Air Blower blades Failure Due to Resonance – The Hidden Role of Isolators
Severe friction marks on the third-stage impeller of a multi-stage air blower system were caused by a damaged vibration isolator. The degraded isolator led to high amplitude vibrations, resulting in mechanical interference and damage to the impellers. This case highlights the importance of vibration isolators, preventive maintenance, and resonance analysis in rotating machinery.
My best Case Study: Air Blower blades Failure Due to Resonance – The Hidden Role of Isolators
During a recent maintenance inspection of a multi-stage air blower system, our team identified a critical issue: severe friction marks on the third -stage impeller , as shown in the image below. The root cause? A damaged vibration isolator.
What Happened?
The blower fan experienced high amplitude vibrations at operating speed 1x, 2x in Axial direction 107 mm/sec rms , eventually leading to contact between the impeller and diffuser housing. The friction marks are a clear indicator of resonance—a condition where the blower's natural frequency aligned with excitation forces (misalignment represent fault frequency).
Critical Finding:
Vibration levels spiked to 107 mm/sec RMS — well above acceptable thresholds.This excessive vibration led to physical damage and near-catastrophic contact inside the blower. After replacing the isolator and rebalancing the fan, vibration dropped to 2.5 mm/sec RMS — a dramatic improvement and confirmation of the root cause.
Key Findings:
The isolator, which is designed to dampen and reduce vibration, was found to be degraded.
Without proper damping, resonant conditions developed, leading to destructive vibration levels.
This excessive vibration caused mechanical interference between rotating and stationary parts, damaging the second
and third stage impellers.
Lessons Learned:
1. Vibration isolators are not just accessories—they are essential components in dynamic equipment.
2. Preventive maintenance must include isolation systems. Visual checks are not enough—dynamic analysis and material integrity assessments are critical.
3. Vibration monitoring and resonance analysis should be part of routine reliability practices.
Takeaway:
This case is a powerful reminder that resonance is a silent destroyer in rotating machinery. A small component like an isolator, when neglected, can lead to major equipment failure and costly downtime.
Good cooperation and support
mohamed tawfik
Mohanad Elmalahy , CMRP® , VA Cat-II
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