How is turbine oil cleanliness measured and maintained?

Measured using:

ISO Cleanliness Codes: Quantifying particle counts at specific sizes.
Particle Counting Instruments: Laser particle counters assess contamination levels.
Maintained by:

Filtration: Implementing appropriate filter systems.
Oil Purification: Removing contaminants through centrifugation or vacuum dehydration.
Good Housekeeping: Clean handling and storage practices.
Seal Maintenance: Preventing ingress of external contaminants.