Turbine oil filtration accuracy standard

The filtration accuracy standard of turbine oil (turbine oil) needs to be determined according to the equipment type, operating conditions and international/industry specifications. The core goal is to protect precision components (such as bearings, speed control systems) and extend the life of the oil. The following are the classification standards and technical points:

General filtration accuracy standards

1. New oil injection standards

- Particle size:

- ISO 4406: ≤16/14/12 (corresponding to NAS 1638 Class 6)

- ASTM D4378: ≤5,000 particles >5μm in 100mL oil sample

- Moisture: ≤100ppm (new oil) or ≤200ppm (operating oil, ASTM D6304)

2. In-service oil maintenance standards

| System type | Target cleanliness (ISO 4406) | Filtration accuracy requirements |

|--------------------|--------------------------|----------------------|

| Ordinary steam turbine | ≤15/13/11 | β≥200 (particles ≥3μm) |

| Gas-steam combined cycle | ≤14/12/10 | β≥1000 (particles ≥1μm) |

| Nuclear power turbine | ≤13/11/9 | Absolute filtration 1μm |

Analysis of key parameters

1. Filtration ratio (β value)

- Definition: βₓ=upstream particle number/downstream particle number (such as β₂₀₀=200 means the interception efficiency of 3μm particles is ≥99.5%).

- Recommended value:

- Main oil circuit: β≥200 (3μm)

- Servo system: β≥1000 (1μm)

2. Moisture control

- Free water: centrifugal separation or coalescing filter treatment to ≤ 50 ppm.

- Dissolved water: vacuum dehydration to ≤15ppm (nuclear power requires ≤10ppm).

Filter equipment selection

1. Offline oil filter (regular maintenance)

- Model example:

- Pall HCP series: β₅₀₀=500 (1μm), integrated vacuum dehydration.

- Hy-Pro RFT series: electrostatic adsorption + β₂₀₀ filtration, moisture ≤25ppm.

- Flow matching: ｓｅｌｅｃｔ according to 10%~20% of the system oil volume (such as 1~2m³/h equipment for a 10m³ oil tank).

2. Online filter (continuous protection)

- Recommended accuracy:

- Main circulation: 3μm absolute filtration (β≥200)

- Bypass: 1μm absolute filtration (β≥1000)

- Brand: Donaldson, Sofima (with differential pressure alarm function).

Comparison with industry standards

| Standards/Specifications | Applicable scenarios | Key requirements |

|---------------------|---------------------------|-----------------------------|

| ISO 4406 | Internationally used | Particle count classification (such as 14/12/10) |

| ASTM D4378 | US power industry | 5μm particle limit |

| DIN 51515 | German steam turbine manufacturer (Siemens) | Moisture ≤50ppm, cleanliness ≤14/12 |

| GB/T 14541 | China power industry | Operating oil particle size ≤NAS 1638 level 8 |

Operation precautions

1. Filter in stages:

- First coarse filtration (10μm) → then fine filtration (1~3μm) to avoid filter element clogging.

2. Temperature control:

- The oil temperature is maintained at 40~60℃ during filtration (optimal viscosity range).

3. Monitoring frequency:

- Particle size: once a month (online monitoring can be real-time).

- Moisture: once a quarter (dew point method or Karl Fischer method).

Typical faults and filtering countermeasures

| Problem phenomenon | Possible cause | Filtration solution |

|---------------------|---------------------|-----------------------------|

| Abnormal bearing wear | Metal particle contamination | Upgrade to β≥1000 (1μm) filter |

| Speed control system stuck | Colloid/water content exceeds the standard | Vacuum oil filter + electrostatic adsorption |

| Sludge deposition | Oxidation product accumulation | White clay filtration or centrifugal separation |

Economic suggestion

- Filter element cost:

- 3μm filter element: ￥500~1500/piece (lifespan is about 2000 hours)

- 1μm filter element: ￥2000~4000/piece (lifespan is about 1000 hours)

- Energy consumption comparison:

- Offline vacuum oil filter: 0.8~1.5kW·h/m³

- Online bypass filtration: 0.2~0.5kW·h/m³

Following the above standards can ensure the cleanliness of turbine oil and reduce the equipment failure rate by more than 30% (such as GE statistical cases). For E-class/F-class gas turbines, it is recommended to use centrifugal separation (water removal) + β≥1000 filtration (particle removal) in combination to achieve the best effect.