reliable operation.
3. Environmental Safety
- The work area must be well-ventilated, with an exhaust system installed to remove harmful gases such as CO and SO₂.
- Keep the ground dry and free of standing water to prevent slipping or electrical short circuits.
- Lay dry sand in areas where molten metal leaks for easy emergency handling.
4. Material Safety
- Store raw materials separately to avoid mixing (e.g., aluminum and copper cannot be mixed).
- Do not put wet raw materials or sealed containers (such as aluminum cans) into the furnace to prevent explosions.
- Molten metal transport routes must be unobstructed. III. Emergency Response Measures
1. Gas Leak: Immediately shut off the fuel valve, stop the blower, open doors and windows for ventilation, and do not use open flames or electrical switches. Inspection and repair should only proceed after the leak has been extinguished.
2. Molten Metal Leak: Quickly cover the leak area with dry sand to prevent it from spreading. Do not use water (water will explode when exposed to high temperatures).
3. Fire: Use a dry powder fire extinguisher or dry sand to extinguish the fire. Do not use water to extinguish metal fires.
4. Burns: Immediately rinse the burned area with plenty of cold water (for 15-20 minutes), then seek medical treatment.
5. Electric Shock: Immediately disconnect the power supply and use insulated tools to remove the injured person from the power source. If the heart has stopped beating, perform CPR and seek medical attention.
Conclusion
The operation of smelting furnaces must strictly follow the standardized procedures and pay close attention to safety details at all times. Only by integrating "safety" throughout the entire operation process can accidents be effectively avoided and production ensured. Practitioners should receive regular safety training to continuously improve their risk awareness and ensure their own and equipment safety.
