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M T R O

FIFTH UNIT

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M T R O

FIFTH UNIT

CONDITIONAL BASED MAINTENANCE

1. What is conditional based maintenance? What are the different types

of condition based maintenance?

Maintenance carried out in response to a significant deterioration

in a condition or performance is called condition based maintenance.

Condition based maintenance differs from both failure

maintenance and fixed time replacement is that it requires monitoring of

some condition indicating parameter of the unit being maintained. This

contacts with failure maintenance which impulses that no successful

condition monitoring is undertaken and with fixed time replacement,

which is based on statistical failure data for a type of unit in general

therefore, condition monitoring undertaken and with fixed time

replacement which is based on statistical failure date for a type of unit in

general therefore condition based maintenance will the more efficient and

adaptable than either of other maintenance actions on indication of

deterioration the unit can be scheduled for shut down at a time chase in

advance of failure let if the production policy details the unit can be lift

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run to failure alternatively the amount of unnecessary preventive

replacement can be reduced while if the consequences of failure

sufficiently dire the condition monitoring can be employed to indicate

possible

Impending failure well before it becomes a significant probability the

advantages to be obtained from the use of condition monitoring are

shown in figure.

2. List out the different types of condition based maintenance?

Condition monitoring fills into two distinct classes

(a) Monitoring which can be carried out without interruptions to

the operation of the unit and (b) monitoring which requires the shut down

the unit or at least the release of the unit from its prime duty clearly the

former category has significant advantages over the latter since no

interruption to plant out put is involved. However there are many

situations where the monitored unit I shut down regard of frequently as

part of the normal plant operating policy for example two shift power

stations in such circumstances of load monitoring used to interrupt

normal plant operation.

3. How does condition based maintenance differ from the other

maintenance actions?

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Condition based maintenance differ from both failure maintenance

and fixed time replacement in that it requires monitoring of some

condition indicating parameter of the Unit being maintained this contrasts

with failure maintenance which implies that no successful condition

monitoring is undertaken and with fixed time rep-placement which is

based on statistical failure data for a type of unit.

In general therefore condition-based maintenance will be more

efficient and adaptable than either of the other maintenance actions. On

indication of deterioration the unit can be scheduled for shutdown at a

time chosen in advance of failure yet if the production policy dictates,

thee unit can be left to run to failure. Alternatively the amount of

unnecessary preventive replacement can be reduced, while if the

consequent of failure sufficiently dire, the condition of monitoring can be

employed to indicate possible impending failure well before it becomes a

significant probability

The advantages to be obtained from the use of condition

monitoring.

4. What are the various on load condition monitoring techniques?

Temperature monitoring

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Lubrication monitoring

Leak detection

Vibration monitoring

Noise monitoring

Corrosion monitoring

5. What are the various off load condition monitoring techniques?

Crack detection

Leak detection

Corrosion monitoring

Vibration monitoring

Lubrication monitoring

Thermal monitoring

6. Describe on load thermal monitoring?

The temperature sensitive aspect of a unit can reading is

monitored.

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The temperature sensors include contact thermometers,

thermocouples, thermostats and temperature chalks and paints and

infrared detectors. Two examples where temperature monitoring can give

warning of mechanical trouble are lubricant

Temperature of bearing outlets and engine cooling water maintenance.

This is a general purpose technique.

7. Describe on load leak detection monitoring?

A number of leave detecting techniques are available including the

soap and water method. The use of properties preparation can make this

method leaks a lower 1ml./s. one

Powerful technique is ultrasonic detection. When a fluid is forced

through a leak under internal or external pressure sound is generated in

the frequencies range 40-80 kHz. The ultrasonic leak detector identifies

this very high frequency which easily separated from the lower

frequencies of ordinances machine noise a typical detector can sense the

pressure of 50mm dia hole in a unit containing a pressure of 0.1 bar at

say 10m distance, or expressed ina flow rate, 10m halogen testing

where a search gas e.g. Action 12,18 inserted into the system under the

presence of the search gas outside the system indicates a leak can be used

to detect leakage test as low a 1 pl/m. unfortunately, it is common to find

sufficient halogens free around a plant to mask the effect of the leak.

8. Describe on load vibration monitoring?

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This can be used to detect a wide range of faults in machinery.

This method has wider application than any other monitoring technique.

For example vibration measurements made near the bearings of a

machine can detect and distinguish between in balance shaft

misalignment, damaged bearings, damaged gears and other transmissions

components, mechanical looseness cavitations or stall and a number of

either faults. Although the basic methods of monitoring are straight

forward of any case very much more information can be extracted from

the measurements if modern signal processing techniques area plied. This

is field which is currently receiving much attention and Consequently

understanding and practical experience are improving rapidly vibration

monitoring is examined in detail.

