Oil purity according to ISO 4406 18/16/13…how do I achieve this?
Manufacturers of hydraulic components usually require a cleanliness class according to ISO 4406 for the operation of their components. This information can usually be found on the product data sheets. If this is not the case, you should contact the manufacturer.
Only if the cleanliness class is maintained can the affected component perform its function properly and reliably. Depending on the application and component, this can have safety-related consequences; a machine downtime due to a defective valve or a defective pump can be very expensive.
A common specification for proportional valves is e.g: “Oil purity according to ISO 4406 (1999) 18/16/13, filter with ß5 > 200″ but what does this mean?
Information about the purity classes according to ISO 4406 and how they are made up can be found here Contribution .
The specification ß5> 200 is to be understood as follows:
The ß value (beta value) according to ISO 16889 is the key parameter for the separation performance of the filter. This value indicates the ratio of particles before and after the filter (Nbefore/Nafter).
βx = Nbefore / Nafter (the x stands for the filter fineness in µm)
ß5> 200 means that out of 1000 particles with a size of 5µm only five particles pass through the filter (1000/200=5). This corresponds to a separation efficiency of 99.5%. The particles that are not retained by the filter enter the circuit and can thus be retained by the filter material during the next filter pass.
Other important features of a filter are the dirt holding capacity (DHC-dirt-hold capacity) and the differential pressure Delta-p. A high dirt holding capacity with a small differential pressure is desirable.
Manufacturers of filters and filter elements offer appropriate design programs for optimal filtration design and can also make recommendations depending on the component and application.
Oil purity is crucial for the safe, long-term and cost-effective operation of a hydraulic system and this can only be ensured with the right filtration. Even fresh oil does not always meet the required purity class according to ISO 4406; there are special filter units (oil service devices) for filling the tank.
Recommended filter ratings
| Group | Component | ISO 4406 Code | Recommended filter fineness |
| PumpsPiston | pump (slow running) | 22/20/16 | 20 µm |
| Gear pump | 19/17/15 | 20 µm | |
| Vane pump | 18/16/14 | 5 µm | |
| Piston pump (fast running) | 17/15/13 | 5 µm | |
| Motors | Gear motor | 20/18/15 | 20 µm |
| Vane motor | 19/17/14 | 10 µm | |
| Radial piston motor | 19/17/13 | 10 µm | |
| Axialkolbenmotor | 18/16/13 | 5 µm | |
| Valves | Directional valve | 20/18/15 | 20 µm |
| Shut-off valve | 20/18/15 | 20 µm | |
| Logic valve | 20/18/15 | 20 µm | |
| Built-in valve | 20/18/15 | 20 µm | |
| Pressure control valve | 19/17/14 | 10 µm | |
| Flow control valve | 19/17/14 | 10 µm | |
| Proportional valve | 18/16/13 | 5 µm | |
| Servo valve <210 bar | 16/14/11 | 3 µm | |
| Servo valve <210 bar | 15/13/10 | 3 µm | |
| Drive | Cylinder | 20/18/15 | 20 µm |
Praise, criticism or questions?
Please feel free to contact us, we look forward to your feedback!
lars.benk@schuhmacher-tech.de ; +49 7424/9495-663
Lars Benk: Profile of a field-tested expert
Basic training: Tool mechanic, specializing in stamping and forming technology.
Further training: State-certified technician with a focus on mechanical engineering.
Additional qualification: Degree in technical business administration, combining technical know-how with business expertise.
Professional experience: More than a decade of active work in the field of hydraulics.
Specialization: Certified specialist in oil analysis (MLA II – Machine Lubrication Specialist), with a specific focus on the maintenance and optimization of machines through professional lubricant analysis. Certified specialist for hydraulic fluids – specialist knowledge for optimal hydraulic systems.
