The contamination classes 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. This method is applicable to those using the methods of previous revisions. Guide to contamination standards 3 contamination basics solid contaminants in fluid systems vary in size, shape, form and quantity. The most common classification methods follow iso 4406 and sae as 4059. Aerospace fluid power contamination classification for. Quantifying fluid cleanliness bsf filtertechniek bv. The figures are differential counts, and the nas class is usually reported as a single figure representing the. Nas 1638 class 6, can be swapped to as4059 class 6b through f to provide the. The table below shows the number of particles100 ml fluid. Sae as 4059 equivalent iso 4406 class based on iso 4406. A class may be designated for each size from a through f.
The figures are differential counts, and the nas class is usually reported as a single figure representing the maximum allowed particle counts i. Few aircraft companies sae as 4059 class 6bf this standard, and very few industrial companies even knew it existed despite the fact that it overcame the deficiencies of nas national aerospace standard nas 1 is a particulate contamination coding system used in the fluid power industry to simplify the commu nication of data from particle counters. The table below gives an indication of the relative sizes of common objects. The most damaging contaminants in hydraulic systems are normally between 6 and 14 microns, and therefore cannot be seen by the naked eye. These numbers correspond to 4, 6 and 14 micron, in. The contamination levels selected are based on the widely accepted nas 1638. The contamination classes selected are based on the widely accepted older nas 1638 cleanliness classes. The contamination levels selected are based on the widely accepted nas 1638 cleanliness classes. The comparison of the nas 1638 classes to as4059 classes and levels is provided and are defined and the differences explained appendix b. Comparison of the nas 1638 classes to as4059 classes is defined and the. Aerospace fluid power cleanliness classification for. This sae aerospace standard as defines cleanliness classes for particulate. Comparison of the nas 1638 classes to as4059 classes is defined and the differences explained appendix b.