The problem of abnormal vertical vibration in multi-stage blowers during operation is often caused by multiple factors working together. Accurately identifying the cause and taking targeted measures is the key to solving the problem.
1、 Unbalanced factors of rotor system
Uneven impeller wear: Long term operation causes local wear or scaling of the impeller, leading to an imbalance in quality distribution. On site monitoring shows that when the wear on one side exceeds 3mm, the vibration amplitude can increase by more than 50%.
Rotor misalignment: Coupling installation errors or unit foundation settlement can cause radial displacement of 0.1-0.3mm, leading to periodic vibrations. Actual test cases show that for every 0.05mm decrease in shaft alignment, the vibration value increases by 12-18 μ m.
Bearing failure: Insufficient lubrication or component wear leading to increased clearance, oil film oscillation during high-speed rotation, and vertical amplitude exceeding the limit (>8mm/s).
2、 Pneumatic interference problem
Abnormal gas-solid two-phase flow: When conveying dusty gas, the accumulation of dust on the blades forms an additional load. Experimental data shows that when the dust accumulation reaches 1.5% of the impeller weight, there will be a second harmonic in the vibration frequency.
System pressure fluctuation: Sudden changes in pipeline characteristics can cause airflow pulsation. When the pressure difference change rate is greater than 15kPa/s, it is easy to induce surge phenomenon.
3、 Basic and installation factors
Loosening of foundation bolts: Long term vibration attenuates the pre tightening force of bolts. On site inspection found that when the loosening rate reaches 30%, the vibration trend significantly increases.
Insufficient basic stiffness: The concrete foundation strength does not meet the standard (compressive strength<C25), and the resonance frequency may be excited at a speed of 1500rpm.
4、 Diagnosis and governance
It is recommended to use spectrum analysis method. When the main frequency of vibration is consistent with the speed frequency, priority should be given to investigating mechanical imbalance; If there are obvious second harmonic components, it is mostly caused by cavitation or scaling. During governance, a systematic process of "shutdown maintenance dynamic balance correction foundation reinforcement" should be followed, and a regular monitoring mechanism should be established. Preventive maintenance can extend the MTBF (mean time between failures) of equipment by more than 40%.
Systematic diagnosis and precise governance are the core of controlling vertical vibration, which requires the combination of multidimensional monitoring data to achieve scientific decision-making.
