DEPARTMENT OF MECHANICAL ENGINEERING ME 6012 - …€¦ · Planned maintenance Jishu hozen (JH)...

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VELTECH HIGHTECH Dr.RANGARAJAN Dr.SAKUNTHALA ENGINEERING COLLEGE

DEPARTMENT OF MECHANICAL ENGINEERING

ME 6012 - MAINTENANCE ENGINEERING QUESTION BANK WITH ANSWER KEY

UNIT – I

Part–A

1 Define reliability. (Nov/Dec 2009) (Nov/Dec 2013) (Nov/Dec 2015) (Nov/Dec 2016)

(April/May 2017)

Reliability is defined as the probability that a component/system, when operating under

given condition, will perform its intended functions adequately for a specified period of

time. It refers to the like hood that equipment will not fail during its operation.

2 What is Mean Time Between Failures (MTBF) and Mean Time To Failure (MTTF)?

(Nov/Dec 2009) (Nov/Dec 2015)

Mean Time between Failures (MTBF) is the mean or average time between successive

failures of a product. Mean time between failures refers to the average time of breakdown

until the device is beyond repair.

Mean time to failure (MTTF) is the length of time a device or other product is expected to

last in operation.

3 Define Mean Time Between Failures (MTBF). (Nov/Dec 2013) (Nov/Dec 2009)

Mean Time between Failures (MTBF) is the mean or average time between successive

failures of a product. Mean time between failures refers to the average time of breakdown

until the device is beyond repair. 4

State the purpose of the maintenance function with an organization. (June 2010)

Identifying the area for implementation of preventive maintenance program.

Planning and scheduling the total maintenance work.

Standardization of maintenance work

Ensuring safety of personnel and equipment. 5

What is failure density? (Nov/Dec 2018)

It is the ratio of number of failures during a given unit interval of time to the total number

of items at the very beginning of test 6

Write down any objectives of planned maintenance. (April/May 2017)

To simplify complex maintenance tasks

To provide a readily manageable maintenance program

To facilitate an effective quality assurance process.

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7 State the principles of maintenance planning.(May/June 2012)

Plant Management in Maintenance work, Production and Maintenance objectives,

Establishment of work order and recording system, Information based decision making,

Adherence to planned maintenance strategy, Planning of maintenance functions.

8 Define the term MWT. (May/June 2012)

Mean Waiting Time for an object in a system is a mathematical term for the amount of

time an object is expected to spend in a system before leaving the system for good.

9 Define maintenance. (May/June 2013)(April/May 2015)

Maintenance is the routine and recurring process of keeping a particular machine or asset

in its normal operating conditions So that it can deliver the expected performance or

service without any loss or damage. 10

Define MTTR.(April/May 2015)

Mean Time to Repair is the arithmetic mean of the time required to perform maintenance

action. MTTR is defined as the Ratio of total maintenance time and number of

maintenance action.

MTTR = Total maintenance time / Number of maintenance action.

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Distinguish between preventive maintenance and breakdown maintenance. (June 2010)

- periodical evaluation of critical equipment, machinery to detect problem

- schedule maintenance task to avoid degradation in operating conditions

- equipment is allowed to function / operate till no failure occurs

- no maintenance work is carried out until equipment fails 12

Differentiate between inherent reliability and achievable reliability. (Nov/Dec 2018)

i) Inherent availability:

It is associated with the quality of the material and design of machine parts.

ii)Achievable availability:

It depends upon other factors such as maintenance and operation. 13

List down the key features of condition monitoring. (Nov/Dec 2015)

Monitors the actual condition of the asset to decide what maintenance needs to be done 14

What is meant by maintenance planning? (Nov/Dec 2016)

Maintenance planning is the task of organizing resources to carry out a job satisfactorily at

reasonable cost within a specified period of time. 15

List the Maintenance categories. (April/May 2017)

Break Down (Reactive) Maintenance

II. Planned Maintenance

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Planned maintenance may further be classified into

1. Preventive Maintenance

2. Corrective Maintenance

3. Predictive Maintenance

4. Condition Based Maintenance

5. Reliability Centred Maintenance

16 List any two benefits of sound maintenance system. (Nov/Dec 2018)

i) Minimization of downtime

ii) improvement in availability of system

iii) Extended life of equipment

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Unit – II

Part–A

1 What are the advantages of condition monitoring? (Nov/Dec 2016)

Improved availability of equipment

Minimized breakdown costs

Improved planning

Improved reliability

Improved morality of the operating personnel 2

List down the key features of condition monitoring. (Nov/Dec 2015)

- Improved availability of equipment

- Minimized breakdown costs

- Improved planning

- Improved reliability

- Improved morality of the operating personnel 3

State the limitations of breakdown maintenance. (Nov/Dec 2018)

i)most repair are poorly planned due to time constraint caused by production and plant

management

ii)this approach focus only on repair or the symptoms of failure and not on the root

cause of failure

4 Define maintenance scheduling. (Nov/Dec 2018)

Maintenance scheduling is a joint maintenance operation activity in which maintenance

agrees to make the resource available at a specific time, when the unit can also be made

available by operations. 5

List the maintenance categories. (April/May 2017)

Basically there are two types of maintenance tasks. They are

I. Break Down (Reactive) Maintenance







5. Reliability Centred Maintenance

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What is TPM? Give the benefits. (April/May 2018)

It may be defined as a concept of maintaining plants and equipment aiming at

significantly increasing the production rate and at the same time increasing employee

morale and job satisfaction.

Benefits:

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Minimization of accidents

High confidence level among employees 7

List out the objectives of corrective maintenance. (Nov/Dec 2009)

1) Eliminate unnecessary repairs

2) Optimize all critical plant systems

3) Eliminate deviations from optimum operation conditions

4) Eliminate breakdowns 8

What is meant by predictive maintenance? (Nov/Dec 2009) (April/May 2017)

Predictive maintenance is a management technique that uses regular evaluation of the

actual operating conditions of plant equipment, production systems and plant management

functions to optimize total plant operation.

9 Distinguish between preventive maintenance and breakdown maintenance. (June 2010)

(April/May 2018)

- periodical evaluation of critical equipment, machinery to detect problem

- schedule maintenance task to avoid degradation in operating conditions

- equipment is allowed to function / operate till no failure occurs

- no maintenance work is carried out until equipment fails

10 What is the importance of TPM? (June 2010)

When this concept is extended to all the employees of the plant shop including materials

men, quality men and others and all the employees work accordingly under consent.

11 What is the importance of condition based maintenance? (June 2010)

- Improved availability of equipment

- Minimized breakdown costs

- Improved planning

- Improved reliability

- Improved morality of the operating personnel 12

Define the term Total Productive Maintenance. (Nov/Dec 2013) (April/May 2015)

Productive maintenance is where the operating personnel are involved in maintenance of

their equipment also. When this concept is extended to all the employees of the plant

shop including materials men, quality men and others and all the employees work

accordingly under consent, it is called “Total Productive Maintenance"

13 What is the use of lubrication? (Nov/Dec 2013)

The primary objective of lubrication is to reduce wear and heat between contacting

surfaces in relative motion. By means of lubrication co-efficient of friction (which

depends on area of contact and amount of load acting) could be reduced. Lubrication

also aids to reduction of rust formation. 14

What is meant by breakdown maintenance approach? (May/June 2007)

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It is a type of maintenance approach in which equipment is allowed to function/ operate

till no failure occurs that no maintenance work is carried out in advance to prevent

failure.

15 What is meant by corrective maintenance approach? (May/June 2007)

Corrective maintenance is the program focused on regular planed tasks that will

maintain all critical machinery and system in optimum operation conditions.

16 What are the goals of preventive maintenance? (May/June 2012)

a)To minimize the number of breakdowns on critical equipment

b)To increase the productive life of all capital equipment

c) To promote better safety and health of the work forces

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Mention the reasons for preventive maintenance to be adopted in the present times.

(April/May 2015)

It prolongs the effective life of the equipment

It detects the problem at earlier stages

It significantly reduces unplanned downtime

18 List the various pillars of TPM. (Nov/Dec 2016)

5s principle Kaizen

Planned maintenance Jishu hozen (JH)

Quality maintenance Training

Office TPM Safety ,health and environment

19 Write down any four objectives of planned maintenance. (April/May 2017)

To simplify complex maintenance tasks

To forecast and plan manpower and materials requirements

To provide a readily manageable maintenance program

To facilitate an effective quality assurance process

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What is the difference between of predictive maintenance and corrective maintenance?

(Nov/Dec 2015)

Predictive maintenance Corrective maintenance

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Reduces the

breakdown losses

Increase the

equipment life

Increases the

breakdown losses

Reduces the equipment

life

21 What is meant by downtime scheduling? (May/June 2012)

It means to decide when the shutdown time will be done and who will do it without

affecting the scheduled activity.

22 What are the types of maintenance? (May/June 2013) (Nov/Dec 2016)

Basically there are two types of maintenance tasks. They are

I. Break Down (Reactive) Maintenance







5. Reliability Centered Maintenance

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UNIT - III

PART - A

1 State the advantages and disadvantages of condition monitoring. (Nov/Dec 2018)

Advantages :

Improved availability of equipment, Minimized breakdown cost.

