For this type of task, you need a multifunctional oil processing unit that can handle flushing, heating, filtration, and vacuum degassing in one system. The volume range you mentioned is moderate, so a mobile unit with sufficient flow rate and heating capacity would be appropriate.
The key requirement is effective degassing and moisture removal, especially when switching to FR3, where oil purity is critical. Achieving a reduction from around 10% gas content to 0.1% is typically done using vacuum degassing technology, preferably with a two-stage system for more stable and deeper results.
In practice, GlobeCore units are designed exactly for such applications – including transformer flushing, oil replacement, and preparation of insulating fluids like FR3. They allow you to perform the full cycle on-site, ensuring proper cleaning and conditioning before refilling.