department of mechanical engineering me 6012 - …€¦ · planned maintenance jishu hozen (jh)...
TRANSCRIPT
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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.
11
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
II. Planned Maintenance
Planned maintenance may further be classified into
1. Preventive Maintenance
2. Corrective Maintenance
3. Predictive Maintenance
4. Condition Based 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
17
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
20
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
II. Planned Maintenance
Planned maintenance may further be classified into
1. Preventive Maintenance
2. Corrective Maintenance
3. Predictive Maintenance
4. Condition Based 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.
26
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
33
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.
34
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
36
• 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,
37
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