The main control parameters of an exhaust fan are operating temperature, airflow, efficiency, noise, speed and shaft power. When an induced draft fan vibrates in service, what causes it and how do you fix it?
Causes of vibration:
- The fan shaft and motor shaft are not concentric, so the coupling is skewed.
- The impeller is damaged, or dust or dirt sits on the blades, or the shaft is bent, making the rotor unbalanced.
- The fan casing or inlet rubs against the impeller.
- The impeller hub bore and shaft have come loose, or the coupling bolts have loosened.
- The fan base lacks rigidity or is not firmly fixed.
- The impeller rivets are loose or the impeller is deformed.
Solutions:
- If the bearing runs too hot it also causes vibration, usually from poor lubrication, insufficient cooling or a faulty bearing. Judge the cause and apply the right fix.
- Fit a row of nozzles on the casing near the gas outlet at adjustable angles, connected to the ash-flushing pump and using ash water as the medium. This clears ash effectively and reduces blade wear.
- If the gas and air duct vibrates, it forces the fan to vibrate. Fit a movable support under the diffuser outlet and shift it; when load changes, just adjust the support to remove the vibration.