What are the standard steps in a transformer oil filling procedure?

Standard steps include preparing the transformer and ensuring dryness, pulling vacuum on the tank to remove air and moisture, filtering and degassing the oil, filling under vacuum to avoid entrapped bubbles, monitoring level and temperature, then sealing and verifying leaks. After filling, the oil is allowed to stabilize and samples may be taken for BDV and moisture. Procedures vary for conservator vs sealed units and for on site vs factory fill.