UNIT – III 07 hours

Condition monitoring
Condition Monitoring – Cost comparison with and without CM – On-load testing and off-load testing – Methods
and instruments for CM – wear-debris analysis

Condition Monitoring:
It is one of the maintenance methods which are used to assess the health and conditions of
equipment, machines, systems or process by absorbing, checking, measuring and monitoring
several parameters. This technique is also called as equipment health monitoring (EHM).

What is equipment health monitoring?

Conditions monitoring is one of the maintenance methods which are used to assess the health
and condition of equipments machines, systems or process by absorbing checking, measuring
and monitoring several parameters. This technique is also called as equipment health monitoring.

Key features of condition monitoring.

1. Links between cause and effect
2. Systems with sufficient response
3. Mechanisms for objective data assessment
4. Benefits outweighing cost
5. Data storage and review facilities.

Key features of condition Monitoring

The key features of effective condition monitoring system include the following:

(i) Links between cause and effect: A clear relationship mostly exists between the
measurement being taken and the condition of the equipment.
(ii) System with sufficient response: The monitoring system must respond quickly
enough to provide warning of deterioration in machine condition for appropriate
action to be taken.
(iii) Mechanisms for objective data assessment: The assessment of the equipment must
be made by comparing readings aganst the existing measurements and /or predefine
and absolute standard.
(iv) Benefits out weighting Cost The benefits of performing condition monitoring to
predict equipment condition must outweigh the implementation and running cost.
(v) Data Storage and review facilities A system for measuring and recording data must
exist to enable the condition of equipment to be predicted.

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Fundamental steps in Condition monitoring:

An effective condition monitoring system follows the following basics steps:

1. Identifying critical systems

2. Selecting suitable techniques for condition monitoring
3. Setting baselines
4. Data collection
5. Data assessment
6. Fault diagnosis and repair
7. System review

Process of condition monitoring

i. Identifying critical system: The first step in condition monitoring is to identify which
equipment would be benefit by applying CM. It is done by examining all equipment in the
industry or by looking only at problem causing equipment. The selected equipment will
probably have a poor record of efficiency, availability, reliability, safety and maintainability.
It is likely to show up increased cost.

ii. Selecting suitable technique: The next step is to understand how the equipment
deteriorates which helps in identifying warning effects and criticality of failure. After
completing the failure analysis, it is then necessary to select the most effective monitoring
technique which could identify and predict the failure. The optimum technique would
consider cost as well as results.

iii. Set threshold value/ baseline: This stage involves identifying where and how often to take
the measurements, collecting the baseline readings and setting the threshold value for alarm

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 or warning. The alarm levels would be referred to a known standard and warning levels set
near the system’s normal reading.

iv. Data collection for equipment: The heart of CM lies in the collection. Storage and
interpolation of data. Processing of large amount of data may be time-consuming. It is
therefore important to make collection and assessment as efficient as possible using few
staff members and incurring the lowest running cost. The methd od data collection may be a
manual system, computerized automated system or a hybrid system. The choice of method
will depend on the level of protection that the equipment warrants and cost of method itself.

v. Condition assessment: Data assessment aimes to detect the deterioration in the equipment.
It needs to be performed each time and a new set of measurements is taken. The new
readings may be checked against absolute threshold levels when compared to past readings
to detect any variations or compared with the readings of other similar equipment being run
under similar operating conditions/ In addition, the readings should be checked for the
validity to ensure false alerts are not being generated.

vi. Fault diagnosis: After identifying a problem, it is necessary to find the cause and to ensure
that correct maintenance action is taken i.e to identify the root cause and solve it instead of
suppressing the warning the symptoms. It may involve specialized knowledge to analyse the
existing data to carry out more detailed checks.

vii. Equipment repair: Based on the fault diagnosis report, the workman can repair the
equipment. The supervision can be done by the maintenance engineer.

viii. System review: Once the repair is done, the equipment has to undergo the stpes ii and vii
for review.

Levels of Condition Monitoring

The level 1 visual inspection is carried out more frequently in daily or weekly maintenanace
schedules basis. It is a kind of normal preventive maintenance. The operator involved in this
level is expected to sense the equipment to be monitored by seeing, leaving, touching and
smelling. The various other instruments such as magnifier lenses, viewing devices, tem[erature
sensors and other hand held instruments can assist in this level.

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At level 2, the operators are assisted by the sensor assisted portable instruments to make various
measurements.

Various methods and instruments for condition monitoring

S.NO Parameters to measure Instrument used

1 Temperature Pistol thermometer, Pyrometer, temperature sensitive

taps
2 Speed and distance Tachometer, odometer
3 Vibration Accelerometer,vibration analyzer
4 Electrical quantities such as Voltmeter,ammeter
volt,amp,ohm
5 Wear Thickness gauges
6 Corrosion Corrosion monitor
7 Fits and clearence Proximitymeter

The level 3 monitoring can be carried out with the help of monitoring the condition of lubricant.
The condition of lubricant of the preesence of wear debris in the lubricant can be used as
indicators of the condition of the system. This technique cannot be used only by mere human
senses. Advanced techniques for anlyzing the lubricant are available now.

Fig. Levels of CM

Mini computers and microprocessors based instruments are used in level 4 monitoring. Data
acquisition for the monitored equipment is done by process transducers, accelerometers, counters
and other sensors at different points of the system. The anlysis and processing of such data can
be carried out by using FFT analyser, data loggers and computer networking.

Types of Condition Monitoring

There are three types of condition monitoring as follows:
(i) Subjective Condition Monitoring: Here the monitoring personnel use their perception
of senses and judgment to note any change of the condition. The guidelines or hints

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 where to book for leakage, bearing play etc. posture or figures illustrating different
conditions of components may also be helpful.
(ii) Aided Subjective or condition monitoring with simple gadgets: Here the monitoring
personnel are simple gadgets to add their ability to perceive conditions better. There
gadgets are discussed more in detail in the objective condition monitoring.
(iii) Objective condition monitoring: Different instruments and facilities are used for
obtaining data giving direct measure of the parametric condition of the components
even while the machine is working.

