Aerospace Fluid Power - Cleanliness Classification for Hydraulic Fluids AS4059D

This SAE Aerospace Standard (AS) defines cleanliness levels for particulate contamination of hydraulic fluids and includes methods of reporting data relating to the contamination levels. The contamination levels selected are an extension and simplification of the widely accepted NAS 1638 cleanliness levels.

The intent of this document is to establish the minimum information required to allow valid comparison and interpretation of contamination levels in hydraulic systems that require contamination control of particulate to insure system performance and reliability.