NAS codes
Table 11
shows the original NAS 1638 contamination limits by maximum particle counts per 100 mL
of fluid or by the weight of contamination per 100 mL of fluid.
Table 11 NAS 1638 codes for maximum contamination limits
Class
Particle size range
1
5 to 15 µm
15 to 25 µm
00
125
22
0
250
44
1
500
89
2
1,000
178
3
2,000
356
4
4,000
712
5
8,000
1,425
6
16,000
2,850
7
32,000
5,700
8
64,000
11,400
9
128,000
22,800
10
256,000
45,600
11
512,000
91,200
12
1,024,000
182,400
1
Same as ARP598
SAE codes
Table 12
shows the SAE AS4059 codes and the cleanliness levels.
Table 12 SAE AS4059 cleanliness levels by particle count
Maximum contamination limits (particles/100 mL)
Size, ISO 4402 calibration, or
optical microscope count
1
> 1 µm
> 5 µm
> 15 µm
> 25 µm
> 50 µm
> 100 µm
Size, ISO 11171 calibration, or
electron microscope
2
> 4 µm(c)
> 6 µm(c)
> 14 µm(c) > 21 µm(c) > 38 µm(c) > 70 µm(c)
Size code
A
B
C
D
E
F
Class 000
195
76
14
3
1
0
Class 00
390
152
27
5
1
0
Class 0
780
304
54
10
2
0
Class 1
1560
609
109
20
4
1
Class 2
3120
1220
217
39
7
1
Class 3
6250
2430
432
76
13
2
Class 4
12,500
4860
864
152
26
4
Class 5
25,000
9730
1730
306
53
8
Class 6
50,000
19,500
3460
612
106
16
26
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