Advantages of Condition Monitoring

⦁ Improved availability of equipment ⦁ Minimized breakdown costs ⦁ Improved morality of
the operating personal and safety. ⦁ Improved reliability ⦁ Improved planning

Disadvantages⦁ Gives only marginal benefits ⦁ Increased running cost ⦁ Sometimes difficult to
organize

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 Cost comparison with and without CM

Explain how cost comparison is done in condition monitoring?

The cost in maintenance department includes wages, spares, overheads, instrument and so
on. It is difficult to allocate accurate proportion of total cost to individual maintenance
components.

The spares, labour cost raises and equipment deteriorate with usage, as shown in figure
the there is steady raise in maintenance cost as plant usage increases.

The above diagram represents expenses against savings and final break down point. The
aggregate graph for the cost of the current maintenance situation and plotted along the
expected costs after installing condition monitoring, The area between two represents
potential savings.

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The cost of installation of CM is high in the starting and operation cost becomes low, but
steady during the life of Condition monitoring equipment.
➢ Introducing Condition monitoring includes both capital and running cost.

Capital cost (Installation):

➢ The cost includes creative access, installing foundation, covering or protecting,
power supply, service acceptance etc. Consulting cost before and after installation is also
included. The cost of training the operator is also included.

Operating cost:
➢ The major cost is man power, fuelling, consumables needed.
➢ Initial cost and saving should result in an early cash outflow for equipment and
training, but soon crosses the breakeven point within acceptable period.
➢ It should then level off into steady profit, it represent satisfying routine on the initial
investment as reduced maintenance cost and improved equipment performance with
overall financial gain.
These are represented in the graph below.

Some of the examples, show the financial benefits to be gained by implementing

condition monitoring techniques, are as follows:
i) A 25 year old flour mill implemented a planned and condition monitoring and achieved
a 43% saving within 12 months,
ii) An estimated benefit of Rs.160 million has been reported by imperial chemical
industries after implementing permanent vibration monitoring systems at a number of
sites.
iii)The successful implementation of an overall condition monitoring plan by British
Petroleum on one site alone has saved a considerable amount of money.
iv) Taxaco’s Pembrock refinery saved nearly Rs.40,000,000 perpendicular year by
implementing an effective energy monitoring and management programme.

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 On-load testing and off-load testing

CM can be done in two methods viz., ‘off load and ‘on load. In OFF-load CM, the machine is
withdrawn from service and disconnected from its normal supply. Measurements, therefore,
tended are to be taken more infrequently to provde satisfactory trending data for diagnosing and
identifying rapidly developing fault conditions. In this system, monitoring equipment is used in
parallel to the equipment to be monitored. Various monitoring points are provided for attaching
such equipment, when needed. Off load monitoring is for interior or inaccessible parts for which
the system needs to be stopped temporarily, to check the condition. However, there may
situations like plants temporary shutdown or time between shifts.

Offload monitoring systems can be periodic or continuous. In periodic monitoring, equipment

are connected during the time of monitoring otr taking data or reading and then removed. In
continuous CM, the monitoring instruments are connected as long as they operate.

Fig. On load CM system

On load monitoring means monitoring or adjusting the parameters while the machine or
equipment is running. Thus it is done for superficial, easily accessible and non interfacing parts
of the equipment which can be carried out without interruption to the operation. On line

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continuous monitoring techniques allow developing faults to be detected before they lead to a
catastrophic failure. It allows the change in maintenance program frm ‘periodic’ or ‘condition
baed’ leading to be more effective maintenance and reduced maintenance costs. In this type of
system, monitoring equipment is built in or installed in series with the running equipment.
Online monitoring systems are generally continuous with provision to by-pass.

On load CM also offers other advantages such as limiting the severity of any damage incurred,
enabling accurate identification of failure cause, enabling better business decisions such as
replacement.

How system approach to condition monitoring can be useful? Explain.

In traditional or holistic approach of condition monitoring, the components of a
equipment are monitored independently. A complete system consists of sub-assemblies
formed of these components. Monitoring of individual components involves recording of
information for result oriented operational control, which is not efficient. This approach
clearly identifies key maintenance and reliability activities, explains their interactions and
how they can be integrated into the whole management process. It enables the
organization of the whole maintenance process rather than focusing on individual
elements or jobs. A good maintenance management process can be considered as having
the following six phases:
• Work identification
• Work planning
• Work scheduling
• Work execution
• History recording
• Analysis

In system approach to maintenance, monitoring of a equipment is done by considering it

as a system. For proper identification and communication of all of the above six phases, a
system approach is developed, it includes proper cataloguing, codification and
computerization of all the actions/activities, assets and materials related to maintenance
of all the departments and work areas and integrating them into one system.

This approach provides an enterprise database that enables to capture and analyze data
about current and historical maintenance work. It also helps keep track of the cost of
maintaining any piece of equipment, work orders and labour time, and key performance
indicators and benchmarks throughout the maintenance operation.

In system approach, a separate sensor is to be used independently, to measure each

characteristics of a component for example, bearings. When this approach is employed,
the output of one sensor can give information, on more than one sub-assembly.
Therefore, monitoring at sub-assembly level reduces the number of sensors, which is the
concept of system condition monitoring technique.
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 Methods and instruments for CM
Various methods and instruments for condition monitoring
S.NO Parameters to measure Instrument used

1 Temperature Pistol thermometer, Pyrometer, temperature sensitive

taps
2 Speed and distance Tachometer, odometer
3 Vibration Accelerometer,vibration analyzer
4 Electrical quantities such as Voltmeter,ammeter
volt,amp,ohm
5 Wear Thickness gauges
6 Corrosion Corrosion monitor
7 Fits and clearence Proximitymeter

Describe the various types of Non-destructive testing techniques for condition

Monitoring
Various condition monitoring methods have been developed for the past 35years and are
in use. A number of strategies and techniques exist for collecting condition data and
interpreting it for taking corrective action.

