Suitable for graphite grinding mills, ball mills, Raymond mills and other powder grinding equipment
The mill ventilation system mainly includes exhaust fan, air duct, dust collector (filter bag/cartridge), air lock valve, dampers, pressure measuring points and sealing parts.
Inspection focuses on airflow, pressure, blockage, wear and dust leakage; cleaning aims to remove accumulated graphite/powder dust to restore ventilation efficiency, avoid overpressure, dust emission and equipment overheating.
1. Safety Preparation Before Inspection & Cleaning
- Implement lockout–tagout (LOTO) for the fan motor, dust collector and related electrical controls.
- Wear full PPE: dust mask/respirator, safety goggles, anti-static gloves, protective clothing.
- Ensure the workshop is well-ventilated; avoid open flames (especially for graphite dust, which is combustible).
- Stop mill feeding and run the system idle for 10–15 minutes to reduce internal dust concentration.
2. Step-by-Step Inspection of the Ventilation System
2.1 Overall System Performance Check
- Measure negative pressure at the mill inlet/outlet and dust collector inlet (normal range: -0.5 to -2.0 kPa, varies by model).
- Abnormally low negative pressure = blockage; excessively high pressure = filter clogging or air leakage.
- Listen for abnormal noise from the fan (rubbing, shaking) indicating impeller imbalance or bearing wear.
- Check for dust leakage at flanges, inspection doors, flexible connections and discharge valves.
2.2 Key Component Inspection
| Component | Inspection Items | Judgment Standard |
|---|---|---|
| Exhaust Fan | Impeller dust buildup, blade deformation, bearing temperature, loose bolts | No obvious dust accumulation; bearing temp <70°C; no vibration |
| Air Duct | Internal blockage, dents, corrosion, loose flanges | Smooth airflow path; no visible powder buildup >5 mm |
| Dust Collector | Filter bag/cartridge damage, wear, glue failure; ash hopper blockage | No breakage or air permeability; ash discharges smoothly |
| Air Lock Valve (Rotary Airlock) | Sealing wear, jamming, uneven rotation | No dust leakage; rotates evenly without abnormal sound |
| Dampers & Valves | Flexible adjustment, scale buildup, poor sealing | Opens/closes smoothly; no air leakage |
| Pressure & Temperature Sensors | Damage, blockage, abnormal readings | Calibrated readings; no dust covering probes |
3. Standard Cleaning Procedure
3.1 General Rules
- Clean from upstream to downstream (mill → duct → dust collector → fan).
- Use low-pressure compressed air (0.2–0.4 MPa) or soft brushes; avoid high-pressure washing to prevent dust diffusion and component rust.
- Collect cleaned dust in sealed containers to avoid secondary pollution.
3.2 Detailed Cleaning Steps
- Clean Air Ducts
- Open duct inspection ports; use scrapers to remove thick dust deposits.
- Blow out residual powder with compressed air, moving from the mill end toward the dust collector.
- Wipe flanges and sealing surfaces; replace worn gaskets if needed.
- Clean the Fan Impeller & Casing
- Remove the fan inspection cover; brush off graphite dust on blades and inner casing.
- For heavy buildup, use a wooden or plastic scraper (do not use metal tools to avoid blade damage).
- Check dynamic balance after cleaning; rebalance if vibration increases.
- Clean Dust Collector & Filters
- For bag filters: Implement pulse jet cleaning first; remove and gently beat bags if heavily clogged.
- For cartridge filters: Clean with low-pressure air from inside out; replace torn or permanently clogged filters.
- Empty ash hoppers completely; check for bridging or caking and break it up manually.
- Clean Air Lock Valve & Dampers
- Disassemble the airlock to clean dust between vanes and housing.
- Lubricate bearings after cleaning.
- Remove dust from damper blades and ensure they move freely.
- Clean Sensors & Ventilation Openings
- Wipe pressure nozzles and temperature probes with clean cloth.
- Clear blockages at fresh air inlets and exhaust outlets.
4. Post-Cleaning Commissioning & Verification
- Close all inspection doors and tighten flanges to restore sealing.
- Remove LOTO and run the ventilation system idle for 15–20 minutes.
- Check:
- Normal negative pressure value restored
- No dust leakage
- Fan runs smoothly without abnormal noise or vibration
- Dust collector discharges ash normally
- Record pressure difference before/after cleaning to evaluate cleaning effect.
5. Recommended Maintenance Frequency
- Daily: Visual check for dust leakage, observe pressure gauge stability.
- Weekly: Brief cleaning of ash hoppers, simple air purging of filters.
- Monthly: Comprehensive cleaning of ducts, fan impeller and filter elements.
- Quarterly: Full disassembly inspection, replace damaged seals/filters.
- Annually: Overhaul of the fan, airlock valve and entire duct system.
6. Common Troubleshooting
- Poor ventilation / Low negative pressure: Duct blockage or filter clogging → clean ducts and replace filters.
- Dust leakage at flanges: Poor sealing or loose bolts → retighten or replace gaskets.
- Fan vibration: Dust buildup on impeller → clean and rebalance.
- High discharge dust concentration: Damaged filter bags → replace immediately.
