Maintenance Management Assignment

OM 315: MAINTENANCE MANAGEMENT

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Station: Visakhapatnam

Identity No. 10MB00199

Learner name D. SREENIVASA RAO

Mobile number 9032984120

Programme MBA

Group General

Paper name (Subject 315 - MAINTENANCE MANAGEMENT

Year/Semester III Year

Study Center CDL-GITAM, Visakhapatnam


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ASSIGNMENT – I

1. Explain in brief functions, objectives and types of maintenance.

Answer

MAINTENANCE OBJECTIVES:

The objectives of maintenance are to ensure the desired plant availability at

an optimum cost within the safety prescription. In other words, it may be mentioned that the objective of maintenance is to minimize the total cost of

unavailability and resources.

Whenever the plant is not available either due to breakdowns or due to planned stoppages, the following costs are incurred.

1. Loss of earnings due to stoppage of equipment 2. Loss of in service materials.

In addition the following costs are incurred on resources: Labor of overhead expenses

Materials in spares and consumables

Cost of storage of spares and facilities.

Hence, maintenance functions are so, organized as to minimize the total cost

of unavailability and resources.

MAINTENANCE FUNCTIONS

The above mentioned objectives are attained by taking certain action

illustrated below:

Action Purpose

Lubrication

Cleaning

Adjustments Return or slow down the process of deterioration or wear

Application of Protective coating

Examination of the state of the

components

Assess the extent of wear and

determine, on that basis, the action required to check a break-down and

the time when such action should be

taken

Analysis of history of behavior of the

machine and its components

Replacement of worn out component

Repair of cracks or other repairable damages

Restore the original operational capacity of the machine and prevent

further damage

Modification of design of the

components or location of the equipment

Affect improvements to reduce the

frequency of attention or to recduce cost of maintaining the equipment.

Capital replacement Replacement of the machine when


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the age of the existing machine

requirement of quality and quantity

of output and emergency of better

machines make it economical to dislodge the present and install a new

machine.

In these, the first four steps are taken with the sole purpose of reducing

friction, wear and effects of environment on the individual parts of a machine.

For example, lubrication reduces friction; cleaning prevents corrosion and

abrasion due to dust; adjustment of level or alignments or by tightening the loose bolts and nuts eliminates undue stresses; and preventive coatings

guard against rust and corrosion. These action increase the useful life of

parts and therefore, constitute an intrinsic part of Preventive Maintenance.

The next two steps, inspection of parts and analysis of history, are meant to

assess the condition of the part, the extent of wear, the action required to remedy the defect and the time when such action should be undertaken.

These activities are undertaken essentially to be able to plan the remedial

measures.

Inspection can be external for abnormal sound or temperature which does

not require a stoppage of the machine. It could even be internal, requiring a

machine to be stopped either purely for inspection or at the time of some other repair or during overhauling of the machine. Historical data on the

other hand, is a chronological record of repairs and replacements carried out

on a machine during its life in the company. Analysis of such a record helps

to estimate the life span of various components and establish the frequency of inspections, repairs, and replacements.

Replacement and repair of components can be undertaken on the basis of inspection reports, analysis of history or complaints of operating personnel.

Another important part of maintenance is the change in some characteristics

of the components which gives frequent trouble, to avoid re-occurrence of that trouble with that frequency. Such an action is taken on the basis of

history of the equipment and evaluation of costs involved. This step can be

defined as "Maintenance Prevention". Cost of maintenance of the machine

rises with the increase in its age. Moreover, passage of time also affects the operational efficiency of the machine. Requirements of quality and quantity of

production go through a change making an old machine more or less obsolete

in relationship to the new demands.

New and better machines emerge in the market. All these factors make it

necessary to replace the existing machines at some stage in their lives by new machines. Maintenance is vitally linked with such action. Analysis to

determine the economics in replacement of machines and their physical

installation, therefore, becomes a responsibility of the maintenance

personnel.


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MAINTENANCE TYPES

A. BREAKDOWN MAINTENANCE

Characteristics of Break-down Maintenance System:

No services except occasional lubrication unless failure occurs

No maintenance men on regular basis Maintenance done by sub-contractors

No organized efforts to find out reasons

No stock of spares No budget

No records

Initially it looks economical

Problems in case of Breakdown

Who is to do repair?

From where to get parts? How do we pay for them?

Who is to go to buy parts?

Results of Breakdown Maintenance System:

Increased Down Time

Increased costs & Pressures

B. ROUTINE MAINTENANCE

A procedure followed regularly i.e.,., A cyclic operation recurring

periodically.

Advantages

Simple to establish & follow Little or no clerical work

High degree of prevention by intercepting developing faults.

A more advanced stage of routine maintenance calls for 'service

instructions on a pre-printed schedule and checklists'.

Examples:

Check all compressors first on Mondays. Lubricate completely two machines daily.

Disadvantages Routine maintenance may not provide the service specified by the

manufacturer

We may ignore information regarding preceding breakdowns

Service required for a machine at different frequencies may be ignored

All similar machines may be serviced at same frequency

irrespective of working hours.

C. PLANNED MAINTENANCE

In this type of service, the emphasis is placed on the machines.

What does the manufacturer prescribe?


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Is the unit utilized for two, or three shifts per day?

Is it working under normal load?

Are the conditions as good as those envisaged by the manufacturer?

Do we allow for extra attention owing to corrosion-including

conditions?

Characteristics of Planned Maintenance

Instructions are more detailed than in routine maintenance

Calls for differently timed service for the same unit Schedule is drawn with dates

Need for establishing the work-load for the crew

Entails considerable planning effort, faithful implementation and

recording Initial list of planned maintenance will be in detail

Advantages of Planned Maintenance Will take into consideration the changes in conditions of use and

increased wear of parts

Inspections, replacement of parts and adjustments are included in the overall plan

Detailed instructions reduce the chance of missing any activity.

Unforeseen work is greatly reduced

Provides as much attention as the equipment requires - to the best judgment and ability of the planner

D. PREVENTIVE MAINTENANCE System which strives to reduce the likelihood of failures.

To achieve prevention of break-downs Planned service is carried out

with the explicit additional objective of detecting wear points and ensuring perfect functioning by replacing parts which could still be

used were it not for the assurance that is required.

Occasional use of statistical analysis/methods for determining life

expectancies of parts.

The system employs Measuring & Inspection Devices. This phase is

Predictive maintenance.

Preventive Maintenance System is more expensive due to more of

planning and replacement of parts before failing.

Preventive Maintenance increases reliability

Preventive Maintenance reduces total work-load

Preventive Maintenance reduces total down time Preventive Maintenance reduces unplanned work

Preventive Maintenance reduces total maintenance cost

Routine maintenance & Planned maintenance also include Preventive maintenance action.

Preventive maintenance could be grouped as under:

Fixed-time Maintenance Condition-based Maintenance


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Opportunity Maintenance engineering and management

E. Corrective Maintenance: Services carried out to restore an item to an acceptable working

condition. Services arising out of

Break-downs

Malfunctioning & Deteriorating conditions

Productive Maintenance An effort to set up the function on a planned and measured

production pattern. The output relates to the number of servicing

tasks completed, e.g., lubrication, inspection, overhaul, etc.

Originally used in USA.

Total Productive Maintenance (TPM)

Efforts with the total participation of employees. Used in Japan.

2. How do you prepare maintenance planning and scheduling? Explain with an example.

Answer

Planning in the context of maintenance means the process by which all

the elements required to perform a task are determined and prepared

prior to starting the job. Planning is a process of detailed analysis that determines and describes the work to be performed, the sequence of

associated tasks, methods to be used for their performance, and the

required resources – including skills, crew size, man hours, parts, special tools and equipment and an estimate of total cost. It also includes

identification of safety precautions, required permits, communication

requirement, and reference documents such as drawings and wiring

diagrams. It addresses essential preparation, execution and start-up efforts. Work estimates and activation of required procurements are parts

of the planning process.

Basic maintenance planning principles are as follows:

i. The planners are organized into a separate department from the craft

maintenance crews to facilitate specializing in planning techniques as well as focusing on future works.

ii. The planning department concentrates on future work (work that has

not been started) in order to provide the maintenance department at

least one week of work backlog that is planned, approved, and ready to execute. This backlog allows crews to work primarily on planned

work. Crew supervisors handle the current day‟s work and problems.

Any problems that arise after commencement of any job are resolved by the craft technicians or supervisors to the planning department.

After every job completion, feedback consists of any problems, plan

changes, or other helpful information so that future work plans and

schedules might be improved. The planners ensure that feedback information gets properly filed to aid future work.


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iii. The planning department maintains a simple, secure file system based

on equipment tag numbers. The file system enables planners to utilize

equipment data and information learned on previous work to prepare and improve work plans, especially on repetitive maintenance tasks.

The majority of maintenance tasks are repetitive over a sufficient

period of time. File cost information assists making repair or replace

decisions. Supervisors and plant engineers are trained to access these files to gather information they need with minimal planner assistance.

iv. Planners use personal experience and file information to develop work

plans to avoid anticipated work delays and quality or safety problems. As a minimum planners are experienced, top level technicians that are

trained in planning techniques.

v. The planning department recognizes the skill of the crafts. In general,

the planner‟s responsibility is „what‟ and the craft technician‟s responsibility is „how‟.

vi. Wrench time is the primary measure of workforce efficiently and of

planning and scheduling effectiveness. Wrench time is proportion of available-to-work time during which craft persons are not being kept

from productively working of a job site by delays such as waiting for

assignment clearance, parts, tools, instructors travel, coordination with other crafts of equipment information.

MAINTENANCE PLANNING AND SCHEDULING

Effective planning and scheduling contribute significantly to the following: Reduced maintenance cost.

Improved utilization of the maintenance workforce by reducing

delays and interruptions. Improved quality of maintenance work by adopting the best

methods and procedures and assigning the most qualified workers

for the job. Planning and Scheduling Objectives

Minimizing the idle time of maintenance workers.

Maximizing the efficient use of work time, material, and equipment.

Maintaining the operating equipment at a responsive level to the need of production in terms of delivery schedule and quality.

Classification of Maintenance Work According to Planning and Scheduling Purposes

Routine maintenance: are maintenance operations of a periodic

nature. They are planned and scheduled and in advance. They are covered by blanket orders.

Emergency or breakdown maintenance: interrupt maintenance

schedules in order to be performed. They are planned and scheduled as they happened.

Design modifications: are planned and scheduled and they depend on eliminating the cause of repeated breakdowns.

Scheduled overhaul and shutdowns of the plant: planned and

scheduled in advanced.


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Overhaul, general repairs, and replacement: planned and

scheduled in advanced.

Preventive maintenance: planned and scheduled in advanced.

An essential part of planning and scheduling is to forecast future work and

to balance the workload between these categories.

The maintenance management system should aim to have over 90% of

the maintenance work planned and scheduled.

Planning

Planning is the process by which the elements required to perform a task are determined in advance of the job start.

Planning It comprises all the functions related to the preparation of:

a. The work order

b. Bill of material c. Purchase requisition

d. Necessary drawings

e. Labor planning sheet including standard times

f. All data needed prior to scheduling and releasing the work order.

