Note: The current standard for the 4µ/6µ/14µ code is ISO 4406 1999
The ISO 4406 target cleanliness level is usually determined by the most sensitive components in the system at specified pressures and operating enviroments. Particle sizes 4µ and 6µ are known as silt generating particles which clog small orfices and build up around valve spools and bores causing them to stick. Particles 16µ and above are known as wear particles and cause premature wear by abrasion leading to component failure.