Disadvantages:

Gives only marginal benefits, Increases running cost

2 List any three typical test conducted on lubricating oil. (Nov/Dec 2018)

Viscosity, Oxidation, Nitration, Oil Contamination.

3 List out key features of conditioning monitoring. (April /May 2013)

Links between cause and effect

Systems with sufficient response

Benefits outweighing cost

4 Why temperature monitoring is necessary? (April /May 2013)

To determine the degree of hotness or coldness or the level of heat intensity of the body.

5 Write down any four uses of condition monitoring. (April /May 2017)

Monitors the actual condition of the asset to decide what maintenance needs to be done.

6 What are the functions of temperature sensitive tapes? (April/May 2017)

Temperature range can be identified by operator or supervisor by looking at the strikers

from a distance itself.

7 What are the instruments used in condition monitoring? (Nov/Dec 2016)

Thermometer, pyrometer, accelerometer, spectroscopy

8 What is meant by reliability centered maintenance? (Nov/Dec 2015)

Reliability centered maintenance is one of the well-established systematic and a step

by step instructional tool for selecting applicable and appropriate maintenance operation

types. It helps in how to analyze all failure modes in a system and define how to prevent

or find those failures early.

9 Define root cause analysis. (Nov/Dec 2015)

Root cause analysis is part of a more general problem-solving process and an integral

part of continuous improvement. Root Cause Analysis (RCA) is a method of problem

solving that aims at identifying the root causes of problems or incidents.

10 What are five types of wear?(April/May 2015)

Rubbing wear, Cutting wear, rolling fatigue, combined rolling and sliding wear, Sever

sliding wear.

11 What is meant by thermography? (April/May 2015)

A Thermography technique uses the distribution of surface temperatures to assess the

structure or behavior of what is under the surface.

Types of Thermography:

i) Passive Thermography

ii) Active Thermography

12 Define condition monitoring. (Nov/Dec 2013)

Condition monitoring (CM) is one of the maintenance methods which are used for assess

both health and conditions of equipment ,machines ,system or process by absorbing,

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checking measuring and monitoring .it is also called as equipment health monitoring

(EHM).

13 Write about wear debris analysis. (Nov/Dec 2013)

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.

14 State advantages of filled system thermometer. (May/June 2012)

1) Excellent stability.

2) Less trouble because of its simple mechanism.

3) More durability against vibration and shock.

4) Smoother movement of pointer action.

5) Better accuracy.

6) Greater sensitivity and faster response to changes in temperatures.

15 What do you understand the term reliability? (June 2010)

Reliability is defined as the probability that a component/system, when operating under

given condition, will perform its intended functions adequately for a specified period of

time. It refers to the like hood that equipment will not fail during its operation

16 Enumerate the benefits of vibration monitoring. (June 2010)

To identify the machine problems such as imbalance, misalignment, mechanical

looseness, bent shaft, bad bearings, gear damage, electrical troubles.

17 State the various method of condition monitoring techniques. (Nov/Dec 2009)

Visual inspections

Sensor assisted inspections

Integrated monitoring systems

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Unit – IV

Part–A

1 Mention the common two factors contributing to gear tooth breakage. (Nov/Dec 2018)

1. Moderate wear: This type of where leaves contacts patterns that show the metal has been affected in the addendum and the dedendum area. Issues with inadequate lubrication commonly

cause it, but it may also be due to contamination in the lubrication as well.

2. Excessive wear: This is wear that has continued to be a problem until a significant amount of material has been affected on the surfaces. You may see pitting on the surface with excessive wear,

typically caused by not seeing the first wear early enough, and it continues to progress.

2 Define root cause analysis. (Nov/Dec 2018)

Root cause analysis is a step by step method that leads to the discovery of the faults first or root

cause

3 List the repair methods for lathe beds. (Apr/May 2018)

1)Scraping 2)Grinding

3)Machining

4 What are the drawbacks of fault tree analysis? (Apr/May 2018)

1) It requires a detailed knowledge of the design, construction and operation of the system.

2) It is not suitable for assessing normal operation.

3) Fault tree may become very large and complex.

5 Write down the basic method of repair of gears. (Apr/May2017)

1)Scraping

2)Grinding 3)Machining

If any breakage occurs on gear teeth, it can be regenerated by deposit of weld.

6 What is meant by logical fault location method? (Apr/May2017)

Logical Fault Location method deals with locating the fault in systematic and orderly manner so as to have a thorough study on cause of fault.

7 What are called age –dependent failure? (Nov/Dec2016)

Time dependent failures are called age-dependent failures.

8 What are the benefits of fault tree diagram? (Nov/Dec2016)

1) Fault tree analysis and failure modes and effects analysis

2) Design for reliability 3) Design for safety

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9 State the application and limitation of thermistors?(Nov/Dec 2015)

1. It is used for varying temperature.

2. It is used in time delay circuit. 3. It is used to gas composition

10 What is work permit? What are the types of work permit? (Nov/Dec2016)

The work permit is a written form used to authorise jobs that expose workers to serious hazards.

Types :

Hot work permit.

Safety permit. Entry permit.

Unit permit.

General permit.

11 Define FCFA. (Apr/May2015)

Fundamental cage frequency amplitude is a rotational frequency of the cage.

12 Discuss briefly the role of corrective maintenance. (Apr/May2015)

It identifies, isolates and rectifies a fault so that the failed equipment, machine or system can be restored to an operational condition with in the tolerances or limit established in service

operation.

13 Write about the skills of operator. (Nov/Dev2013)

Knowledge of Production Procedures

Ability to Read Blueprints, Schematics and Manuals

Analytical Skills Attention to Detail

Teamwork

14 Give the use of man power planning. (Nov/Dev2013)

It helps in growth and diversification of business. Through manpower planning, human

resources can be readily available and they can be utilized in best manner.

15 Give any four repair method for spindles. (May/Jun2012)

Repairing spindles includes processing and disassembly, spindle assessment, grinding and other

subsequent repair such as machining and bearing replacement ,reassembly and testing for efficiency and additional maintenance procedures such as acoustic and stability control as well as

vibration evaluation.

16 What do you understand the term EOQ? (JUNE2010)

EOQ is the acronym for economic order quantity. The economic order quantity is the optimum

quantity of an item to be purchased at one time in order to minimize the combined annual costs of

ordering and carrying the item in inventory. EOQ is also referred to as the optimum lot size.

17 List the critical aspects of both routine and shut down maintenance. (JUNE2010)

1. Shutdown Maintenance is maintenance that can only be performed while equipment is not in use.

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2. Routine maintenance means maintenance activities that are scheduled in advance and occur on a regular basis, such as weekly, monthly, quarterly, semi-annually or annually, which are

normally included as an annually recurring cost in maintenance

18 Differentiate between fault tree diagram and reliability block diagram. (Nov/Dec 2009)

Fault Tree Diagram Reliability Block Diagram

1. Fault tree works in the ‘failure

space’ and looks at system failure combination.

1.RBD works in the ‘success

space’ and thus , it looks at system successes combination.

2. It is used to access fixed

probabilities.

2.It includes time varying

distribution for the success and

other properties such as repair distribution .

19 List the design consideration of guide ways. (Nov/Dec 2009)

The shape of the slide way is designed based on 1. Load to be carried by it and direction in which these loads are supplied.

2. Position of transmission element.

3. Characteristics of wear. 4. Ease of chip disposal.

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UNIT - V

PART - A

1 What is job card? (Nov/Dec 2018)

Job cards contain necessary details for performing individual job in maintenance

organizations. Job card may be in the form of a card, sheet or printout

2 State the major phases in preventive maintenance of material handling equipment. (Nov/Dec

2018)

There are three stages of preventive maintenance are:

Inspection

Repair

overhaul

3 State the role of equipment recording maintenance. (April/May 2018)

Equipment records are information containing the details of installation, service, repair,

maintenance activities, schedules and plans for future implementation. Equipment records are

to be used to maintain control on maintenance cost, reliability and availability.

4 List computing hardware required for maintenance. (April/May 2018)

Job card, purchase order, inventory record, equipment details, operator details.

5 Write any four repair method for material handling equipment. (April/May 2017)

Conveyors: Rollers and belts are checked adjusted or repaired. Couplings, packing, safety guards, steel

structure, gear transmission, bearings, fastener joints, threaded components etc.

Cranes:

The repairable parts of the system after inspection are corrected for repair and minor defects are rectified system such as open gear transmission, coupling riveted and bolts joints.

6 What is meant by job order system? (April/May 2017)

Work order system is the information system used by the industry to keep the track of its

maintenance works and to perform any meaningful analysis on its policies and procedure

7 What is job card? List down its uses. (Nov/Dec 2016)

A job card is a detailed description of work that is performed for a work order. You use

the Job Cards application to create and manage job cards. When you create a job card, you specify planning and scheduling information that can be used by the Task Cards and Work

Order Tracking applications

8 What is meant by equipment record? (Nov/Dec 2016)

Equipment records are information containing the details of installation, service, repair, maintenance activities, schedules and plans for future implementation. Equipment records are

to be used to maintain control on maintenance cost, reliability and availability.

