Reporting Fluid Cleanliness: Explanation of ISO 4406:99

The industry standard for reporting fluid cleanliness is ISO 4406:99, also known as ISO Cleanliness Code.  Laser particle counting is the most common method used.  The laser counts the quantity and size of the particles it sees.  The full report shows the quantity of particles that are of the value and larger for each of the following particle size (in microns): 4µm, 6µm, 10µm, 14µm, 21µm, 38µm and 70µm.  The ISO Cleanliness Code correlates to the quantity of particles that are 4µm and larger, 6µm and larger, and 14µm and larger.

The table below shows the ISO Code and the quantity of particles of each size and larger as measured per milliliter(ml).

The example below (Table 1) shows the a typical ISO Cleanliness Code of 17/13/11 and how each number represents the quantity of particles of each size (and larger) per one milliliter.

These values are typically used to monitor the cleanliness of the oil.  As filter specialists, we use the ISO Cleanliness Code along with High Purity filters to monitor the effectiveness of filtration we prescribe to solve a specific problem.

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Table 1

Equipment or component manufacturers will often specify the ISO Cleanliness Code to best protect their equipment. We will use this information to best recommend the filtration media we think will best result in achieving the specified ISO Cleanliness Codes.

Very often we will add the Parker iCount to our equipment packages as an economical means to report particle counts in real time. Note that these instruments are not intended to replace ongoing oil sampling and analysis programs, but to enhance them and to alert the client when conditions might change. Note that this does not provide wear metals analysis but only particle counts. Please see Machinery Lubrication for more details on how to use this information.

UntitledThe Parker iCount is useful in measuring contamination in distillate fuels. Industrial filtration equipment manufacturers do not report cleanliness using ISO 4406 but ASTM D6217. I was recently asked how we might use ISO 4406 to report fuel cleanliness. In this instance, the OEM does not want their equipment to exposed to any particles larger than 10 micron. The exact ISO Cleanliness Code is open for discussion and debate. Assuming that a kidney loop or off-line filtration system is continuously processing a fuel tank, an ISO Cleanliness Code of 13/10/7 would clearly meet the specification.


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