Maintaining an FD (forced draft) fan is essential for safe and efficient boiler or furnace operation. Because the FD fan supplies combustion air, any failure can reduce efficiency, cause unstable flames or even force a shutdown of the entire steam or process system. A structured maintenance program keeps the fan reliable and extends its service life.
The first step is a regular visual inspection. With the system safely shut down and locked out, inspect the fan casing, inlet and outlet for damage, corrosion or build-up of dust and debris. Check access doors, gaskets and inspection covers for air leaks. On combustion air systems, leaks on the suction side can pull in unfiltered air and dust, while leaks on the discharge side can waste energy and disturb burner air patterns.
The impeller must be kept clean and balanced. Over time, dust and fine particles can accumulate on the blades, changing the fan’s balance and reducing performance. Periodically clean the impeller with appropriate methods, taking care not to damage coatings or wear protection. After cleaning, check blade condition for erosion, cracks or weld damage. A heavily worn or cracked impeller must be repaired or replaced to avoid catastrophic failure.
Bearings and lubrication are critical maintenance points. For grease-lubricated bearings, follow the manufacturer’s schedule for type and amount of grease, avoiding both over- and under-lubrication. For oil-lubricated bearings, check oil level and condition and change it at recommended intervals. Listen for unusual bearing noise, and monitor temperature—abnormally high temperatures can indicate misalignment, overload or impending bearing failure.
If the FD fan is belt-driven, regularly inspect belts, pulleys and alignment. Check belt tension and look for signs of cracking, glazing or fraying. Misaligned pulleys or incorrect tension shorten belt life and increase vibration. For direct-drive fans, verify shaft alignment between motor and fan and check the coupling for wear and proper lubrication if applicable.
Ongoing vibration monitoring is one of the best tools for early fault detection. High vibration levels can indicate imbalance, loose foundation bolts, bearing issues or structural resonance. Periodic vibration measurements or continuous monitoring devices help detect changes before they become serious problems. Checking motor current and temperature also provides useful information about overall fan health.
Finally, document all maintenance activities in a service log. Record inspections, cleaning, lubrication, repairs and measured values such as vibration and temperature. This history helps you recognise trends and schedule overhauls at convenient times rather than reacting to unexpected failures.
In summary, maintaining an FD fan means inspecting and cleaning the impeller, caring for bearings and belts, monitoring vibration and temperature, and following a structured schedule based on the manufacturer’s recommendations and the fan’s actual operating conditions.
