Vibration Analysis Basics for Bearing Condition Monitoring

What is measured

An accelerometer fixed to the bearing housing measures vibration. The signal can be reported as acceleration, velocity or displacement. Velocity in mm/s is common for general machine health, and acceleration is more useful for high-frequency faults such as early bearing damage.

Overall level and the trend

The simplest use is to record the overall vibration level at the same points on a regular route. A single reading matters less than the trend: a steady rise tells you the condition is changing. Compare readings with similar machines and with guidance such as ISO 10816 / ISO 20816 for the machine class.

Frequency analysis

Splitting the signal into frequencies shows what is causing the vibration. Different faults appear at different frequencies:

• Imbalance appears at once per shaft revolution (1x).
• Misalignment often shows at 1x and 2x, especially in the axial direction.
• Looseness produces harmonics of running speed.
• Bearing defects show at characteristic frequencies that depend on the bearing geometry, usually at higher frequencies.

Getting started

Choose critical machines, mark the measuring points so readings are repeatable, record a baseline when the machine is known to be healthy, and set alert levels. A portable meter is a reasonable starting point; permanently mounted sensors suit machines that cannot be reached safely.

Limits of the method

Vibration shows that something has changed; it does not always say why. Use it together with temperature checks, lubricant condition and visual inspection.