9 Differentiate between fault tree diagram and reliability block diagram. (Nov/Dec 2015)

s.no Fault trees diagram Reliability block diagram

1 Fault tree work in the “failure

space” and looks at system

failure combinations

RBD works in the “success space”

and thus it looks at system

successes combinations

2. It is used to access fixed probabilities each event that

comprises the trees has a

fixture probability

It includes time-varying distributions for the success

reliability equation and other

properties such as a repair

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10 State the various phrases present in a good maintenance management system. (Nov/Dec 2015)

Work identification

Planning

Execution Recording

Analysis

11 List any three material handling equipments. (April/May 2015)

Material handling equipment include carts hand truck, forklifts, conveyors, shelf pickers,

motorized pallet jacks , tractors and other specialized industrial trucks powered by electric

motor or internal combustion engine

12 Mention the benefit of computer in maintenance. (April/May 2015)

Professional computer maintenance can prevent unseen problems from snowballing into data

loss, and maximizes the efficiency of your technology. It can help you regain lost time from

slow computers and minimize costly downtime time and emergency repairs

13 Write short notes about hydraulic and pneumatic repair shop. (Nov/Dec 2013)

Pneumatic systems are like hydraulic systems, but they use compressed air instead of a fluid

to transmit power. They rely on a constant source of compressed air to control energy and actuate motion devices

14 Define coding scheme. (Nov/Dec 2013)

The coding scheme is a Standard which tells the user's machine which character represents which set of bytes. Specifying the coding scheme used is very important as without it, the

machine could interpret the given bytes as a different character than intended.

15 Discuss the degree of maintenance required for crane. (May/June 2012

Required maintenance and repairs on overhead crane systems, the crane operator should

conduct inspections on a daily basis before and after use. According to OSHA, the safety check

must include all hoists and cranes prior to use at the beginning of each shift.

16 List the important advantages of computer in maintenance. (May/June 2012)

Longer Computer Life. Reduced Likelihood of Lost Files.

Faster Speed Protection Against Threats

17 What is Weibull distribution? (June 2010)

In this issue, we will take a closer look at a specific distribution that is widely used in life data

analysis - the Weibull distribution.β is the shape parameter, also known as the Weibull slope

η is the scale parameter. γ is the location parameter

18 List the importance of safety engineering. (June 2010)

Safety engineering aims to manage risk in the workplace by eliminating or reducing it to

acceptable levels. ... As its name implies, safety engineering is about reducing failure or, should failure occur, minimizing it so that the consequences will not be life-threatening.

19 State the objectives of CMMs. (Nov/Dec 2009)

Reduce maintenance costs (stretch maintenance cycles) Reduce adverse impacts of

maintenance activities (if it works, don't fix it) Improve asset reliability (ensure assets are functional and capable) Improve asset availability (minimize asset downtime)

20 State the benefits of keeping equipment record. (Nov/Dec 2009)

Proper maintenance and tracking of equipment maintenance log aids in enabling

your equipment to run in optimal condition. Record keeping also proves to be useful when you decide to sell your equipment as soon as it is time to update your assets.

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VELTECH HIGHTECH Dr.RANGARAJAN Dr.SAKUNTHALA ENGINEERING COLLEGE

DEPARTMENT OF MECHANICAL ENGINEERING

ME 6012 - MAINTENANCE ENGINEERING QUESTION BANK WITH ANSWER KEY

Unit – I

Part - B

1 State the various objectives of maintenance planning. (April/May 2018)

The most important objective:

- Maximization of availability of equipment and facilities so as to help in achieving

the ultimate goals of the organization.

The following are the objectives of planned maintenance activity:

To achieve minimum breakdown and to keep the plant in good working condition

at the lowest possible cost.

To ensure the availability of the machines and services in an optimum working

condition.

To keep the machines and other facilities in a condition to be used to achieve the

maximum profit without any interruption or hindrance.

To keep the time schedule of delivery to the customers or to the sections for

further processing.

To meet the availability requirements for critical equipments.

To keep the maintenance costs as low as possible for non-critical equipments.

To control the cost of maintenance related activities

To meet the quality requirements of the product.

To increase the profits of production systems

To provide effective and trained supervision

2

Derive an expression for determining the mean time to failure (MTTF). (April/May

2018)

Let t, is the time to failure for the first specimen, t is the time to failure for the second

specimen and tn is the time to failure for the N specimen. Hence the mean time to

failure for N specimens are

HTTF = (t1+t2+.......tn) /n = 1/N

It is difficult to record the failure for each component when the numbers of specimens

tested are large. Instead, we can record the number which fails.

If n1 is the number of specimens that failed during the first hour, n2 is the number that

failed during the second hour and nk is the number that failed during the kth hour.

Then the mean time to failure for N specimens is

MTTF = (n1 + 2n2 + 3n3 +....knk) / N

2

It is better to represent the time as interval of the time as such as. Hence the

time interval is ∆t instead of one hour. Then MTTF is calculated as

MTTF = (n1 ∆t +2n2 ∆t +..... + knk∆t +..... + lnl ∆t) /N

MTTF = (n1 ∆t +2n2 ∆t +..... + knk∆t +..... + rnr ∆t) /N

MTTF = 1/N ∑ knk∆t (k = 1 to r)

Where n1 is the number of specimens that failed during the first interval, n2 is

the number of specimens that failed during the second interval and nk is the

number of specimens that failed during the kth time interval and so on.

3

State the benefits of sound maintenance management system. (April/May 2017)

(April/May 2018)

The profit of any industry depends only on the return of the investment.

The capital cost and operating cost are the major factors involved in any

industrial investment. The life of the equipment and maintenance schedule

information provided by manufacturer may not be realized in practice to make

the need for having a sound management system.

The following are the benefits of sound maintenance management system.

Minimization of down time.

Improvement in availability of system.

Extended life of equipment.

Safety and smooth operation of the process

Provide adequate back up supply

Minimization of normal expected wear and tear of

equipment.

Safety of the personal involved in the organization.

Increased reliability of the system.

Provide proper working environment.

Cost effective maintenance boost the profit of the production system.

4

State the steps necessary to reduce the maintenance cost in an industry. (April/May

2018)

Maintenance should be one of the key strategies to keeping the plant's assets

healthy. While equipment upkeep and parts replacements are necessary, there are

steps that can reduce maintenance costs without decreasing industry processing

facility's operational efficiencies.

Examine the necessary things to do and not:

When first purchasing the equipment in an industry, ensure the review its maintenance

requirements with the manufacturers and the subject matter experts, whether those are

engineers or senior m It should confirm that all of the suggested maintenance is

actually needed, as unnecessary maintenance can actually induce equipment failure.

Select a suitable measurement system:

3

Preventive maintenance should be performed based on the most applicable

measurement system for the equipment.

Pick the optimal time to perform maintenance:

Preventive maintenance should be scheduled maintenance, tuned to the specific needs

of the production schedule.

This way, processing plant can take assets out of service at a time that allows

maximizing the uptime or efficiency.

Most companies complete their preventive maintenance in the cooler months of

the year.

Compressor and evaporator rebuilds are easier to perform in the winter because

the temperatures are not as hot, requiring less of a refrigeration load.

This offsets labour costs, maintenance professionals.

Maximize the efficiency of the industry staff:

By training production workers to provide preventive maintenance assistance on a

daily or weekly basis, have to maximize the efficiency of processing plant staff and

take the preventive maintenance burden off of the senior professionals.

Preventive maintenance tasks that production workers can complete include:

Cleaning up the equipment Inspecting specific items

Watching particular equipment characteristics. However, once a monitored

characteristic is showing signs of needing preventive maintenance, you need to

bring in a subject matter expert to complete the work or provide additional planning.

Develop an overall maintenance strategy:

Preventive maintenance is only one type of maintenance that should be part of the

overall strategy, including: Preventive maintenance, Predictive maintenance,

Reactive maintenance.

If preventive maintenance in conjunction with a predictive and reactive maintenance

strategy, maintenance costs can control while managing downtime and maximizing

uptime.

5 Discuss maintenance as a business. (June 2010)

Maintenance Engineering is the discipline and profession of applying engineering

concepts to the optimization of equipment, procedures, and departmental budgets to

achieve better maintainability, reliability, and availability of equipment. Maintenance,

and hence maintenance engineering, is increasing in importance due to rising amounts

of equipment, systems, machineries and infrastructure. A person practicing

Maintenance Engineering is known as a Maintenance Engineer.

a) Plant management in maintenance work:

The main role of a maintenance function is to provide safe and effective operation of

the equipment to achieve the desired targets on time with economics usage of resources.

b) Production and maintenance objectives:

The plant operation is driven by the production targets. The objective of maintenance

function is to support this target. The achievement of desired goals of the production

system is to be supported by both the production and maintenance department to ensure

smooth and successful operation of the industry.

c) Establishment of work order and recording system:

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The maintenance system should have proper work and recording system. The work

order for the maintenance function indicates the nature of work to be performed and the

series of operations to be followed to execute a particular job. It is necessary to maintain

proper records and entries to monitor the maintenance function.

d) Information based decision making:

The maintenance objectives are successfully achieved by the use of reliable information

system. This information is used to meet the manpower and spare parts re4quirements

of the industry.

e) Adherence to planned maintenance strategy:

A sound maintenance management should adhere to the planned maintenance stratergy.

