This is part 2 of an ongoing series on Vibration Analysis for Condition Based Maintenance. Application is on Industrial machinery to improve Reliability, Availability and Performance of industrial machine to enhance business performance.

1. VIBRATION ANALYSIS FOR CBM
BASIC CONCEPTS – UNIT 2
BY DIBYENDU DE

2. VIBRATION MONITORING
Degrees of Freedom?
Degrees of Freedom determines the direction
in which we measure vibration

3. Measurement direction - Horizontal,
Vertical, Axial.

4. MEASUREMENT DIRECTION - HORIZONTAL, VERTICAL,
AXIAL.
Horizontal Vertical
Axial
Instrument

5. CONCEPT OF PHASE - 1
Masses C and D are in sync or
are in-step
That is they move together
Hence the masses are vibrating
in phase

6. CONCEPT OF PHASE – 2
While Mass X is now at the upper
limit
Mass Y is at the neutral position and
moving downwards towards the
lower limit
Hence Masses X & Y are moving 90
degrees out of phase

7. CONCEPT OF PHASE – 3
While Mass A is now at the upper
limit
Mass B is at the lower limit
Hence Masses A & B are moving 180
degrees out of phase

8. UNITS OF VIBRATION
Displacement in
Microns or Mils
1mil = 1/1000 inch
Velocity in
mm/sec or
inch/sec
Acceleration in
meter/sec^2 or ‘g’
Frequency in CPM
or Hz
Hz x 60 = CPM

9. Vibration
Energy
Mass, Stiffness, Space
Natural Frequency Motion
Time
Strain
Kinetic
Force
Overall
Time wave form
Orbit
Signatures
Envelope
Cepstrum
Faults = Unbalance, Misalignment, Bearings, Product defect etc
frequency
Low
Medium
High
d
v
a
Spike Energy
Patterns

10. VIBRATION - CAR ANALOGY
Low Frequency
Long period (T)
High displacement
Average Velocity
Low Acceleration
Medium Frequency
Medium period (T)
Average displacement
Average Velocity
Average Acceleration
High Frequency
Short period (T)
Low displacement
Average Velocity
High Acceleration

11. VIBRATION
Displacement:
Sensitive to low
frequencies.
Good guide for imbalance,
& other low frequency faults.
Velocity:
Has average sensitivity throughout the frequency range.
Reasonably sensitive to imbalance, misalignment, looseness and
rolling element bearing damage.
Acceleration:
Sensitive to high
frequencies.
Good for rolling element
bearing damage.

12. EXERCISE – CHOOSE APPROPRIATE PARAMETER
• Anti friction Bearings – velocity and acceleration
• Gears
• Journal Bearings
• Bush Bearings
• Pump casing
• VFD shaft
• Thrust bearing
• Pipes and fluid flows

13. EXERCISE – CHOOSE APPROPRIATE PARAMETER &
DIRECTION
• Motor
• Pump
• Cooling Tower Fan
• On steel and concrete structures
• Foundations
• Slow speed anti-friction bearing
• Vibrating Screen
• Steam Turbines

14. EXERCISE - FAILURE MODES – PARAMETER?
Pitting of anti-friction bearings
Wear out and/or clearances of journal bearings
Lubrication starvation
Unbalance, misalignment, looseness
Screw wear out and shear of extruders
Leakage of mechanical seals
Gear teeth sheared from root
Cavitation
Cracks in shafts
Cracks in structures

15. EXERCISE – THINK OVER THE QUESTIONS
• Which is the weakest bearing?
• Which direction is the weakest?
• What might be the failure modes?
• What would be the parameters?
• What is the most important direction
• What would be the most important
technique?
• What would define the health of the
machine? FAN
BEARING
6320
BEARING
NU320
BEARING
NU219
BEARING 6219
& NU219
BLOWER ASSEMBLY

16. THANK YOU FOR COMPLETING UNIT 2
CONTACT: FOR FACILITATED TRAINING
DIBYENDU DE, EMAIL ID: DDE337@GMAIL.COM