The training content covers:- - Condition based monitoring - basics - Need for Condition based monitoring - Vibration analysis - Common Machinery Faults Requiring Diagnosis by Vibration Analysis - Unbalance - Misalignment - Bearing Defect & its analysis - Gear Defect & analysis - Looseness

1. Condition Monitoring Overview

2. 25 April 2020 NEI Digital Office
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3. What is Condition Monitoring?
• Process of obtaining useful health information of critical machineries.
• The process use to monitor the upcoming failures of critical machineries.
• The process of condition monitoring includes diagnostics and prognostics.
• Monitoring is performed using various techniques such as vibration analysis, Acoustic emission (AE), shock-pulse measurement etc.
Condition Monitoring - Introduction
Why Condition Monitoring?
• To improve Equipment Reliability
• To minimize downtime.
• To maximize component life
• To maximize equipment performance and throughput.
Source:- Condition Monitoring at NBC

4. What is Vibration?
• Vibration is the movement of a body about a reference. The reference is the position of the mass when it is at rest.
• In rotating machinery, the centre-line of the shaft is the reference.
• Objects that are vibrating back and forth, from one position to another.
• Vibration occurs when an object responds to some form of excitation or force. Excitation is generally referred to as a
forcing function.
Basics of Condition Monitoring – Vibration Analysis
For most industrial machinery, some potential forcing functions include:
• Imbalance of rotating components
• Misalignment of couplings, bearings, gears and sheaves
• Defects and deterioration of Rolling Element Bearings
• Gear Wear
• Belt Defects
• Electrical Problems (imbalanced magnetic forces) in motors
• Hydraulic Instabilities in Journal bearings
• Aerodynamic/Hydraulic forces in fans, blowers, and pumps
• Eccentricity of rotating components such as V-belt pulleys or Gears

5. How is Vibration Measured?
Vibration Analysis Basics
• Vibration is measured by mounting vibration transducer( Displacement probe, velocity probe, accelerometer) upon casing
• The transducers convert mechanical energy into an electrical signal ( a number value). The number values are plotted over time
• The plotted movement is known as Time waveform
• X-axis = Frequency
• Y-axis = Amplitude
Frequency
• Frequency is defined as how often an event occurs per unit time. The rate at which a bearing housing is vibrating is called a vibrating
frequency
• Frequency of a vibration cycle is plotted in the frequency spectrum. This transition is accomplished by the Fast Fourier Transform.
• The spectrum represents the amplitude and frequency of the periodic cycles from the waveform.
Time domain Frequency domain

6. Common Machinery Faults Requiring Diagnosis by Vibration Analysis
Diagnosis of Common Mechanical Faults by Vibration Analysis
1.Unbalance(Static, Couple, Dynamic, Over-hung rotor).
2. Misalignment(Angular, Parallel, Combination).
3. Eccentric Rotor, Bent Shaft.
4. Mechanical Looseness, Structural Weakness, Soft Foot.
5. Mechanical Rubbing.
6. Problems Of Belt Driven Machines.
7. Journal Bearing Defects.
8. Antifriction Bearing Defects (Inner race, Outer race, Cage, Rolling Elements).
9.Problems of Hydrodynamic & Aerodynamic Machines (Blade Or Vane, Flow turbulence, Cavitation).
10.Gear Problems (Tooth wear, Tooth load, Gear eccentricity, Backlash, Gear misalignment, Cracked Or Broken Tooth).
11.Electrical Problems of AC & DC Motor ( Variable Air Gap, Rotor Bar Defect, Problems of SCRs).

