This procedure applies to full-plant emergency stops caused by power failure, fire, dust explosion risk, equipment failure (vibration, overheat, seizure), personal safety hazard, or manual emergency button (EPO) activation.
The core goal is: protect personnel first → prevent equipment damage → avoid dust explosion/secondary hazards → restore safely in sequence.
1. Precondition: Types of Full-Plant Emergency Stop
- Manual E-Stop: Operator presses the main emergency stop button (on control panel or field)
- Automatic Interlock E-Stop: Triggered by system alarms — fire, high dust concentration, severe vibration (>7 mm/s), motor overheat, coupling damage, belt breakage, gas detection, or main power loss
- Full Power Outage: Unplanned grid failure
2. Golden Rules for All Emergency Stops
- Personnel safety first: Evacuate the danger zone immediately; no inspection before confirming safety.
- No forced restart: Never reset E-stop and restart before identifying and eliminating the cause.
- Dust explosion prevention: Graphite powder is combustible — avoid secondary dust blowing, open flames, or static sparks.
- Preserve equipment: Avoid sudden restart shocks to vertical roller mill, gearbox, couplings, fans, and conveyors.
- Lockout-Tagout (LOTO): Apply electrical isolation before any inspection.
3. Step-by-Step Full-Plant E-Stop Handling
Stage 1: Immediate Response (0–3 minutes)
- Sound alarm & notify teamActivate the plant alarm, inform the control room, field operators, and maintenance team via radio.
- Personnel evacuation & isolationAll staff leave the grinding workshop, dust collection area, and conveyor corridors; cordon off the equipment zone.
- Confirm E-stop causeControl room checks: power failure? fire alarm? vibration trip? motor overcurrent? dust concentration alarm?
- Cut off main power (if safe)If fire, smoke, or electrical fault occurs, turn off the main incoming power switch to prevent short circuit or explosion.
Stage 2: System Shutdown Status Confirmation (3–10 minutes)
Check that all equipment has stopped safely (no rotation, no abnormal noise):
- Main drive: Motor, gearbox, vertical roller mill, grinding rollers
- Conveying system: Belt conveyors, screw conveyors, bucket elevators
- Air system: Fans, air classifier, dust collector fan, compressed air system
- Feeding system: Raw material silo discharge, metering feeders
- Dust control: Pulse jet cleaning, bag filter, spark extinguishing system
Stage 3: Hazard Elimination & Site Inspection (10–30 minutes)
Focus on high-risk points for graphite powder plants:
- Dust explosion checkInspect baghouse, pipes, and grinding room for accumulated dust, sparks, or smoldering.
- Equipment damage check
- VRM: Severe vibration → check grinding bed, rollers, couplings, bearings
- Fans/motors: Overheat → check coupling alignment, bearing temperature, winding
- Conveyors: Blockage, belt slip, or breakage
- Electrical checkCircuit breakers, cables, control cabinets for overheating, short circuit, or water ingress
- Blockage checkFeed pipes, air ducts, and discharge chutes for material clogging (common after sudden E-stop)
Stage 4: Reset & Preparation for Restart (Only After Fault Cleared)
- Release emergency stop buttons (control room + field)
- Reset tripped circuit breakers and interlock alarms
- Clean accumulated graphite powder to avoid secondary dust
- Manually rotate (if possible) VRM rollers, fans, and couplings to confirm no jamming
- Check lubrication oil levels, hydraulic pressure, and cooling system
Stage 5: Sequential Restart (Critical — No Simultaneous Full-Plant Start)
Restart in reverse order of normal production flow to prevent blockage and overload:
- Auxiliary systems firstCompressed air → lubrication system → cooling system → dust collector (baghouse)
- Air & conveying systemsMain fan → air classifier → discharge conveyors
- Grinding systemVertical roller mill (low speed idle first) → feeders (start with small feed rate)
- Gradual load increaseSlowly raise feed rate, fan speed, and grinding pressure to normal operating parameters
Stage 6: Post-Restart Monitoring (30–60 minutes)
Monitor:
- Vibration (<4.5 mm/s RMS)
- Bearing/motor temperature (<70°C)
- System pressure difference
- Dust collector pressure drop
- No abnormal noise or smell
4. Key Handling by Hazard Type
| Emergency Cause | Special Handling |
|---|---|
| Power failure | Do not restart immediately; wait 10–15 minutes for voltage stability; avoid voltage shock |
| Severe vibration | Check coupling alignment, bearing damage, grinding bed imbalance; clean accumulated material before restart |
| Fire / dust explosion risk | Stop all fans immediately (prevent oxygen supply); use powder fire extinguisher; do not use water |
| Motor/gearbox overheat | Isolate power; cool naturally; check lubrication and alignment before restart |
| Pipe blockage | Clear blockage manually; restart conveying first, then feeding |
5. Strict Prohibitions During E-Stop
- Do not touch rotating parts or open guards while equipment is coasting
- Do not restart without clearing alarms or blockages
- Do not start fans during a fire risk (avoids spreading flame/dust)
- Do not skip LOTO before inspection
- Do not increase feed rate rapidly after restart
6. Post-Emergency Management
- Record E-stop time, cause, equipment status, and handling measures
- Analyze root cause (e.g., poor maintenance, misoperation, component fatigue)
- Repair or replace damaged parts (couplings, bearings, sensors)
- Train operators on emergency response
- Test interlock and E-stop functions monthly