Cleaning a transformer tank typically takes 4 to 8 hours, depending on the cleaning method, the degree of contamination, and whether deep maintenance operations such as core lifting are performed.
Time Allocation for Different Cleaning Stages
Preliminary Preparation (0.5–1 hour) This includes power outage, oil draining, lifting the transformer body, and removing accessories. To prevent insulation from getting damp, the time the transformer body is exposed to air should be strictly controlled: when the relative humidity is less than 75%, it should not exceed 16 hours.
Main Cleaning Stage (2–5 hours)
Mechanical Cleaning: Use a scraper and wire brush to remove oil sludge and rust from the bottom of the tank, requiring approximately 1–2 hours.
Alkaline Washing Treatment: Immerse the tank in a mixed solution of sodium carbonate and sodium hydroxide at 80–100℃, continuously heating and soaking for about 1 hour to dissolve the oil. Then rinse several times with clean water.
Internal Flushing: Flushing the inner walls and oil passages with qualified transformer oil or pressurized oil flow to ensure no residual impurities remain. This process takes approximately 1–2 hours.
Drying and Finishing (1–2 hours): After cleaning, the inside of the tank must be thoroughly dried. This can be done using hot air circulation or natural air drying to prevent moisture from affecting the insulating oil's performance. Some processes also require applying a clear varnish to the inner walls and then drying it.