➢ The success of condition monitoring depends in the efficiency of identifying the

deteriorating trend in the machine components. For this purpose, it is essential to
recognize the source or cause of failure. There is variety of technologies that can and
should be used as part of a condition monitoring program. The extensive range of
monitoring techniques available is listed in table.

Type Method On/off Comments

line
Visual Human eye On/off Covers a wide range of highly effective
Inspection condition checking and surface inspection
methods.
Off
Can be used for internal inspection of
machines, good for detecting surface
corrosion, wear and severe defects like
cracks.

Permits detailed inspection of inaccessible

CCTV environment machine parts. Image
recording and high resolution analysis is a

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 post-processing
possibility.
Vibration Overall On Represents the vibration of a rotating or
monitoring vibration level reciprocating machine as a single, number
which can be trended and used as a basis for
the detection of common machine faults,
but fault diagnosis is not possible and
Frequency detection capability can be compromised.
(spectrum)
Analysis On Represents the vibration of a rotating or
reciprocating machine as a frequency
spectrum which reveals the discrete
frequency component content of the
vibration. Provides the basis for fault
Shock pulse detection, diagnosis and severity
monitoring On assessment.
(SPM), Spike
energy and On All of these techniques use high frequency
Kurtosis vibration signals to detect and diagnosis a
range of faults including rolling element
Structural bearing damage, lubrication failure and leak
Monitoring detection.

Off

A variety of vibration-based techniques

exists for the detection and location of
structural faults. The majority of such
techniques involve imparting a known
vibration into the structure and analysing
the resulting response.
Temperature Temperature ON Simple and effective aids to visual
Monitoring crayons, paints inspection. Can resolve body temperature to
and taps perform from a distance at a glance.

Range from stick-on thermometric strips to

Thermometers, On permanently installed thermocouple
Thermocouples sensors. Can give visual temperature
readout or an electrical input to a hard-
wired monitoring system.

Infra-red meter On Non-contacting device which measures

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 radiated body heat to estimate the surface
temperature of a component.
Covers a wide range of temperature but acts
only on a small area.

Infra-red On As above but can cover a much wider

camera surface area. Can provide a detailed surface
temperature picture and can be calibrated to
give quantitative measurement.

Crack Dye penetrant On/Off Detects cracks which break the surface of
monitoring the material.

Magnetic flux On/Off Detects cracks at/near the surface of ferrous

materials.

Corrosion Weight loss

monitoring coupons

Vibration monitoring system

What is Vibration Analysis?

Vibration analysis is defined as a process for measuring the vibration levels and frequencies of
machinery and then using that information to analyze how healthy the machines and their
components are. While the inner-workings and formulas used to calculate various forms of
vibration can get complicated, it all starts with using an accelerometer to measure vibration.
Anytime a piece of machinery is running, it is making vibrations. An accelerometer attached to
the machine generates a voltage signal that corresponds to the amount of vibration and the
frequency of vibration the machine is producing, usually how many times per second or minute
the vibration occurs.
All data collected from the accelerometer goes directly into a data collector (software), which
records the signal as either amplitude vs. time (known as time waveform), amplitude vs.
frequency (known as fast Fourier transform), or both. All of this data is analyzed by computer
program algorithms, which in turn is analyzed by engineers or trained vibration analysts to
determine the health of the machine and identify possible impending problems like looseness,
unbalance, misalignment, lubrication issues and more. Vibration analysis can detect problems
such as:
• Imbalance • Mechanical looseness
• Bearing failures • Misalignment

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• Resonance and natural frequencies • Empty space or bubbles (cavitation) in
• Electrical motor faults pumps
• Bent shafts • Critical speeds
• Gearbox failures
Example: a damaged bearing track causing a bearing roller to generate vibration each time
it contacts the spall (similar to a pothole on a highway). If three bearing rollers hit the spall
per revolution, you should see a vibration signal of three times the fan's running speed.

Vibration Analysis Methodology

While accelerometers are still the most common tool used to collect vibration data, modern
technology and improved sensor technology have allowed for non-contact, high-speed laser
sensors that can detect issues accelerometers can't. This allows for a more accurate and more
localized analysis, and opens up vibration analysis to more methodology. Vibration analysis is
generally broken down into four principles, and each principle gives you specific information
on the working conditions and features of the vibrating parts.

1. Time domain: When a vibration signal is picked up from a transducer (device that
converts a physical quantity into an electrical signal) and displayed on the screen of an
oscilloscope, it's called a waveform. This signal is in the time domain. The time domain
is amplitude plotted against time. While most machine vibration issues are detected using
spectrum analysis, some types are more easily seen in waveform.

2. Frequency domain: When the waveform discussed earlier is subjected to spectrum

analysis, the end result is a picture of frequency vs. amplitude, known as a spectrum. The
spectrum is in the frequency domain like the vibration is in the time domain. Most in-
depth analysis of machinery vibration is done in the frequency domain or using spectrum
analysis.
3. Joint domain: Because vibration signals vary with time, calculating more than one
spectrum at once can be useful. To do this, a joint time technique called Gabor-Wigner-
Wavelet can be utilized. This technique is used to calculate variations of the fast Fourier
transform (discussed below), including short-time Fourier transform (STFT).
4. Modal analysis: Modal analysis takes measured frequency response functions of a piece
of machinery and puts them into a computer model. The computer model can be
displayed with animations of all the different vibration modes. The model can be adjusted
by either adding to or taking away things like mass or stiffness to see the effects.

Forms of analysis, calculations and algorithms

Outside of these four basic principles lie numerous forms of analysis, calculations and
algorithms used to determine different aspects of vibration analysis. These include:

• Time waveform: A time waveform is acceleration vs. time displayed as tables and plots.
Time waveforms show a short time sample of raw vibration, revealing clues to the
condition of machinery not always clear in the frequency spectrum. A method of
employing time waveform vibration signals as a vibration analysis tool is by using FFT.

• Fast Fourier Transform (FFT): FFT is defined as an algorithm used to calculate a

spectrum from a time waveform. In other words, it's a calculation intended to break down

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 a signal into all its frequencies. If you'll recall time domain and frequency domain
discussed above, FFT converts a signal from the time domain into the frequency domain.
Fast Fourier transform is most often used for detecting machine faults like misalignment
or unbalance.

