ISO 11500:2022

This document specifies an automatic particle counting procedure for determining the number and sizes of particles present in hydraulic-fluid bottle samples of clear, homogeneous, single-phase liquids using an automatic particle counter (APC) that works on the light-extinction principle.
This document is applicable to the monitoring of:
a)       the cleanliness level of fluids circulating in hydraulic systems;
b)       the progress of a flushing operation;
c)        the cleanliness level of support equipment and test rigs;
d)       the cleanliness level of packaged stock fluid.
NOTE            Measurements can be made with particles suspended in the original liquid or in a sample of the liquid diluted with a compatible liquid when APC coincidence error limits are exceeded.