9. Describe on load corrosion monitoring?

Corrosion rate can be determined more accurately placing

coupons. Ultrasonic measurement will detect the change in dimensions

due to corrosion a new technique for remote measurement of corrosion

thickness employees a pulsed laser to drill. A fixed depth per pulse and a

light detector to indicate when the hole has reached the bright metal

10. Explain off-load vibration monitoring?

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The response of a unit to vibration forcing can reveal much

information. One of th4 most common vibration tests for rotating

machines is the run-down test, which takes advantages of system

resonances to magnify vibrations.

11. What are the various types of contact sensors used for thermal

monitoring?

Devices, which take up the temperature of the body which they are

in contact and then transmit information on their own. Temperature are

most commonly used they can provided temperature indicator locally and

remotely or control some function from the temperature. Both accuracy

and response time of contact sensors affected by attachment

Method. Good thermal contact is important. This is used provided for

surface measurement by embedding or welding the sensor to the body.

Response times are related to the volume of the sensor so the smaller

devices are more suitable if temperature very rapidly.

Liquid expansion sensors

Bimetallic expansion sensors

Thermocouple sensors

Resistance sensors

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Liquid expansion sensors: Liquid expansion sensors are the most

commonly used devices mercury or alcohol in gals thermometers is

accurate but fragile device liquid in metal sensors. All these sensors are

large (up to 9 *13 mm) and are therefore unreadable for surface

measurement.

12. Describe off load corrosion monitoring?

Corrosion can be determined m0ore accurately by placing coupons

is the plant and removing them for weighing at intervals. Ultrasonic

measurements will detect the change in dimensions due to corrosion. A

new technique for remote measurement of

Corrosion thickness employee a pulsed laser to drill. A fixed depth per

pulse and a light detector to indicate when the hole has reached the bright

metal.

13. What are the various types of non-contact sensors?

Non-contact sensor energy radiation from body carries with the

absolute temperature of the bodys and the emissive o the radiation

surface, a according to the Stefan-bolt Mann law.

This enables surface temperature to be detected from the energy

radiated without any direct current.

The various types of non contact sensors are

Optical pyrometer

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Radiation pyrometer

The seaming infrared camera

14. Describe any one technique of vibration monitoring?

This can be used to detect a wide range of faults in machinery.

This method has wider application than any other monitoring technique.

For example vibration measurements made near the bearings of a

machine can detect and distinguish between in balance shaft

misalignment, damaged bearings, damaged gears and other transmissions

components, mechanical looseness cavitations or stall and a number of

either faults. Although the basic methods of monitoring are straight

forward of any case very much more information can be extracted from

the measurements if modern signal processing techniques area plied. This

is field which is currently receiving much attention and consequently

understanding and practical experience are improving rapidly vibration

monitoring is examined in detail.

15. Describe the total signal monitoring in vibration?

This is the most string forward method resulting in only location.

The total signal, product up by the transducer is employed time arranged

and drop layer on a meter or recorded for use the schematic of a typical

act of equipment is show to gauge such equipment is compact being

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typically contained in box of about 200mm cube and weighing only 2.5

kg. brook describes the application of typical portable equipment to

signal monitoring. The vibration reading to obtain in potted on the

machine record, whole should be dearly laid out in tabular form or

alternately in graphical farm. A change is the Measurement between

inspections indicates that some machines change may have occurred

untilled experience with the machine change may have accrued. Until

experience with the machine has been built up it is very difficult to

provide whether a particular change is signing ward.

16. Describe peak signal monitoring in vibration?

Figure of merit some types of mauler migrated such as bearing

failure cause impulses to be transmitted to the transducer and pitted have

in a roller bearing. For example emits and impulse such time a ball comes

in contact with pit. Though this caused an increase in the vibration

control, which is a measure of the amount of impulse generating damage

is called the figure of merit the normal vibration instruments. It is not

possible to register peak values of vibrations contain transients of

duration less than 10ms. However this presents no significant restriction

for vibration monitoring. This measurement of peak vibration barrels is

an additional means of detection damage.

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17. How does the used oil is reconditioned?

Lubricant examination can cover the debris deposited the debris in

suspension on the condition of the oil.

Debris deposited the larger articles carried along by the lubricant

can be collected the load UN filters magnetic collectors.

1. Filters: The rate of build up of debris on a filter ion readily

monitored on load by measuring the pressure drop across the filter

removal of the filter which can be carried out on-load if the machine is

suitably designed, and subsequent examination of the debris under the

scope to establish size and shape or with a spectrograph to determine the

element of content provinces the more sophisticated method of detecting

a significant change in any component visited by the lubricant. It is good

practice to store the debris on an adhesive substrate the part of the routine

condition records.

18. Describe shock pulse monitoring in vibration and noise?

Impulses emanating from impacts between damaged surface

described in the shock pulse monitoring method which was developed

initially by S.P.M Instruments Ltd of Sweden.