This also includes the use of manufacturer information on the life and maintenance

schedules of the equipment and other material resources available.

f) Planning of maintenance function:

All the maintenance function is to be carefully executed by a way of proper planning to

ensure the effective utilization of manpower and materials.

g) Manpower for maintenance:

The manpower requirement of the maintenance system must be carefully evaluated

based on the time and motion study. The requirements should also satisfy the need

arising in case of overhauls, component replacement, emergency and unscheduled

repair.

h) Work force control:

Determination of exact work force required to meet the maintenance objectives of the

system is difficult task due to the element of uncertainty. Hence the proper control and

monitoring of workforce are needs to be ensured.

i) Role of spare parts:

A good maintenance management system requires appropriate tools. So the system

should have good quality tools and that too available in required quantities to ensure the

proper function of the maintenance work.

k) Training of maintenance work force:

Training of the workforce must be integral part of any good maintenance management

system. Training helps the workforce to learn about the modern techniques, recent

trends in maintenance and to chalk out a strategy to meet the growing demands of the

industry.

6 Explain design for reliability in detail. (June 2010)

Reliability:

Reliability may be defined in several ways:

The idea that an item is fit for a purpose with respect to time.

In the most discrete and practical sense: "Items that do not fail in use are

reliable" and "Items that do fail in use are not reliable".

The capacity of a designed, produced or maintained item to perform as

required over time.

The capacity of a population of designed, produced or maintained items to

perform as required over time.

The resistance to failure of an item over time.

The probability of an item to perform a required function under stated

5

conditions for a specified period of time.

In line with the creation of safety cases for safety, the goal is to provide a robust

set of qualitative and quantitative evidence that an item or system will not

contain unacceptable risk.

7

What is equipment availability and what are the three basic approaches to define and

quantity availability. (Nov/Dec 2015)

Availability: It is the ratio of the time at which the equipment is available for the

designated operation service to the total time of operation and maintenance of the

equipment. It is also defined as the ration of equipments uptime to the equipment

uptime and down time over a specified period of time.

The uptime of machine equipment is the time for which it is in actually available to

complete the desired function. The downtime or outage of a machine is the period

of time during which it is not in an acceptable working condition.

The three types of availability are;

(i) Inherent availability

(ii) Achieved availability

(iii) Operational availability

Inherent availability:

It is the probability that a system or equipment shall operate satisfactorily

when used under prescribed conditions in a ideal support environment without any

scheduled or preventive maintenance at any given time.

Inherent availability = MTBM/ MTBM+MTTR

Achieved availability:

It is the probability that a system or equipment shall operate satisfactorily

when used under prescribed conditions in an ideal support environment with

periodic preventive and corrective maintenance at any given time.

Achieved availability = MTBM/ MTBM+M

Operational Availability:

In industrial system a certain amount of delay will be always caused by time

element such as supply downtime and administrative downtime.

Operational availability = MTBM/ MTBM+MDT

Where MDT is the mean downtime is the satisfied mean of the downtimes including

the supply downtime and administrative downtime.

In general availability of a system is a complex function of reliability,

maintainability and supply effectiveness.

As = f (Rs, Ms, Se)

6

8

What is the difference between reliability cost and maintainability cost? (May/June

2012)

9 Discuss about maintenance economic. (April/May 2017)

Maintenance Cost

Budgets are allocated for all the activities in planning stage itself which includes the

maintenance cost. The cost of maintenance is difficult to measure due to random

nature of failures. The words on maintenance history may be useful in determining the

cost.

The maintenance cost is comprised of two factor:

⦁ Fixed cost

⦁ Variable cost

(i) Fixed cost: This includes the cost of support facilities including the

maintenance staff.

(ii) Variable cost: This includes the consumption of spare parts,

replacement of components and cost other facilities requirements of

maintenance.

The evaluation of maintenance cost should consider the following factors

⦁ The evaluation of maintenance cost should consider the following factors.

⦁ Cost of maintenance from the recorded data.

⦁ Level and requirements of maintenance.

⦁ Cost of replacement of components and assemblies subjected to wear and tear.

⦁ Accounting the number of break downs with their levels

⦁ Downtime of the equipment for want of maintenance repair.

⦁ Penalty cost due to loss of production.

⦁ Cost of manpower involved.

⦁ Cost of additional manpower requirement for emergency breakdown and

maintenance.

Advantages of life cycle costing:

Integration of engineering, economics and financial aspects lead to the way of robust

metric for the selection and purchase equipment required for the industry.

7

Reduced operating and maintenance cost of equipments due to cost analysis over

span of time.

It leads to the selection of proper and economically viable equipment.

Estimation of economic life of equipment:

The economic life of equipment depends on the maintenance and repair costs,

availability and operational efficiency. A plot of cumulative efficiency and maintenance

and repair cost per cumulative hours Vs operating hours of the equipment to find the

economic life of the equipment.

Maintenance Cost:

Budgets are allocated for all the activities in planning stage itself which includes the

maintenance cost. The cost of maintenance is difficult to measure due to random nature

of failures.

The records on maintenance history may be useful in determining the cost. The analysis

of maintenance cost is helpful in taking a decision regarding replacement of a machine

or any of its components.

Maintenance Budget:

The maintenance budget is used to set aside certain amount of money to meet the

expenditures incurred in achieving the objectives of maintenance. The following are the

types of maintenance budget,

(i) Appropriation Budget

Budget used to allocate money for each activity independently.

(ii) Fixed Budget

Fixed used to allocate money for a specified period of time.

(iii) Variable Budget

Dynamic allocation of expenditure based on maintenance requirements and activities.

The evaluation of maintenance cost should consider the following factors:

The evaluation of maintenance cost should consider the following factors.

Cost of maintenance from the recorded data.

Level and requirements of maintenance.

8

Cost of replacement of components and assemblies subjected to wear and tear.

Accounting the number of break downs with their levels

Downtime of the equipment for want of maintenance repair.

Penalty cost due to loss of production.

Cost of manpower involved.

Cost of additional manpower requirement for emergency breakdown and

maintenance.

Cost minimization in maintenance organization:

Centralized planning, scheduling and control

Grouping of specialized workforce

Effective labour utilization strategies

Budgetary control and proper check mechanism to implement the cost control

strategies.

Proper and effective use of contract maintenance system to reduce the

overhead costs on equipment and manpower.

Purchase of reliable equipment and spares.

Use of skilled and trained workforce.

Proper selection of suitable type of spares, materials and lubricating.

Proper safety education and formulating the safe practice.

Constant appraisal and education to workforce about the objectives, strategies

and modern techniques adopted in the area of maintenance

10 Explain in detail the test plan for determination of MTBF. (Nov/Dec 2013)

Let t, is the time to failure for the first specimen, t is the time to failure for the second

specimen and tn is the time to failure for the N specimen. Hence the mean time to

failure for N specimens are

HTTF = (t1+t2+.......tn) /n = 1/N

It is difficult to record the failure for each component when the numbers of specimens

tested are large. Instead, we can record the number which fails.

If n1 is the number of specimens that failed during the first hour, n2 is the number that

failed during the second hour and nk is the number that failed during the kth hour.

Then the mean time to failure for N specimens is

MTTF = (n1 + 2n2 + 3n3 +....knk) / N

It is better to represent the time as interval of the time as such as. Hence the

time interval is ∆t instead of one hour. Then MTTF is calculated as

MTTF = (n1 ∆t +2n2 ∆t +..... + knk∆t +..... + lnl ∆t) /N

MTTF = (n1 ∆t +2n2 ∆t +..... + knk∆t +..... + rnr ∆t) /N

MTTF = 1/N ∑ knk∆t (k = 1 to r)

Where n1 is the number of specimens that failed during the first interval, n2 is

the number of specimens that failed during the second interval and nk is the

number of specimens that failed during the kth time interval and so on.

11 Explain the objectives and principles of planned maintenance.(Nov/Dec 2018)

9

Objectives of planned maintenance:

The most important objective of the maintenance is the maximization of availability of

equipments and facilities so as to help in achieving the ultimate goals of the

organization. The following are the objectives of planned maintenance activity:

To achieve minimum breakdown and to keep the plant in good working condition

at the lowest possible cost.

To ensure the availability of the machines and services in an optimum working

condition.

To keep the machines and other facilities in a condition to be used to achieve the

maximum profit without any interruption or hindrance.

To keep the time schedule of delivery to the customers or to the sections for further

processing.

To meet the availability requirements for critical equipments.

To keep the maintenance costs as low as possible for non-critical equipments.

To control the cost of maintenance related activities

Principles of planned maintenance:

Maintenance principles are followed in a system to guide the staff to work efficiently

and effectively to achieve the overall objectives of the maintenance system.

(i) Plant Management in Maintenance work

The main role of the maintenance function is to provide safe and effective operation of

the equipment to achieve the desired targets on time with economic usage of resource.

