Introduction to the Induction Furnace
The induction furnace is a crucial melting device widely used in metallurgy for its efficiency, precise temperature control, and clean operation. Its maintenance is vital to ensure safety, longevity, and optimal performance. Below are eight key points requiring attention during the maintenance of an intermediate frequency induction furnace.
Maintenance Guidelines for Intermediate Frequency Furnaces:
Conduct a systematic shutdown inspection weekly or bi-weekly to evaluate all machine functions. This proactive approach helps understand equipment status and prevent unexpected failures. Daily checks and periodic detailed inspections are essential.
To ensure optimal operation, the following steps must be taken daily:
(1) Temperature Monitoring: Use an infrared thermometer to monitor the temperature of key components at three critical stages:
First Measurement: 5-10 minutes after starting the first heat, with power at approximately one-third capacity.
Second Measurement: When the furnace charge is nearly fully melted.
Third Measurement: At the end of the final full-power heat of the day.
Record all measurements to identify trends and address issues promptly. Components to monitor include SCRs (thyristors), snubber circuit resistors/capacitors, and voltage-equalizing resistors.
(2) Connection Check: Inspect daily for loose screws on power cables and busbars.
(3) Cooling Water Verification: Before startup, confirm that both the power supply and furnace coil cooling water pumps are operational. Maintain water pressure at 1.5-1.7 bar in the power cabinet and 1.5-2.0 bar for the furnace body.
(4) Cleanliness: Keep the area around the furnace body and water-cooled cables free of iron filings and other metallic debris to prevent short circuits.
Start the water pumps at least 10 minutes before operating the equipment. Inspect thoroughly for any water leaks or seepage. Address any issues immediately to avoid unscheduled production interruptions.
If an SCR shows abnormal temperature, investigate immediately. Potential causes include kinked water hoses restricting flow, or scale/dirt buildup inside the SCR cooling jacket.
If the temperature of a resistor in the rectifier's RC snubber circuit differs significantly from others, inspect immediately for a failed (open) capacitor or a damaged resistor. Typically, a faulty snubber circuit may cause noticeable humming or vibration in the reactor during startup.
During scheduled maintenance, focus on:
(1) Cable Management: Check that cables above the inverter's snubber circuits are securely fastened and not dangling. Use cable ties to prevent them from shorting against inductive resistors and damaging thyristors (KK tubes).
(2) Fastener Tightening: Tighten all electrical connection screws and water hose clamps weekly to prevent failures from loosening or detachment.
(3) Hydraulic Oil Level: Check the hydraulic oil level weekly, ensuring it is maintained at a minimum of 80% of capacity.
(4) Water System Corrosion: In areas with poor water quality, inspect the water spray nozzles/pipes inside the medium-frequency power supply cabinet for corrosion. If severe, prepare a complete spare water distribution manifold for quick replacement. Never weld a single damaged nozzle back onto the operating system, as this causes significant downtime. For open-loop cooling systems, replace the distribution manifold every three months; for fully closed systems, aim for every six months to a year.
To clean scaled cooling jackets (e.g., on SCRs), circulate a 20% dilute hydrochloric acid solution for 10-15 minutes. Crucially, after cleaning, flush the system thoroughly with clean water and dry it using compressed air to prevent residual acid from corroding the jackets.
Maintain hydraulic oil cleanliness and proper volume. Replace the hydraulic oil every six months and clean the filters monthly. Note: The hydraulic station typically contains two filters. Ensure they are mounted on the station's frame, not placed directly at the bottom, to prevent metal particles from being drawn into and damaging the hydraulic pump.
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