Iso Cleanliness Code
Why does ISO 4406 use three numbers?
It consolidates the full particle-size distribution into a concise code for ≥4, ≥6, and ≥14 µm, enabling standardized reporting across industries.
How does a code of 22/18/13 translate to particle counts?
It means 20,000–40,000 particles/mL (≥4 µm), 1,300–2,500 particles/mL (≥6 µm), and 40–80 particles/mL (≥14 µm).
What is the impact of lowering the code by one digit?
The contaminant level is cut in half; increasing by one digit doubles the particle count.
Does ISO 4406 distinguish particle types?
No; it only quantifies quantity, not type (e.g., metal vs. dust), requiring additional analysis for root-cause identification.
The ISO Cleanliness Code (ISO 4406:1999/2017) is a universal standard for quantifying particulate contamination in lubricants and hydraulic fluids. It is expressed as a three-number code (e.g., 19/17/14) representing particle counts per milliliter for sizes ≥4 µm, ≥6 µm, and ≥14 µm, enabling standardized reporting across industries.
On the shop floor, the ISO Cleanliness Code is used to set target cleanliness levels for sensitive components like hydraulic pumps and bearings, track fluid degradation via oil analysis, and validate filtration effectiveness. Each code increment represents a doubling of particle count, while a decrement represents a halving. This standard helps maintenance teams ensure equipment reliability and prevent wear by monitoring and controlling contamination levels in lubricants and hydraulic fluids.
Accepting 'new' oil as clean: Bulk lubricants often arrive at 19/17/15 or higher, causing immediate wear if not filtered before use.
Ignoring the 4 µm and 6 µm counts: Focusing only on the 14 µm number misses the majority of damaging particles (2–15 µm range) that cause abrasive wear.
No targeted cleanliness goals: Operating without component-specific targets (e.g., running 22/21/19 oil in a system requiring 16/14/11) leads to shortened asset life and unpredictable breakdowns.