The time it takes for problems to occur after magnesium oxide insulation layer gets damp depends on the degree of moisture, ambient temperature and humidity, and operating conditions. Mild moisture may cause abnormalities within several weeks, while severe moisture can lead to equipment failure within 24 hours. The following are typical development cycles under different conditions:
1. Severe Moisture (Insulation Resistance < 10 MΩ): High Risk Within 24 Hours
Symptoms: Moisture has penetrated deep into the magnesium oxide layer, forming a conductive path;
Development Speed: After power is applied, heat accelerates the expansion of water vapor, which may trigger breakdown, short circuit, or leakage protection within 1–3 start-stop cycles;
Case Study: If high-temperature operation is initiated immediately after moisture absorption, bulging of the casing and Mg(OH)₂ crystallization can occur within 8–24 hours.
Practical data shows that after the insulation resistance of the heating tube drops from 50 MΩ to 2 MΩ, a leakage alarm occurs on average within 1.8 days.
2. Moderate Moisture Intake (Insulation Resistance 10–50 MΩ): Gradual deterioration within 1–4 weeks
Manifestations: Localized moisture absorption, no stable conductive path yet formed;
Progress Rate: In high humidity (>80% RH) or frequent start-stop environments, insulation performance decreases at a rate of 10–30% per week;
Risk Points: Condensation easily occurs during hot and cold cycles, accelerating internal degradation, typically triggering a controller alarm after 2–3 weeks.
3. Mild Moisture Intake (Insulation Resistance 50–100 MΩ): Latent period of several weeks to several months
Manifestations: Only slight surface moisture absorption, initially without obvious abnormalities;
Progress Rate: If the environment is dry and operation is stable, it may persist for a long time; however, if continuously exposed to a humid environment, it gradually declines to the danger zone within 1–3 months;
High Concealment: The equipment can still heat, but efficiency decreases slowly, easily overlooked.
Key Factors Accelerating Deterioration
|
Factor |
Impact Description |
|
High Ambient Humidity (>80% RH) |
Continuous humidification accelerates moisture penetration. |
|
Frequent Temperature Cycling |
Alternating hot and cold temperatures cause condensation, promoting the MgO → Mg(OH)₂ reaction. |
|
Electrified Operation |
Under voltage, ion migration accelerates, localized heating exacerbates water vapor pressure. |
|
Sealing Failure |
Aging or cracking of the sealing adhesive allows continuous moisture intrusion, which cannot heal itself. |
Once a continuous downward trend in insulation resistance is detected, even if the equipment is still operational, it should be addressed within one week to avoid sudden shutdown.
