The oil filtration rate selection


  • Fluid Cleanliness Standards
  • Recommendations for cleanliness class for your system
  • Recommendations for Locations of Filters at your system

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There are a lot of different standards for the classification of solid particle contamination in lubrication and hydraulic fluids: ISO 4406/1999, NAS 1638, SAE AS4059, GOST 17216-2001, etc.

To determine the cleanliness level by  ISO 4406/1999 the solid particles present in 100 ml fluid are counted, sorted according to size & quantity and classified into particle ranges, defined by two (Microscopic counting) or three (automatic particle counter) numbers divided by slashes:


There are approximate comparison tables for other standards,

from Parker catalog:


and from Donaldson catalog:


There is very important to clean even brand new oil before fill the hydraulic tank. These tests results are good examples why it necessary to do:


The cleanliness level required in lubricating and hydraulic systems is determined by the most sensitive component. There are generic recommendations of cleanliness class,

from HYDAC catalog:


from Parker catalog:


from Donaldson catalog:


Using these tables we can get the recommended ISO cleanliness level for our system.

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