How to Clean and Maintain the Lubrication Oil Filtration System

This guide applies to lubrication oil filtration systems for grinding mill gearboxes, bearings, and main drive units—including duplex filters, cartridge filters, oil coolers, oil pumps, pipelines, and pressure control components.

Core Purpose

Maintain clean lubricating oil, remove metal wear debris, sludge, moisture, and dust; ensure stable oil flow and pressure; prevent filter clogging, bypass valve opening, and contaminated oil from damaging gears and bearings.

1. Safety Preparation

1. Follow lockout-tagout (LOTO) for the lubrication pump, motor, and control circuit.
2. Wear oil-resistant gloves, safety goggles, and protective clothing.
3. Prepare clean oil collection pans, lint-free rags, and sealed containers for waste oil.
4. For systems in graphite/powder mills: avoid dust entering the oil circuit during disassembly.

2. Pre-Maintenance Inspection

Before cleaning, check these key indicators:

• Differential pressure (ΔP) across filter: Normal ≤0.1–0.15 MPa; alarm threshold usually 0.2 MPa.
• Oil flow rate, supply pressure, and return pressure stability.
• Leakage at flanges, filter housings, and pipe joints.
• Bypass valve status (must remain closed under normal conditions).
• Oil appearance: cloudiness (moisture), dark discoloration (oxidation), visible particles.

3. Step-by-Step Cleaning & Maintenance

3.1 Filter Element (Cartridge) Maintenance

The filter cartridge is the core component and requires regular replacement/cleaning:

1. Close the inlet/outlet ball valves of the filter group.
2. Slowly loosen the vent plug to release pressure, then open the filter housing.
3. Remove the filter cartridge carefully to avoid dropping debris into the housing.

• Disposable filter cartridges: Replace directly when ΔP exceeds the limit or service life expires.
• Washable metal mesh / wire mesh filters:
  • Soak in clean diesel or kerosene for 10–15 minutes.
  • Gently brush with a soft brush; blow clean with low-pressure compressed air (0.2–0.3 MPa) from inside to outside.
  • Discard if mesh is broken, deformed, or permanently clogged.

1. Inspect the filter housing gasket; replace if hardened, cracked, or leaking.

3.2 Filter Housing & Chamber Cleaning

1. Use lint-free cloths to wipe inner walls of the housing.
2. Remove sludge, metal chips, and sediment at the bottom.
3. Flush with a small amount of clean lubricating oil and drain completely.
4. Ensure no residual cleaning solvent remains inside.

3.3 Oil Pipeline Cleaning

1. Check for oil sludge, coking, or deposits in main supply/return lines.
2. For light blockage: circulate clean flushing oil at low speed for 1–2 hours.
3. For heavy contamination: disconnect pipes and flush with clean oil or compressed air.
4. Retighten all flange bolts and replace aged sealing gaskets.

3.4 Oil Pump & Strainer Cleaning

1. Remove the inlet strainer of the gear pump or screw pump.
2. Clean debris with kerosene and compressed air.
3. Inspect pump gears/rotors for wear; check shaft seals for leakage.
4. Lubricate pump bearings if required.

3.5 Oil Cooler Cleaning

1. Clean external dust (especially for air-cooled coolers) with compressed air.
2. For water-cooled coolers:
   • Clean scale and sludge in water channels with descaling agent.
   • Check for oil-water mixing (sign of tube leakage).
3. Verify heat exchange efficiency by monitoring oil inlet/outlet temperature.

3.6 Control Components & Instruments

1. Clean differential pressure gauges, pressure transmitters, and temperature sensors.
2. Test the bypass valve: ensure it opens only at set pressure and closes tightly.
3. Calibrate pressure switches and alarm signals if necessary.

3.7 Oil Tank & Breathing Filter Maintenance

1. Clean the tank bottom sediment and sludge during periodic oil changes.
2. Replace or clean the air breather filter (desiccant type for dusty mills) to prevent moisture and dust intake.
3. Check the oil level indicator for blockage or fogging.

4. Post-Maintenance Commissioning

1. Reinstall all components and tighten connections.
2. Vent air from the filter housing and top pipelines.
3. Start the lubrication pump at low speed and check for leaks.
4. Run the system for 15–30 minutes and monitor:
   • Filter differential pressure
   • Oil supply pressure and flow
   • No abnormal noise or overheating
5. Confirm the bypass valve remains closed during normal operation.

5. Recommended Maintenance Frequency

• Daily: Check filter differential pressure, oil pressure, and leakage.
• Weekly: Inspect breather filters; clean surface dust.
• Monthly: Clean pump inlet strainers; check filter status.
• Quarterly: Clean or replace filter cartridges; inspect pipelines.
• Semi-annually: Full system flushing; clean oil cooler and tank.
• Annually: Overhaul valves, sensors, and pump parts during major maintenance.

6. Common Troubleshooting

7. Key Best Practices

1. Never run the system with a missing or damaged filter element.
2. Use matching-grade filter cartridges to avoid bypass or insufficient filtration.
3. Perform oil sampling analysis regularly to decide cleaning intervals.
4. Keep the workshop dust-controlled to reduce filtration load.
5. Record differential pressure trends to predict clogging and avoid unplanned shutdowns.