(ii) Production and Maintenance objectives

The plant operation is driven by the production targets. The objective of maintenance

function is to support these targets. The achievement of desired goals of the production

system is to be supported by both the production and maintenance department to ensure

smooth and successful operation of the industry.

(iii) Establishment of Work order and Recording system

The maintenance system should have proper work order and recording system. The

work order for the maintenance function indicates the nature of work to be performed

and the series of operations to be followed to execute a particular job. It is necessary to

maintain proper records and entries to monitor the maintenance functions. This record

is useful in formulating the future maintenance plans and scheduling to meet the desired

objectives of the organization.

(iv) Information Based Decision Making

The maintenance objectives are successfully achieved by the use of reliable information

system. This information is used to meet the manpower and spare parts requirements of

the industry.

(v) Adherence to Planned Maintenance Strategy

10

A sound maintenance management should adhere to the planned maintenance

strategy. This also includes the use of manufacturer’s information on the life and

maintenance schedules of the equipment and other materials.

(vi) Planning of Maintenance Functions

All the maintenance functions are to be carefully executed by a way of proper

planning to ensure the effective utilization of manpower and materials.

(vii) Manpower for Maintenance

The manpower requirements of the maintenance system must be carefully

evaluated based on the time and motion study. The requirements should also

satisfies the need arising in cases of overhauls, component replacement,

emergency and unscheduled repairs.

(viii) Workforce Control

Determination of exact workforce required to meet the maintenance

objectives of the system is difficult task due to the element of uncertainty.

Hence the proper control and monitoring of workforce are needs to be

ensured.

(ix) Role of Spare Parts

A good maintenance management system requires appropriate tools. So the system

should have good quality tools and that too available in required quantities to ensure

the proper function of the maintenance works.

(x) Training of the Maintenance Workforce

Training of the workforce must be integral part of any good maintenance

management system. Training helps the workforce to learn about the modern

techniques, recent trends in maintenance, knowledge of sophisticated

instruments and to chalk out a strategy to meet the growing demands of the

industry.

12 Explain MTBF, MTTF, MTTR and failure rate. (Nov/Dec 2016) (April/May 2017)

Total working hours of equipment

MTBF = --------------------------------------------------

Number of failure

Total working hours of equipment

MTTF = --------------------------------------------------

Number of failure

Total maintenance time

MTTR = --------------------------------------------------

Number of Maintenance action

1

Failure Rate = -----------------

MTBF

11

13

Explain with clear illustrations about the factors affecting availability. (April/May

2017)

MTBF

MTBM

MTTR

MDT

14

Discuss about any two types of maintenance organization model with a neat sketch.

(Nov/Dec 2018)

Line Organization

Line and Staff Organization

15 Explain the various roles of stakeholders in maintenance scheduling. (Nov/Dec 2018)

12

Unit – II

Part - B

1 Briefly describe the accelerated testing. (Nov/Dec 2013)

Accelerated life testing is the process of testing a product by subjecting it to conditions

(stress, strain, temperatures, voltage, vibration rate, pressure etc.) in excess of its normal

service parameters in an effort to uncover faults and potential modes of failure in a short

amount of time. By analyzing the product's response to such tests, we can make predictions

about the service life and maintenance intervals of a product.

ALT is primarily used to speed up tests. This is particularly useful in several cases:

Low failure - Testing even a very large sample at normal conditions would yield few or

no failures in a reasonable time.

High longevity - The product must be reliable for a much longer time than can be

reasonably tested at normal conditions.

High wear-out - The primary cause of failure occurs over an extended amount of time.

For instance, a reliability test on components that must last years at use conditions (high

longevity) would need to yield results in a much shorter time. If the test wanted to estimate

how frequently the components needed to be replaced, then the category of low failure would

also be applicable. Furthermore, if the components wore out from gradual use rather than

extreme use (such as a large sudden shock), the wear out category would be involved. If a

sudden shock was the primary cause of failure, a Highly Accelerated Life Test may be more

appropriate.

2 Explain the methods of lubrication. (April/May 2018) (Nov/Dec 2013)

Lubricants:

Any material used to reduce friction between wearing surfaces with high coefficient of

friction, by establishing low-viscous film are called lubricants. Lubricants are available in

liquid, solid and gaseous forms. Solid lubricants are used for industrial applications when oil

or grease are not suitable. Graphite is used when the loading at the contact points is heavy.

Methods of Lubrication:

Hydrostatic Lubrication

Hydrodynamic or Fluid film lubrication

Boundary lubrication

Elastic hydrodynamic lubrication (EHD)

Extreme pressure (EP) Lubrication

In general the method of lubrication is characterized by the friction and wears characteristics

of wearing surface. Based on the value of ‘R’ which is defined as follows, the method of

lubrication is chosen.

R = Mean fluid film thickness / Surface Roughness (CLA)

Where, R is less than or equal to 1 for boundary lubrication. R is in between 5 and less than

or equal to 100 for fluid film lubrication R is between 1 and 5 for mixed lubrication.

13

Hydrostatic Lubrication:

In hydrostatic lubrication systems, a thin film of lubrication is created between the

journal and the bearing by supplying lubricant under pressure with an external source like

pump. Since the lubricant is supplied under pressure, this type of bearing is called externally

pressurized bearing.

Compared to hydrostatic bearing, hydrodynamic bearings are simple in

construction, easy to maintain and lower in initial as well as maintenance.

Hydrodynamic or Fluid Film Lubrication:

In heavily loaded bearings such a thrust bearings and horizontal journal bearings

apart from viscosity of fluid, higher fluid pressure is also required to support the

load until the film is established.

If the pressure is extremely it is called as hydrostatic lubrication and if generated

internally within the bearing by dynamic action, it is referred to as hydrodynamic

lubrication. In hydrodynamic lubrication, a fluid wedge is formed by the relative

surface motion of the journals or the thrust runners over their bearing surfaces.

Thrust bearings:

In hydrodynamic lubrication, the wearing surfaces are completely separated by

a film of oil. This type of lubrication is similar to motorized speed moving on

water.

When not moving the boat begins to move, it experiences a resistance due to

the viscosity of water. This causes a slight lift of leading edge of the boat and

allows a small amount of water between it and supporting water film increases

until a constant velocity is reached.

Journal Bearing:

During operation, the journal has the tendency is drawn into contact area and

when the speed increase an oil wedge increase until the journal is lifted up

vertically but also pushed to the side by pressure of oil wedge. When the

journal is rotating at a constant velocity, film thickness will exist only at the

left center and not at the bottom of the bearing.

Boundary Lubrication

When a full fluid film is not developed between rubbing surfaces, the thickness

of film may be reduced so that dry contact is formed at high points or asperities

of mating surfaces. This condition is a characteristic of boundary lubrication.

14

Extreme Pressure Lubrication

Anti wear agents which are normally used in boundary lubrication will not be

effective beyond certain temperature (250 degree Celsius). In heavy loading

applications, oil temperature raises beyond the anti wear protection.

Elasto-hydrodynamic (EHD) Lubrication

The lubrication principle is applicable to rolling bodies such as ball or roller

bearings, is known as Elasto-hydrodynamic (EHD) Lubrication. The formation

of the lubricant film between the mating bearing surfaces is called the elasto-

hydrodynamic (EHD) mechanism of lubrication.

The contact between the large end of the roller and the inner race rib is called

elasto-hydrodynamic contact or a hydrodynamic contact. As the rib loads are

much lower than the roller loads, the film at the rib end contact is usually twice

as thick as on the roller contact.

3 Compare TQM & TPM. (April/May 2018)

- Concept of maintaining plants and equipment aiming at significantly increasing the

production rate and at the same time increasing employee morale and job satisfaction.

Benefits:

Minimization of accidents

High confidence level among employees

In many of the aspects, TPM is found to have similarity with the total quality management

(TQM) program.

Similarities:

Empowerment of employees to initiate corrective action, bench marking and

documentation.

Top level management committed to the program.

Long range outlook perspective.

The main objectives are to achieving zero defects zero accidents and zero breakdowns in all

functional areas of an organization. Also the objectives include creating different team of

people to have active participation aiming at minimization of defects and to inculcate

autonomous policy.

Dissimilarities:

Category Total quality Management

(TQM)

Total Productive

Maintenance (TPM)

Objective To have quality To have reliable equipment

Means of achieving Through systematized Through active participation

of management employees

Target Minimized defective Elimination losses and

Preventive maintenance

15

4

Discuss the various stages involved in implementation of TPM. (May/June 2007)

(April/May 2018)

5

With a suitable example, illustrate repair cycle. (April/May 2018)

Discuss about the repairable and repair cycle in tools management. (Nov/Dec 2013)

Repair cycle

The repetitive performance of all maintenance activities in

between two over hauling is termed as repair cycle.

The time period for a repair cycle dependent on the time

intervals in between two activities.

The various maintenance activities may be classified into four categories which are as

follows.

Inspection (I)

Minor Repair (R1)

Medium or Major Repair (R2)

Overhauling (O)

- It is clear that first an inspection activity is scheduled followed by minor/ major repair

activities.

- Then an inspection takes place followed by a major repair. Again a second inspection

is followed by major repair.

- Like this is goes and completes one repair cycle. The set of these activities between

two consecutive overhauling is defined as a repair cycle.

