A praiseworthy step because it should give identical results - in theory. Equally, sizes that are not critical can be omitted. This was based upon the size distribution of A.
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NAS saw widespread acceptance in the s and s by industries where reliability was a prerequisite, in areas such as offshore oil production, iron and steel industries, etc.
Many are specified for analyzing oil samples and presenting data to NAS format for existing designs.
What Happened to NAS ?
It converts the particle counts at various size ranges into convenient broad-base classes. The level of contamination or conversely, the level of cleanliness considered acceptable, depends on the type of hydraulic system. How to Ensure Hydraulic System Reliability. The most significant changes are: Toggle navigation Toggle search. A check of the wear debris levels in the fluid condition report may indicate if the level of contamination being generated internally is abnormal.
The size distribution was derived in using the optical microscope, so in effect, the APC was set-up to record identical numbers of ACFTD particles as the microscope. This involves circulating the fluid in the reservoir through external filters for an extended period, or ideally, until the target cleanliness level is achieved.
Create your own user feedback survey. To truly evaluate the performance of filters, the beta ratio or capture efficiency, at a given particle size, must be obtained. Current Issue Archive Advertise.
Medium-Sized Gear Machining Company. It involves a relentless cycle of fluid sampling and remedial action as necessary to ensure the appropriate fluid cleanliness level is continuously maintained. This may increase the restriction pressure drop across the filter and consequently the filter may no longer be able to handle its designed 40059 rate.
This information should be considered before upgrading the elements in existing filter housings. Is NAS dead? This was based upon the size distribution of A. The particle numbers can range from single particles to many millions; saf, a power series is used to cover the number range with a convenient number of classes.
This is a result of recent changes to the ISO contamination standards for automatic particle counter APC calibration 3which necessitated the review of NAS and resulted in its withdrawal for newly designed systems.
How to Define and Achieve Hydraulic Fluid Cleanliness
Any metal-generating components should be identified and changed-out. If a check of the existing filters reveals that this level of filtration is not present somewhere in the system, then either the level of filtration must be upgraded or the target cleanliness level must be revised downward.
APC users are recommended to switch to the new AS standard. Specifying cleanliness over the complete size range - AS 6A through F. Create your own user feedback survey. In Table 3 it can be seen that the particle counts are defined by a number relating to the quantity of particles and a letter relating to the size.
Another aspect that is giving rise for concern is the statement in clause 6. It also gave the overseeing-ISO committee the opportunity to obtain traceability for the particle size distribution PSD of the calibration material.
Machine Oil Case Study: SAE D is currently a defunct standard. This distribution was based on particle contamination inside delivered aircraft hydraulic components in the s.
If you obtain the latest issue of NAS you will find the following statements: Because this situation could cause an uproar within the industry when companies would have to change specifications, the ISO committee decided to take the road of least resistance and selected new size descriptors that would give the same particle counts while retaining integer sizes. The basis of the code is seen in Table 3.