Graphite dust is fine, conductive, cohesive, and combustible, so bag filter maintenance must focus on preventing clogging, static buildup, dust explosions, and moisture-induced caking. Below is a complete, site-practical procedure for cleaning and upkeep.
1. Pre-Maintenance Safety Rules (Non-Negotiable)
- Lockout / Tagout (LOTO)Cut off power to the fan, pulse-jet system, and control cabinet; hang safety tags to prevent accidental startup.
- Pressure ReleaseFully release air pressure in the compressed air bag and pipeline before opening the inspection door.
- PPE RequirementsWear anti-static coveralls, N95+/P100 respirator, anti-static gloves, safety goggles, and anti-static shoes.
- Explosion PreventionNo open flames, no friction sparks; use only explosion-proof vacuum cleaners; ensure all equipment is reliably grounded.
- Humidity CheckKeep workshop relative humidity 40%–55% to avoid static or dust caking.
2. Daily & Shift Maintenance (No Shutdown Required)
Do these every 8-hour shift to keep the filter stable:
- Check differential pressure (normal range: 800–1500 Pa)
-
1500 Pa: bag clogging → shorten pulse cleaning interval
- <500 Pa: possible bag damage or air leakage → inspect immediately
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- Monitor pulse-jet cleaning system:
- Compressed air pressure: 0.4–0.6 MPa (optimal for graphite)
- Check for damaged solenoid valves, blocked nozzles, or air leaks
- Empty dust hopper completely (no graphite accumulation)Graphite dust may self-heate if piled too long; avoid bridging/caking.
- Visually inspect discharge pipes and observation windows for dust leakage.
3. Regular Bag Filter Cleaning (Shutdown Required)
3.1 Weekly Light Cleaning
- Start automatic pulse cleaning continuously for 10–15 minutes to remove surface graphite dust.
- Use an explosion-proof vacuum to clean ash hoppers, air chambers, and pulse valves.
- Wipe the control panel and pressure sensors with a dry cloth.
3.2 Monthly Deep Cleaning (Full Bag Maintenance)
- Open the top cover and clean the upper box and tube sheet with an explosion-proof vacuum.
- Inspect each filter bag one by one:
- Gently pat or use low-pressure compressed air (≤0.3 MPa) to blow from inside to outside
- Never use high-pressure air directly → breaks fibers; never wash with water → causes graphite caking
- Clean the pulse-jet pipes and nozzles to remove graphite buildup.
- Check and tighten all seals, door latches, and flanges to stop air leakage.
3.3 Quarterly Overhaul Cleaning
- Remove filter bags (handle gently to avoid tearing).
- Deep clean bags with dry cleaning only (industrial dust removal station or low-pressure air cleaning).
- Clean the box interior, support cages, and ash hopper thoroughly.
- Inspect and maintain the ash discharge device (air lock/rotary valve).
- Calibrate differential pressure transmitters and temperature/humidity sensors.
4. Filter Bag Inspection & Replacement Standards
Replace bags immediately if any of the following occur:
- Breakage, holes, or fraying edges → direct dust discharge
- Permanent caking/clogging that cannot be cleaned by pulse-jet
- Aging, hardening, or loss of air permeability
- Differential pressure remains high (>1800 Pa) after cleaning
- Conductive damage (graphite is conductive; damaged static-resistant bags cause safety risks)
Recommended Bag Material for Graphite
- Anti-static polyester filter bag (conductive fiber)
- PTFE membrane laminated bags for fine graphite (≥1000 mesh)
- Service life: 6–12 months under normal working conditions
5. Key Component Maintenance
5.1 Pulse-Jet Cleaning System
- Replace damaged solenoid valves, diaphragm, and gaskets promptly.
- Adjust cleaning cycle:
- Coarse graphite: 10–20 seconds
- Fine/ultrafine graphite: 5–10 seconds (more frequent cleaning)
- Drain water from the air compressor tank daily to avoid wet air causing bag caking.
5.2 Ash Hopper & Discharge System
- Install vibration motors or heating devices to prevent graphite bridging.
- Lubricate the rotary airlock valve monthly; check for air leakage and wear.
- Never allow graphite dust to accumulate over 1/3 of the hopper height.
5.3 Sealing & Earthing
- Check door seals, flange gaskets, and observation window seals weekly.
- Ensure the filter housing, bags, and ductwork have reliable grounding resistance ≤4Ω to eliminate static.
6. Common Troubleshooting
| Problem | Cause | Solution |
|---|---|---|
| High differential pressure | Bag clogging, too long cleaning interval, wet dust | Shorten pulse interval, dry compressed air, clean bags |
| Low differential pressure | Bag broken, air leakage, cage deformation | Replace bags, tighten seals, replace cages |
| Dust emission at outlet | Bag damage, poor sealing, cage burrs | Replace bags, repair seals, polish or change cages |
| Graphite caking on bags | High humidity, wet compressed air, insufficient cleaning | Control humidity, drain air compressor, increase pulse pressure |
| Pulse system not working | Diaphragm damage, blocked nozzles, low air pressure | Replace diaphragm, clean nozzles, adjust air pressure |
7. Long-Term Maintenance Tips
- Keep the filter interior above dew point to avoid condensation.
- After long shutdowns, run pulse cleaning for 10 minutes before restarting.
- Establish a maintenance log to record pressure, cleaning cycles, bag replacement, and failures.
- Do not mix different types of graphite powder to avoid quality cross-contamination.