• Phase measurement: When talking about vibration analysis, phase is a relative time
difference between two signals measured in units of angle as opposed to time. It only
works if the two signals being compared are of the same frequency. Phase measurement
is used in tandem with FFT to decipher machine faults like loose parts, misalignment and
unbalance.

• Order analysis: Order analysis is a variation of FFT analysis and is mostly used to
quantify vibrations of machines with varying revolutions per minute (RPM). In other
words, order analysis is frequency analysis where the spectrum's frequency axis is shown
in orders of RPM rather than hertz. The term "orders" refers to a frequency that is a
multiple of a reference rotational speed. For example, if a vibration signal is equal to
twice the frequency of the motor's rotation, the order is two.

• Power spectral density (PSD): Power spectral density is calculated by multiplying the
amplitude from the FFT by its different forms to normalize it with the frequency bin
width (bin width refers to the grouped x-axis values). Think of PSD as looking at
"random" vibrations or motion at many different frequencies. PSD accurately compares
random vibration signals that have different signal lengths.

• Envelope analysis: Envelope analysis is a form of vibration analysis that can detect
impacts with very low energy often hidden by other vibration signals. It's a popular
diagnostic tool for damaged gear teeth and roller bearings.

• Orbit: The orbit is defined as a plot of a sleeve bearing journal's centerline. It's
measured by placing two probes in the bearing housing 90 degrees apart. Data from these
probes can be displayed digitally and used to detect shaft vibrations caused by oil whirl -
oil whirling around inside, causing the journal to move.
• Resonance analysis: Resonance analysis identifies all the natural vibrations and
frequencies in machines. The presence of resonance means high vibration, which could
reach damaging levels.

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Time domain: When a vibration signal is picked up from a transducer (device that converts a
physical quantity into an electrical signal) and displayed on the screen of an oscilloscope, it's
called a waveform. This signal is in the time domain. The time domain is amplitude plotted
against time. While most machine vibration issues are detected using spectrum analysis, some
types are more easily seen in waveform.

Wave form analysis consists of recording the time history of the vent on a storage oscilloscope
or a real time analyser. By using this methid, descrete damage occuring in gears such as broken
teeth on gears and cracks in the inner and outer races of the bearings can be identified relatively
easily. An example of time domain waveform is shown in figure below where the waveform of
the casing vibration acceleration of a single stage gear box with a broken tooth is presented.
Indices are also used in vibration analysis. The peak level and root mean square RMS level are
often used to quantify the time signal. The peak value and RMS value may not be reliable in
detecting damage in continuously operating systems. Therefore, the ratio of peak value to RMS
value called as crest factor is used as trending parameter as it includes both parameters.
Synchronous averaging is the time signal averaged over a large number of cycles and
synchronous with the running speed of the machine. This technique removes all background
noises and it is also used to monitor the periodic events which are not exactly synchronous
diagnosis where multiple shafts are present. All components not synchronous with the shaft of
interest can be deleted.

The orbit analysis is used in monitoring journal bearing wear. Here two transducers are used to
take the vibration measurement. The outputs are phase shifted by 90 degree on an oscilloscope
where the time base is substituted with the signal from one of the transducers.

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When the shaft relative displacement sensors are used, the pattern obtained is the sahft orbit and
it can be used to indicate journal bearing wear, shaft misalignment, shaft imbalance and shaft
rub.
Statistical analysis can also be carried out on time domain data. This method follows the
probability density technique. The probability density is the probability of finding instantaneous
values within a certain amplitude interval divided by the size of the interval. All signals will have
characteristic probability density curve shapes. These curves if derived from machinery vibration
signals can subsequently be used in monitoring machine condition.

Frequency domain: When the waveform discussed earlier is subjected to spectrum analysis, the
end result is a picture of frequency vs. amplitude, known as a spectrum. The spectrum is in the
frequency domain like the vibration is in the time domain. Most in-depth analysis of machinery
vibration is done in the frequency domain or using spectrum analysis.

Signature spectrum analysis takes the incoming signal and breaks it into its individual
frequencies by using either an analogue filter or a software process called Fourier analysis. This
process is extremely powerful and is used extensively for trending and diagnosis. It relies on the
ability to link particular frequencies to particular components such as bearings or gears.
However, spectra generate large volumes of information which require expert staff of software to
interpret them.

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Enveloped spectrum analysis technique is applied in condition monitoring when background
vibrations have to be suppressed. Thus, it limits the monitoring to the appropriate frequency
range. The enveloped spectrum has been shown to be particularly useful in monitoring machine
elements that fail by producing relatively short duration impulse. This feature is a typical of
incipient damage in rolling element bearings. Often, incipient damage in rolling element bearings
cannot be detected using signature spectrum analysis as the energy contributions by these
impulses are usually swamped by vibration components of more dominant elements. This
technique involves first, a high pass filtering operation to remove dominating low-frequency
components in the spectrum. The resulting signal is then rectified partially or fully. A normal
frequency spectrum is then derived using either a real time analyser or computer.

Broad band technique acquires overall ot broad band vibration readings from select points on a
mchaine. Overall readings are obtained by taking the raw signals from transducer and obtaining
peak, peak-to –peak or RMS values of the signal. They can then be recorded. These data are
compared with either a baseline reading from a new machine or vibration severity charts to
determine the relative condition of machine. Broadband or overall RMS data are strictly a gross
value or number that represents the total vibration of the machine at the specific measurement
point where the data were acquired. It does not provide any information pertaining to the actual
machine problem or failure mode. This technique can be best used as a gross scan of the
operating condition of critical process machinery.

Narrowband trending such as broad band monitors the total energy for a specific bandwidth of
vibration frequncies. Unlike broadband, narrowband analysis uses vibration frequencies that
represent specific machine components or failure modes. This method provides the means to
quickly monitor the emchanical condition of critical machine components. This technique
provides the ability to monitor the condition of gear sets, bearings and other machine
compoenets without manualanalysis of vibration signatures.