- This typical repair cycle covers three inspection and two minor and major repair

activities.

- This can be represented O1 –I1 –R11 –R21 –I2 –R1 –I3 R2.

16

From the above it is understood that the repair cycle is mainly time dependent between

activities.

An index number generally known as repair completely number is used to denote the

complexity repairing equipments. More the complexity number more will be the

activities involved and in turn more staffing requires completing the repair cycle.

6

Explain the importance of lubricating of moving parts of industrial machineries. (April/May

2018)

In industrial equipments, the surface of the mechanical parts will have physical

contact on the neighboring parts to establish a relative motion between them.

During operation of the equipments, those contacting surfaces are subjected to

friction which depends on the area of material, properties of material etc which

is undesirable.

This leads to progressive damage resulting in material loss which is defined as

wear. Friction and wear also generate heat and responsible for the overall loss

in system efficiency. All these contribute to significant economic costs due to

equipment failure, cost for replacement and down time.

The primary objective of lubrication is to reduce wear and heat between

contacting surfaces in relative motion. By means of lubrication coefficient of friction could be reduced and the and turn heat and wear of the surfaces.

Lubrication also aids to

reduce oxidation and rust formation

provide insulation in transformer application

transmit mechanical power in hydro fluid power systems

seal against dust, dirt and water.

Selecting the right lubricant, the right amount of lubricant and the correct

application of the lubricant are essential to the successful performance of any

bearing because bearing lubricants serve three purposes:

To reduce friction by separating mating surfaces.

To transfer heat (with oil lubrication)

To product from corrosion and with grease lubrication, dirt ingress

The success of these three factors depends heavily on the film thickness on the

raceway and at the rib/roller end contact.

7 Describe vibration analysis for maintenance. (Nov/Dec 2009)

17

9 List out the sequencing of activities carried out in machine shutdown. (May/June 2012)

Inspection (I)

Minor Repair (R1)

Medium or Major Repair (R2)

Overhauling (O)

10

What do you understand by maintenance categories? Explain common types and explain the

basis of their selection. (Nov/Dec 2015)

18

UNIT - III

PART-B

1. In detail discuss the process involved in condition monitoring. (Nov/Dec 2018)

Explain various methods and instruments used for conditioning monitoring. (Nov/Dec

2016)

Describe six categories of equipment condition monitoring methods. (May/June 2012)

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 line Comments

1.Visual

Inspection

Human eye

On/off

Covers a wide range of highly

effective 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.

Closed circuit

television

(CCTV)

On/off

Permits detailed inspection of

inaccessible environment machine

parts. Image recording and high

resolution analysis is a post-

processing possibility.

2. Vibration

Monitoring

Shock pulse

monitoring On

(SPM), Spike

energy and

Kurtosis

On

provides the basis for fault

detection, diagnosis and severity

assessment.

Structural

monitoring Off

All of these techniques use high

frequency vibration signals to

detect and diagnosis a range of

faults including rolling element

bearing damage, lubrication failure

and leak detection.

19

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.

3.Temperature

Monitoring

Temperature

crayons, paints

and taps

On

Simple and effective aids to visual

inspection. Can resolve body

temperature to perform from a

distance at a glance.

Thermometers,

thermocouples On

Range from stick-on thermometric

strips to permanently installed

thermocouple sensors. Can give

visual temperature readout or an

electrical input to a hard-wired

monitoring system.

Infra-red camera On

Can provide a detailed surface

temperature picture and can be

calibrated to give quantitative

measurement.

4. Lubrication

analysis

Magnetic plugs

and filters On/Off

Analysis of debris picked up by

plugs or filter in an oil washed

systems. Mainly large debris

picked up, 100- 1000microns.

Ferrography N/A

Analytical technique used to

separate ferrous debris by size to

enable microscopic examination.

Non-ferrous debris can also be

separated but not graded.

Spectroscopy N/A

Analytical technique is used to

determine the chemical

composition of the oil and debris.

Generally, for small debris size 0-

10 microns. A contract service

usually available.

5. Crack

monitoring

Dye penetrant On/Off Detects cracks which break the

surface of the material.

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

of ferrous materials.

20

6. Eddy

current On/Off

7. Ultrasonic On/Off

8. Radiography Off

9. Weight loss

coupons Off

Coupons are weighed and weight loss is equated

to material thickness loss due to corrosion.

10. Incremental

bore holes On

A series of fine plugged holes of incremental

depths which are periodically unplugged and

scrutinized for leakage.

11. Electrical

resistance On

Electrical element and potentiometer are used to

assess resistance change due to material loss.

Capable of detecting material thickness

reduction of loss than 1mm.

2. With neat flow chart, explain onload and offload testing used in conditioning monitoring.

(Nov/Dec 2018)

LOAD TESTING

o Load testing is the process of putting demand on a system or device and measuring

its response.

o Load testing is performed to determine a system’s behavior under both normal and

anticipated peak load conditions.

o It helps to identify the maximum operating capacity of an application as well as any

bottlenecks and determine which element is causing degradation.

o When the load placed on the system is raised beyond normal usage patterns, in order

to test the system's response at unusually high or peak loads, it is known as stress testing.

o The load is usually so great that error conditions are the expected result, although no

clear boundary exists when an activity ceases to be a load test and becomes a stress test.

o There is little agreement on what the specific goals of load testing are.

o The term is often used synonymously with concurrency testing, software performance

testing, reliability testing, and volume testing.

o Load testing is a type of non-functional testing.

21

3. Explain how cost comparison is done in conditioning monitoring. (April/May 2018)

Explain cost comparison with and without condition monitoring with example. (April/May

2017)

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 cost of installation of CM is high in the starting and operation cost

becomes low, but steady during the life of Condition monitoring equipment.

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, fueling, 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.

22

Finalcial benefits by implementing condition monitoring techniques are;

i) A 25 year old flour mill implemented a planned and condition monitoring and

achieved a 43% saving within 12 months,

ii) An esimated 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.

4. Discuss how infrared thermography inspection is more advantages over other temperature

monitoring techniques. (April/May 2018)

Infrared 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 conserved with emissivity.

Types of thermography:

Passive thermorgraphy & Active thermography

23

Working of infrared themography:

The infrared (IR) comera is the central piece, if surface emissivity is sufficiency high,

relevant temperature difference on the surface being tested can be measured.

5. How the monitoring of wear debris analysis in the lube oil is achieved. (April/May 2018)

Using a Scanning Electron Microscope of a carefully taken sample of debris suspended in

lubricating oil (taken from filters or magnetic chip detectors). Instruments then reveal the

elements contained, their proportions, size and morphology. Using this method, the site, the

mechanical failure mechanism and the time to eventual failure may be determined. This is

called WDA - Wear Debris Analysis.

⦁ The lubrication oil in any system is often required to perform a number of functions such

as to reduce friction to cool components and to clean load bearing surfaces.

⦁ Over the time the oil is likely to degrade losing its lubrication properties due to chemical

breakdown and becoming contaminated by the ingress of collates fuels and other

lubricants.

⦁ The properties of the oil can be monitored in a number of ways acidity for oxidation

viscosity for lubrication flash point for contamination and chemical composition for

chemical degradation.

⦁ In addition to the oil properties the presence of wear particles in the oil can also be used

to predict a number of faults by observing their size, quantity, shape and material

composition.

⦁ These particles may be caused by year ingress (failure or filter) or corrosion of

components.

⦁ The chemical analysis of particles can often identify particular component which are

foiling for example, if silicon is found in the oil then a breach has occurred between the

outside and the lubricating systems.

⦁ Lubricant analysis is an important and to condition monitoring.

⦁ Laboratories recommended that samples of machine lubricant be taken as scheduled

intervals to determine the condition of the lubricating film that is critical to machine train

operation.

⦁ Oil monitoring is an extremely effective tool for assessing the condition of the oil itself

and the components with which the soil comes into contact.

⦁ It is particularly useful in equipment where vibration analysis is difficult to carry out

perhaps where components are remote from possible transducer mounting points.

6. Explain with the neat diagram pistol thermometers. (Nov/Dec 2016)

Pistol thermometers:

24

7. What is thermal monitoring? Explain its principle and uses of thermograph? (Nov/Dec

2015)

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 intensity of a body.

Instruments for measuring ordinary temperature are known as thermometers and these

measuring high temperature are known as pyrometer. On large engines, sir handlers,

temperature transducers are included for all major bearings some packages include shut down

circuits and alarms of temperature gets above certain limits. The hardware for infrared is

becoming more and more powerful. An infrared gun takes on spot temperature without

imaging capacity.

Types of thermography:

Passive thermorgraphy

Active thermography

It is an externally applied thermal stimulation is needed to generate meaningful

thermal contrasts that will yield to the detection of sub surface abnormalities.

Methods of observation:

The two methods of observation possible are reflection and transmission.

- In reflection, greater resolution is obtained but the thickness of the material inspected is

small.

- In transmission a greater thickness of material can be inspected but the depth information

is lost since the thermal front has the some distance to travel whether or not its strength

is reduced by the presence of a defect.

