vibration monitoring (condition based monitoring)

1. INTRODUCTION TO
VIBRATION MONITORING
KEVIN
CIM05

2. WHAT IS VIBRATION?
• When a body is displaced from its equilibrium
position by the application of external force and
then released, it commences to vibrate.

3. Causes of vibration
• Unbalanced rotating parts
• Eccentric rotor
• Bent shafts
• Misalignment
• Mechanical looseness
• Excess wear

4. INTRODUCTION
• All operating machines gives rise to vibration.
• As the condition of machine starts deteriorating, the
corresponding vibration level also increases.
• By monitoring this vibration, it is possible to obtain
information about the machines condition

5. • Mechanical vibration is used as the reliable parameter to
measure vibration.

6. Machinery signatures.
• When the complex waveforms of machinery vibration are
broken down into spectral components, it may be defined
as the sum of harmonic functions of discrete amplitudes
and frequency, this is called as machinery signature.

7. Complex waveform

8. Machinery signatures in unbalanced shaft.

9. Broken spectral components

10. Selection of transducers

11. WHAT IS TRANSDUCER?
• A transducer is a device which transforms a non-electrical
physical quantity (i.e. temperature, sound or light) into an
electrical signal (i.e. voltage, current, capacity…)
• In other word it is a device that is capable of converting
the physical quantity into a proportional electrical quantity
such as voltage or current.

12. Selection of transducers.
• Sensitivity: The transducer must be sensitive enough to
produce detectable output.
• Operating Range: The transducer should maintain the range
requirement and have a good resolution over the entire range.
• Accuracy: it is defined as how close the output of the
transducer is to the expected value. High accuracy is required.
• Response time
It is also defined as the time required to observe the change
in output as a result of a change in input .

13. • Reliability:
Reliability is the ratio of how many times a system operates
properly, divided by how many times it is used.
• Size: Depending on the application of the transducer, the
size may be of primary importance
• Operating Principle: The transducer are many times
selected on the basis of operating principle used by them.
The operating principle used may be resistive, inductive,
capacitive , optoelectronic, piezo electric etc

14. • Environmental Compatibility: the transducer is selected
based on the various environmental conditions it can
work.
• Insensitivity to unwanted signals: The transducer
should be minimally sensitive to unwanted signals and
highly sensitive to desired signals.
• Cost: The cost of a transducer is an important
consideration, especially when many sensors are needed
for one machine

15. Based on vibration pickups
• Three important vibration pickups are
• Displacement
• Velocity
• Acceleration

16. DISPLACEMENT PICKUP
• Here the coil is excited by
the high frequency
oscillator.
• Varying the distance
between coil and shaft
produces change in
inductance and output
voltage proportional to
displacement.

17. Velocity pickup
• This probe is mounted on
vibrating surface.
• Relative motion between
coil and core produces
output voltage proportional
to velocity.

18. Acceleration pickup
• The spring mass system
converts acceleration to
force, that force when
applied to piezoelectric
material produces change
in voltage proportional to
acceleration

19. Thank you