Hydac FCU 1310 - Overview; Definition of the Cleanliness Classes; Cleanliness Class Acc. to ISO 4406:1999

Appendix
Overview / Definition of the cleanliness classes
In the following chapter, you will find the definition of the cleanliness classes
ISO 4406 / SAE AS 4059 and NAS 1638.
Cleanliness class acc. to ISO 4406:1999
In ISO 4406:1999, particle counts are determined cumulatively, i.e. > 4 µm
(c)
,
>6 µm
(c)
and >14 µm
(c)
(manually by filtering the fluid through an analysis
membrane or automatically using particle counters) and allocated to
measurement references.
The goal of allocating particle counts to references is to facilitate the
assessment of fluid cleanliness ratings.
In 1999 the "old" ISO 4406:1987 was revised and the size ranges of the
particle sizes undergoing analysis redefined. The counting method and
calibration were also changed.
This is important for the user in his everyday work:
even though the measurement references of the particles undergoing
analysis have changed, the cleanliness code will change only in individual
cases. When drafting the "new" ISO 4406:1999 it was ensured that not all the
existing cleanliness provisions for systems had to be changed.
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