This is a crucial issue. Whether a centrifugal fan impeller needs balancing depends primarily on vibration data, operating status, and component appearance. The specific methods are as follows:
1. Vibration Anomaly Judgment (Most Direct Basis)
Measure the vibration velocity of the fan during operation. If the effective value exceeds the standard threshold (generally ≥4.5 mm/s for speeds ≤3000 r/min; ≥2.8 mm/s for speeds >3000 r/min), balancing correction should be considered.
Vibration exhibits obvious periodicity and intensifies with increasing speed, without other clear malfunction causes (such as loose bolts or damaged bearings).
Use a vibration analyzer. If the first harmonic frequency (the same frequency as the motor speed) vibration component accounts for more than 70%, it is highly likely that the impeller is unbalanced.
2. Abnormal Operating Status
The fan makes obvious abnormal noises during operation, accompanied by machine vibration, which does not improve after being shut down and restarted.
Abnormally high bearing temperature. After ruling out poor lubrication and damaged bearings, impeller balancing needs to be investigated.
Unstable airflow and pressure cause operational fluctuations due to an imbalance in impeller rotation.
3. Component Appearance and Operating Condition Inspection
The impeller surface shows obvious dust accumulation, scale buildup, or localized wear and corrosion, resulting in uneven mass distribution.
The impeller was not balanced after repairs (e.g., blade welding, repair) or blade replacement.
After long-term operation, the impeller may deform, the blade angles may be inconsistent, or the blades may be damaged by foreign object impacts.
4. Auxiliary Verification Methods
After shutdown, manually rotate the impeller to check for any "jamming" or "unbalanced" phenomena during rotation.
After removing the impeller, perform a static balance test separately. If the impeller cannot remain stationary at any angle (excluding the influence of components such as the bushing), it indicates severe static imbalance.
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