Boiler Vibration Problems

Sources of Vibration

• Burner fan: The forced draft fan is the most common source of vibration. Dirt on the impeller, bearing wear, or impeller damage cause imbalance.
• Feed pump: Cavitation, bearing wear, misalignment, or impeller damage cause pump vibration. Hot feedwater increases cavitation risk.
• Combustion pulsation: Unstable combustion can create pressure pulsations that vibrate the boiler casing. Usually caused by poor fuel/air mixing or burner problems.
• Structural resonance: A structural element of the boiler or support frame may vibrate at its natural frequency. Usually caused by a change in operating conditions (speed, load).
• Loose components: Loose mounting bolts, pipe supports, or casing panels can rattle and vibrate.

Diagnosis Approach

1. Identify the source. Use a vibration meter or simply place a hand on each component to feel where vibration is strongest.
2. Determine the frequency. Low frequency (1 to 10 Hz) suggests imbalance or misalignment. High frequency (20+ Hz) suggests bearing or gear problems.
3. Check for changes. Did the vibration start after a maintenance event, load change, or fuel change?
4. Measure and trend. Record vibration amplitude and frequency. Compare to baseline and manufacturer limits.
5. Use vibration analysis. FFT (frequency spectrum) analysis identifies specific frequencies that correspond to specific faults (imbalance, misalignment, bearing defect, etc.). See our Vibration Analysis Basics guide.

Common Fixes

• Fan vibration: Clean the impeller. Check bearings. Replace if worn. Verify balance.
• Pump vibration: Check alignment (use laser alignment). Replace bearings. Verify NPSH to eliminate cavitation. Check impeller condition.
• Combustion pulsation: Clean burner. Check fuel pressure and combustion air. Retune combustion. Verify flame stability at all firing rates.
• Loose components: Tighten all mounting bolts, pipe supports, and casing panels. Use thread-locking compound on frequently loosened fasteners.