Condition monitoring

1. PRESENTATION
ON
CONDITION MONITORING
By. A.BHAGAWATI

2. MAINTENANCE
•ON FAILURE
•FIXED TIME(PREVENTIVE)
•PREDICTIVE
•DESIGN OUT

3. STRATEGY
Upto 1920s : On Failure maintenance
1920-1960s: Preventive Maintenance
1970s : Predictive Maintenance
1985 : TPM- Zero Defects
- Zero Breakdown

4. STRATEGY
On Failure Fixed time Predictive Design Out
Definition Fix it when
it breaks
Conduct
maintenance at
regular intervals
Maintenance
based upon
known
condition
Redesign to
eliminate root
cause of failure
Advantage (when
implemented
correctly)
Cheap, No
pre care or
management
Can be planned
for spares,
labour
Spot a potential
failure
Less
maintenance
required
Disadvantage
(when
implemented
wrongly)
High stock
level, loss of
production,
Unsafe
Unnecessary
replacement of
parts, spares,
can induce
failure
Costly if
implemented
incorrectly.
Cold be highly
expensive
Examples Headlights,
Streetlights
Oil change Bearings M/c undergoing
repetitive
failure (Seal)

5. PREDICTIVE MAINTENANCE
• ADVANTAGEs
• Impending equipment failure
can be detected
• Can run equipment to near
failure
• Maintenance can be planned
• Root cause can be detected,
scope for redesign
• DISADVANTAGEs
• Can be costly if
implemented wrongly

6. INTRODUCTION
• Human Condition Monitoring
- Heart beat, pulse, Pathology, Usg
• Industrial Condition Monitoring
 Early Bearing Condition Analyzer- Screwdriver
 1850: Railroad wheel tappers
 1945: Oil Analysis, Canadian P. Railways
 1970s: Established use of Vibration, Oil
analysis, Thermal Imaging
 1983: First PC based CM system

7. CM TOOLS
• VIBRATION ANALYSIS
• WEAR DEBRIS MONITORING
• THERMOGRAPHY

8. VIBRATION MONITORING
• Versatile Tool for CM for rotating and
reciprocating equipments
• Wide range of techniques and instrumentation
• Careful selection & application of techniques
essential for success.

9. PROBLEM IDENTIFICATION
• Unbalance
• Misalignment
• Looseness
• Defective Bearings
• Resonance
• Eccentricity
• Bend shaft
• Worn gears
• Drive belt problem
• Distortion (Soft-foot & Piping strain)
• Motor Electrical Problem

10. VIBRATION
• All machines vibrate.
• An increase in vibration level is a sign
of trouble & amplitude of vibration
depends upon the extent of defect in
the machinery component
• Each trouble will create vibration with
different characteristics

11. VIBRATION FUNDAMENTALS
• What causes vibration: Induced force & freedom for
movement
• It is the motion of mechanical parts back & forth from
its position of rest/neutral position
• HARMFUL EFFECTS
 Increased load on BRGs, reduced BRG life
 Higher forces on mountings, foundation loosening &
damage of support structure
 Increased stresses of M/c; Risk of fatigue
 Decreased equipment efficiency
 Increased maintenance cost due to more component
failure & unplanned operation
 Reduced output quality-REJECTION BY QC
 Unsafe operating Environment

12. CHARECTERISTICS OF VIBRATION
• AMPLITUDE
• FREQUENCY
• PHASE
Amplitude : Magnitude of Vibration
- Displacement (Micron)
- Velocity (mm/sec)
- Acceleration (g)
- Spike Energy (gSE)

13. AMPLITUDE
• RMS: Energy contained in the time wave form
• PEAK: 1.41 * RMS
• PEAK-TO-PEAK: 2 * PEAK
• AVERAGE: Area under curve

14. FREQUENCY
• Period of Vibration is the Time required to
complete one full cycle
• Frequency = 1/ time period
• If the time required to complete one cycle is
1/60 th of a second, frequency : 60 cycles per
second or 60 CPS or 60 Hertz (1 CPS=1 Hertz)
• Vibration frequency is measured in Cycles per
minutes (CPM) as it is easier to relate this
characteristic to rotational speed of the machine
Hence a vibration occuring at 60 Hz will be
expressed occuring at 3600 CPM (1 * RPM)

15. PARAMETER SELECTION
• Frequency sensitivity
Displacement up to 600 CPM
Velocity 600-60000 CPM
Acceleration > 60000 CPM
Spike Energy Ultrasonic range

16. DISPLACEMENT vs VELOCITY vs
ACCELERATION
DISPLACEMENT VELOCITY ACCELRATION
Sensitive to low
frequencies. Good
guide for
imbalance & other
low frequency
faults
Has average
sensitivity th’out
frequency range,
sensitive for
imbalance,
misalignment,
looseness & later
stage of rolling
element bearing
damage
Sensitive to high
frequencies. Good
guide for rolling
bearing damage,
gear related
problems &
cavitations etc.