Good planning is a prerequisite for sound scheduling.

Planning Procedures

The planning process comprises all the functions related to the

preparation of the work order, bill of material, purchase requisition, necessary drawings, labor planning sheet, job standards, and all the data

needed prior to scheduling and releasing the work order. An effective

planning procedure should include the following steps:

i. Determine the job content (may require site visits)

ii. Develop a work plan. This gives the sequence of activities in the

job and establishing the best methods and procedures to accomplish the job.

iii. Establish crew size for the job.

iv. Plan and order parts and material. v. Check if special equipment and tools are needed and obtain them

vi. Assign workers with appropriate skills

vii. Review safety procedures

viii. Set priorities ix. Assign cost accounts

x. Complete the work order

xi. Review the backlog and develop plans for controlling it xii. Predict the maintenance load using an effective forecasting

technique.

Basic Levels of Planning Process (Depend on the Planning Horizon)


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Long-range planning: it covers a period of 3 to 5 years and sets

plans for future activities and long-range improvement.

Medium-range planning: it covers a period of 1 month to 1 year. Short-rang planning: it covers a period of 1 day to 1 week. It

focuses on the determination of all the elements required to

perform maintenance tasks in advance.

Long and Medium-Range Planning

Sets plans for future activities and long-range improvement. Needs to

utilize the following: Sound forecasting techniques to estimate the maintenance load.

Reliable job standards times to estimate staffing requirements.

Aggregate planning tools such as linear programming to determine

resource requirements.

Medium-Range Planning

Specify how the maintenance workers will operate. Provide details of major overhauls, construction jobs, preventive

maintenance plans, and plant shutdowns.

Balances the need for staffing over the period covered. Estimates required spare parts and material acquisition.

Short-Range Planning

It focuses on the determination of all the elements required to perform maintenance tasks in advance.

Scheduling Maintenance scheduling is the process by which jobs are matched with

resources and sequenced to be executed at certain points in time. Basic

maintenance scheduling principles are as follows:

i. Job plans providing number of persons required, lowest required

craft skill level, craft work hours per skill level and job duration

information and necessary for advance scheduling. ii. Weekly and daily schedules must be adhered to as closely as

possible. Proper priorities must be placed on new work orders to

prevent undue interruption of these schedules. iii. A scheduler develops a one week schedule for each crew based on

a craft hours available forecast that shows highest skills levels

available, job priorities, and information from job plans. iv. The one week schedule assigns work for every available work hour.

The schedule allows for emergencies and high priority, reactive jobs

by scheduling a sufficient amount of work hours on easily

interrupted tasks. Preference is given to completing higher priority work by under-utilizing available skill levels over completing lower

priority work.

v. The crew supervisor develops a daily schedule one day in advance using current job progress, the one week schedule and new high

priority, reactive jobs as a guide.

vi. Wrench time is the primary measure of work force efficiency and of

planning and scheduling effectiveness. Work that is planned before assignment reduces unnecessary delays during jobs and work that


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is scheduled reduces delays between jobs. Schedule compliance is

the measure of adherence to the one week schedule and its

effectiveness.

Is the process by which jobs are matched with resources and sequenced

to be executed at a certain points in time. Scheduling deals with the

specific time and phasing of planned jobs together with the orders to perform the work, monitoring the work, controlling it, and reporting on job

progress. Successful planning needs a feedback from scheduling.

Reliable Schedule Must Take Into Consideration

A job priority ranking reflecting the criticality of the job.

The availability of all materials needed for the work order in the

plant. The production master schedule and close coordination with

operation.

Realistic estimates and what is likely to happen rather than what scheduler desires.

Flexibility in the schedule.

Maintenance Schedule Can be Prepared at Three Levels (Depend on The

Time Horizon)

Long-range (master) schedule

Weekly schedule Daily schedule

Long-Range (master) Schedule Covering a period of 3 months to 1 year.

Based on existing maintenance work orders (blanket work order,

backlog, PM, anticipated EM). Balancing long-term demand for maintenance work with available

resources.

Spare parts and material could be identified and ordered in

advance. Subject to revision and updating to reflect changes in the plans and

maintenance work.

Weekly Schedule

Covering 1 week.

Generated from the master schedule. Takes into account current operations schedules and economic

considerations.

Allow 10% to 15% of the workforce to be available for emergency

work. The schedule prepared for the current week and the following one

in order to consider the available backlog.

The work orders scheduled in this week are sequenced based in priority.

CPM and integer programming techniques can be used to generate

a schedule.


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Daily Schedule

Covering 1 day.

Generated from weekly schedule. Prepared the day before.

Interrupted to perform EM.

Priorities are used to schedule the jobs.

Elements of Sound Scheduling

Requirements for effective scheduling:

Written work orders that are derived from a well-conceived planning process. (Work to be done, methods to be followed, crafts

needed, spare parts needed, and priority).

Time standards.

Information about craft availability for each shift. Stocks of spare parts and information on restocking.

Information on the availability of special equipment and tools

necessary for maintenance work. Access to the plant production schedule and knowledge about when

the facilities will be available for service without interrupting

production schedule. Well-define priorities for maintenance work.

Information about jobs already scheduled that are behind the

schedule (backlog).

Scheduling Procedures

Sort backlog work orders by crafts.

Arrange orders by priority. Compile a list of completed and carry over jobs.

Consider job duration, location, travel distance, and the possibility

of combining jobs in the same area. Schedule multi-craft jobs to start at the beginning of every shift.

Issue a daily schedule (not for shutdown maintenance).

Authorize a supervisor to make work assignments (dispatching).

Maintenance Job Priority System

Priorities are established to ensure that the most critical work is

scheduled first. It is developed under coordination with operations staff.

It should be dynamic.

It must be updated periodically to reflect changes in operation and maintenance strategies.

It typically includes three to ten levels of priority.

Scheduling Techniques The objective of the scheduling techniques is to construct a time chart

showing:

The start and finish for each job. The interdependencies among jobs.

The critical jobs that require special attention and effective

monitoring.

Scheduling Techniques


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Such techniques are:

Modified Gantt chart

CPM PERT

Integer and stochastic programming.

3. What is zero based budgets? Explain the sources of collecting maintenance costing and their applications.

Answer

There is tremendous pressure on maintenance managers to improve their

budget performance.

Traditional budget methods do not seem to be effective in the

maintenance arena because maintenance expenditures are made up of

1000's of seemingly unrelated events. Maintenance does not seem to be volume related (higher output equals higher maintenance).

The breakdowns and other maintenance activities are hard to predict and do not necessarily reflect what happened last year. To successfully budget

(and therefore predict) maintenance expenditures we must divide the

whole maintenance demand into its basic parts

A zero based budget breaks the overall demand for maintenance services

into its constituents, that is, assets or areas. Look at each asset (or group

of like assets) to determine the maintenance exposure. In addition to the unit or asset list, a zero based budget has allocations for certain areas

that are hard to define as individual assets such as the electrical

distribution system or the paved parking area and sidewalks.

Prior computerization of maintenance simplifies the construction of a zero

based budget. The computer can easily generate an asset and areas list.

Many systems allow you to create classes of equipment where like equipment is aggregated into one line.

If the system has been in use for more than a year you can attach the hours and material dollars for each asset and area. Some systems have a

reason for repair (see chapter on work orders). The reason for repair

would roughly correspond to the categories below. Most systems allow export of the files to a spread sheet for further manipulation.

All maintenance activity can be traced back to one of the eight demands

that follow. Shops that are craft dominated have a more complicated

problem. After the budget is completed they must go back to the individual demands and break-out the labor by craft.

The eight reasons for maintenance resources are:

1. PM- preventive maintenance hours/materials. Based on your

facility and equipment size, use, construction and the standard times of

the PM activities you can predict how much time and materials PM's will take. In a TPM shop some of the PM hours will come from operators. The


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simplest formula is to multiply the number of services by the time for

each service. Also look at the materials used for each service. Include

some time for the short repairs that the mechanic will get done during the PM. Since you have some flexibility in scheduling you can consider PM's as

a level demand throughout the year.

Specifically PM work includes all the inspection, adjustment, bolt tightening, oiling, cleaning, and readings that are initiated by task lists.

The task lists are initiated on a periodic (quarterly, annual) basis.

2. CM-corrective maintenance hours/materials. Also called

scheduled repairs or planned maintenance. As your PM inspectors inspect

each part of the facility and all equipment they write-up repairs

(deficiencies). These write-ups become your backlog of corrective maintenance (CM) for your maintenance schedule. The repairs are

considered scheduled repairs as long as they don't interrupt jobs in

process.

You can look at previous years to get an idea of the hours for this activity.

Since you have control of the schedule this demand can be considered level throughout the year. These scheduled repair hours are inserted by

equipment, by group of like equipment or by area.

There is a tremendous advantage to this type of work because you can plan the work and accumulate several jobs for a location or schedule them

together or assemble several jobs with the same materials or craft (fix all

the small roof problems at several locations) at the same time. I estimate that every hour spent planning these scheduled jobs you will save 5 hours

on the site.

3. UM- all types of user maintenance (hours/materials) is all requests

from users/customers from the routine broken pulley on a conveyor to a

$1,000,000 catastrophic breakdown. This includes UM-R (Routine work),

UM-P (Small projects), UM-B (breakdowns).

UM is the most common source of work in a breakdown driven

organization. Without inspection and inspectors the users find problems first. Users also are the first to find vandalism, breakdown and damage.

Responsive user complaint handling is essential if you are to be viewed as

effective. In fact, most users will judge you entirely on how you respond to their complaints (other benchmarks usually don't have as much impact

on their quality of life).

UM includes both breakdowns and routine service requests. UM includes servicing minor user requests for hanging pictures, moving furniture and

other personal service.

At the beginning of the year budget the same amount of hours for UM as

the previous year by asset or category. At the end of the year you can

back off emergency component of UM as the PM system starts to take

effect. For purposes of budgeting UM creates a level demand. In fact emergencies will tend to bunch. Many factories use outside contractors to


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level the demand for UM. In larger facilities this work will look more and

more level. See seasonal demands (SM) for a special case of UM demand.

4. SM- Seasonal Maintenance hours/materials. This includes all

special seasonal demands. Your entire grounds maintenance effort is

cer¬tainly driven by season. Review of roofing systems before summer

and winter or checking air conditioning before summer are seasonal demands.

Some businesses are seasonal. Cleaning the Candy Cane line before it starts up in July would be a seasonal demand. You can also use this

category to pick-up some percentage of the seasonally driven

emergencies or seasonally driven PM. Budget hours at the beginning of

each season by asset or group based on his¬tory.

5. RM- Replacement / Rehabilitation / Remodel Maintenance hours /

materials. In some organizations this category is capital improvement and is handled outside the normal maintenance budget.

RM also includes all maintenance improvements and efficiency improvements. At some point, units which have not been maintained for

a period of time or have reached the end of their useful life will have to be

rebuilt or replaced. The rebuilding effort should be added to your

maintenance budget as a capital replacement line item separate from any current maintenance activity. If your people are doing the modernization

to bring units up to PM standards then the hours will have to be budgeted.

