The filtration accuracy standards for industrial oils (such as lubricating oil, hydraulic oil, and transformer oil) depend on the oil type, equipment requirements, and operating conditions. Filtration accuracy is typically expressed in microns (μm), and different application scenarios have specific requirements for cleanliness (ISO 4406 or NAS 1638 standards) and particulate matter control. The following are the filtration accuracy standards and applicable scenarios for common industrial oils:

1. General-purpose lubricants (gear oil, bearing oil, etc.)

- Filtration accuracy:

- General lubrication systems: 10-25μm

- Precision lubrication systems (e.g., high-speed bearings, turbines): 3-10μm

- Cleanliness standard: ISO 4406 16/14/12 or higher (depending on equipment requirements)

2. Hydraulic oil (high-pressure/precision hydraulic systems)

- Filtration accuracy:

- General hydraulic systems: 10-25μm

- High-pressure hydraulic systems (servovalves, proportional valves): 3-5μm (or even 1-3μm)

- Cleanliness standard:

- ISO 4406 15/13/10 (general systems)

- ISO 4406 13/11/8 (precision systems, such as aviation and injection molding machines)

3. Transformer Oil (Insulating Oil)

- Filtration Refinement:

- Conventional Purification: 5-10μm (Removes moisture and particles)

- Ultra-Purification (UHV Transformer): 1-3μm

- Cleanliness Standard:

- Particle count ≤ 1000/100mL (≥ 5μm), Moisture ≤ 10ppm (GB/T 7595)

4. Turbine Oil (Steam Turbine Oil)

- Filtration Refinement: 5-10μm

- Cleanliness Standard: ISO 4406 14/12/9 (Higher requirements for high-precision units)

5. Compressor Oil (Air Compressor Oil)

- Filtration Refinement: 10-15μm

- Cleanliness Standard: ISO 4406 16/14/12

6. Metalworking Fluid (Cutting Oil, Emulsion)

- Filtration Refinement:

- Coarse Filtration: 25-50μm (chip removal)

- Fine Filtration: 5-10μm (extends tool life)

Key Standard References

1. ISO 4406: Internationally recognized standard for oil cleanliness levels (e.g., 18/16/13 indicates particle counts of varying sizes).

2. NAS 1638: American aerospace standard, commonly used in high-precision hydraulic systems (e.g., NAS Level 5 requires extremely low particle counts).

3. GB/T 14039: Chinese standard for hydraulic oil cleanliness levels (equivalent to ISO 4406).

Notes on Selecting Filter Fineness

- Equipment Manufacturer's Requirements: Prioritize the cleanliness specifications in the equipment manual (e.g., hydraulic servo valves typically require ≤5μm).

- Oil Contamination Level: Highly contaminated oils require coarse filtration (e.g., 20μm) first, then gradually increase the fineness.

- Filter Element Type:

- Depth filters (e.g., glass fiber) are suitable for high-precision filtration.

- Surface filter elements (metal mesh) are suitable for intercepting large particles.

Example Applications

- Wind turbine gearbox lubricant: Filtration accuracy 3-5μm, ISO 4406 14/12/9.

- Construction machinery hydraulic oil: Filtration accuracy 10μm, ISO 4406 17/15/12.

For specific data, it is recommended to consult the equipment specifications or the oil supplier's recommended values for final confirmation.