Cleanliness classes - brief overview
Cleanliness class - ISO 4406:1999
For 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 key figures.
The goal of allocating particle counts to references is to facilitate the assessment of
fluid cleanliness.
In 1999 the "old" ISO 4406:1987 was revised and the size ranges of the particle
sizes to be analyzed were redefined. The counting method and calibration were also
changed.
Important for the user in his everyday work:
Even though the size ranges of the particles to be analyzed have changed, the
cleanliness code will change only in individual cases. When the "new" ISO
4406:1999 was created, not all the existing cleanliness provisions for systems were
changed.
Table - ISO 4406
Allocation of particle counts to cleanliness classes:
Number of particles / 100 ml Number of particles / 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
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