Appendix
Overview - ISO 4406 / SAE AS 4059 and NAS 1638 classes
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.
ISO 4406 table
Allocation of particle counts to cleanliness classes:
Particle count / 100 ml
Particle count / 100 ml
Class
More than
Up to (and
including)
Class
More than
Up to (and
including)
0
0
1
15
16,000
32,000
1
1
2
16
32,000
64,000
2
2
4
17
64,000
130,000
3
4
8
18
130,000
250,000
4
8
16
19
250,000
500,000
5
16
32
20
500,000
1,000,000
6
32
64
21
1,000,000
2,000,000
7
64
130
22
2,000,000
4,000,000
8
130
250
23
4,000,000
8,000,000
9
250
500
24
8,000,000
16,000,000
10
500
1,000
25
16,000,000
32,000,000
11
1,000
2,000
26
32,000,000
64,000,000
12
2,000
4,000
27
64,000,000
130,000,000
13
4,000
8,000
28
130,000,000
250,000,000
14
8,000
16,000
FCU 8111 /-Aviation
en(us)
/
BEWA FCU8111 3690427a en-us 2017-01-23.doc
2017-01-23
