Appendix C
NAS1638 Cleanliness Code System
43
NAS1638 Cleanliness Code System
The NAS system was originally developed in 1964 to define contamination classes
for the contamination contained within aircraft components. The application of this
standard was extended to industrial hydraulic systems simply because nothing else
existed at the time. The coding system defines the maximum numbers permitted
of 100ml volume at various size intervals (differential counts) rather than using
cumulative counts as in ISO 4406:1999. Although there is no guidance given in
the standard on how to quote the levels, most industrial users quote a single code
which is the highest recorded in all sizes and this convention is used on the PML²
software.
Figure I
CONTAMINATION LEVEL CLASSES
according to NAS1638 (January 1964).
The contamination classes are defined by a number (from 00 to 12) which indicates
the maximum number of particles per 100 ml, counted on a differential basis, in a
given size bracket.
Summary of Contents for PML2
Page 1: ...PML Analyser UserGuide 200 052 EN www mpfiltri co uk ...
Page 6: ...6 Introduction Figure 1 ...
Page 38: ...38 Warranty ...
Page 62: ...Appendix K 62 Fault Finding ...