The impacts generate shock pulse waves through the machine body

and they are detected using a pies electric transducer similar to an

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accelerometer except that it is termed mechanically and electrically to

have a resonant frequency at 32 KHz. The transducer resonant of this

frequency in response in each pulse. The signal generated by the

transducer is filtered to separate the resonant frequency from the ground

of vibrations

the magnitude of each resonance is held for an sufficient time for read on

meter, by this method and the peak amplitude of the signal from a

transducer to the magnitude.

19. What are the causes of vibration and noise in a machine tool?

All machines vibrate. It is difficult to balance moving parts. So

vibnrations originate in unbalanced rotating parts and in accelerations of

components moving along linear parts components which make rap or

roll on adjacent components generate vibrating because of the roughness

in the mating surfaces. In the fit between making components results in

impacts lead bearing components subject to load cycles detect under the

loads and hence transmit vibrations.

Machine vibrations cause noise, the level of which depends on the

surface area of the vibrating parts and the efficiency of transmission of

noise from the machine for health and environmental reasons much effort

is being devoted to reducing the vibrations in machines and the efficiency

of transmission of these vibrations.

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10 MARK QUESTIONS

1. What are the different types of on load conditions based

maintenance explain anyone of the following?

2. Explain the on load vibration monitoring with example

3. Explain on load thermal heat monitoring with example

4. Explain on load lubricant monitoring with example

5. Explain on load leak detection monitoring with example

6. Explain on load vibration monitoring with example

7. Explain on load noise monitoring

8. Explain load corrosion monitoring with example

9. Explain the crack detection monitoring

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1. Explain the following crack detection techniques?

(i) Ultrasonic testing (ii) Radiographic examination (iii)

Flux testing of magnetic materials.

Ultrasonic testing: Ultra sound generated the surface of the component

will be reflected at any surfaces in the two path of the sound whether they

are manufactured or faults the time delay between generation of the

sound pulse and detection of the reflection is displayed to give a measure

of the distance the surface from the force. The generation and

propagation of ultra sound in the frequency range 0.25 10 MHz. is very

directional of so suitable orientation of the transmitter enables

imperfections such as crack as be displayed from out side of the surfaces

of the component the technique has been developed to high degree of

sophistication. Cracks can be detected by examination from one end and

a suitable step the range of operation is 5 15 mm in steel.

Radio Graphic Examination: Imperfections can be photographed using

either x-rays or gamma rays from radio active source not special

photographic material a change in thickness of 2% can be detected

member thickness normally limited to 50mm. The method usually

requires dismantling of the unit being examined and raised problems

associated with processes of personal.

Flux detection of magnetic materials: A crack as small as crosses

the path of magnetic field which is included locally into the surface of the

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material using U-type magnet causes the magnetic fields and hence the

crack is revealed using magnetic powder.

2. Explain the various techniques of lubricant monitoring with

examples?

Lubricant Monitoring: It is not possible to examine the working

a part of the complexed machines on load not is converted to strip down

the machine. However the oil which circulates through the machine

carries with it evidence of the condition of parts encountered examination

of the oil and any particles it has carried with it allow monitoring of the

machine on load of it at shut down. Numbers of techniques are applied.

Some are very simple others pain staking rests and expensive equipment.

Lubricant monitoring techniques: Lubricant examination can over

the debris in suspension or the condition of the oil.

Debris deposited: The larger particles carried along the lubricant can be

collected on-load in filters or magnetic collectors.

1)Filters: The rate of build up of debris on a filter ion readily

monitored on load by measuring the pressure drop across the filter

removal of the filter which can be carried out on-load if the machine is

suitably designed, and subsequent examination of the debris under the

scope to establish size and shape or with a spectrograph to determine the

element of content provinces the more sophisticated method of detecting

a significant change in any component visited by the lubricant. It is good

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practice to store the debris on an adhesive substrate the part of the routine

condition records.

2)Magnetic debris collectors are a convention way of the capturing

ferrous comforts Magnetic plugs can be designed to be readily removed

on-load and one prosperity magnetic debris collector can be monitored

without giving an indication of debris built-up.

Debris in suspend: The smaller particle collected by the lubricant will

remain in the suspension gives the earliest warning of component damage

quantities loss of lubricant during the running and the dilute effect of

tapping-up with demerits free fresh oil.

3. Explain the detection of various malfunctions by thermal

monitoring?

In addition to the prince function of monitoring a process or system

temperature as a check the control are working correctly there is a range

of general faults that can be detected by thermal monitoring.

1) Bearing damage

2) Failure of a coolant

3) Incorrect heat generation

4) Built-up of unwanted materials

5) Damaging to insulating materials

6) Faults in electrical components

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