17. BENDING OF A WIRE
• Consider the example of repeatedly bending a piece of wire, there are two ways to
reduce the time required to achieve fatigue. One is to increase the distance
(DISPLACEMENT) that the wire is bent. The farther the wire is bent each time, the
less time it will take to reach fatigue. The other is to increase the number times per
minute or second (FREQUENCY) the wire is bent. The more times per minute the
wire is flexed, the less time it will take to reach fatigue failure. Thus the severity of
vibration is dependent on both Displacement and Frequency.
• An example: a vibration of 6 mils at 120 CPM would be in the GOOD range where as
the same vibration at 3600 CPM is considered VERY ROUGH. Hence severity of
vibration not only depends on displacement but also on frequency.
• Benefits of Vibration Velocity Measurement over displacement:
 Vibration velocity is a direct indicator of fatigue since it takes into account both
displacement and frequency.
 It is not necessary to know the frequency of vibration in order to evaluate the severity
of vibration velocity since frequency is already a part of velocity.
 A measurement of overall vibration velocity is a valid indicator of the overall
condition of a machine whether the vibration is simple (one frequency) or complex
(multiple frequency).

18. SUMMATION-1
Low Displacement
& very high
frequency
Accln=d*f*f is very
high. Failure is due to
applied force
Monitor
acceleration
Medium velocity
& medium
frequency
Velocity= d * f
Failure is due to
fatigue
Measure
velocity
High displacement
& low frequency
Vel. is moderate, no
fatigue
Accln is Low, no
failure due to applied
force. Failure is due to
Stress.
Measure
displacement

19. FREQUENCY ANALYSIS
• Characteristics of the Oscillating force caused by individual M/c defect is the
frequency of the oscillating force.
• Frequency of vibration is equal to the frequency of this force.
• Frequency of vibration is therefore indicative of the type of m/c defects.
• Normally any m/c undergo different kinds of defects at a time.
• Only the severity of different defects are of different extent.
• Vibration components of different frequencies (which is characteristics of the defect)
therefore are present in the m/c simultaneously.
• Overall vibration is therefore the resultant of the vibration components of different
frequencies.
• In frequency analysis, the overall vibration is sensed..
• Does mathematical calculation to find out the individual vibration components.
• Calculate amplitude & frequency of the individual vibration components & display
the information in graphical manner.
• The technique is sometime referred to as Spectrum analysis/signature analysis.
• FFT TRANSFORM (FAST FOURIER TRANSFORM)
• The process of transforming time domain signal to frequency domain.
• Time domain signal must first be sampled and digitalized.

20. SPIKE ENERGY
• A measurement parameter designed to detect low amplitude
transient impacts generated within the audiosonic/ultrasonic
frequency range by microscopic surface flaws in rolling element
bearing and gears.
• The acceleration signal is processed via a high pass filter& a
peak detection circuit to produce a numerical value which is the
product of : The number and amplitude of the impacts in a unit
of time.
• The value is expressed in gSE (IRD)
dB (Shock Pulse-SPM)
• It is primarily bearing condition monitoring parameter

21. PHASE
• The position of a vibrating part at a given instant w.r.t. a fixed point or
another vibrating object.
• The part of a vibration cycle through which one part of object moves relative
to another part.
• The unit of phase is degree where one complete cycle of vibration is 360
degree.
• Phase analysis Applications:
 Conforms m/c defect
 Distinguishes misalignment Vs Bent shaft
 Distinguishes unbalance Vs eccentricity
 Detects mechanical looseness
 Detects resonance
 Detects type of unbalance
 Used for balancing.

22. ADVANCED TECHNIQUES
• Phase Analysis
• Time wave analysis
• Amplitude Vs Time analysis
• Amplitude Vs Phase Vs RPM
• Bode Shape analysis
• Orbit analysis

23. CHART
Frequency in
Terms of RPM
Most Likely
cause
Other possible reason
1 * RPM Unbalance
2 * RPM Looseness
3 * RPM Misalignment
<1 * RPM Oil whirl
Synchronous Electrical Prob
2 * syn Fr Torque pulse
Harmonics Bad gears
Very High Fr Bad Bearing(AF

24. VIBRATION STANDARD
• Published Standard-ISO 2372
• Manufacturer’s guidelines
• Comparison
• Trending

25. WEAR DEBIS ANALYSIS
• All machines wear out
• To predict internal condition of machine in a non intrusive way
by the study of worn particle or debris
• SCOPE:Determines:
 When abnormal wear has begun
 Root cause of wear/failure
 Which component is failing
 Requirement of lubricant replacement
 Suitability of lubricants
 Seal/Filter condition
CAN PROVIDE EARLIEST DIAGNOSTIC WARNING_
BEFORE VIBRATION CAN SENSE DANGER

26. 7 STEPS FOR WDA
• Sample collection
• Codification
• Physical & Chemical Test
• Incubation
• Slide preparation
• Microscopic examination
• Report Preparation

27. WDA METHODS
• Spectroscopy
• Ferrography
• Magnetic Plug
FERROGRAPHY
-Particle Quantifier
-Analytical Ferrography- severity of wear
Mode of wear
size of wear
concentration of wear
component under wear

28. THERMOGRAPHY
• Thermography (Thermal imaging) is a methode
of redefining the appearance of an object in
terms of temperature
• An infrared camera generates only B & W
image. By using a complicated algorithms this
is converted to colored image.
• A colored thermogram gives immediate feeling
of temperature

29. THANK YOU
A. Bhagawati