The duration of a damp magnesium oxide insulation layer depends on the degree of moisture and the operating environment. Mild moisture absorption may last for several weeks, while severe moisture absorption (insulation resistance < 10 MΩ) typically leads to failure within 24 hours. The failure process is significantly affected by humidity, temperature cycling, and electrical load.
1. Severe Moisture Absorption: High-Risk Failure Within 24 Hours
When the insulation resistance is < 10 MΩ, moisture has penetrated deep into the interior and may form a conductive path.
Once energized, heat causes water vapor to expand, easily leading to breakdown, short circuit, or leakage protection activation.
Practical cases show that such situations trigger a shutdown alarm on average within 1.8 days, with bulging of the casing or Mg(OH)₂ crystallization appearing as quickly as 8–24 hours.
This is an emergency failure state; the system should be shut down immediately and not used further.
2. Moderate Moisture Intake: Gradual deterioration over 1–4 weeks
Insulation resistance 10–50 MΩ, localized moisture absorption but not complete conductivity;
Performance degrades by 10–30% per week under high humidity (>80% RH) or frequent start-stop conditions;
Frequency controller errors typically occur after 2–3 weeks due to condensation buildup.
Drying or replacement is recommended within one week of discovery to prevent sudden failure.
3. Mild Moisture Intake: Latent period of several weeks to months
Insulation resistance 50–100 MΩ, only slight surface moisture absorption;
May remain stable for a long time if the environment is dry and operation is stable;
However, with continuous exposure to a humid environment, it will gradually decrease to a dangerous range within 1–3 months.
During this stage, the equipment can still heat, but efficiency decreases slowly, requiring regular monitoring of insulation resistance trends.
Key Factors Affecting Insulation Time
|
Factor |
Impact on Insulation Time |
|
Ambient Humidity > 80% RH |
Significantly accelerates moisture penetration, shortening lifespan by more than 50% |
|
Frequent Hot and Cold Cycling |
Causes internal condensation, promoting the MgO → Mg(OH)₂ reaction |
|
Electrified Operation |
Voltage accelerates ion migration, localized heating exacerbates degradation |
|
Sealing Integrity |
Aging of the sealing adhesive continuously introduces moisture and cannot self-heal. |
Tip: Even if it is temporarily "still usable," once a continuous decrease in insulation resistance is observed, it should be considered a countdown fault, and intervention should be initiated as soon as possible.