Vibration Analysis Measurement Parameters

All of these vibration analysis techniques help to identify three major parameters: acceleration,
velocity (RMS) and displacement. Each of these parameters emphasizes certain frequency ranges
in their own way and can be analyzed together to diagnose issues. Let's take a look at each
parameter.

• Acceleration: Acceleration places greater importance on high frequencies. An

acceleration signal is not exclusive, however. The acceleration signal can be converted to
velocity or displacement.

• Displacement: Just like acceleration places greater importance on high frequencies,

displacement looks at low frequencies. Displacement measurements are generally only
used when examining the broad picture of mechanical vibrations. You might use
displacement to discover unbalance in a rotating part due to a significant amount of
displacement at the rotational frequencies of the machine's shaft.

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 • Velocity: Velocity is related to the destructive force of vibration, making it the most
important parameter. It places equal importance on both high and low frequencies.
Usually, the RMS value of velocity (measured in the range of 10 to 10,000 Hz) shows the
best sign of vibration severity. RMS is calculated by multiplying peak amplitude by
0.707.
Below is an example of what acceleration, displacement and velocity look like on the same
signal. You can see some peaks at the same frequencies, but each has different amplitudes. This
is a good visual of how each parameter assigns different importance to frequency ranges.

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Benefits of Continuous Vibration Monitoring
If implemented properly, continuous vibration monitoring helps you optimize machinery
performance. With the use of modern technology, you can take continuous vibration readings on
various equipment in real time and have the data sent directly to your smartphone, tablet or
desktop via the cloud.
• Monitor critical equipment: Critical equipment is any piece of equipment or machine
that could cause you to take a big financial hit if a failure were to occur. Continuous
vibration monitoring helps detect discrepancies in the vibration spectrum, which can
reveal lubrication issues and bearing defects well before major issues appear.
• Monitor heavily used equipment: Many plants operate 24/7, only stopping monthly or
quarterly for routine maintenance. Stopping more than this can cost the plant a significant
amount of money. Online continuous vibration monitoring helps monitor the condition of
heavily used machinery or troubled machinery and sends alerts when that condition
changes.
• Monitor difficult-to-access equipment: Performing maintenance on equipment located
in hard-to-reach places is difficult. Machines on rooftops, cooling towers and those
operating in high-temperature areas can be continuously monitored for vibration
abnormalities, allowing maintenance to be done at a convenient time. This prevents
unplanned downtime and keeps maintenance staff from accessing these locations
unnecessarily.

Vibration Analysis Case Study

The tools and techniques used in the vibration analysis process can be a bit confusing on paper,
so let's take a look at a real-world example from IVC Technologies. This particular case study
examines the testing of an air-handling unit in a pharmaceutical facility. The unit is needed to
run two supply fans at capacity to meet enclosed air-flow requirements. The air-handling unit has
two direct-coupled fans, each equipped with a 150-horspower motor. The initial assessment of
the fan unit showed the unit to run normally when one fan was running, but once the second fan
was turned on, vibration issues presented themselves at certain set points.

Vibration analysis revealed that once fan No. 2 was turned on, a slight increase in vibration
amplitude across all three points of measurement occurred, while fan No. 1 remained the same.
Testing showed the highest amplitude appeared in the motor outboard vertical at 0.456 inches
per second, with a dominant peak at 841 cycles per minute, according to IVC Technologies. This
indicated the problem might be a structural resonance vibration, since spectral data showed no
other signs of mechanical issues.

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As the consultant, recommended the company inspect the frame's structure and the dynamic
absorber of fan No. 2. A bump test was also recommended to further locate and analyze the
resonance vibration.

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Temperature monitoring system

What is thermal monitoring and what thermal monitoring are used in industries Explain
principle and uses of thermograph

Temperature is defined as a measure of velocity of fluid particles. It is a property which is used

to determine the degree of hotness or coldness or the level of heat integrity of a body.
Instruments for measuring ordinary temperature are known as thermometers and these
measuring high temperature are known as pyrometer. On large engines, compressors, boilers,
turbines and for all major bearings temperature transducers are included, sometimes added with
shut down circuits and alarms if temperature gets above certain limits.

The hardware for infrared is becoming more and more powerful. An infrared gun take spot
temperature without imaging capacity.

The techniques used in such monitoring may be one or more of the followings.
• Temperature crayons & tapes.
• Thermometer and optical pyrometers.
• Softening comes / wave paints.
• Bimetallic strips
• Thermocouples and fusible plugs
• Thermisters
• Thermo diodes and thermo resistors.
Temperature crayons and taps: Temperature monitoring by feel of hand or by simple
measuring items / instruments, like thermometers, temperature crayons and tapes etc. is an age
old practice of finding out defects or defective components. Temperature stickers are the most
common and cost effectives. Thermo – diodes & thermo – transistors

Thermodiodes It is a widely use method for measuring temperature. When the

temperature of doped semiconductors changes, the mobility of their charge carriers
changes and this effects the state at which electrons and holes can diffuse across a PN
Junction.The difference in voltage and current through the junction is a function of the
temperature.

Thermo Transistors in thermo-transistor the voltage across the junction between the base and
the emitter depends on the temperature. A common method is the use of two transistors with
different collector currents to find the difference in the base emitter voltage between them. The
difference is the measure of temperature. It can be combined with circuit components on a single
chip to give a temperature sensor.

Infrafed Thermography. This technique uses the distribution of surface temperature to assess
the structure or behavior of what is under the surface. It is non contact sensing method concerned
with the measurement of radiated electromagnetic theory. The energy emitted by a surface at a
given temperature is called spectral radiance and it is the property concerned with emissivity.

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 Types of thermography

Passive thermorgraphy The temperature difference (T) of 1 to 2ºc is generally found

suspicious. A T of 4ºc value is a strong evidence of abnormal behaviours. In most of the
applications, passive thermography is ralter qualitative since the goal is simply to
pinpoint of the type go / no – go.

Active thermography It is an externally applied thermal stimulation is needed to

generate meaningful thermal constrasts that will yield to the detection of sub surface
abnormalities

Discuss the benefits from condition based maintenance.

