3 July 2022

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

 

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