The two most likely to be encountered in the oil & gas, and process industries are The ISO Cleanliness Code (ISO 4406), and The NAS 1638 cleanliness standard. An introduction to each of these allowable particle contamination standards is provided below.

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.

Jan 26, 2023 · Oil cleanliness is generally defined by two different particle count rating systems: the National Aerospace Standard (NAS) 1638 and the International Standards Organization (ISO) 4406.

ISO 4406 is a three part code (e.g. 18/17/13), where the first number encodes the number of particles greater than 4µm in size, the second number refers to particles greater than 6µm, and the third number quantifies particles greater than 14µm (>4/>6/>14)*.

Purity classes according to NAS 1638 is due to the requirements for modern hydraulic systems of aircraft. Compared to the IS standard, NAS 1638 also distinguishes particles larger than 15 μm. According to NAS 1638, particles are counted in five size classes and for e

The next time you are asked about NAS, AS4059 or ISO cleanliness standards, you will be well equipped to explain classification systems and how to obtain the appropriate cleanliness levels for machinery and components.

NAS GRADE (National Aerospace Standard 1638) is a widely adopted standard to measure the contamination degree of hydraulic oil. Are you ready to save money and extend equipment …

NAS VALUE/ ISO CODE PATCH COMPARISON CHART

Graphical illustration of a particel dispersion acc. to NAS 1638 and ISO 4406. a larger spectrum of particles can be described compared to ISO 4406. Depth filter (s. figure): Separation is realized in the depth of the medium via unstrucured fleece, e.g. out of plastic or glass fibers.

"Can you explain the NAS value in hydraulic and engine oils? Does it vary with a change in viscosity?" The National Aerospace Standard (NAS) 1638 was developed in the 1960s to help control the contamination levels of hydraulic fluid within hydraulic components.