SAE AS4059D

The SAE aerospace standard (AS) AS4059D defines cleanliness classes for particulate contamination of hydraulic fluids and includes methods of reporting related data. The contamination classes selected are based on the widely accepted older NAS 1638 cleanliness classes. The table below shows the number of particles/100 mL fluid based on differential particle count, assuming use of an automated particle counter such as the Hiac or Accusizer 780, calibrated per ISO 11171.

SAE AS4059 Rev. E Table 2 (Cleanliness Classes for Differential Counts), (Particles per 100 ml)

code 6-14 µm 14-21 µm 21-38 µm 38-70 µm >70 µm
0  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