1. Safety:
The injury and fatal accidents can possibly be reduced by adopting the safety measures in
equipment and system. So, the condition based maintenance enables the system by
indicating the future failure in the form of giving signal to the operator.
2. Extended useful life:
The continuous monitoring enables the system to avoid sudden failures which is not
unscheduled. It extends the life of the equipment considerably.
3. Enhanced availability:
The breakdowns are minimized through proper maintenance which leads to increase the
availability. It is achieved by reducing the down time.
4. Reduction in maintenance time:
The repair time and fault correction time can be reduced by condition based maintenance.
5. Improved output:
The output of the process is directly linked with the availability, enabled life of the
equipment, reduced maintenance time. The condition based maintenance improves these
three factors which lead to improve the quality of products.
6. Quality product:
The better quality products could be ensured through condition based maintenance with
healthy equipment in the process line. The quality of the products will satisfy the
customer expectation.
7. Improved reliability:
Since the condition monitoring can predict the possible failures, it is possible to remove
or replace a piece of equipment before any series consequences arises and hence, the
reliability of the equipment can be improved.
8. Improved planning:
Condition monitoring also helps in improving maintenance and production planning. This
is due to the fact that the ability to predict the onset of failure ensures that the
organisation of materials and staffing can be carried out in advance, and fitted into any
existing schedules. The reduction in unexpected failures should reduce the need to
reschedule or cancel the existing work.

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 Wear-debris analysis

What is wear debris analysis? What are the wear debris analysis techniques commonly
used and compare their performance and uses?
Wear debris analysis (WDA) is related to oil analysis only in that the particles to be studied are
collected through drawing a sample of lubricating oil, wear debris analysis provides direct
information about the wearing condition of the machine train, where as the lubricating oil
analysis determines the actual condition of the oil sample.
Particles in the lubricant of a machine can provide significant information about the
condition of the machine. This information is obtained from the study of particle shape,
composition, size and quantity.
Wear debris analysis is normally conducted in two stages. The first method is routine
monitoring and trending of the solid content of the machine lubricant. The continuous trending
of wear rate monitors the performance of machine and provides early warning and diagnosis.
In simple terms, the quantity, composition, and size of particulate matter in the lubricating oil
are indicative of the mechanical condition of the machine. A normal machine will contain low
levels of solids with a size less than 10 micrometers.
Different mechanical systems have different life and minimum component wear.
International organization for standardization (ISO) set up cleanliness codes for proper
lubricating analysis defined as the number of particles per millilitre greater than 5,15,25,50 and
100 microns.
The second method involves analysis of the particulate matter in each lubricating oil sample
is run through a particle counter. The counter passes the lubricant stream through a beam that
measures the number and sizes of the solid particle contained in the fluid.
If the wear debris concentration indicates that are too many particles in a given size range,
then further investigation is required. The solid components are then inspected under a
microscope. The results of this test include particle identification, possible sources, suggestions
on corrections, and picture of the particles.
Five basic types of wear can be identified according to the classification of particles: rubbing
wear, cutting wear, rolling fatigue wear, combined rolling and sliding wear, and severe sliding
wear. The following table summarises the different types of wear and its description.

SI. No Types of wear Description

1 Rubbing wear Particles<20 micron chord dimension and =1 micron thick. Results
from flaking of pieces from mixed shear layer mainly benign.
2 Cutting wear Swarf like chips of fine wire coils. Caused by abrasive cutting tool
action.
3 Rolling fatigue Chunky, several micron thick from, e.g. gear wear, 20-50 micron
chord width, primary result of rolling contact bearing failure.
4 Combined Typically ferrous, 1 to >10 micron diameter generated when micro
rolling and cracks occur under rolling contact fatigue condition.
sliding wear
5 Severe sliding Large>50micron chord width, several microns thick. Surfaces
wear heavily striated with long straight edges. Typically, found in gear
wear, caused by excessive loads or heat in the gear system.

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WEAR DEBRIS ANALYSIS METHODS
A wide variety of basic techniques is used in the detection, and evaluation, of the wear debris
present in a lubrication system. The monitoring equipment which has evolved from these
techniques may be used on-line or off-line. The various basic techniques used are briefly
described as follows:
(a) Optical methods:
There are three techniques used by applying optical method.
i) Light of obstruction technique
This technique uses the change in light intensity which occurs when particle debris pass
though a light beam. The intensity change is detected using a photodiode and the output
is calibrated to give the particle size for the flow conditions. Any change in flow
conditions and particle properties requires a recalibration of the instrument.
ii) Time of transition technique
This technique uses a scanning laser beam and is based on the principle that the time of
interaction of a particle within the beam depends directly on the particle size. The
technique is independent of the type of fluid used and therefore does not require
calibration.
iii)Forward reflectance technique
This technique is based upon the reflectance of light at a very shallow angle of incidence.
The light is reflected forward in a narrow angle band, and occurs at an intensity
depending upon the surface area which is impinged by the light beam. This in turn
depends upon the particle size.
(b) Filler blockage:
This technique depends upon the change in the pressure characteristics which occur when an
orifice is blocked by debris within the liquid passing though that orifice.
In practice, screen or mesh is used which consists of a number of same-sized orifices.
Any particles in the fluid which are larger than the orifice size will cause a blockage,
thereby decreasing the flow rate through the mesh.
(c) Magnetic attraction:
This technique uses the magnetic susceptibility of ferrous contaminants to separate the debris
from the carrying fluid. The separation is brought about by a variety of methods such as the use
of a permanent magnet or a magnetic filter. Those instruments which separate the debris in a
manner suitable for further examination and analysis are generally offline monitors. Magnetic
plug method is an on-line debris collector. This technique collects the ferrous debris from the
passing fluid by using magnetized sensing heads. The debris is allowed to build up over a
specified period of time, and the wear rate is calculated from the weight collected or the change
in magnetic flux. The debris is released back into the system at the end of each measuring cycle
by demagnetizing the collecting zone.