Since you have control of the rebuild schedule you may be able to use

rebuilds as a crew balancing tool. A special case of RM is Management

decision. This work is generated by a manager when they decide to change something in, on or around a machine, other asset or the building.

The reasons for the decision might range from energy efficiency, improve

usage, legal problems or even a whim (I hate yellow presses, paint

them!).

Maintenance demands for the whole operation (not tracked by individual

but by location). After the base demand is cataloged by equipment or area of the plant look into some of the budget busters below. A well designed

budget can be ruined by excessive social demands generated by visiting

dignitaries or a large construction project's effect on the rest of your operation.

6. SD- Social Demands (sometimes known as hidden demands because

they don't always show up on work orders). This is also called PS for Personal Service. Your primary mission is maintenance of the equipment

and facility. You may be called upon for other duties in your organization.

These duties may include supplying clean-up people, running tours, preparation for visiting dignitaries, set up of special events (like running

sound cable), providing chauffeur services, picking-up or delivery of

papers or packages, organizing picnics or work on non-organization

equipment and facilities (charity work). Estimate your hours for these activities.


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7. ED- Expansion demands. Any expansion in the size of your facility,

size of your work force, additions to the scope of your control will add hours to your overall requirements. New buildings, assembly lines, major

changes to the plant require start-up time. New facilities disrupt current

activities as well as taking direct time. Adding satellite facilities will result

in additional lost time until systems are well in place. Estimate additional time if an expansion is contemplated.

8. CD- Catastrophic Demands. It seems that every location has characteristic catastrophes. Add time for one or two catastrophes. You

can review your records for the actual amount of time spent in a typical

catastrophe. This can include floods, hur¬ricanes, trucks taking out the

side of the buildings, fires, etc.

How to Set-up a maintenance budget

1. Start the process by compiling a list of all machinery, equipment that

you maintain. As much as possible arrange the list by department or cost

center. This will facilitate report printing at a later stage. If you have a CMMS, (Computerized Maintenance Management System), print an asset

or equipment list. This list might have as few as hundreds, thousands or

more entries depending of the size of your plant.

2. Add to this list areas of the plant and site that require maintenance

resources that don't lend themselves to the unit concept. Typical areas

include roofs, pavement, electrical distribution system, piping, doors/windows, etc.

3. Look at the list and see if there are any units that can logically be grouped together. A wire harness assembly plant might have 50 braiding

machines of similar usage and vintage. These could logically be

aggregated into one line. Putting similar units or areas together simplifies

the process and also makes predictions more accurate.

4. Collect any maintenance data available by unit or area for the last

several years if available. Your CMMS would facilitate this step. If the data is coming from the CMMS then see if it has an export capability. Some

systems will send data to spread sheet files without re-entry. Inquire if

your accounting or cost accounting group can shed any light on the costs to maintain certain areas, departments, assets or production lines.

5. We recommend this whole mass of information be designed in a

computer spread sheet Excel. Create a template to duplicate the form at the end of this section. The equipment, areas and groups of units/areas

are listed in the template. An alternate recommendation would be to enter

the data into a database manager. There are advantages to both approaches. Most budgets are usually run from spread sheets.

6. After the individual units and the general assets are listed add the

global lines (that apply to the whole site) social, expansion, catastrophes. Look into your history or estimate the impact of these areas. The three


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areas can be added as hours and materials or as percentages depending

on the need. If these areas have traditionally been non-work order items

now would be a good time to set-up the codes to put them on work orders. Once accounted for these costs can be studied year to year.

7. Once assets have been inserted into the template, this document

becomes the basis for your zero based budget. Back-up the filled in template. You have many hours in at this point so make your back-ups

now and keep them up to date! The other point is that this computerized

list might have other uses so a copy might be useful for another reason.

8. Review each unit, area or group and estimate your PM, CM, UM, RM,

SM costs and hours. A useable history of costs from accounting or from

the CMMS greatly simplifies this process.

9. Add in your estimates for SD- Social, ED-Expansion and CD-Catastrophe related demands against the department. These can be as

percentages of the above areas or as actual hours and material costs.

10. Your material costs are the sum of all material columns, your hours

are the sum of all hour columns. You would then apply the costs of your

labor, fringe benefits and maintenance overheads to determine your

budget.

When management wants reductions to your budget you have a new level

of discussion. All changes need to be justified in terms of higher or lower levels of service on individual assets or areas. Now when cuts are needed

you can talk about which assets will be allowed to deteriorate or which

departments will not be served as well.

Almost every business has deferred maintenance. You may see a problem

slowly developing and put off the work. You could be short of funds, be

planning a major rehabilitation, planning to sell the unit or property or lack the requisite skills. Some organizations run their whole operation with

excessive amounts of deferred maintenance Distribute your zero based

budget to the users, staff, and top management for comments.

If your current actual hours available are only a small percentage of your

budgeted demand then something will have to be done. Either deterioration is taking place or your customers are unsatisfied or both.

One solution is to use contractors to make up the short fall. Some

organizations are using this strategy to maintain maximum flexibility.

Using the budget to schedule the need for outsourcing

Some organizations use outsourcing strategies where they crew for 75% to 80% of demand and use outside vendors during peak periods. The

most effective way to predict the need for contract labor is to recast the

budget on a monthly basis. Using the hours per month you can see which

months will exceed your crew available hours.


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The process is similar to a staffing exercise. If your core crew has 1400

hours available a month the contractor would have to supply and labor

above 1400 hours. The budget will show which months it would be likely that contracting will be needed. Moving project work can be used to

minimize contractor needs in a given month.

4. Discuss in detail the spare parts inventory management.

Answer

The aim of spare parts inventory management is to make available to

maintenance, the right spare part, at the right place, at the right time, in

the right quantity, at the right price and at the lowest total cost to the

enterprise. Of these, the first four represent the service to the maintenance engineer and must be give first priority. The next part

means paying the least for a purchased item by locating and negotiating

with the suppliers for a reasonable price-provided the item meets the technical needs of maintenance. The last part of the aim minimizes the

total cost, consisting of the cost of administering the system and

procedures, the price paid for the parts and the cost of machine downtime incurred if the needed part was not available when required.

Types of spare parts

The three basic types of spare parts are:

PM spares

Those are replaced during preventive or opportunity maintenance.

Repair parts (breakdown spares)

Those are required to replace parts that fail during service and

Overhaul (shutdown) parts

Those required during planned overhaul or shutdown of the plant.

The quantity and the time of requirement cannot be predicted for the

repair parts. Only, the chance of their requirement can sometimes be

predicted. Statistical methods are needed for their inventory control.

Life cycle of spare parts

Spare parts go through the following six stages in their life cycle:

i. Design and specification (The right spare)

ii. Determination of initial requirement (The right quantity)

iii. Procurement (the right price) iv. Storage and preservation (minimum custodial and inventory

carrying cost)

v. Issue and replenishment (minimum downtime cost through inventory control)

vi. Disposal of damaged, surplus and obsolete spares (minimum

damage and maximum disposal value)


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Stage 1: Design and specification

Stringent specifications, high quality of manufacture and careful operation

/ maintenance of the machine reduce consumption and cost due to replacement of spares. Ideally, spare parts from the OEM (Original

Equipment Manufacturer) should be used. Spares have a huge range -

each one have several specifications, which are not available to the user.

Without actual fitting it is not possible to tell whether a part will fit or not. This is clearly not practicable as spares are stocked in advance of

requirement. It will be worth paying for a certificate or warranty for the

spare part from its supplier, at least for critical and expensive parts. Only large consumers such as railways, airlines, transport fleets, armed forces

etc. can assess the life of parts by destructive or accelerated life testing or

from the quality records of the manufacturer. One should never buy from

unauthorized dealers or unproved suppliers.

Stage 2: Determination of initial requirements

The machine supplier usually gives a “Recommend list of spares” to the user. This list should be scrutinized for additions that are basically profit-

oriented. The supplier should be asked to give consumption rate for

various spares. The supplier should be asked to give consumption rate for various spares. The maintenance engineer can then better assess the

spares to be stocked for a chosen initial period-say, for one to two years

based on his experience with similar items, number of machines installed,

age of machines, operating conditions, engineering factors and the inventory control system in operation. Casual selection of spare parts at

this stage will create a large inventory of nonmoving spares. In initial

stages only a few will need replenishment.

Spare parts planning begin with the selection of the machine. At this

stage weight must be given to the following:

Complete range of parts serviced by the manufacturer including

those from his sub-suppliers to be available, along with illustrated

catalogues for applicable models. Assurance of supply for the lifetime of the machine

Supply of manufacturing drawings as needed

Availability of observed/estimated consumption rates (not sales data) of spare parts.

Technical data/specifications for assessing failure rate

Warranty for quality and for life of supplied spares Guidance in identification, storage (for sensitive items) and

preservation.

Using this information and his own experience, the maintenance engineer assesses the initial requirement for a period that will cover on lead-time or

one-review period for spares for all types of maintenance, insurance items

and repair pool.

Stage 3: Procurement

For highly specialized equipment or for that likely to go out of production,

the user should assess their availability. There is not much room for competitive procurement of spares except at the time of buying the


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machine. Machines using standard replenishment parts should be

preferred. Non-standard parts are always expensive, and often difficult to

get.

Stage 4: Receipt, storage and Preservation

On receipt, the spare parts are checked for correctness of quantity and

quality before storing them. The principle here is a place for everything in its place. Spares are stocked machine-wise. Items common to more than

one machine are stocked together. The location of each spare is marked

on the bin card for the spare. These bin-cards are also the account cards, which indicate the receipt and issue (and stock balance) and particulars

(part number etc) of the spare. Mentioning details of interchangeable or

substitute spares are a great help in an emergency.

Security of spares in custody is the responsibility of the storekeeper.

Small and expensive spares can be easily pilfered. They are kept in a

locker. Spares are issued only to authorized maintenance personnel who needed them for their work. Physical stock of all items should be checked

with ledger balance annually and differences reconciled. Errors are

investigated to avoid recurrence.

Different preservatives and methods are needed for different spares.

Corrosion is the greatest enemy of all spares. Ball and roller bearings are

easily damaged by dust/humid and should be kept in original packing till needed. Heat sensitive electronic items like transistors should be kept in

cool places. Rubber and textile items should not be exposed to direct

sunlight or to come in contact with mineral oils.

Stage 5: Issue and replenishment

The replenishment of parts withdrawn from stock involves two basic questions, namely, How much to order? and When to order? The quantity

the time of replenishment has to be determined scientifically as they

profoundly affect the cost effectiveness of inventory management.

Stage 6: Disposal of damaged, surplus and obsolete spare parts

An organization expecting good resale value for its surplus spare parts

should ask itself, whether it would buy second hand spares from another unit at any price other than scrap value. One can never be sure as to how

long the parts had been in stock and what deterioration had set in during

storage. Such spares get some value only when they are sold along with the used machine itself. Further, it is not wise to dispose off spare parts

applicable to existing machines simply because they had not been used.

Only stock of insurance spares exceeding.

