7 December 2023

# Vibration | Basic Theory of Vibration

Vibration VIBRATION MONITORING

WHAT IS VIBRATION  ?

WHAT CAUSES VIBRATION  ?

HOW DO WE MEASURE VIBRATION  ?

HOW DO WE ANALYSE VIBRATION  ? Measurement direction – Horizontal, Vertical, Axial.  General rule of direction

• We measure H direction for machines on the foundation.
• We measure V direction for machines on structures
• We measure A direction when we suspect misalignment
• There are advantages, but there are exceptions to this rule.

Modes of Amplitudes

• DISPLACEMENT
• VELOCITY
• ACCELERATION
• SPIKE ENERGY

Physical Significance Of Vibration  Amplitude

Displacement : Strain Indicator

Velocity           : Fatigue Indicator

Acceleration   : Force Indicator

The significance

• Displacement gives the strain energy
• Velocity gives the kinetic energy
• Acceleration gives the force
• Spike energy/HFD/gE are special ways to measure acceleration only.

UNITS OF MEASUREMENT

DISPLACEMENT      –  MICRONS

VELOCITY      –  MM / SEC.

ACCELERATION      –  MM / SEC2 , G

AMPLITUDE DESCRIPTORS

• RMS –  Displacement,  Velocity
• PEAK –    1.414 RMS  Displacement, Velocity, Acceleration
• PEAK-TO-PEAK –    2 * PEAK  Displacement

ISO 2372    Amplitude & Frequency

Amplitude:

It is the magnitude of Vibration signal.

Units: Micron, MM/Sec, M/Sec2

Frequency:

How many times oscillation is occurring for a given time period?

Units: CPS(Hz), CPM #### Star Performer

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