This page contains information about the ISO Code analyte.
ISO Code
Method: ISO 4406
Units: None
ISO codes are a simple way to quantify particulate matter by size. These codes were established by the International Standards Organization (ISO), a world-wide federation of national standards bodies. In our business, they apply to all non-engine lubricating fluids, with one of the greatest benefits accruing to close tolerance hydraulic systems.
Here's how ISO codes work.
Under the ISO Code system, 28 code numbers are set up, each representing a given range of particles per milliliter, ranging from 0.01 to 2,500,000 particles. The smaller the code number, the fewer the number of particles. Note that the size of each range is double the number of the range that preceeds it.
| ISO Code | Minimum (Included ≥) | Maximum (Excluded <) |
|---|---|---|
| 1 | 0.01 | 0.02 |
| 2 | 0.02 | 0.04 |
| 3 | 0.04 | 0.08 |
| 4 | 0.08 | 0.16 |
| 5 | 0.16 | 0.32 |
| 6 | 0.32 | 0.64 |
| 7 | 0.64 | 1.3 |
| 8 | 1.3 | 2.5 |
| 9 | 2.5 | 5 |
| 10 | 5 | 10 |
| 11 | 10 | 20 |
| 12 | 20 | 40 |
| 13 | 40 | 80 |
| 14 | 80 | 160 |
| 15 | 160 | 320 |
| 16 | 320 | 640 |
| 17 | 640 | 1,300 |
| 18 | 1,300 | 2,500 |
| 19 | 2,500 | 5,000 |
| 20 | 5,000 | 10,000 |
| 21 | 10,000 | 20,000 |
| 22 | 20,000 | 40,000 |
| 23 | 40,000 | 80,000 |
| 24 | 80,000 | 160,000 |
| 25 | 160,000 | 320,000 |
| 26 | 320,000 | 640,000 |
| 27 | 640,000 | 1,300,000 |
| 28 | 1,300,000 | 2,500,000 |
The ISO standard (ISO 4406.2) establishes a three-factor code (X/Y/Z) to express fluid cleanliness. The first factor (X) represents the number of particles larger than 4 microns and the second (Y) represents the number of particles larger than 6 microns, and the last (Z) represents the number of particles larger than 14 microns.
i.e.
X = number of particles ≥4 microns
Y = number of particles ≥6 microns
Z = number of particles ≥14 microns
By way of an example, consider a sample where the number of particles ≥4 microns was 48,405, the number of particles ≥6 microns was 15,382, and the number of particles ≥14 microns was 1,043, this would yield an ISO 4406 Code of 23/21/17.
Consulting the ISO Code table above we arrive at this ISO Code.
| Channel | Count of Particles | Range | ISO Code |
|---|---|---|---|
| ≥4 microns | 48,405 | 40,000 - 80,000 | 23 |
| ≥6 microns | 15,382 | 10,000 - 20,000 | 21 |
| ≥14 microns | 1,043 | 640 - 1,300 | 17 |
Particle counting is not a suitable test for engine oils due to the presence of soot. Also, samples containing water or samples that are too dark to obtain an accurate reading are also exempt from particle analysis.
Additionally, earlier versions of this standard only included a two factor code, consisting of the 6 micron and 14 micron channels only. i.e. the 4 micron channel was not represented.