Cost control for spare parts: Role of maintenance

Cost due to and of spare parts occurs as (a) cost due to non-availability

when required for the machine, (b) consumption value (c) inventory carrying cost, and (d) capital cost of non-moving items. To minimize the

need for troublesome repair parts, operations must prevent failures, and

maintenance must ensure that maintenance is done on time is of high

quality. Maintenance must give top priority to eliminate failures requiring


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the high costs items that are also critical. Worn parts can often be rebuilt

at a fraction of the price of new parts.

Organizing for effective spare parts management

In large organizations there should be a spare parts cell consisting of a

representative each of maintenance, purchasing and stores. Apart from

initiating the indents, this cell should operate the MIS and continuously look for improvement in inventory control and const control introduce

computers for MIS, carry out various analyses and in general act as

internal consultants in the complex area of spare parts management. They should report to a senior level in expertise in this area. They should

report to the chief of materials. This places the responsibility of planning

and providing spare parts squarely where it belongs. In small

organizations, only those maintenance engineers who are trained in scientific inventory control of spare parts should be allowed to indent

spares parts. Their services should be utilized during a period updating of

the system as a whole.

5. Describe in detail safety and environmental issues in maintenance

management.

Answer

The modern concept of safety assurance tries to stress the importance of involvement of all the people, right from the top most owner of the

company to the lower most workers in these safety and environment

movement of the company. Terminologies like „total safety management‟, „Sustainable development‟ etc are the result of such modern thinking to

bring a holistic view into the subject.

The analysis of the causes of many safety and environmental accidents,

have invariably identified „improper maintenance‟ as one the major

reasons. While simple preventive maintenance activities like inspections,

timely replacements etc would be quite economical the neglect of the same has been the reason for enormous loss of revenue running to million

of rupees as a result of the accidents emanating from such causes, not to

speak of the invaluable loss of precious lives. Needless to emphasize, safety and environmental issues need to be made an integral part of the

maintenance management function, without which the basic-objective of

the maintenance function of assurance of plant availability is not complete.

The components of safety and environmental issues and their

relation to maintenance management There are various issues concerned with the safety and environmental

performance of an enterprise. Each of these issues has also linkage with

the operation and maintenance management functions. These are:

Corporate objectives and Goals

The top management of the organizations is expected to clearly specify

the corporate objectives and goals it would like to practice in terms of environment and safety assurance. Many a times, this is done through a


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widely publicized policy statement. The policy and objectives of the

operation and maintenance functions are expected to dovetail them into

the corporate safety and environmental objectives.

Documentation of process equipment

Another important requirement for the safety and environmental

assurance for the company is the meticulous documentation of the vital specifications of the process and equipment in terms of their compliance

to safety and environmental standards, statutory or otherwise. This

documentation can be either independently prepared or integrated into the operation and maintenance manuals of the plant processes or

equipment.

Risk management As it may not be possible to totally eliminate the risks to zero level,

specifically in case of large complex process plants it would be required to

scientifically analyze the risks involved and prepare plans to mitigate them. Risk management involves use of multi disciplinary knowledge and

participation to identify all possible hazards and also identify solutions to

keep their risks at acceptable levels. The contribution of operation and maintenance in risk management is to contribute to the analysis process

through inputs regarding various hazards of operation and maintenance

processes. For example, many of the accidents in chemical process plants

are due to typical maintenance operations like structure welding, catalyst change, overhauling etc. Hence the maintenance functions having

intrinsic knowledge of these processes needed to contribute in the process

of study of these risks.

Change management

In process plants, many of the environmental and safety failures arise from the failure to manage changes, both in the technology applications

or systems. The Flixborough accident happened due to the failure to

manage properly of a reactor. Hence process safety guidelines insist on

well laid out procedures for change management. As maintenance activities are the most prominent examples of unknown changes, due to

their unique nature each time, these requirements are mainly applicable

to the maintenance function.

Human factor

The untrained or improperly placed worker is likely to commit mistakes, which may lead to safety or environmental consequences. Apart from

this, there are other human factors like attitude, ergonomics, work culture

etc. which have great bearing on the safety and environmental

performance. Nurturing the human factors to enable achievement of best safety results is equally applicable to all plant functions, including

operational and maintenance.

Investigation of incidents

There is requirement, statutory or otherwise, to intensely investigating

incidents, so that underlying causes can be found out and corrective

actions for future improvements can be prescribed. The role of operation and maintenance personnel are important in such investigations, as they


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have to provide the correct sequence of activities before, during and after

the incident to the investigating team and also implement the suggestions

emanating from such investigations.

Safety and environmental audits

There is increasing tendency to integrate the safety and environment

audit requirements in the maintenance audits. The audits are mainly to identify whether the existing systems, techniques and procedures comply

with the stated and required standards and suggest improvements

wherever required. The maintenance executive is an important team member of the safety and environment audit team in many process

plants.

Maintenance techniques for safety and environmental improvements

The primary function of maintenance management is to ensure the

availability of the plant and equipment. However, intrinsic to this requirement is the necessity to also provide maximum reliability and

safety. Hence maintenance management needs to integrate their

techniques to simultaneously improve safety and environmental aspects of operation and maintenance of plant and equipment.

Classification of plant and equipment

It is normally required for the maintenance management function to classify the equipment into various categories so that resource allocation

can be facilitated according to their critically. A factorization method is

sometimes used to rank the equipment in term of their critically. Apart from the conventional broad factors of operational criticality, maintenance

intensiveness, quality of products, it is emphasized that safety and

environmental factor is also considered in such classification.

Preventive and predictive maintenance scheduling

Regular checklists and preventive maintenance schedules should include

important safety and environmental checkpoints. Nowadays preventive maintenance if often supported by instrument oriented measurements

called condition monitoring. Many of these monitoring instruments can be

used as dual purpose techniques, for example, measurement of thickness of reactor wall thickness using ultrasonic gauges not only predicts wear

and tear from maintenance replacement angle but also identifies potential

dangerous situations of excessive material deterioration, cracks etc. Similarly, thermograph can identify both insulation wear and thermal

breakdowns in high temperature reformers, furnaces etc.

Shutdown maintenance planning Long shutdowns for annual turnarounds and major overhaul are important

requirements of many process plants and heavier and complex

equipment. Due to the tight time schedule under which such shutdown maintenance are executed, there are many possibilities process of such

activities needs to meticulously include the steps required to ensure safety

and environmental standards.


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Communication between maintenance and other departments

Many safety and environmental hazards have emanated from improper

communication between maintenance and other departments, especially the operations department. Proper information systems like log book

entries, work order systems, work permit systems, lock out systems in

case of electrical hazards etc, are some of the requirements to ensure

communication, thus enabling safety.

Maintenance training

All maintenance personal working in plant facility should be trained in the basic understanding of the process and mechanical hazards. The training

should include mechanical skills, theory, on-the-job / apprentice training,

safe work practices training and specialized craft training. Maintenance

staff often forgets after a period thus the company often loses valuable work information. Several accidents have occurred due to such corporate

memory lapses. The techniques useful under such circumstances are:

Refresher training of all staff Use of incident investigation in training

Publicity campaigns on safety

Close supervision of new staff Continuous updation if maintenance instructions

Safety compliance audits

Counseling poorly performing staff


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ASSIGNMENT – II

6. What is the difference between maintenance technology and maintenance engineering? What steps are needed to introduce

and sustain HRD, specifically for maintenance in an organization?

Explain.

Answer

Maintenance engineering: A large variety of faults occur infrequently but they are spread over years

in the life of the machine there is rarely a second occurrence to learn from

experience in these cases the maintenance engineering.

Has to use his own judgment and deductive logics to meet the situation of

downtime caused this large range of infrequent failures. In these cases,

most of the downtime occurs due to the delay caused by hit and miss type of diagnosis. The supplier rarely covers in the training technology, the

problems due to aging that appear in the later life of a machine. Finally

the engineer has no guidance on improving on the design, operation ,preventive maintenance ,diagnosis and repair techniques/technology of

the existing design to make maintenance easier. This too is the task of

maintenance engineering. It should cover the following topics:

Maintainability design features.

Diagnostic and fault location; Fault –Tree

Analysis(FTA);symptom/fault correlation; Basic theory or reliability and maintainability

Weibull and other statistical analysis for assessing component and

machine life Developing new repair techniques and tools and processes

New repair materials

Spare parts forecasting-essentially a combined statistical and

engineering task.

Maintenance management

Management of maintenance relates to optimizing the resources of maintenance, namely, labor, accessories, workshop machines and tools

real time and spare parts. IT should include the following topics:

Assessing manpower for maintenance tasks i.e.; for installation preventive maintenance, inspections. Unscheduled and planned

repair and modifications.

Scheduling the above tasks with manpower and other resources

Obtaining the best results from own maintenance work force through good leadership, human relations, team building and

motivation

Forecasting the requirement and time for maintenance tools accessories and spare parts.

Using computers for the above, day-to-day work and long term

planning

Organizing own workshop facilities. Selecting and organizing maintenance work that is to be outsourced


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Operating company policies and procedures that are applicable to

all employees.

Role of Human Resource Development

How can an organization grow unless its most important instrument itself

grows? The term „growth applied to an individual in an organization means

developing his qualities to make him more useful to the organization. Behavioral scientists have discovered that the individual growth for self

also contributes to the growth of the organization. A constructive look at

the areas where the personal and organizational expectations or needs could match or be complimentary ,will help to bring out ways and means

to develop human being as a resource. Some expectations are common to

all while others vary to some extent with the job.

Here we deal with HRD for maintenance where specific needs for

maintenance have been considered. Maintenance can have several aims,

all of them converging on delivery of service in a cost effective manner. They are:

TO Maintain high level of equipment reliability and maintainability

as contributors to production /operations To maximize economy in equipment management for its entire life

To cultivate equipment related expertise and skills amongst

maintenance personnel

To create vigorous and enthusiastic work environment. To maximize overall equipment effectiveness through total

employee involvement.

Human side of maintenance:

More than anything else maintenance personnel need recognition of their

contribution–not just in terms of monetary benefits, but by treating them as equal partners in the organization. Their next expectation is for

priority.

For the resources that they need for doing a better job Low Morale amongst maintenance personnel is at least partly due to partisanship of

the on the part of management. Reversing this will greatly improve HRD

for maintenance.

Interdepartmental conflicts affecting HRD:

The most visible conflict between production/operations and maintenance is due to the former competing with the latter for getting their share of

machine time production for output and maintenance for preventive

maintenance. When mature thinking prevails this balance is well struck

mutually and productivity rises. Even more important is their attitudes become mutually supportive. when maintenance and production take

unenlightened views about their role there is an escalating conflict .

Hardening of attitudes over a period of time males for difficulties in HRD for maintenance Evidently a mutual respect for the personnel of these

departments would be created by the HRD. There are many reasons for

the above situation and solution .Among them the following main ones

need to be tackled:


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Ignorance/incompetence of a maintenance in their professional

areas namely maintenance technology, maintenance engineering

and maintenance management. Maintenance must learn to reduce repair effort by creative

application of maintainability principles .

Maintenance must first establish a strong self concept and identity.

Going all put to undertake the role with utmost dedication alone can achieve this.

