Diesel fuel standards Australia AS3570

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ISO 4406 microscopic view - the circle size is 0.5 mm

ISO 4406 is the reporting standard for fluid cleanliness. According to this standard, a code number is assigned to particle count values derived at three different micron levels: greater than 4 microns, greater than 6 microns and greater than 14 microns. The ISO code is assigned based upon Table 1 below:

Table 1 – ISO 4406 Fluid Cleanliness Guide

ISO 4406 Fluid Cleanliness Guide

4µm / 6µm / 14µm and per / ml

For example: An ISO cleanliness code of 18/16/13 refers to the following:
18 = 4µm particles, 16 = 6µm particles, and 13 = 14µm particles.

By referring this information to the chart above, you can see the range of the actual particles within the index.
18 shows between 1,300 to 2,500 – 4µm particles, per ml of fluid sample
16 shows between 320 to 640 – 6µm particles, per ml of fluid sample
13 show between 40 to 80 – 14µm particles, per mil of fluid sample

It is recommended by most new diesel injector manufacturers to have an ISO Cleanliness Code in the range of 15/12/10 to 12/9/6.

ISO Cleanliness Code

Diesel generators fuel consumption

Guide to Contamination Standards - by Parker Hannifin

This guidebook, by Parker Hannifin, is aimed at engineers, technicians and quality control personnel involved in contamination control. Its purpose is to make available accepted and widely-used cleanliness specification levels for liquid samples. The tables in this guide allow users of using automatic portable particle counters to see the relationship between raw particle counts at various sizes and the reporting code numbers of various contamination standards.


Note that some of the table entries are defined as cumulative counts (e.g. “> 6µm”) and others are defined as differential counts (e.g. 6–14µm”). Instances of particle sizes given as “µm” refer to ACFTD (i.e. Air Cleaner Fine Test Dust) distributions. Instances of particle sizes given as “µm(c)” refer to MTD (i.e. ISO Medium Test Dust) distributions.
All standards are in counts per volume, and provide easy methods for converting particle counts into limits that are simple to interpret. By noting the requirements of the standard, particle counts can be accurately converted to contamination levels.