Strict safety measures must be taken for the first energization after magnesium oxide refilling to prevent accidents such as insulation breakdown, short circuits, and fires. The following are key safety measures:
1. Ensure Sufficient Cooling and Process Completion
The material must be allowed to cool naturally in the furnace to <200℃ after sintering, and then continue cooling to room temperature (approximately 25℃) after removal from the furnace. Cooling time is typically 1–2 hours. Forced cooling, such as water cooling or air cooling, is strictly prohibited to avoid thermal stress leading to cracks.
Energizing before sufficient cooling may cause internal moisture vaporization and pressure buildup, leading to tube bursting.
2. Pass Cold Performance Tests
Insulation resistance ≥500 MΩ (measured using a 500V DC megohmmeter);
Withstand voltage test passed: AC 2000V, no breakdown or flashover for 1 minute;
Ambient humidity ≤30% to prevent surface leakage interference.
Testing must use calibrated instruments, and data must be traceable. Powering on is strictly prohibited if standards are not met.
3. Low-Power Preheat Startup: Apply 50% of the rated voltage initially and run for 10–15 minutes. Observe whether the temperature rise is stable, the current does not change abruptly, and there are no abnormal noises or smoke. After confirming normal operation, gradually increase the power to 100%.
This effectively exposes hidden defects and avoids sudden failures under full load.
4. Implement Safety Protection and Monitoring: The power supply circuit must be connected to a leakage current protection device and an overcurrent alarm system. If the equipment supports this, enable online insulation monitoring to track resistance changes in real time. Operators should wear protective equipment and maintain a safe distance.
In case of tripping, abnormal noises, smoke, or other abnormalities, immediately disconnect the power and investigate.
5. Check Physical Condition and Sealing: Confirm that the metal casing is free from deformation, cracks, or bulges; the cable outlet is properly sealed using ceramic or metal sealant, with a protection rating of IP65 or higher; the leads are securely crimped, with a contact resistance <0.03Ω, and free from oxidation or loosening.
Poor sealing is a major cause of subsequent moisture absorption and insulation degradation, and must be thoroughly checked.