(d) Wear:
This is a technique whereby the electrical resistance of an wear debris contained within the
flowing fluid are allowed to impinges upon the sensor, causing a wearing away
of the sensor material, and hence increasing its electrical resistance. The change in resistance
depends upon the rate change in sensor wear and therefore, upon the hardness,
sharpness and frequency of the particles striking the sensor.

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(e) Ultrasound:
This technique uses a pulsed ultrasonic acoustical beam focused into a fluid, such that it will
sense the presence of particulate matter within that liquid. Maximum sensitivity is achieved at
the focus of the acoustic beam. Hence, any passing debris will interrupt the beam and cause a
change in the strength of the reflected pulse signal, as seen by the receiver. The rate of change in
the strength of the reflected pulse can be used to quantify and size the particles present in the
fluid stream.

(f) Radioactivity:
This technique involves the monitoring of irradiated wear particles which have resulted from the
wear of an irradiated component. The method is carried out by either, monitoring the particles
using gamma ray detection units within the vicinity of the irradiated work part, or by monitoring
the decrease in radioactivity of the component itself.

(g) Electrical conductance:

A technique which depends upon the electrical conductivity of the debris within a non-
conducting fluid. The capture of conductive particles between two electrical terminals results in
bridging the gap between them, and this causes a short circuit which indicates their presence.
The capture is brought about by using a magnetic plug arrangement and therefore the debris must
be ferromagnetic.

(h) Image analysis:

Basically a technique involving the computer analysis of video camera images of dried and
cleaned particles extracted from a carrier fluid. The particles are first extracted using filtration or
magnetic separation etc. Onto a substrate for viewing by means of an optical microscope. The
microscope image is translated into an electronic digital picture through a video camera and an
image processing system. The electronic image is then analysed using computer software
techniques to produce information with respect to size, shape, texture, colour etc.

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 Wear Debris Analysis Case Study
The clinker hammer crusher is one of the main pieces of equipment in cement production and is
used for the crushing of clinker, the main product of cement kilns, into smaller parts for the
preparation of grinding. At CEMEX Egypt, the bearings used in the clinker crusher are spherical
roller bearings. These bearings are lubricated with a lithium complex thickened grease with a
synthetic base oil designed for high-temperature applications.

Fig. Clinker Hammer Crusher

At the CEMEX plant, bearing failures can lead to a halt in cement production. To maintain
continuous operation, it is critical for the bearings to operate smoothly. As part of the predictive
maintenance program, vibration analysis is used to monitor the condition of the crusher.
A grease sample to analyze wear debris was taken at the first shutdown of the clinker crusher as
part of a new program to monitor the performance of equipment. Vibration monitoring of the
outboard bearing in the third clinker crusher line at a speed of 360 RPM provided no warning
signals. During the next scheduled shutdown, the bearing was opened and a sample of grease
was taken. Wear debris analysis was performed on the grease sample to find the cause of the
bearing failure that occurred.

Wear Debris Analysis

Wear debris analysis was carried out on used greases by extracting magnetic particles from the
sample using a magnet. Microscopic analysis of the sample identified numerous small and large
spherical particles. Research has shown that spherical wear debris can reveal the severity of
rolling-contact fatigue wear. Because large spherical particles (50 microns) are the product of
high metal-to-metal contact and high frictional temperature, their presence is considered a
supporting symptom for assessing the wear severity levels.

52ZM Stereoscopic Zoom Microscope Magnet Used to Extract Wear Debris

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Wear particles were considered to be a critical alarm indicating the need to change the bearing
before a forced outage occurs.

Follow-up Inspection
During shutdown, the crusher's outboard bearing was replaced. To check for potential defects,
the bearing was opened and visually inspected. A close look of the outer race of the defective
bearing showed signs of severe wearing.

Large and Small Spherical Particles Found in a Bearing Grease Sample

Defective Bearing Shows Signs of Severe Wear

This case study illustrates the efficiency of condition monitoring based on the detection of debris
in grease, which can be a resourceful tool in controlling machine condition and should integrate
diagnostic devices.

References
1. Sabrin Gebarin and Jim Fitch. "Origin of Spherical Particles in Lubricants." Practicing Oil
Analysis magazine, March 2005.
2. Ray Garvey. "Enhanced 5200 Minilab Offers Improved Oil Analysis." Practicing Oil
Analysis magazine, July 2005.
3. Jian Ding. "Determining Fatigue Wear Using Wear Particle Analysis Tools." Practicing Oil
Analysis magazine, September 2003

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Using a variety of methodology, used oil analysis can better predict the type of wear
occurring and the component part experiencing wear.

Spectrochemical Analysis
The most common method employed is spectrochemical analysis, which directly measures
the concentration of wear metals in parts per million (ppm), such as iron, chrome, tin
aluminum, copper, lead, etc. ICP and Emission Rotrode are the two most common
instrumentations for used oil trending analysis. Though there is a particle size limit of 8 to
10 micron for absolute concentration measurement for these instruments the methodology
is relevant and applicable since wear limits established for different equipment designs are
based on measurements using this type of instrumentation. The fact that wear particles are
larger than 10 micron does not mean the spectrometer does not see the particle, the
instrument just sees less of the overall surface area. By determining which types of metals
are showing up in the spectrochemical analysis, such as copper, iron, or tin, a
determination can be made as to which equipment components are experiencing the wear.

Particle Quantifier Index (PQ Index)

PQ Index is an excellent trending tool for monitoring the relative amount of ferrous (iron)
particles in a used oil sample. The higher the PQ Index reading the higher the relative
amount of iron within a sample due to wear or contributing to wear. Gearboxes will
normally generate more iron than hydraulic systems, therefore trending limits would be
higher for a gearbox. This test is often used in conjunction with spectrochemical iron
readings quantified in parts per million (ppm) to determine general iron particle size and
rate of wear. PQ Index can predict accelerated wear or impending catastrophic wear,
especially if there is a sudden upswing in the trend analysis.

