Turbine lubricating oil filtration accuracy

The filtration accuracy of turbine oil (lubricating oil) is a key parameter to ensure the cleanliness of the oil and reduce equipment wear. The following are the key standards and recommendations for turbine oil filtration accuracy:

1. Filtration accuracy level

The turbine oil system usually adopts a combination of main filtration + bypass fine filtration to meet the needs of different working conditions:

- Main system filtration (online filtration):

- Accuracy: 5–10 μm (β₅≥200, that is, the filtration efficiency of 5μm particles is ≥99.5%).

- Function: Protect the main components, such as oil pumps and bearings, and intercept most particulate pollutants.

- Bypass fine filtration (offline or circulation filtration):

- Accuracy: 1–3 μm (β₃≥200).

- Function: Deeply purify the oil and extend the life of the oil product. It is suitable for units with high precision requirements (such as gas turbines).

2. Cleanliness standard (ISO 4406)

The cleanliness of turbine oil usually needs to meet the following requirements:

- New oil: ≤ ISO 16/14/11 (corresponding to NAS level 6).

- Operating oil: ≤ ISO 18/16/13 (NAS level 8), some high-pressure units have higher requirements (such as ISO 15/13/10).

> Note: Gas turbines usually have stricter requirements than steam turbines (such as ISO 14/12/9).

3. Key influencing factors

- Oil viscosity: High-viscosity oil (such as ISO VG 68) needs to be preheated to 40–60°C to reduce viscosity and improve filtration efficiency.

- Filter element type:

- Choose glass fiber or multi-layer composite filter elements, which are resistant to high temperature and oil corrosion.

- Avoid cellulose filter elements (easy to absorb moisture, resulting in excessive moisture).

- System design: The bypass filter flow rate is recommended to be 5–10% of the total system oil volume.

4. Maintenance recommendations

- Regular inspection: Monitor particle contamination (such as ISO 4406), moisture (≤100ppm) and viscosity every 3 months.

- Filter element replacement: ｒｅｐｌａｃｅ immediately when the pressure difference exceeds 0.15–0.2 MPa or the contamination alarm occurs.

- Vacuum dehydration: If the moisture exceeds the standard (＞ 100 ppm), fine filtration and vacuum dehydration treatment must be combined.

Note: The specific accuracy needs to be adjusted according to the requirements of the equipment manufacturer, the degree of oil aging and the operating conditions (such as high temperature, high load). Regular oil analysis is recommended to optimize the filtration solution.