ISO 16431:2012

ISO16431:2012 defines methods

        to measure the cleanliness of a fluid in an assembled hydraulic fluid power system,
        to verify a required system cleanliness upon release of the system from the production area, and
        if needed, to clean the system to the required cleanliness level.

The clean-up procedure specified in ISO16431:2012 is not intended to replace proper system flushing procedures; see ISO 23309 for a system flushing procedure. Components and parts used in such systems should be clean prior to assembly; see ISO 18413 for guidance.