Appendix
NAS 1638
Like ISO 4406, NAS 1638 describes particle concentrations in fluids. The
analysis methods can be applied in the same manner as ISO 4406:1999.
In contrast to ISO 4406, certain particle ranges are counted in NAS 1638 and
attributed to key figures.
The following table shows the cleanliness classes in relation to the particle
concentration determined:
Maximum particle count / 100 ml
2…5
µm
5…15
µm
15…25
µm
25…50
µm
50…100
µm
> 100
µm
C
lean
lin
ess
cl
as
s
00
625
125
22
4
1
0
0
1,250
250
44
8
2
0
1
2,500
500
88
16
3
1
2
5,000
1,000
178
32
6
1
3
10,000
2,000
356
64
11
2
4
20,000
4,000
712
128
22
4
5
40,000
8,000
1,425
253
45
8
6
80,000
16,000
2,850
506
90
16
7
160,000
32,000
5,700
1,012
180
32
8
320,000
64,000
11,400
2,025
360
64
9
640,000
128,000
22,800
4,050
720
128
10
1,280,000
256,000
45,600
8,100
1,440
256
11
2,560,000
512,000
91,200
16,200
2,880
512
12
5,120,000
1,024,000
182,400
32,400
5,760
1,024
13
10,240,000
2,048,000
364,800
64,800
11,520
2,048
14
20,480,000
4,096,000
729,000
129,600
23,040
4,096
Increasing the class by 1 causes the particle count to double on average.
FCU 2000-4 series
en(us)
112 / 120
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