ISO cleanliness standards [page 5 of 'ferrous particle problem']
We have seen that microscopic ferrous particles can cause the most severe damage in a fluid systems - worse than larger particles.
Do you have this damaging fine ferrous contaminant in your system? How could you tell? They will not be visible to the naked eye.
The smallest spot that can be seen by the naked eye = 40 microns, but we are worried about particles maybe a 1/10th of that or smaller. Here we show some of them in comparison to a hair:
So, just because you can’t see it doesn’t mean it’s not there!
Whats worse, even ISO cleanliness standards don’t look at this important contaminant. Cleanliness standards relate to the amount of particles by number in a given quantity of oil.
ISO Cleanliness Standards
New ISO 4406 1999 standard now shows cleanliness looking at particles greater than:
4 microns (it was 2 microns)
6 microns (it was 5 microns)
14 microns (it was 15 microns)
The code relates to the number of particles equal to or greater than 4, 6 & 14 micrometers in a fluid sample of 100 millilitres volume
Example
ISO4406 Code
16( c ) / 14( c ) / 12 ( c )
>4 µm © = 350 particles
>6 µm © = 100 particles
>14 µm © = 30 particles
System owners therefore often have an unsatisfactory amount of contamination in their system, even if they are unaware of it.
Even new oil can be contaminated and not supplied to the cleanliness standards required for a modern hydraulic system.
Fresh barrels of oil have a code of ISO 23/21/18.
<2 micron - Between 4 and 8 million particles
<6 micron - Between 1 and 2 million particles
<14 micron - Between 130,000 and 250,000 particles
ISO Target Level 16/14/11
<2 micron - Between 32,000 and 64,000 particles
<6 micron - Between 8,000 and 16,000 particles
<14 micron - Between 1,000 and 2,000 particles