ISO-4407 Manual Particle Count

International Standards Organization (ISO) specifies the code to be used in defining the quantity of solid particles in the fluid used in a given hydraulic fluid power system.  Method for manual microscopic coding the level of contamination by solid particles.  The purpose of this code is to simplify the reporting of particle count data by converting the numbers of particles into broad classes or codes, where an increase in one code is generally a doubling of the contamination level.  This is the determination of particulate contamination by the techniques using a microscope.  The code for particle count comprises the following three-(3) part scales:
  > 2 m



  > 5 m


> 15 m

This method is for determining the level of particulate contamination in liquids used in hydraulic systems by counting the number of particles deposited on the surface of a membrane filter using an optical microscope. It includes particle counting by two manual methods and image analysis, using either transmitted or incident lighting systems.

Particle sizes greater than or equal to 2 micrometers (m) can be sized and counted by this method, but the resolution and accuracy of the results will depend upon the optical system used and the capabilities of the operator.

All hydraulic fluids with a wide range of contamination levels can be analyzed according to this International Standard. However, the counting uncertainty at the larger particle sizes increases if the volume filtered is reduced to allow smaller sized particles to be counted, where a fine precipitate or a high particle concentration is present.



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