Direct Reading Ferrography

Though similar to PQ Index, Direct Reading Ferrography is used less often within ALS
Tribology than PQ Index since it is more costly and time consuming. Direct Reading
Ferrography is a trending tool employed to monitor the relative level of ferrous wear
material within an oil sample. The method uses an instrument that passes the sample
through a magnetic field to capture and quantify the relative amount of ferrous wear
particles.

Wear Particle Analysis—Patch Test

A common method for making a more detailed determination of wear occurrence,
especially for non-ferrous materials is to employ a Patch Test Examination using a
microscope for Wear Particle Analysis. A measured portion of used oil is filter through a
filter patch and visually examined microscopically for a qualitative report on the wear
material captured. Observation will generally be accompanied by a photo of the filtered
wear material on a test report.

LazerNet Fines
Some ALS Tribology laboratories use Lasernet Fines instrumentation, which was
developed by Lockheed Martin with the Naval Research Laboratory for military
application. Using direct digital imaging LaserView test results classify particles larger

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than 20 micron into cutting wear, severe sliding wear, fatigue wear, and nonmetallic
material. The analysis economically combines features of particle count determination with
quantifying wear particle classification for industrial, gear and drivetrain components
without subjective interpretation. More information is provided than just using PQ Index.
The test data compliments other wear analysis techniques by using laser imaging and
advanced image processing software to identify and measure:
● Type of wear mechanism
● Rate and severity of wear processes
● Wear particle size distribution
● Particulate contamination and oil cleanliness
Data Reported
Wear mode statistics for particles >20 um which include:
● Cutting wear, size range number/ml, mean size (um), maximum size (um)
● Severe sliding wear, size range number/ml, mean size (um), maximum size (um)
● Fatigue wear, size range number/ml l, mean size (um), maximum size (um)
● Nonmetallic particles, size range number/ml, mean size (um), maximum size (um)
Particle counting and industry cleanliness codes include:
● Particle ISO Cleanliness Rating for >4, >6, >14 micron
● Maximum Particle Size
● Mean Particle Size
Analytical Ferrography (MPE)
Analytical Ferrography, referred to within ALS Tribology as Microscopic Particle
Examination or MPE, utilizes a skilled analyst examining a prepared ferrogram slide with a
computer aided microscopic to identify the composition of the material present in a used
lubricating oil sample.

Wear material and other debris suspended in a lubricant is deposited and separated onto a
ferrogram slide maker. The sample is diluted to improve particle separation onto the
ferrogram slide. Magnetic separation of wear material from the lubricating fluid attracts
ferrous particles out of the oil onto the ferrogram slide maker. Though the method is biased
to ferrous material, other nonferrous wear particle and contaminants are also captured and
identified. The slide is examined under a microscope to distinguish composition,
morphology (shape and origin of particle), particle size and relative concentration of the
ferrous and non-ferrous wear particles. Treatment of the ferrogram with heating and
chemicals will further distinguish identification of the metallurgical composition of the
wear material.

The skilled analyst performs the analytical ferrography to provide a root cause for wear
mechanisms based on the morphology and composition of the particles, as well as which
equipment component the wear particles originated from. The analyst will report material
composition and wear morphology that will include, but is not limited to the following:
● Ferrous wear particles
– High alloy steel
– Low alloy steel
– Dark metallic oxides and cast iron
– Red oxides (rust)

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● White nonferrous metal particles
● Yellow metals wear particles
● Contaminants, dirt (silica), fibers and other particulates
● Fatigue Wear
● Sliding Wear
● Cutting Wear—Abrasive Wear
● Adhesive Wear
● Corrosive Wear

Other methodology:
Particle Count—ISO Cleanliness Rating
Some laboratories use particle count for determining wear material. This methodology
would have some disadvantages if employed strictly for this purpose. Many times
equipment such as gear boxes and drivetrain components inherently contain a large
concentration of particles because they may not be filtered and are not regarded as “clean
systems”. Therefore, the particle count determination does not necessarily correlate with
wear conditions since the particles counted can be wear material along with anything else
in the oil system. On the other hand, “clean systems” such as hydraulic and turbine oils
should be monitored for particle count determination in order to maintain the required level
of oil cleanliness the equipment specifies. There is a direct correlation between oil
cleanliness in “clean systems” equipment life.

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What is meant by Thermography?
A Thermography technique uses the distribution of surface temperatures to assess the structure
or behaviour of what is under the surface.
Types of Thermography: i) Passive Thermography ii) Active Thermography

Name the types of pyrometers.

i) Total radiation pyrometers
ii) Infra red pyrometers
iii) Optical pyrometers

List down the features of Resistance Temperature Detectors (RTD).

i) High degree of accuracy.
ii) Resistance thermometer is interchangeable in a process without compensation
or recalibration.
iii) It is normally designed for fast response as well as accuracy to provide close control
of processes.

What are the five types of wear?

Rubbing wear, Cutting wear, rolling fatigue, combined rolling and sliding wear, Severe sliding
wear.

What are the functions of Temperature Sensitive Tapes?

A tape having four of five 20 mm diameter dots of special paints, each of which changes its
colour at a particular temperature is stuck to the heat prone parts of the equipment.

4. What is wear debris analysis?

Concentration and characterization of wear metals and other contaminants, suspended in used
oil, mainly from the machine components, through which the oil interfaces and generates some
wear metals and wear particles.

Contaminants (wear debris or wear particles) generated due to interaction between the various
components / parts of the machine and carried away by the lubricant to sumps,
these are known as Wear Debris Analysis or Contaminant Analysis or Wear Particle Analysis.

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Unit-III Condition monitoring
1. What is condition monitoring? Explain the process involved in condition monitoring?
2. Explain the types and levels of condition monitoring?
3. Explain the cost comparison with and without condition monitoring?
4. Describe the various methods and instruments for condition monitoring?
5. Explain in detail wear debris analysis?
6. How system approach to condition monitoring can be useful? Explain.
7. Discuss the benefits from conditioned based maintenance.
8. Explain various methods and instruments for condition monitoring.
9. Briefly explain the leakage monitoring.
10. Write short notes on 1) Check mode 2) Learning mode 3. Testing mode
11. Explain with a neat sketch the graphical representation of condition monitoring.

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