Maintenance must learn to live with the fact that services are

forgotten after crisis is over. This gives them greater responsibility of convincing higher management and colleagues about their utility.

They must understand that their role is to support the user of the

machine.

Within the maintenance function there has to be a teamwork-mechanical ,electrical and instrument/electronic technicians have to

work in conjunction with each other

Teamwork must extend to sharing problems with related maintenance, disciplines, production /operations and stores.

Problem solving teams should be formed at the level of operators

and machines .they should attack joint problems under the guidance of the steering committee consisting of senior level

manages of both these departments.

Introducing HRD for maintenance THE starring point of HRD is the senior most maintenance engineer

/manager talking to his colleagues and subordinated to take the following

steps.: Identify the short and long term goals for maintenance; typically

reducing the downtime of selected machines to a lower level.;

reducing cost on spares ;increasing part rebuilding. For each goal undertakes a series of brainstorming sessions with

related persons at mixed levels on deterrents. That come in the

way of achieving that goal.

Prioritize these and select a few key deterrents and carryout further brainstorming to identify why these deterrents existed

After this stage the major problem areas will become clear as

perceived by the participants of the brainstorming session . This will fall into five main classes :

Knowledge skill ,attitudes, workload and the organization

These problems must now be solved step by step, again involving personnel at all levels. These steps (such as developing

excellence through various types of training, leadership , stress

management, teambuilding etc.


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7. Discuss in detail the replacement of unit machines and

components.

Answer

There are two kinds of replacement problems with regard to unit machines

and components. one related to determination of replacement interval for

unit machines or single component equipment whose operating cost increases with age and the other which deals with components wherein

there is no age related increase in operating cost, but which are subject to

sudden and catastrophic failures. The replacement problems with regard to unit machines and components therefore can be classified as

either deterministic in which the timing of equipment replacement which

in turn is dictated by the increasing trend of the of the operating and

maintenance cost and also the outcome of the replacement action are assumed to be known with certainty, or probabilistic in which timing and

outcome of the replacement action depend on chance, since it is generally

very difficult to predict with certainty when the failure of the component will occur.

Jardine calls these two classes of problems with regard to unit machines and components as short-term deterministic and short-term probabilistic

respectively to emphasize the fact that the interval between replacements

is comparatively short more likely to be measured in weeks or months

rather than in years as in the case of capital equipment. Thus incase of unit machines and components one need not take into account the effect

of inflation or interest on borrowed capital since even if the replacement

interval is a couple of years or so ,the effect of inflation can possibly be ignored for purpose of analysis and therefore discounting their present

worth equivalent annual cost.

Thus we find replacement problems concerning, which may be considered

to be single component equipment for the for the purpose of replacement

analysis as already stated , and components do not require engineering

economic analysis since time, value of money is comparatively insignificant and may be ignored. on the other hand these replacement

problems are amenable to quantitative procedures which are basically

optimization procedures and thus can be considered as applications of operations research.

Determination of optimal Replacement Interval for an equipment whose operating cost increases with use

To reduce the operating and maintenance cost a replacement can be

performed and after the replacement the trend of the operating cost is known since it is assumed that the replacement always the operating cost

to that of new equipment. Thus the operating cost trends following each

replacement are identical and the interval between replacements is constant and of length t.

Bi-annually major surveys are performed on equipment as per statutory

requirement .between two consecutive surveys, the operating cost of the equipment increases due to the deterioration of certain parts of the


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equipment. Some of these deteriorating parts can be replaced to bring

down the operating cost of the equipment .these replacements cost

money in terms of materials and wages that is cost of spares and cost of manpower and thus a balance has to be maintained between the money

spent on replacements and the savings obtained by reducing the

operating cost.

Let c(t) be the operating cost at unit time at time t after replacement

Let c(r) be the cost of replacement.

The replacement policy is to perform n equally spaced replacements at

intervals of tr between two consecutive surveys

The objective is to determine the optimal replacement interval which will minimize the operating and replacement costs between two consecutive

surveys. now if we denote the total cost C(tr)then

C(tr)= replacement cost between surveys + operating cost between

surveys.

Replacement cost between surveys=number of replacement between

surveys * cost of one replacement =nCr

And operating cost between surveys =number of intervals between surveys *operating cost of each interval between surveys.

= (n+1)[c(t)dt

Therefore c(tr)=nCr+(n+1)[c(t)dt

Determination of optimal replacement interval for a

component/equipment subject to sudden failures

Here we discuss the available models for determination of the optimal

replacement interval for such items of equipment and components. This problem of decision making under uncertainty since it is impossible to

predict with certainty when failure will occur or stated more generally

when the transition from one state to other will occur. This is a class of short-term probabilistic problem and for this class of problems we need to

invoke the assumptions stated before namely, the total cost of

replacement after the failure must be greater than before. There are only two states and conditions of the equipment/component, good or failed,

and that the condition or state is always known ,and finally the hazard

rate of equipment or component must be increasing ,that is the value of

the Weibull shaped parameter, beta, be greater than one.

There are two preventive replacement procedures which are adopted

namely the constant interval policy in which the preventive replacement of the equipment is carried out at fixed intervals and the problem is to

determine the optimal interval between replacements to minimize the

total expected cost per unit time and the age based policy where in

instead of fixed intervals one determines the optimal replacement age for


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the item. The first procedure is known as block replacement policy and

the second procedure is known as age replacement policy.

Block Replacement policy:

Failure is unexpected to any component of the equipment .we may

assume that failure replacement is more costly than preventive

replacement. This is true in most of the cases because a preventive replacements can be adequately planned and necessary arrangements

made for it to reduce both time and cost. and there is a possibility that a

failure may cost damage to the other components of the equipment making the total replacement cost much greater after the failure. In order

to reduce the number of failures and thereby reduce the total expected

cost of replacements, preventive replacements can be carried out at

specific intervals but for this one has to ensure that a proper balance is maintained between amount spent on preventive replacement and the

resulting benefit from preventive replacement namely expected reduction

in failure replacement and expected failure replacement cost. Thus we want to determine the optimum interval between preventive replacements

to minimize the total expected case of replacement per unit time. Given

that cp is the cost a preventive replacement, Cf the cost of failure replacement(Cf>Cp)and tp is the fixed interval between preventive

replacements , then the total expected cost per unit time for one cycle

C(tp)=Total expected cost in interval (0,tp) / length of the interval

But the total expected cost =cost of a preventive replacement in interval

(0,tp)+expected cost of failure replacement=Cp+Cr.H(tp)

Where H(tp)=expected no of failures in (0,tp)

So C(tp)= Cp+Cr.H(tp) / tp

Age replacement policy:

Determination of optimal preventive replacement age:

In this case we consider the above problem but instead of making preventive replacements at fixed intervals thus incurring the possibility of

carrying out a preventive replacement shortly after a failure replacement

.the time at which the preventive replacement is performed depends on the age of the equipment or component, which is the elapsed time from

the previous replacement. Thus the policy to perform preventive

replacements after the equipment has reached a specific age tp with failure replacements being performed whenever necessary.

The objective is determine the optimal age of replacement of the item to

minimize the total expected cost of replacement per unit time.

Let Cp=cost or preventive replacement

Cr=cost of failure replacement with Cr>Cp

And ft is the failure density function of the times of failure o the item. Now in this case there are two possible cycles of operation. Namely once where


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no failure occurs and the item reaches its planned replacement age, tp

and the other cycle which failure occurs before its planned replacement

necessitating a failure replacement.

Thus the total cost of replacement per unit time,

C(tp)= total expected replacement cost per cycle/expected length of the

cycle

Where total expected replacement cost per cycle

=cost preventive replacement*probability of a preventive cycle + cost of failure replacement *probability o a failure cycle

= Cp.R(tp)+Cr[1-R(tp)] and the expected length of the cycle is equal to

=length of preventive cycle * probability of preventive cycle

+expected length of the failure cycle =tp.R(tp)+M(tp)where M(tp) is the expected length of the failure cycle.

So = Cp.R(tp)+Cr[1-R(tp)] / tp.R(tp)+M(tp)

8. Explain the types of maintenance. Also describe the planning and

scheduling of a plant shutdown.

Answer

The dictionary defines maintenance as follows: “the work of keeping something in proper condition; upkeep.” This would imply that

maintenance should be actions taken to prevent a device or component

from failing or to repair normal equipment degradation experienced with the operation of the device to keep it in proper working order.

Unfortunately, data obtained in many studies over the past decade

indicates that most private and government facilities do not expend the necessary resources to maintain equipment in proper working order.

Rather, they wait for equipment failure to occur and then take whatever

actions are necessary to repair or replace the equipment. Nothing lasts

forever and all equipment has associated with it some predefined life expectancy or operational life. For example, equipment may be designed

to operate at full design load for 5,000 hours and may be designed to go

through 15,000 start and stop cycles.

The need for maintenance is predicated on actual or impending failure –

ideally, maintenance is performed to keep equipment and systems running efficiently for at least design life of the component(s). As such,

the practical operation of a component is time-based function. If one were

to graph the failure rate a component population versus time, it is likely

the graph would take the “bathtub” shape shown in Figure. In the figure the Y axis represents the failure rate and the X axis is time. From its

shape, the curve can be divided into three distinct: infant mortality, useful

life, and wear-out periods.

The initial infant mortality period of bathtub curve is characterized by high

failure rate followed by a period of decreasing failure. Many of the failures

associated with this region are linked to poor design, poor installation, or misapplication. The infant mortality period is followed by a nearly constant


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failure rate period known as useful life. There are many theories on why

components fail in this region, most acknowledge that poor O&M often

plays significant role. It is also generally agreed that exceptional maintenance practices encompassing preventive and predictive elements

can extend this period. The wear-out period is characterized by a rapid

increasing failure rate with time. In most cases this period encompasses

the normal distribution of design life failures.

The design life of most equipment requires periodic maintenance. Belts

need adjustment, alignment needs to be maintained, proper lubrication on

rotating equipment is required, and so on. In some cases, certain

components need replacement, (e.g., a wheel bearing on a motor vehicle) to ensure the main piece of equipment (in this case a car) last for its

design life. Anytime we fail to perform maintenance activities intended by

the equipment‟s designer, we shorten the operating life of the equipment. But what options do we have? Over the last 30 years, different

approaches to how maintenance can be performed to ensure equipment

reaches or exceeds its design life have been developed in the United States. In addition to waiting for a piece of equipment to fail (reactive

maintenance), we can utilize preventive maintenance, predictive maintenance, or reliability centered maintenance.

Reactive Maintenance Reactive maintenance is basically the “run it till it breaks” maintenance

mode. No actions or efforts are taken to maintain the equipment as the

designer originally intended to ensure design life is reached.

Studies as recent as the winter of 2000 indicate this is still the

predominant mode of maintenance in the United States. The referenced study breaks down the average maintenance program as follows:

>55% Reactive

31% Preventive 12% Predictive

2% Other


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Note that more than 55% of maintenance resources and activities of an

average facility are still reactive.

Advantages to reactive maintenance can be viewed as a double-edged

sword. If we are dealing with new equipment, we can expect minimal

incidents of failure. If our maintenance program is purely reactive, we will

not expend manpower dollars or incur capital cost until something breaks.

