The ISO 4406 rating of solid contamination, written like 18/16/13. Each number is a range code for the count of particles per mL at or above 4, 6 and 14 microns, and each step up roughly doubles the count. Servo hydraulics typically target 15/13/10 or cleaner, while gearboxes tolerate around 19/17/14. New oil out of the drum often arrives dirtier than the target, which is why filter carts and kidney loops exist.
ISO cleanliness code on the press came back 22/20/17 against a 17/15/12 target, get the filter cart on it.
Dropping two codes roughly quarters the particle count, and bearing and pump makers credit that kind of cleanup with large gains in component life.
Also heard as
- ISO code
- ISO 4406
- cleanliness code
Related terms
Particle count
Count of solid particles per volume of oil, sorted by size, used to track dirt and wear debris.
Kidney loop
Off-line filtration circuit that continuously pumps reservoir oil through a filter and back.
Abrasive wear
Wear caused by hard particles or hard surface peaks plowing and cutting through a softer surface.
Desiccant breather
Vent filter packed with drying beads that cleans and dries the air a gearbox or tank breathes in.