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 scrapers and wire brushes to remove oil sludge and rust from the bottom of the tank, taking approximately 1–2 hours.
Alkaline Washing Treatment: Immerse the tank in a mixed solution of sodium carbonate and sodium hydroxide at 80–100°C, 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. Hot air circulation or natural air drying can be used to prevent moisture from affecting the insulating oil's performance. Some processes also require applying varnish to the inner walls and drying it.
Key Factors Affecting Cleaning Time
Degree of Contamination: Tanks that have not been cleaned for a long time have thick layers of sludge, making cleaning more difficult and time-consuming.
Whether Core Lifting is Required: If the core needs to be lifted out for combined cleaning, the overall operation time increases significantly.
Site Conditions: Outdoor operations are affected by weather; poor ventilation or high humidity will prolong drying time.
