A boiler has to breathe, drawing air in for combustion and pushing flue gas out. ID and FD fans do that breathing and control the draught that keeps the fire steady.
The FD fan forces air in and the ID fan draws flue gas out, and together they set the draught through the furnace. When they are balanced, the boiler burns steadily and safely.
This guide explains what ID and FD fans do, why draught control matters, and how to keep them running reliably.
What ID and FD Fans Do
The FD fan, or forced draught fan, pushes combustion air into the furnace so the bagasse has the oxygen it needs to burn. It supplies the main air for combustion.
The ID fan, or induced draught fan, draws the flue gas out of the boiler and up the stack. It removes the burnt gases and pulls the draught through the furnace.
Working together, the two fans set the flow of air and gas through the boiler, which is the draught that keeps the fire burning steadily.
Why Draught Control Matters
The draught sets how much air reaches the fire and how freely the flue gas leaves. Too little and the fuel burns poorly, too much and heat is carried away up the stack.
Balancing the FD and ID fans keeps the furnace at the right draught so the bagasse burns fully and the boiler stays safe. That balance protects both efficiency and steady steam.
Good draught control also keeps the furnace pressure where it should be, which matters for safe and clean operation.
Signs the Fans Need Attention
ID and FD fans in trouble show up in the burn and the draught.
- Draught that is hard to hold steady
- Bagasse burning poorly from too little or too much air
- Heat carried away up the stack from over draught
- Vibration or noise from a fan
- Fan performance falling from wear or fouling
What Makes Good ID and FD Fans?
These fans are judged by steady output and reliable, balanced running.
Steady, Controllable Output
The fans must deliver steady air and draught that can be controlled to match the fire. Good control keeps the burn and the draught where they should be.
Strong Build for Hard Duty
ID fans in particular handle hot, dusty flue gas, so they need a strong build that resists wear. A robust fan holds its performance through the season.
Keeping the Fans Running
Routine attention keeps ID and FD fans controlling the draught.
- Keep the FD and ID fans balanced for steady draught
- Watch the burn and the furnace draught during the crush
- Check fans for wear, fouling, and vibration
- Maintain bearings and drives for reliable running
Common Questions About ID and FD Fans
The FD fan forces combustion air into the boiler and the ID fan draws flue gas out. Together they set the draught that keeps the bagasse burning steadily.
The draught sets how much air reaches the fire and how the flue gas leaves. Too little and the fuel burns poorly, too much and heat is lost up the stack.
The FD fan pushes air into the furnace, while the ID fan draws flue gas out of it. Balancing the two keeps the furnace at the right draught.
The ID fan handles hot, dusty flue gas, which is harder on the fan than clean air. A strong build and regular checks keep it performing.
Keep the Boiler Breathing
ID and FD fans keep the boiler breathing by moving air in and flue gas out, and their balance sets the draught the fire needs. Steady draught means a steady, efficient burn.
If your draught is hard to hold, the fans and their balance are worth reviewing. Explore our boiler and co-generation equipment to keep the boiler breathing well.
See our boiler and co-generation equipment and keep your boiler breathing with steady draught.
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