6 Common Faults of Rotating Machinery

Successful predictive maintenance programs are dependent on the expertise and tools of the teams behind the machines being maintained. We’ve identified 6 common machine faults you’ll likely encounter on your maintenance routes.

Bearing defects include wear and tear on any part of a bearing. This can mean abrasion, pressure damage, fluting, and corrosion. These issues typically occur as a result of another underlying machine fault such as misalignment or poor installation.

The Fix:  
     1. Shutdown and lockout.
2. Remove the bearing.
3. Perform bearing failure analysis.
4. Inspect and measure shaft and house fits for wear.


Cavitation is when cavities (low pressure vapor bubbles) form in the liquid on the suction side of the pump. When these cavities get into the impeller section, pressure balances and they often implode into the impeller surface.

The Fix:
1. Check and record suction, discharge pressure, and flow.
2. Compare these values to the original specifications and BEP of the pump curve.
3. Check for flow restrictions such as improperly positioned valves or tank levels.
4. Check fluid for proper viscosity.
5. Shutdown and lockout.
6. Check the impeller and volute for wear or blockages.
7. Make repairs or corrections as needed.


Gear Wear involves removal or displacement of material on the surface of the gear teeth due to mechanical, chemical, or electrical action. The three major types of wear are adhesion, abrasion, and polishing. Common causes of gear wear are misalignment or insufficient lubrication.

The fix
1. Perform lubrication analysis.
2. Shutdown and lockout.
3. Inspect the gear tooth running pattern for wear and proper alignment.
4. Repair/correct as needed.
5 Retake vibration readings and analyze.


Misalignment occurs when the shaft centerlines of the driver and driven machine(s) are not aligned in the vertical and horizontal planes. This is common after replacing machinery improperly.

The Fix
1. Shutdown and lockout.
2. Check for loose fasteners and foundation deterioration.
3. Inspect coupling for wear and proper maintenance.
4. Perform a precision alignment.


Structural resonance is the excessive vibration of a component such as a machine base or supporting structures. This is caused by the natural frequency coinciding with a forcing frequency. Resonance can be challenging to correct particularly if there have been changes in a machine’s operation.

The fix
1. Determine if there has been a change in the machine’s operation since installation.
2. Check the machine for its structure and connections such as pipes, stiffening brackets, and ductwork for looseness or deterioration.
3. Repair/correct as necessary.
4. Retake vibration readings and analyze.


Unbalance is the uneven distribution of mass around a rotating axis. Common causes of unbalance are buildup from foreign matter (dirt, paint, rust), broken blades or vanes, and missing fasteners in the rotating element.

The fix:
1. Shutdown and lockout.
2. Check for loose fasteners and foundation deterioration.
3. If present, check vibration isolator condition.
4. Inspect rotating components for cleanliness, wear, and debris build up.
5. Repair/correct as necessary.
6. Retake vibration readings and analyze.
7. If vibration readings are still high, schedule for field balance.

Of course, you don’t have to rely on your own expertise alone to identify machine faults. That’s what modern technology and our team of experts are here for. Check out the RT-300, a wireless vibration data collector that provides automatic machine health assessments. Its built in Machine Defender application makes it easy for you to check your machines for the faults described above. If you really want to take charge of your maintenance program by becoming the expert your team needs, check out our training page for information on hands-on training and class schedules.

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