Since we do not see any associated maintenance cost, we could view this

period as saving money. The downside is reality. In reality, during the time we believe we are saving maintenance and capital cost, we are really

spending more dollars than we would have under a different maintenance

approach. We are spending more dollars associated with capital cost

because, while waiting for the equipment to break, we are shortening the life of the equipment resulting in more frequent replacement. We may

incur cost upon failure of the primary device associated with its failure

causing the failure of a secondary device. This is an increased cost we would not have experienced if our maintenance program was more

proactive. Our labor cost associated with repair will probably be higher

than normal because the failure will most likely require more extensive repairs than would have been required if the piece of equipment had not

been run to failure. Chances are the piece of equipment will fail during off

hours or close to the end of the normal workday. If it is a critical piece of

equipment that needs to be back on-line quickly, we will have to pay maintenance overtime cost.

Since we expect to run equipment to failure, we will require a large material inventory of repair parts. This is a cost we could minimize under

a different maintenance strategy.

Advantages

Low cost

Less staff

Disadvantages

Increased cost due to unplanned downtime of equipment.

Increased labor cost, especially if overtime is needed. Cost involved with repair or replacement of equipment.

Possible secondary equipment or process damage from equipment

failure. Inefficient use of staff resources.

Preventive Maintenance

Preventive maintenance can be defined as follows: Actions performed on a time- or machine-run-based schedule that detect, preclude, or mitigate

degradation of a component or system with the aim of sustaining or

extending its useful life through controlling degradation to an acceptable level.

The U.S. Navy pioneered preventive maintenance as a means to increase

the reliability of their vessels. By simply expending the necessary resources to conduct maintenance activities intended by the equipment


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designer, equipment life is extended and its reliability is increased. In

addition to an increase in reliability, dollars are saved over that of a

program just using reactive maintenance. Studies indicate that this savings can amount to as much as 12% to 18% on the average.

Depending on the facilities current maintenance practices, present

equipment reliability, and facility downtime, there is little doubt that many

facilities purely reliant on reactive maintenance could save much more than 18% by instituting a proper preventive maintenance program.

While preventive maintenance is not the optimum maintenance program, it does have several advantages over that of a purely reactive program.

By performing the preventive maintenance as the equipment designer

envisioned, we will extend the life of the equipment closer to design. This

translates into dollar savings. Preventive maintenance (lubrication, filter change, etc.) will generally run the equipment more efficiently resulting in

dollar savings. While we will not prevent equipment catastrophic failures,

we will decrease the number of failures. Minimizing failures translate into maintenance and capital cost savings.

Advantages Cost effective in many capital-intensive processes.

Flexibility allows for the adjustment of maintenance periodicity.

Increased component life cycle.

Energy savings. Reduced equipment or process failure.

Estimated 12% to 18% cost savings over reactive maintenance

program.

Disadvantages

Catastrophic failures still likely to occur. Labor intensive.

Includes performance of unneeded maintenance.

Potential for incidental damage to components in conducting

unneeded maintenance.

Predictive Maintenance

Predictive maintenance can be defined as follows: Measurements that detect the onset of system degradation (lower functional state), thereby

allowing causal stressors to be eliminated or controlled prior to any

significant deterioration in the component physical state. Results indicate current and future functional capability.

Basically, predictive maintenance differs from preventive maintenance by

basing maintenance need on the actual condition of the machine rather than on some preset schedule. You will recall that preventive maintenance

is time-based. Activities such as changing lubricant are based on time, like

calendar time or equipment run time. For example, most people change the oil in their vehicles every 3,000 to 5,000 miles traveled. This is

effectively basing the oil change needs on equipment run time. No

concern is given to the actual condition and performance capability of the

oil. It is changed because it is time. This methodology would be analogous to a preventive maintenance task. If, on the other hand, the operator of


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the car discounted the vehicle run time and had the oil analyzed at some

periodicity to determine its actual condition and lubrication properties,

he/she may be able to extend the oil change until the vehicle had traveled 10,000 miles. This is the fundamental difference between predictive

maintenance and preventive maintenance, whereby predictive

maintenance is used to define needed maintenance task based on

quantified material/equipment condition.

The advantages of predictive maintenance are many. A well-orchestrated

predictive maintenance program will all but eliminate catastrophic equipment failures. We will be able to schedule maintenance activities to

minimize or delete overtime cost. We will be able to minimize inventory

and order parts, as required, well ahead of time to support the

downstream maintenance needs. We can optimize the operation of the equipment, saving energy cost and increasing plant reliability. Past studies

have estimated that a properly functioning predictive maintenance

program can provide a savings of 8% to 12% over a program utilizing preventive maintenance alone. Depending on a facility‟s reliance on

reactive maintenance and material condition, it could easily recognize

savings opportunities exceeding 30% to 40%. In fact, independent surveys indicate the following industrial average savings resultant from

initiation of a functional predictive maintenance program:

Return on investment: 10 times Reduction in maintenance costs: 25% to 30%

Elimination of breakdowns: 70% to 75%

Reduction in downtime: 35% to 45% Increase in production: 20% to 25%.

On the down side, to initially start into the predictive maintenance world is not inexpensive. Much of the equipment requires cost in excess of

$50,000. Training of in-plant personnel to effectively utilize predictive

maintenance technologies will require considerable funding. Program

development will require an understanding of predictive maintenance and a firm commitment to make the program work by all facility organizations

and management.

Reliability Centered Maintenance

Reliability centered maintenance (RCM) magazine provides the following

definition of RCM: “a process used to determine the maintenance requirements of any physical asset in its operating context.”

Basically, RCM methodology deals with some key issues not dealt with by

other maintenance programs. It recognizes that all equipment in a facility is not of equal importance to either the process or facility safety. It

recognizes that equipment design and operation differs and that different

equipment will have a higher probability to undergo failures from different degradation mechanisms than others. It also approaches the structuring

of a maintenance program recognizing that a facility does not have

unlimited financial and personnel resources and that the use of both need

to be prioritized and optimized. In a nutshell, RCM is a systematic approach to evaluate a facility‟s equipment and resources to best mate


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the two and result in a high degree of facility reliability and cost-

effectiveness. RCM is highly reliant on predictive maintenance but also

recognizes that maintenance activities on equipment that is inexpensive and unimportant to facility reliability may best be left to a reactive

maintenance approach. The following maintenance program breakdowns

of continually top-performing facilities would echo the RCM approach to

utilize all available maintenance approaches with the predominant methodology being predictive.

<10% Reactive 25% to 35% Preventive

45% to 55% Predictive.

Because RCM is so heavily weighted in utilization of predictive maintenance technologies, its program advantages and disadvantages

mirror those of predictive maintenance. In addition to these advantages,

RCM will allow a facility to more closely match resources to needs while improving reliability and decreasing cost.

Advantages Can be the most efficient maintenance program.

Lower costs by eliminating unnecessary maintenance or overhauls.

Minimize frequency of overhauls.

Reduced probability of sudden equipment failures. Able to focus maintenance activities on critical components.

Increased component reliability.

Incorporates root cause analysis.

Disadvantages

Can have significant startup cost, training, equipment, etc. Savings potential not readily seen by management.

Planning and scheduling of a plant shutdown

Usually Periodic overhauls of plant and equipment constitute major plant

shutdowns, and these jobs pose planning problems, which are quite

different from those for the normal workload of the maintenance department. Plant shutdowns are essentially projects since they are non-

routine large and take significant amount of time and complex of a

multiplicity of interrelated activities which must be executed in a defined order for completing the entire task. All these activities have to be carried

out in a coordinate manner. Therefore plant shutdowns must be

recognized and managed as separate undertakings calling for different

methods of planning scheduling and monitoring of progress. Accordingly project planning methods are generally used for planning of

maintenance shutdowns. Major plant shutdowns may involve upwards of

few hundreds of activities and many tens of these activities may be simultaneous

Network planning method is used for planning these shutdowns. Moreover

for smaller shutdowns such network analysis may be manual with

extraction into a bar chart to facilitate control. For large projects network planning and associated scheduling and controls must be computerized.


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Establishment of a shutdown program

Planning of a plant shutdown consists of the following activities:

1. Preparation of the shutdown and startup procedures(listing of

operations in proper sequence together with cautions and special

instructions if any) 2. Preparation of a preliminary activity list and breaking it down under

trades and disciplines, such as mechanical, electrical piping

hydraulic pneumatic etc. 3. Preparation of the detailed activity list and estimation of activity

times and resource requirements.

4. Definition of precedence relationships and construction of the

activity network. 5. Network with the maintenance contractor and manpower contractor

as needed.

6. Negotiations with the maintenance contractor and manpower contractor as needed.

7. Carrying out preparatory work.

8. Assembling /collecting necessary tools and tackles and protective clothing as needed.

The monitoring and review of progress (control of the shutdown project )is

taken up once the actual shutdown commences.

For large shutdowns, planning takes a long time and must be started 8-10

weeks before the shutdown is due to start. Accordingly an essential prerequisite of a formal system of planning of individual shutdown is an is

an annual plan showing the timing of each of the major shutdowns , the

most important features of the 50-day planning programs are as follows:

1. A formal meeting of the management to decide and agree on the

extent of the shutdown (planned scope of work).

2. Availability of a good data retrieval system of estimating activity times and resource requirements/loadings for standard repetitive

activities.

3. Active association of personnel responsible for implementing the shutdown. The planning engineers must encourage these persons

to comment on the construction of the activity network /logic

diagrams for the particular areas of work. 4. Availability f computer service /computing facilities

5. Availability of adequate arrangements for issuing work orders and

for monitoring of progress.

6. Proper planning and control of preparatory work.

Monitoring of progress ,issue of necessary job instructions as and

whenever needed, review of activities and updating of the activity network are the basic activities which ensure the proper implementation of detailed

program.


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The monitoring of progress should be done on an hourly basis and

progress reports should be delivered to the central planning

office/maintenance planning bureau every two or four hours.

The progress report must contain the following information:

1. Estimated completion time for all „life‟ activities 2. Actual completion time of activities.

3. Review if pending activities

4. Excesses and shortfalls on resources and 5. Additional work arisen or expected to arise.

9. What is condition based maintenance? Discuss condition

monitoring techniques.

Answer

In a continuous growing global market Productivity is playing a key role to

stay competitive, for any manufacturing company. Productivity can be

achieved through availability and availability can be increased through adopting the efficient maintenance practices, by focusing on different

types of maintenance and strategies.

Condition based Maintenance or predictive maintenance, uses primarily non destructive testing techniques, visual inspection, and performance

data to assess machinery condition. It replaces arbitrarily timed

maintenance tasks with appropriate maintenance task at only when warranted by equipment condition. Condition-monitoring maintenance

task intervals must be properly understood and task intervals should be

determined based on the expected P-F interval. The P-F interval governs the frequency with which the predictive task must be done. Technological

advances are accepted and applied to CBM systems, which includes

improved knowledge of failure mechanisms, advancements in failure

forecasting techniques, advancements in monitoring and sensor devices, advancements in diagnostic and prognostic software, acceptance of

communication protocols, developments in maintenance software

applications and computer networking technologies.

