NAS 1638
NAS 1638 is an older standard developed in 1964 to define classes of contamination in aircraft components and hydraulic fluids. The classes refer to maximum number the particles in 100mL in different size classes. The table below shows the classification values that may still be in use for older specifications based on Hiac particle counters, but this standard officially became invalid in 2001. Most users use a single code number based on the highest particle count in any of the size bins.
code |
5-15 µm |
15-25 µm |
25-50 µm |
50-100 µm |
over 100 µm |
00 |
125 |
22 |
4 |
1 |
0 |
0 |
250 |
44 |
8 |
2 |
0 |
1 |
500 |
89 |
16 |
3 |
1 |
2 |
1000 |
178 |
32 |
6 |
1 |
3 |
2000 |
356 |
63 |
11 |
2 |
4 |
4000 |
712 |
126 |
22 |
4 |
5 |
8000 |
1425 |
253 |
45 |
8 |
6 |
16000 |
2850 |
506 |
90 |
16 |
7 |
32000 |
5700 |
1012 |
190 |
32 |
8 |
64000 |
11400 |
2025 |
360 |
64 |
9 |
128000 |
22800 |
4050 |
720 |
128 |
10 |
256000 |
45600 |
8100 |
1440 |
256 |
11 |
512000 |
91200 |
16200 |
2880 |
512 |
12 |
1024000 |
182400 |
32400 |
5760 |
1024 |
Learn how the AccuSizer A2000CMS can automate your particulate contamination measurements and report directly in NAS 1638 format.