The role of turbine oil filtration system

The turbine oil filtration system is a core component to ensure the stable operation of key equipment such as steam turbines and gas turbines. Its role is not limited to simple impurity removal, but to control the oil quality in multiple dimensions to ensure the reliability of the unit under high temperature, high pressure and high speed conditions. The following is a detailed analysis of the role of the turbine oil filtration system:

Core functions

1. Particle contamination control (key protection)

- Mechanism of action:

- Filter out hard contaminants such as metal wear particles (such as bearing alloy chips), sealing material debris, and pipeline rust.

- Prevent particles from entering the bearing oil film (≤5μm particles can cause bearing scratches).

- Technical indicators:

- ISO 4406 standard requirements: During normal operation, the oil cleanliness must be maintained at ≤15/13/10 (corresponding to the number of particles: 4μm/6μm/14μm).

- High-end fields such as nuclear power require ≤12/10/8.

2. Water removal (anti-emulsification protection)

- Hazards:

- When the water content is greater than 500ppm, the oil film strength decreases by 40%, causing hydrogen-induced cracking (HIC).

- Reacts with additives to generate acidic substances, accelerating sludge formation.

- Solutions:

- The vacuum dehydration system reduces the water content to ≤100ppm (ASTM D6304).

- Coalescing separator treats free water (applicable to turbine oil water content greater than 1000ppm).

3. Gas management (anti-cavitation)

- Risk points:

- When the dissolved air content is greater than 8% (volume ratio), the oil pump is prone to cavitation.

- Excessive foaming causes oil tank overflow and pressure fluctuations in the lubrication system.

- Control measures:

- The vacuum degassing tower controls the gas content to ≤0.5% (ISO 9120).

- Addition of defoaming agent (concentration of silicone defoaming agent ≤10ppm).

 Extended functions

1. Extended oil life

- Oxidation inhibition:

- The filter system integrates a temperature sensor (＞65℃ triggers an alarm) to avoid thermal oxidation.

- Electrostatic adsorption filters remove oxidized colloidal particles <1μm.

- Acid value control:

- Online TAN (total acid value) monitoring, combined with an alkali value filter to maintain TAN≤0.3mg KOH/g.

2. System energy efficiency optimization

- Viscosity adjustment:

- Constant temperature filtration (40±2℃) maintains ISO VG32/46 viscosity ±10% deviation.

- Reduce energy loss caused by abnormal viscosity (such as gearbox efficiency can ｄｒｏｐ by up to 15%).

3. Intelligent early warning

- Status monitoring:

- Pressure differential sensor (ΔP＞0.15MPa prompts filter element replacement).

- Online particle counter uploads data to the DCS system in real time.

Operation and maintenance points

1. Filter element selection:

- Glass fiber filter element (temperature resistance 120℃) is used on the high pressure side.

- Stainless steel sintered filter element is used in the start-up phase of gas turbine (resistance to high shear force).

2. Flushing specification:

- Oil system circulation flushing is required before the new unit is put into operation:

- Reach NAS level 5 cleanliness (≤1600 particles of >5μm in every 100ml of oil).

- Use temporary high-gradient magnetic filter (magnetic field strength ≥1T).

3. Fault emergency:

- Automatically switch to standby filter when pressure difference rises suddenly (switching time <2s).

- Excessive water content triggers bypass adsorption tank (instantaneous processing capacity of molecular sieve 10L/min).

Economic benefit analysis

- Typical case: After a 600MW steam turbine adopts a three-stage filtration system:

- The bearing replacement cycle is extended from 3 years to 5 years.

- Annual oil consumption is reduced by 35% (reduced oil replenishment).

- The number of unplanned shutdowns is reduced by 80%.

The turbine oil filtration system is a comprehensive solution that integrates mechanical protection, chemical stability, and condition monitoring. Modern systems have developed predictive maintenance functions, which can provide early warning of potential failures through oil quality trend analysis, becoming an indispensable part of smart power plants. During operation and maintenance, special attention should be paid to the balance between filtration accuracy and system pressure ｄｒｏｐ to avoid energy waste caused by excessive filtration.