Understanding ISO 4406: Oil Cleanliness Standards Explained | LUWATECH Blog
ISO 4406 is the core international standard for oil cleanliness in hydraulic and lubrication systems. This guide explains code interpretation, measurement methods, and real-world applications.
What is ISO 4406?
ISO 4406 is the international standard for classifying the cleanliness level of oil used in hydraulic and lubrication systems. It uses a three-number code representing the concentration of solid particles at different sizes, providing a universal language for specifying and measuring fluid cleanliness.
Understanding the Cleanliness Code
An ISO 4406 code like 18/16/13 breaks down as:
- First number: Scale number for particles ≥4μm per milliliter
- Second number: Scale number for particles ≥6μm per milliliter
- Third number: Scale number for particles ≥14μm per milliliter
The lower the number, the cleaner the fluid.
Cleanliness Requirements by Industry
| Application | Recommended ISO 4406 |
|---|---|
| Aerospace hydraulics | 13/11/8 or better |
| Precision servo hydraulics | 15/13/10 |
| Industrial hydraulics | 18/16/13 |
| Gearbox lubrication | 19/17/14 |
| Engine lubricating oil | 20/18/15 |
How to Measure Cleanliness
Particle counters like the LUWATECH LWB-6 and LWL-3 series directly measure particle distribution in oil samples and automatically calculate the ISO 4406 code. Portable units are ideal for field testing; online units enable 24/7 continuous monitoring.
Recommended LUWATECH Products
- Field testing: LWB-6 Portable Particle Counter
- Online monitoring: LWL-3 Online Particle Counter
- Lab analysis: LWT-2A Desktop Particle Counter