The resolution is weak in transmission hence it is necessary to use more sensitive

detection equipment. The approach in reflection is good for detection of defects located closer

to the heating surface while the transmissive approach reveals defects located to the near

surface.

8. Discuss the maintenance scheduling in detail. (April/May 2015)

Generally, the maintenance scheduling embraces the following activities.

⦁ Inspection

⦁ Repair

⦁ Overhauling

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9. Discuss the various types of NDT for conditioning monitoring. (April/May 2015)

NDT plays important role in crack monitoring. NDT is defined as a method of inspecting on

object without impaling its future usefulness major methods include:

⦁ Penetrant testing

⦁ Magnetic particle testing

⦁ Ultrasonic testing

⦁ Radiography testing

There are also some ranges of other new techniques that have particular specialized

applications in limited fields. They include

⦁ Eddy current testing

⦁ Acoustic emission methods

⦁ Thermography

⦁ Holography

⦁ Leak testing Liquid Penetrate Test Introduction

10. What is leakage monitoring? Explain some of the leakage medium used for conditioning

monitoring. (June 2010)

Leakage monitoring is mostly used for quality assurance and metallographic analysis

to assess the quality of metals and quality of procedures during making, shaping and breaking

of metals in industries.

Leakage monitoring program does not measure total crack depth and width but change

in crack width. This change in crack width is called crack displacement the crack

displacement measured by the sensors may be driven by any combination of the factors listed

below

⦁ Differential thermal expansion

⦁ Structural changes in various components of machine

⦁ Shrinkage and thrusting of different components temperature and humidity changes

⦁ Fatigue and aging of components etc.

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UNIT – IV

Part - B

1 Explain with neat sketch about fault tree analysis. (Nov/Dec 2018)

Basically, the steps involved in a fault tree analysis are:

1. Define the Top Event

2. Know the system

3. Construct the tree

4. Validate the tree

5. Evaluate the tree

6. Study tradeoffs

7. Consider alternatives and recommend actions

2 Describe about various steps involved in Failure Mode and Effect Analysis (FMEA). (Nov/Dec

2018)

27

3

(i)List the possible causes of failure of bearing and explain how to overcome them.

(ii)with the aid of suitable sketches, describe the method of repairing cracks in machine bed by

(1) Riveting (2) Hot clamping (Apr/May 2018)

Repair methods of bearing:

Failure Condition Cause Solution

Flaking Raceway surface

is flaked and look

very rough

Rolling fatigue, overload,

poor shaft or housing

accuracy, installation error,

rusting

Avoid installation error

increasing viscosity of

lubricant and adequate

lubrication.

Peeling Is a cluster of

small spalls

Occur in roller bearings, if

mating surface is rough and

poor lubrication.

Controlling surface

roughness and dust,

proper selection of lubricant

Spalling Scratches in

spinning direction

on raceway

surface and

rolling contact

surfaces

Poor mounting and removing

practice, slippage of rolling

elements, oil film

discontinuation

Adopting improved

mounting and removing

procedures, correction of

preload, proper selection of

lubricant and lubricating

systems.

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(1)

Riveting

Smearing Surface is

roughened an tiny

particles adhere

Slippage of rolling

elements due to poor

lubricant characteristics

By making sound oil film,

using extreme pressure

lubricant, precautious on

radial clearance and pre-load to avoid slippage.

Stepped wear

Worn surfaces

and reduced

dimensions

compared to other

portions, mostly

roughed and

scored.

Ingress of solid foreign

objects, poor lubrication

and skewing of rollers.

Selecting optimum

lubricant and lubrication

system filtering

lubricating oil avoiding

misalignment.

Chipping

Partial chipping

of inner, outer

ring and rolling

elements

Impact of excessive load

poor handling trapping of

large solid foreign objects.

Improved sealing

characteristics, better

handling, avoiding impact or

excessive loading.

Cracking

Splits, and cracks

in bearing rings

and

rolling elements

Excessive load and

impacts very loose

fitting large flaking

Preventing creep.

Correction of fit avoiding

impact and heavy load

Rust and

corrosion

Rusting and

corrosion of

bearing

surfaces

Way in for water and

corrosive materials (acid)

condensation of moisture in

air, poor packaging and storing conditions.

Effective sealing, periodic lubrication of lubricating oil,

carefully handling bearing.

Seizing

Due to heat,

disabled

spinning,

discolouration, softening and

welding of

raceway surfaces

ad rib surface.

Low heat dissipation, poor

lubrication, improper

lubricant, very small

clearance, excessive load and roller skewing and

installation error.

Effective heat dissipation

selecting suitable lubricant

and optimal lubricating

feed rate, avoiding mis-alignment, enhanced

operating conditions.

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Hot clamping

4

Briefly discuss on following as regard to bearings

(i) Failures (ii) Characterization of failures

(iii) Causes

(iv) Solution (Apr/May 2018)

Same as 3……………..

5 Describe the procedural steps in the failure analysis with suitable example. (Apr/May 2017)

Same as 2……………..

6 Explain the procedural steps in sequence fault location with suitable example. (Apr/May 2017)

Causes of failures in pump:

Using low-quality fluids and poor contamination control

Failure of seals and hence leakage of fluid

Cracked or bent pulleys due to improper handling or installation

Shaft breakage due to bearing overload

Pump housing or casting breakage due to excessive vibration

Undersized shaft in an end suction pump

7 (i) Briefly explain various repair method of machine slide ways and spindles. (ii) What is failure analysis? Narrate its development. (Nov/Dec 2016)

Repair methods for spindles:

Machine spindles are a part of different tools and equipment that are used in

a lot of different jobs like those in automotive and manufacturing areas.

Spindles require appropriate maintenance and repair.

In fact, restoration of machine tool spindles has become a necessary industry.

While methods used in spindle repair depend on the specifications and extent

of the restoration required, basic essential methods guide are followed for

every repair. The essential methods used in the spindle repair procedure are

described under:

(i) Processing and dismantling

Before dismantling of spindle, it is very important to take photograph and

catalog the machine spindles. This information is required for logging and

tracking the alterations made to the spindle. The spindle may be taken apart after

the processing step.

(ii) Assessment of spindle

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Close inspecting the spindle and its parts is required in machine spindle

assessment. Every part and component of the spindle like the spindle housing,

end caps, spindle pulleys, collar locks, shaft and spindle taper are inspected and

taken into account. In order to determine dimensions that are in need of tuning

and other configuration, the assessment step also involves measuring and

recording every component accurately.

(iii) Machining process

The grinding process is used as a primary machining process for

spindles. Grinding is a process that is designed to fine-tune the measurement of

the spindle back to factory-set default dimensions. Finishing processes such as

polishing, lapping etc. Are done to get required surface finish. The spindle is

returned to a ‘like new’ condition by grinding and lapping. This process helps to

avoid unnecessary expenditure of money to replace the damaged spindle with a

new one. There might also be a requirement to put the spindle through subsequent

repairs like machining and bearing placement.

8

Explain the following in detail (i) Logical fault location methods

(ii) Sequential fault location methods (Nov/Dec 2016)

Fault-tree analysis is a method of analyzing system reliability and safety. It provides an

objective basis for analyzing system design, justifying system changes, performing trade-

off studies, analyzing common failure modes, and demonstrating compliance with safety

and environment requirements.

SEQUENTIAL FAULT LOCATION METHODS

Root cause analysis (RCA)

Root Cause Failure Analysis (RCFA)

Failure modes and effects analysis (FMEA)

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9

(i) Discuss the repair method for bearings (ii) List the few causes of failures in an electro mechanical system like compressor,

pumps and elevators. (Apr/May 2015)

Same as 1 & 6

10 (i) Explain the repair methods for spindles. (ii) Discuss the merits of criticality matrix. (Apr/May 2015)

(i) Same as 7

(ii) In maintenance criticality matrix, or risk matrix, is a tool that helps companies and

plants assess the criticality of a given risk. Structures often use it when they want to

manage, anticipate and annihilate potential failures.

Criticality matrix will help you analyze the various critical elements within your

maintenance service: production line, equipment or technicians, and will allow you to

manage it in a very dynamic manner.

11 Briefly explain the procedure for repair cycle of gears and lead screw. (Jun 2010)

Basic method of repair of gears:

Recertification, Reconditioning and Remanufacturing.

12 Explain the logical fault location method. (June 2010)

13 How do we monitor and report maintenance and capital improvement accomplishments? (Nov/Dec 2013)

(i) Logical fault location methods

(ii) Sequential fault location methods

o Root cause analysis (RCA)

o Root Cause Failure Analysis (RCFA)

o Failure modes and effects analysis (FMEA)

14 (i) Explain the repair method for gears. (May/June 2012)

(ii) Discuss the steps involved in performing FMEA.

Basic method of repair of gears:

Recertification, Reconditioning and Remanufacturing.

32

Failure modes and effects analysis (FMEA) is a step-by-step approach for identifying

all possible failures in a design, a manufacturing or assembly process, or a product or

service. “Failure modes” means the ways, or modes, in which something might fail.

