Lubricating oil purifier filtration accuracy grade

The filtration accuracy level of lubricating oil is a key indicator of the performance of the oil filter. It is usually expressed in microns (µm) to measure the size of particles that the filter element can intercept. The following are common filtration accuracy levels and their application scenarios:

Classification according to ISO 4406/SAE AS4059 standards

- Coarse Filtration

- Accuracy range: 30µm ~ 100µm

- Application: Pre-filtration stage, protect downstream equipment, remove large particle impurities (such as metal debris, dust).

- Typical equipment: primary filtration of industrial gearboxes and heavy machinery.

- Medium Filtration

- Accuracy range: 10µm ~ 25µm

- Application: Maintenance filtration of general industrial lubricating oils (hydraulic oils, circulating oils) to extend oil life.

- Fine Filtration

- Accuracy range: 3µm ~ 5µm

- Application: high-precision hydraulic systems (such as servo valves, turbines), key equipment lubrication systems.

- Ultra-fine Filtration

- Accuracy range: 0.5µm ~ 1µm

- Application: aviation hydraulic oil, turbine oil, high cleanliness requirements (such as semiconductor equipment).

Rating by β value (filtration ratio)

- βₓ value: indicates the filtration efficiency of the filter element for particles of a specific particle size (such as β₃=200, indicating that the filtration efficiency for 3µm particles is 99.5%).

- β≥75: high-efficiency filter element (corresponding to ISO 16889 standard).

- β≥200: ultra-high-efficiency filter element (commonly used in critical systems).

Industry standard reference

- ISO 4406: defines particle contamination levels based on oil cleanliness codes (such as 18/16/13).

- NAS 1638: American aerospace standard, divided into 14 levels (such as NAS Class 6 represents the limit of the number of particles in every 100ml of oil).

- SAE AS4059: Common standard for automotive and aviation hydraulic systems.

Oil filter type and precision matching

- Plate and frame oil purifier: usually 10µm~50µm, used for coarse filtration.

- Vacuum oil purifier: can be combined with 1µm~5µm fine filtration, suitable for simultaneous removal of moisture and particles.

- Coalescing separation oil purifier: for moisture and particles (such as 1µm~10µm).

- Electrostatic oil purifier: can handle submicron particles (<0.1µm).

Selection recommendations

- Hydraulic system: 3µm~5µm (ISO 15/13/11) is recommended.

- Turbine oil: 1µm~3µm is recommended (NAS Class 6 or below).

- Gearbox oil: 10µm~25µm (adjusted according to wear conditions).

Note: The higher the filtration accuracy, the better. You need to balance the oil viscosity, system pressure, flow requirements and cost. High-precision filtration may increase the pressure difference and shorten the filter life. It is necessary to cooperate with pollution monitoring (such as a particle counter) to optimize the maintenance cycle.