The measurement precision and sensitivity of the CM technique being

used need to be understood because they affect the reaction time available to reduce or eliminate the consequences of the functional failure.

Condition monitoring maintenance tasks must be applicable and cost

effective. The aim of this paper is to give brief introduction of various CBM

techniques, selection of condition monitoring techniques and understanding of P-F interval, Advancement in CBM, Standardization of

CBM system, CBM approach on rail vehicles, advantages &disadvantages

of CBM.

Today, most maintenance actions are carried out by either the

predetermined preventive- or the corrective approach. The predetermined

preventive approach has fixed maintenance intervals in order to prevent components, sub-systems or systems to degrade. Corrective maintenance


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is performed after an obvious fault or breakdown has occurred. Both

approaches have shown to be costly in many applications due to lost

production, cost of keeping spare parts, quality deficiencies etc.

Basically, predictive maintenance or Condition Based Maintenance (CBM)

differs from preventive maintenance by basing maintenance need on the

actual condition of the machine rather than on some preset schedule. As the preventive maintenance is time-based and activities such as changing

lubricant are based on time, like calendar time or equipment run time. For

example, most people change the engine oil in their car/jeep at every 3,000 to 5,000 KMs vehicles traveled. No concern is given to the actual

condition and performance capability of the oil. This methodology would

be analogous to a preventive maintenance task. If on the other hand, the

operator of the car discounted the vehicle run time and had the oil analyzed at some periodicity to determine its actual condition and

lubrication properties, he/she may be able to extend the oil change until

the vehicle had traveled 10,000 KMs. This is the fundamental difference between predictive maintenance and preventive maintenance, whereby

predictive maintenance is used to define needed maintenance task based

on quantified material/equipment condition.

Condition Based Maintenance (CBM) or predictive maintenance is a

technology that strives to identify incipient faults before they become

critical which enables more accurate planning of the preventive maintenance. It may also be defined as Maintenance actions based on

actual condition obtained from in-situ, non-invasive tests, operating and

condition measurement. Or “CBM is a set of maintenance actions based on real-time or near-real time assessment of equipment condition which is

obtained from embedded sensors and/or external tests & measurements

taken by portable equipment.”

CBM or predictive maintenance is the means of improving productivity,

product quality and overall effectiveness of manufacturing and production

plants. CBM or Predictive maintenance is not vibration monitoring or thermal imaging or lubricating oil analysis or any of the other

nondestructive testing techniques, as predictive maintenance tools.

Rather, it is a philosophy or attitude that simply stated uses the actual operating condition of plant equipment and systems to optimize total plant

operation. A comprehensive predictive maintenance management

program utilizes a combination of the most cost-effective tools, i.e. thermal imaging, vibration monitoring, tribology, and other nondestructive

testing methods, to obtain the actual operating condition of critical plant

systems and based on this factual data all maintenance activities on an

as-needed basis are scheduled. Including CBM or predictive maintenance in a comprehensive maintenance management program will provide the

ability to optimize the availability of process machinery and greatly reduce

the cost of maintenance. It will also provide the means to improve product quality, productivity and profitability.

The maintenance organization in a company probably has one of the most

important functions, looking after assets and keeping track of equipment in order to secure productivity. A company with no or a poor maintenance


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organization will loose a lot of money due to lost production capacity, cost

of keeping spare parts, quality deficiencies, damages for absent or late

deliveries etc.

A relationship between failure rate versus change in maintenance

philosophy is showing decline trend as illustrated in figure below, also

representing the strengths and weaknesses of the different maintenance types.

The addition of a comprehensive predictive maintenance program can and

will provide factual data on the actual operating condition of critical

assets, including their efficiency, as well as the actual mechanical condition of each machine-train and the operating efficiency of each

process system. Instead of relying on industrial or in-plant average-life

statistics, i.e. mean-time-to failure, to schedule maintenance activities,

predictive maintenance uses direct monitoring of the mechanical condition, system efficiency and other indicators to determine the actual

mean-time-to-failure or loss of efficiency for each machine-train and

system in the plant. This data provides maintenance management the factual data needed for effective planning and scheduling maintenance

activities.

Methods advances and applications

Test & Inspection (TPM)

There are many sources of machinery health and production availability information available to an organization's maintenance and operations

staff. Two of the most commonly used sources of information are

scheduled inspection of machinery and condition monitoring.


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Inspection Routes can be split into 3 areas

Rounds

Where an operator or engineer completes a set circuit as a cursory status

check. Will often involve the making of notes or observations.

Adjustments

Often associated with the TPM philosophy, this type of route involves the

checking of settings, making the required changes, lubrication, cleaning etc.

Measurements

Gathering of plant panel data, oil levels, hours running, temperatures, overall vibration readings, quality tests.

All of the above can be achieved through the use of a clipboard, data entry grid and the use of a data entry clerk. Unfortunately paper based

Inspection data almost invariably ends up in a filing cabinet somewhere

and is only reviewed in the event of a problem or breakdown.

Methods of Inspection Data gathering

Paper Systems Log sheets, inspection instructions, production line test / fault books.

Electronic Clipboard Involves the gathering of data in an electronic format using a hand held

device and the downloading of this data into a software package.

Vibration Analysis

Vibration measurement systems fall into the following categories:

Single Value Methods Hand Held meters

SPM Units

Acoustic Emission Units Vibration Pens

4-20mA sensors

Time Frequency Methods

Hand Held Data-collectors

On line systems

Single Value Measurements

The variety of single value measurements is endless, from the ISO filtered levels mentioned in ISO 10816 [1] to the „magic numbers‟ offered by

some of the technology vendors; promising to solve all of your plant

condition problems within one simple solution. ISO 10816-3 is

summarised as a supporting appendix to this text.


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Please note single value methods are either „generic‟ or „specific‟. The

generic case is where a value will indicate the presence of „a problem‟ but

cannot categorise the problem into a specific fault (e.g. Unbalance, looseness, misalignment, cavitation etc.). The specific methods

concentrate on issues such as bearing faults and try to eliminate the

influence of „other‟ faults through the use of algorithms and electronic

design.

The following table outlines the more common types of measurement with

comments on applications and a brief technical description of the method.

Single Value Method Summary

Method Description Applications

ISO Filtered Velocity

2Hz – 1kHz filtered Velocity

Works as a general condition indicator.

SPM Carpet and Peak

related to the

demodulation of a sensor resonance

around 30kHz.

One of the better single value bearing

indicator methods. Some problems on

larger bearings and gear units.

Acoustic

Emission

Distress & dB,

demodulates a 100kHz carrier which is

sensitive to stress

waves.

Better general indicator than ISO

velocity, without the ISO comfort zone.

Vibration Meters

/ pens

Combine velocity,

bearing and

acceleration

techniques (sometimes include

thermal)

Look for ISO Velocity, envelope & high

frequency acceleration for best

performance.

4-20mA sensors Filtered data converted to DCS/PLC

compatible signal.

ISO velocity version available, envelope version still awaited.

Can be used to „home in‟ on specific

problems by special order.

Single value vibration methods have two major advantages and only one

real disadvantage; these are low cost, simple interpretation and lack of

accuracy respectively. The overall CM system implications of single value methods are discussed within the later sections of this text.

Single value data are easy to trend and interpret as shown by the inset

plot below.

Time Frequency Measurements

This type of measurement involves the detection and display of specific components of a time history sensor output. The use of specific frequency

components lends itself to the detection of faults down to a single

mechanical component (e.g. bearing, gear, impeller).

Once again, various methods, techniques and signal conditioning systems

are used to detect specific components of the raw time history data.


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Impacts are created as a rolling

element collides with a damaged

area.

These impacts show as transients

within the time domain. The Demodulator extracts these

transients.

Extracted impact frequencies are then displayed on an envelope

spectrum (shown opposite)

Displacement (Low Frequency)

Where the measurement of absolute movement is required, measured using LVDT‟s or eddy current probes. Particularly useful in detecting the

relative position of a rotor versus a structure and in the diagnosis of plain

bearing faults through the use of orbit plots.

Velocity (Mid Frequency)

The most commonly used method for fault identification, mainly due to

the scalar consistency of the method (i.e. 25mm/s is high almost irrespective of the machine type). Used to detect signs of mechanical

problems in the frequency range 20Hz – 2000Hz. Detection capabilities

cover the following fault conditions.

Unbalance, Misalignment, Looseness, Resonance, Cavitation, Blade problems, Turbulence

Acceleration (High Frequency) Amplitude Demodulation Methods used to extract impacts from the

standard acceleration spectra through the extraction of the amplitude-

modulated component and the display of the demodulated components within an auto-spectrum plot.

There are two main types of envelope measurement, namely:

Band Pass Filtered Enveloping Allows the time history associated with the excitation of a specific

frequency band pass through to the demodulator circuit. This method

avoids the possibility of phase cancellation and is better at isolating the transient activity.

High Pass Filtered Enveloping Sets a High Pass filter and allows all measured time data above the HP

filter pass to the demodulator, this method is regarded as less effective by

vibration practitioners.

General Acceleration


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Where rotating machine related frequency components are expected

above 2kHz, velocity measurement is not accurate due to sensor noise

levels. Acceleration time frequency analysis tends to be used for the detection of fault components from:

Any gear assembly (gearbox, timing gear, gear pump)

Where amplitude demodulation methods are not available (to

detect a „haystack‟ within the high frequency spectra) High speed screw assemblies.

Turbochargers

Blading problems on turbo-machinery High frequency resonances

Detection of gear and rub related transients

Thermal Techniques Thermal measurement systems fall into the following categories

Point/Zone Measurement

Dedicated temperature sensor Hand held

Point/Zone Measurement

These methods measure the temperature of a specific sensor touching the

structure or the emitted temperature from a radiating area. They come in hand held and fixed variants and are very convenient and robust.

Thermography Infrared detection systems provide a thermal picture of the target object,

both accurate and visually clear.

The following table outlines the more common types of measurement with

comments on applications and a brief technical description of the method.

Thermal Measurement Summary Table

Method Description Applications

Point temperature Usually a thermocouple or

RTD. Often „imbedded‟, can

be provided as an encapsulated sensor for

permanent fit.

Can be used on all

accessible surfaces.

Walk around versions take time to settle

and are less robust

than the pyrometer.

Area Pyrometer Measures the emitted IR radiation from a surface.

Often with a Laser sight or

area indicator.

Very good for walk around temperature

checks on machines

and panels.

Temperature Paint /

Stickers

Chemical indicators

calibrated to change colour

at a specific temperature.

Great for inspection

rounds.

Thermography Hand held still or video camera sensitive to emitted

IR.

The ultimate, high-resolution thermal

picture. Camera

costs £10k up,


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service £500 per

day.

Camera use and

interpretation does require „good‟

training.

