BOILER ID FAN COMPONENTS
Objective
To provide a clear understanding of ID fan components, function, and maintenance practices.
System Overview
ID Fan creates negative pressure inside the furnace by extracting flue gases and pushing them toward pollution control equipment.
Major Components
1. Impeller
Type: Backward curved / radial- Function: Converts mechanical energy into kinetic energy
- Design Considerations:
- Tip speed
- Blade angle
- Wear resistance
2. Shaft
Material: EN8 / EN24 alloy steel
- Key Parameters:
- Torque transmission
- Critical speed
- Alignment tolerance
3. Bearings
- Type: Plummer block
- Load Handling:
- Radial + axial loads
- Monitoring:
- Temperature (< 90°C typical)
- Vibration levels
4. Casing
Scroll design for pressure conversion- Internal wear plates recommended in abrasive conditions
5. Inlet System
Bell mouth design reduces entry losses- Ensures uniform velocity profile
6. Dampers
Used for flow regulation- Types:
- Inlet vane control
- Outlet damper
7. Drive Arrangement
- Direct coupling preferred for high power
- Belt drive used for flexibility
Wear Protection System
- AR plates (6–10 mm typical)
- Hard facing on blade leading edges
- Replaceable liners recommended
Common Failures & Causes
Problem | Cause | Solution |
High vibration | Imbalance / misalignment | Dynamic balancing |
Bearing failure | Poor lubrication | Scheduled greasing |
Blade erosion | Ash + sand | Install liners |
Low efficiency | Leakage / damper issue | Seal & recalibrate |
Maintenance Best Practices
- Daily: Check vibration & sound
- Weekly: Inspect bearings & lubrication
- Monthly: Check alignment & bolts
- Shutdown: Inspect impeller wear
Key Takeaway
👉 Life of ID fan depends on:
- Impeller design
- Material selection
- Wear protection
- Maintenance discipline