7. What is Unbalance?
Unbalance
Centre of rotation
Centre of Mass
Heavy Spot
• Unbalance is defined as the state or condition of a rotating body whose
center of rotation is not its center of gravity or center of mass .
• This condition results in a heavy spot on the rotor. The heavy spot
produces a centrifugal force.
Diagnosis of Unbalance
• Static
• Couple
• Dynamic
• Overhung Rotor
Types of Unbalance
• Unbalance results in a 1X rpm vibration component with a steady amplitude 1X RPM
Type of Unbalance Dominant
Frequency
Dominant Plane Phase reading
Static 1x rpm Radial Radial In Phase
Dynamic 1x rpm Radial Radial 0-180 out
Couple 1x rpm Radial/Axial Radial Out of phase General FFT for Unbalance condition

8. What is Misalignment?
Misalignment
• Misalignment is the condition between two or more coupled shafts
whose axes either intersect at an angle or are not perfectly parallel.
Type of Misalignment
• Offset or parallel Misalignment
• Angular Misalignment
• Combination of parallel and angular
Offset Misalignment
Angular Misalignment
Diagnosis of Misalignment
• Vibration due to misalignment causes excessive radial load on bearings, leading to premature bearing failure
Type Predominant Frequency Dominant Plane Phase
Parallel 1 x and 2 x rpm Radial Radial 180 degree out of
phase
Angular 1 x and 2 x rpm Axial Axial 180 degree out of
phase
Combination 1 x and 2 x rpm Radial and Axial Both radial and axial 180
degree out of phase

9. What is bearing defect?
Bearing Defect
• The service life of a rolling bearings rotating under load is terminated by material fatigue, unless it is fail-safe by wear at the running
surfaces of rings and rolling elements; or by lubrication failure.
Major Modes of Bearing Failure
1] Fatigue
• Classical Fatigue- Classical fatigue damage begins with the formation of minute cracks below the
surface . As loading continue it develops pitting in the contact areas .
• Fatigue caused by foreign particle cycling.
• Fatigue caused by wear
• Fatigue Caused by poor lubrication
2] Wear
• Wear is a common cause of bearing failure
• Wear occurs mainly due to dirt, foreign particles, water or cooling agent entering the bearing
through inadequate sealing.
3] Corrosion Damage
4] Faulty Mounting and Poor Lubrication
Fatigue Failure
Worn Failure

10. Diagnosis of Bearing Failure
Bearing Defect Analysis
• Every component of bearing emits its fundamental frequency
• Calculate fundamental frequency using mathematical formulas
• Find out the presence of this fundamental frequency into FFT spectrum
Fundamental Frequency
What do the bearing frequencies mean?
If:
FTF = 0.381 * RPM (Fundamental Train Frequency)
BSF = 1.981 * RPM (Ball Spin Frequency)
BPFO = 3.047 * RPM (Ball Pass Frequency Outer Race)
BPFI = 4.952 * RPM (Ball Pass Frequency Inner Race)
During one shaft revolution:
• The cage rotates 0.381 revolutions
• The ball spins 1.981 revolutions
• 4.952 balls pass an inner race defect
• 3.047 balls pass an outer race defect
Find at FFT for
diagnosis

11. What is Gear Defect?
Gear Defect
• If Meshing between gears causes the power transmission loss it leads to indication of gear defect.
• The gear defect generally occurs due to machining errors, tooth deflection, looseness and gear eccentricity.
Gear Mesh Frequency (GMF)
GMF (Gear Mesh Frequency)
Z1 .RPM1 = Z2 .RPM2
where Z = no. of teeth and RPM shaft speed
Mating gears produce only one ‘Gear Mesh Frequency’
Gear Mesh Frequency is the most basic gear frequency

12. Types of Gear Box Defect
Gear Defect Analysis
• Tooth wear
• Gear Eccentricity and Backlash
• Gear Misalignment
• Cracked or Broken Tooth
• Hunting Tooth
Spur gear produce vibration in radial direction and helical gear produce in radial & axial directions.
Sideband spacing reveals the defective gear or pinion. All analysis should be done at maximum load.
Analysis

13. What is Looseness?
Looseness
Looseness is the state or condition of a machine where its fasteners or rotating elements are no longer held fast or rigid to its host
Type of Looseness
1] Structural Looseness
• Base Mount
• Split Casings
• Bearing Caps
• Bearing Support
2] Rotating Element Looseness
• Impellers
• Fans
• Bearings
• Couplings
Analysis of Looseness
Type Predominant frequency Dominant Plane Phase
Structural 1x, 2x,3x….10x at low amplitude Radial Varies with type
Rotating 1x predominant Radial Vary from start up to start up
FFT Spectrum- Harmonics increases upto 10 x as severity increases