Cleaning oil in industrial gearboxes can be achieved through:

Offline Filtration: Circulating oil through external filtration units without interrupting gearbox operation.
Flushing: Running a cleaning fluid or the same oil at higher flow rates to remove contaminants.
Vacuum Dehydration: Removing water and gases under vacuum conditions.
Magnetic Filtration: Extracting metal particles using magnetic filters.
Centrifugation: Separating contaminants based on density differences.