This SAE Aerospace Standard (AS) defines contamination classes and levels for particulate contamination of hydraulic fluids and includes methods of reporting related data (Appendix A). The contamination levels selected are based on the widely accepted NAS 1638 cleanliness classes. The conversion from NAS 1638 cleanliness class specifications to AS4059 class specifications is defined. The comparison of the NAS 1638 classes to AS4059 classes and levels is provided and are defined and the differences explained (Appendix B). NAS 1638 classes based on weight of particles are not applicable to these classes and are not included. A contamination code has been added to describe the contamination levels of the fluid at the specified particle size ranges.
ISO 4406 versus NAS 1638 The recommended standard for defini-tion of oil cleanliness level is ISO 4406. If NAS 1638 is used, the number of par - ticles in a 100 ml sample larger than 6 and/or 14 microns must be within the range specified by the ISO 4406 code. Cleanliness level required for ME-System. The NAS 1638 cleanliness standard was developed for aerospace components in the US and is still widely used for industrial and aerospace fluid power applications. The figures are differential counts, and the NAS class is usually reported as a single figure representing the maximum allowed particle counts (i.e. Worst case) for designated particle.
AS4059F
Latest
AS4059E
Historical
AS4059D
Historical
AS4059C
Historical
AS4059B
Historical
AS4059A
Historical
AS4059
Historical
Issuing Committee: A-6C1 Contamination and Filtration Committee
Pages: 10
Rationale:Revision F of this standard has been prepared to include comments received from the international community, principally to simplify the coding system to either a single number contamination class that is the same as the obsolete NAS 1638 class, or as a contamination code indicating the contamination levels at a number of distinct particle size ranges. Also, normative references to using the obsolete calibration procedure ISO4402 were removed.
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