Oil Analysis

The science of oil analysis falls into 4 main areas, which are listed below:

Fluid Physical Properties (Viscosity, appearance)

Fluid Chemical Properties (TBN, TAN, additives, contamination, % water)

Fluid Contamination (ISO Cleanliness, Ferrography, Spectroscopy,

dissolved gases[Transformer ]) Machine Health (wear metals associated with plant components)

Laboratory based oil analysis can provide the Fluid components, however the return of well informed machine health data from an oil analysis

service provider will require the following:

A real understanding of the machine and the associated

contamination risks. The ability to analyse oil data and relate that to the specific

machine using the lubricant.

Wear mode analysis through machine knowledge, particle shape, texture and composition

Some pitfalls

Beware the following types of oil analysis service provider: Free analysis with the supply of oil - The oil lab should be

independent as far as possible from the lubrication supply, free

service means there is a hidden charge and any margin calls will fall on the side of „replace the oil‟.

„Lights out‟ analysis facilities – These are production line facilities

that provide a production line output, they tend to automate the diagnosis and the Machine Health aspects are virtually useless.

Oil analysis labs that sub contract both the Fluid and the Machine

Health components of the analysis. This results in the provision of a

„Lights out‟ quality of analysis with an added mark up on price.

On site screening

If your reliance on optimal lubrication and hydraulic oil cleanliness is very high OR the volume of oil for analysis is prohibitively expensive OR the

option of lab based oil analysis is not there (shipping, nuclear, highly

contaminated). The use of on-site testing methods warrants consideration.

Visual appearance and smell

In the most extreme cases metal particles can be seen to glitter and water will come out of solution to provide a water layer. In these cases the full

laboratory analysis route is rather „late‟.


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Here are a few simple guides to the visual inspection of oil for water

content and odour relating to contaminants.

Water Contamination

As little as 1 % water can reduce the life of a Journal bearing by 90 %

The plot inset below shows how little water is required to make the oil appear cloudy. When one considers the dramatic effect of oil on

mechanical components such as rolling element and journal bearings, the

level of vigilance is clear.

A hot plate crackle test will also indicate the presence of water as a

contaminant.

Smell

A lot of caution should be exercised when smelling oil samples. Do not

place the bottle directly under your nose. Remember that there may be

toxic chemicals in the sample. Rather, wave your hand above the opening

to waft the scent toward your face. Sometimes it helps to heat the oil,

which increases the likelihood of detecting certain contaminants and

degradation by-products.

Typical Odours From:

Oxidation - sour or pungent odour, acrid (rotten egg) smell or something

similar to stale cheese

Thermal Failure - smell of burnt food

Bacteria - stench, road-kill smell

Running High Temperatures - no odour

Contaminants - solvents, refrigerants, degreasers, hydrogen sulphide,

gasoline, diesel, kerosene and process chemicals

Amino Acids - fish odour


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Nitro Compounds - almond-like scent

Esters (Synthetic Lubricants) and Ketones - perfume odour

Other On-site screening Alternatives

Viscosity Tests – Basic systems test at ambient temperature, the better systems offer temperature setting and measurement combined.

Chemical Tests –TAN, TBN etc. (can be bought as a lab kit from most oil analysis hardware providers)

ISO screening – A variety of methods are available, most are reliable and repeatable for oil screening

Combined analysers – These vary from a multi-function device that is

virtually automatic to those with an excess of operations to collate the complete set of analysis results. Always look for the average sample

processing time when considering a Combination Oil analyser (you may be

unpleasantly surprised). The better analysers will take Contamination level, ferrous index and viscosity from a single sample.

Transformer Oil Sampling The sampling and analysis of transformer oil is one of the „must do‟s‟ of

the Predictive Maintenance world. If nothing else the following 4 tests

must be included in any analysis:

Dielectric Strength (kV)

Dielectric strength is the ability of transformer oil to withstand electrical

stress without failure. Moisture, sediment and conducting particles tend to

reduce the dielectric strength of the oil.

Moisture Content (PPM)

Water in power equipment is attracted to areas of greater electrical stress

and this is where it is most dangerous. Moisture accelerates the

deterioration process of paper and oil, as well as badly maintained

breathers and oil leaks. The moisture detected in the oil, by doing a

moisture test, is directly related to the operating temperature of the

transformer windings where the continuous migration of moisture is

taking place as the temperature varies.

PCB Content

Polychlorinated Biphenyl is classified as a toxic material. No legislation has

been finalized to date, however, a risk analysis should be carried out to

identify and manage the product to prevent any contamination. COSHH

1994 and EPA 1990 provide guidelines for the reduction and handling of

PCB‟s.

On-line monitoring of CbM data

The complete coverage of this area is entirely beyond the scope of this

technical paper. On-line systems are available to measure all CbM related


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data where a sensor exists. The scope includes the following areas of

CbM:

Vibration in all of its guises Temperature

Oil Debris and optical particle count

Pressure Volume analysis on Diesel and Gas Engines

And will normally accept inputs from SCADA, DCS, 4-20mA sensors etc.

10.Discuss in detail importance, types and methodology of

maintenance audit.

Answer We are aware that maintenance function is a supporting activity to make

the planned availability of a plant and equipment possible. Since it is not

direct function connected to profits of organization like production finance and marketing, it is possible that the necessity of maintenance to be

properly managed is overlooked by top management at the same time

need to be at the optimum levels as either over maintenance or under maintenance ,both are likely to affect the costs incurred by the

organization .We have already seen that though the actual maintenance

cost may be only a small proportion like the tip of an iceberg the

consequential cost if improper maintenance could run to millions of rupees.

We have seen that maintenance management requires many features to be compiled by different levels of personnel in the organization.

Maintenance management requires attention from of management right

from the chief executive level to the bottom most worker level. These requirements and functions need to be standardized , monitored ,analyzed

and corrective actions prescribed from time to time. Hence the

importance of maintenance audit is very much emphasized.

Maintenance audit when properly and regularly conducted will have the

following benefits:

Helps in confirming, the function is performing towards the objectives that are set forth for it.

To compare the performance indices of the function with that of the

target as well as similar benchmarks for the industry sector or with the world class best benchmarks

To identify weak areas for performance improvement and

implementation strategies thereof.

To get certified towards proper system functioning from the auditing agency which may be requirement of a statutory and

standard agency

To apply and obtain popular awards like the total productive Maintenance (TPM)award etc.

Types of Audit:

There are various types of audit that are possible to be carried out in an organization. it would be useful to understand these terminologies so that


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one is able to understand and and appreciate their purpose and

requirements for different situations .These are briefly described below.:

Statutory Audit is the audit required by the law enacted by the

parliament or legislatures of a country. sometimes other statutory

or semi-statutory organizations like international labour

organization ,international standards organization etc also make specific provisions for

such statutory audits. On the other hand Voluntary audit is the

audit taken by an organization in its own interest.

Internal Audit is the audit taken by the internal department or

personnel of the company. Normally one department auditing the

functions of the other department.

External Audit is the audit conducted by an external agency

(neutral third party) either due to the wish of the company management to identify problems for improvement or mandated by

an enforcing agency like the government.

Preliminary Audit is normally conducted for a brief period of time

to identify major thrust problem areas in a function. The problem so

identified may be subjected to detailed examination and problem

solving at a later stage. On the other hand a Detailed Audit is carried out to study the complete features and requirements of a

specific function. normally the team members conduct such audit

for a considerable period

Management Audit is the audit carried out to check and identify

the suitableness of system and procedures of a management function .the audit carried out for an ISO-9000 certification is an

example of such an audit.

Technical Audit is the process of study of technical component of a plant with or without experimentation and instrument monitoring

to identify improvements in both hardware and software aspects.

For example environment audit of a factory involving measurement of pollution parameters is predominantly a technical audit.

All these types of audits have some amount of overlapping in their purposes and applicability. Example, a statutory audit can also be a result

o the voluntary requirement of the company. Or a external audit team

may co-opt an internal member to enhance the understanding of the

process being audited. All these type of audits have similar methodologies also.

Methodology of maintenance audit: Initial orientation: The auditing team has an initial meeting with the

representatives of the company‟s senior management and the regulating

agency, if any. In this meeting, the goals scope and coverage information

requirement, schedule of the meting, the techniques of the audit to be employed are presented in a summarized form. The initial meeting


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enables both the auditing and auditee groups to understand each others

concern well and lays the foundation for a detailed interaction at later

stages.

Preliminary preparation: During this step the auditors team studies

the management and technical information obtained in the initial

orientation and prepares a plan for addressing the major concern expressed by company management or the regulator .Accordingly the

most important areas of enquiry are identified and details audit visit plan

and schedule are prepared. It covers the areas of audit, identification of management personnel to be interviewed, facilities and work area to be

visited , data requirements etc.

Preliminary questionnaire survey: The auditors prepare a detailed questionnaire on the various issues of concern in maintenance

management and circulate in advance to the company management

personnel. The questionnaire contains a systematic identification of elements and series of questions to collect information about the same.

The questionnaire enables collection of documented information from a

large cross section of target personnel. The answers to the questionnaire are compiled and conclusion are arrived at as to the selected areas and

management personnel to be concentrated upon during the next steps.

Plan Visits: The auditing team undertakes a filed visit to the plant for collecting field information. During this visit interviews are held with

senior managers, supervisors and technicians etc to obtain a first hand

feeling of the management factors and concerns and feelings. During this visit additional information required in terms of work process, plant

performance parameters operations-maintenance interactions etc are also

collected.

In some special audits, plant visits are also taken up to a comparable third

party organization to make comparative analysis of the system and

technical parameters. At the end of the plant visits the auditing team would have the data essential to understand the companies maintenance

strategies, challenges and plans it also enables to fully understand the

present resources structure in terms of organization ,manpower, budget etc and its deployment.

Data analysis: During this step of the audit, the study team digests, summarizes and analyses all types of data and information gathered.

Profiles of maintenance management are developed and compared to the

companies past performance, and to the performance of the industry and

to similar companies. Many of the criteria used to evaluate effectiveness and efficiency can be measured quantitatively in terms of costs and

savings, man-hours percent adherence to schedule or budget energy

consumption, reliability, availability and so forth. However truly compared benchmarks may not be readily available. Accordingly the auditor must

consider the company‟s performance within the context of its unique

environment. Seasoned judgment both in tempering quantitative

evaluations and in measuring less tangible performance factors must be used.


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Development of Conclusions and Recommendations: Based on the

above evaluation the auditing team develops conclusions about the efficiency and effectiveness of the maintenance management system. The

factors that were observed to be examples of good management practices

are listed with supporting evidence and data and thus conclusions as to

the strengths of the system are identified .Similarly the possible sources of problems are also identified, documented and possible consequences, if

these problems are not tackled are also listed. Alternative strategies to

overcome the problem are identified and evaluated to indicate the most suitable option for problem solving.

Report Submission: The audit team prepared a comprehensive report

indicating the scope of the audit ,methodology adopted information gathered , analysis performed and recommendations arrived at as a result

of the audit Normally a draft report is submitted to ascertain the feedback

of the company management and the final report incorporating the suggestions and the feedback . The report submission is often

accompanied by a direct presentation to the management/regulatory

agency where the action plans for implementation of the suggestions and the requirement of the involvement of the auditors further can also be

discussed.

Maintenance Management Assignment

Documents

Transcript of Maintenance Management Assignment