15

(i) Discuss in detail about sequential fault location method

(ii) Describe the following symbols associated with fault tree analysis method (1) Diamond

(2) Rectangle

(3) Circle (May/June 2012)

Sequential Fault Location Methods:

Root cause analysis (RCA)

Root Cause Failure Analysis (RCFA)

Failure modes and effects analysis (FMEA)

Secondary failure or undesired event but not

developed further

Fault or undesired event caused by one or more

proceeding causes acting through logic gates.

Primary failure or basic fault that requires no further

development

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UNIT - V

PART-B

1. Explain about a typical work order flow diagram. (Nov/Dec 2018)

2. Explain the general structure of computerized maintenance management system. (Nov/Dec

2018)

Explain the role of computers in maintenance with suitable example. (April/May 2017)

There is a need to integrate the decision support tools in maintenance

function. Support tools in maintenance planning and execution for the

efficient discharge of the maintenance function.

There is an increasing trend in application of information based decision

support systems in different departments of modern industry.

Thus computers have become an indispensable requirement in

maintenance management

Computer is an efficient and reliable tool for maintenance personal to plan

and implement their programmers.

The success of CMMS depends on the quality of integration of computer

system in maintenance management. CMMS is used to track all maintenance costs and equipment repairs. This

tracking is accomplished by the monitoring of work orders. This task will

provide necessary information to track and plan and maintenance budgets. Effective cost control through CMMS is also achieved by the monitoring of

purchase and inventory costs. This will track spare part costs and aims to avoid

excessive inventories. This module also helps in vendor selection and monitor

the shipping time.

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A computerized maintenance management system includes the following

aspects: • Development of a database

• Analysis of available part records Development of maintenance schedules

Availability of maintenance materials

• Feedback control

• Project management.

3. Discuss briefly the maintenance requirement for the belt conveyors.

Explain the necessity and uses of equipment records. (April/May 2018)

Maintenance requirement for the belt conveyors are;

Conveyer systems need to be inspected on a regular basis. The important areas

include rollers, bearings, chains and belts. All of these moving parts are subject

to wear and tear.

Check conveyers to detect any belt slippage, dragging or defective rollers.

Be sure that a necessary guards are in place to protect workers from

mechanical injury. Moving machine parts should be lubricated regularly

according to manufacturers’ instructions.

Frequently overlooked are conveyor rollers, belts, chains during regular

maintenance procedures. So proper attention is required for the same.

Moving equipment parts are subject to breaks caused by metal fatigue, loose

bearings and obstructions.

Check conveyors regularly to detector any belt slippage, dragging or defective

rollers. Control static electricity through bonding and grounding to minimize

static charges.

Necessity and Uses of Equipment Records:

Equipment records are information containing the details of installation, service,

repair, maintenance activities, conditions, defects, schedules and plans for future

implementation. Equipment records are to be used to maintain control on

maintenance cost, reliability and availability.

Clear picture about the details of maintenance programs is obtained

Information about completed, pending and regular jobs carried out

to the equipment are available

Records disseminated to various units of the industry

Helps in standardization of procedures

Evaluation of performance of maintenance tasks

Provide details of frequency of maintenance requirements for each

equipment

Comparison of time taken for completing the maintenance job with

the past records.

Provide strategies for better maintenance management.

4. Describe briefly the structure of a computer assisted maintenance system.

Discuss any two methods of job evolution in details. (April/May 2018)

35

Explain in detail computerized maintenance management system.

Explain job order system with an example. (Nov/Dec 2016)

Structure of a Computer Assisted Maintenance System:

Same as 2

Two methods of job evolution

1. Ranking method

Jobs are arranged from highest to lowest in such a way of their value or merit to the

organization

2. Classification method

A predetermined number of job groups or job classes are established and jobs are

assigned to these classifications.

5. Explain various repair methods for the followings

(i) conveyor

(ii) chain, rope, trolley

(iii) Hydraulic lift. (Nov/Dec 2016)

1. The proper maintenance of material handling equipment is extremely essential for

preventing the occurrence of bottle neck or points of congestions production line

flow can be maintained only if the material handling equipments is in proper

working order.

2. Out of money maintenance techniques available preventive maintenance is one of

the best maintenance techniques suggested in case of material handling

equipments.

3. Preventive maintenance helps to keep the material handling equipments always

running conditions there by minimizing the interruption during operation. A

periodic inspection and minor alignments may be adequate to prevent the

equipment breakdown.

4. Preventive maintenance also includes lubrication adjustment and repair.

There are three stages of preventive maintenance and they are;

• Inspection

• Repair

• Overhaul

6. Explain the repair method for material handling equipment. (Nov/Dec 2015)

A typical scheduled repair method for material handling equipment:

• Check/lubricate all bearings, universal joints, and pulleys.

• Check chain tension, wear and lubricate

• Check sprocket alignment, wear and screw set.

• Check flat belt tension, wear and acing

• Check V-belt tension, wear and sheave alignment.

• Check general condition of system

• Operate entire system after service

• List any items requiring replacement or repair.

Portable crane:

• It is necessary to keep loads within design limits on portable cranes that are mounted

on wheels platforms.

• Frequent inspection of brakes, load hoisting and lowering mechanism

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• Inspection of boom, base and platform for any sign of stress Eg: cracks, bends, breaks

Over head cranes:

• Keep the attachments in overhead cranes loaded within the rating capacity.

• Maintain safety factors for replacement parts according to manufacturer specifications

• Check welded connections for cracks, bends abrasion and corrosion Maintenance

Conveyers:

• Conveyer system need to be inspected on a regular basis. The important areas

include rollers, bearings chains and belts. All of these moving parts are subjected to wear and

tear

• Check conveyers to detect any bolt slippage, dragging or defective rollers.

• Moving equipment parts are subjected to breaks caused by metal fatigue, loose bearing

and obstructions.

7. Explain the need and importance of equipment record with suitable example. (Apr/May

2015)

Same as 3……

8. What is job card system? State its benefits. (Nov/Dec 2009)

Job order entry:

The general work order entry requires the following information to be filled by the

user:

Equipment number that requires maintenance Priority and description of the work

Estimated cost of work

Job order backlog:

The backlog is the storage area for all active work order Work order system: The

work order system is the information system for the maintenance organization it is

an important for an organization to maintain proper records to perform any

meaningful analysis on its politicizes and procedures.

The computerized maintenance management system allows computer tracking and

analysis of work orders as well as plant equipment data.

9. Explain the preventive maintenance strategies for the cranes.

Explain about the maintenance monitoring execution and control. (Nov/Dec 2009)

STAGES OF PREVENTIVE MAINTENANCE FOR CRANES

a) Inspection:

All parts, open or covered are inspected for wear and tear. Worn out or

unworkable components like wire ropes, wheels, bearings, bolts etc are

removed. Brakes are adjusted and necessary lubrication applied.

b) Repair:

The repairable parts of the system after inspection are corrected for small

repairs and minor defects are rectified. Systems like open gear transmission,

couplings, riveted and bolted joints, trolley, brakes, guards, etc may be

repaired according to the needs.

c) Overhaul:

Overhauling involves dismantling the complete mechanism and replacing all

damaged components. Crane structure, buffers, rails, open gear transmission,

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pulley blocks, etc may be replaced and various sub mechanism may be

aligned and adjusted to ensure smooth operation.

10. Explain various hydraulic and pneumatic equipment used in material handling purpose.

How to maintain it? (June 2010)

Material handlers such as construction equipment, cranes, forklifts, and shipyard hoists use

hydraulic power because loads are very heavy and the working environment is often harsh.

Hydraulic systems are self-contained within each unit, which easily accommodates mobility.

On the downside, hydraulics require frequent maintenance and fluid can leak if seals become

worn.

The ability to precisely automate material handling increases efficiency and reduces costs.

Pneumatic actuators offer that precision, especially when fitted with positioning sensors, and

they are ideal for industrial environments where sanitation is an issue. They are strong but

can be quite small, and they can be used with different types of mounts, too.

Pneumatic systems require an air compressor relatively close-by, but many industrial

facilities use compressed air for multiple purposes.

The most used pneumatic actuator in material handling applications is the pneumatic cylinder,

especially the double-acting cylinder.

11. Explain the maintenance work quality. (Nov/Dec 2013)

It refers recording data about equipment and property including maintenance

activities, specifications, purchase date, expected lifetime, warranty information, service

contracts, service history, spare parts and anything else that might be of help of

management or maintenance workers. The CMMS may also generate metrics such as the

Facility Condition Index (FCI) to measure effectiveness of asset management.

12. Describe about the software maintenance and distribution. (Nov/Dec 2013)

Because of the vast quantity of technical and economical data involved in

maintenance management, computer support is very desirable. Installing a

computer-aided system brings these economies and can be

a. Less overtime worked

b. Less time given to corrective maintenance

c. Reduced loss of production due to breakdowns

d. Less time spent on the administrative tasks of the maintenance service

e. Longer lifetime of the equipment, because of better preventive maintenance

f. Reduced energy consumption

No need to say that, as with all other computer aided technologies, maintenance

planning and control should be well structured.

The maintenance planning software should be integrated with all other computer

applications like production planning, inventory planning, and computer aided

design, as a better design influences the frequency and amount of maintenance

required.

Expert systems could also be useful in inspection and fault diagnosis

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