wo Types of Transformer Oil Tanks and Their Maintenance Features

There are two types of transformer oil tanks:

• Tanks with an openable top cover. The top cover is fastened to the tank shell by numerous bolts around the tank flange.

• Welded steel plate tanks with an opening at the top. The welding process must ensure zero oil leakage. The transformer core and winding assembly (active part) is placed inside the tank shell.

For medium and small-sized transformers, their total weight after oil filling is relatively light compared with large transformers. Therefore, when maintenance of the active part is required, the entire oil-filled transformer can be moved to a location equipped with hoisting equipment. The tank cover can then be opened and the active part lifted out for thorough inspection and necessary repairs.

Large power transformers adopt the bell-type tank design. For maintenance, instead of hoisting the heavy active part, the lighter tank shell is lifted. This type of tank shell is fitted with a bolted flange at the bottom. After removing all fastening bolts around the flange, the bell-shaped upper tank shell can be hoisted away, fully exposing the active part to air. Since the tank shell weighs far less than the active part, hoisting it does not require heavy-duty lifting equipment. Only light hoisting tools prepared on-site at the transformer installation location are sufficient for the operation.