Cleanliness Code Of A Lubricating Oil

NOTES: For automatic particle counter analysis, the contaminant code is determined by allocating a first scale number to the total number of particles equal to or larger than 4 μm, allocating a second scale number to the total number of particles equal to or larger than 6 μm and allocating a third scale number to the total number of particles equal to or larger than 14 μm, and then writing these three numbers one after another separated by oblique strokes (slashes). For an example, see 22/18/13 in the table above. For analysis by microscope, use a "—" in place of the first scale number and allocate the second and third numbers based on the counts at 5 μm and 15 μm, respectively.
Reproducibility below scale number 8 is affected by the actual number of particles counted in the fluid sample. Raw counts should be more than 20 particles. If this is not possible, then the scale number for that size range shall be labelled with the symbol ≥.
EXAMPLE: A code of 14/12/≥ 7 signifies that there are more than 80 and up to and including 160 particles equal to or larger than 4 μm per millilitre and more than 20 and up to and including 40 particles equal to or larger than 6 μm per millilitre. The third part of the code, ≥ 7, indicates that there are more than 0.64 and up to and including 1.3 particles equal to or larger than 14 μm per millilitre, but less than 20 particles were counted, which lowers statistical confidence. Because of this lower confidence, the 14 μm part of the code could actually be higher than 7, indicating a particle count more than 1.3 particles per millilitre.