preventive maintenance part i

7/23/2019 Preventive Maintenance Part I

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Preventive Maintenance

Introduction

It is necessary to keep materials, tools and equipment in good condition in

order to achieve desired result. If the working equipments are in good

running condition, the products obtained will be of required quality

and the process will be reliable. Therefore it is necessary to maintain

the plant.

Maintenance is a set of organized activities that are carried out in order to

keep the item in its best operational condition with minimum cost

required.

Maintenance Engineering is the discipline and profession of applyingengineering concepts to the optimization of equipment, procedures, and

departmental budgets to achieve better maintainability, reliability, and

availability of equipment.

Maintenance, and hence maintenance engineering, is increasing in

importance due to rising amounts of equipment, systems, machineries and

infrastructure. Since the Industrial Revolution, devices, equipment,

machinery and structures have grown increasingly complex, requiring a host

of personnel, vocations and related systems needed to maintain them.

Maintenance Definition

ritish standard !lossary of Terms defined maintenance as"

The combination of all technical and administrative actions including

supervision actions intended to retain an item in or restore it to a state in

which it can perform a required function!"

Maintenance Activities

#ctivities of maintenance function could be either repair or replacement

activities, which are necessary for an item to reach its acceptable

productivity condition or these activities, should be carried out with a

minimum possible cost.


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Maintenance Cost

ecause of breakdowns, both the machinery as well as the manpower

is left idle, per force.

These results in production, delay in schedules and emergency repairs.

The downtime costs generally exceed the preventive maintenance costs

of inspection, service and scheduled repairs.

Costs associated with maintenance are"

$. %owntime cost due to equipment breakdown.

&. 'ost of spares and other material used for repairs.

(. 'ost of maintenance labor and overheads of maintenance department.). *osses due to inefficient operations of machines.

+. 'apital requirement for replacement of machines.

Maintenance History

In thepre#world $ar II, people thought of maintenance as an added cost to

the plant which did not increase the value of finished product. Therefore, the

maintenance at that era was restricted to fixing the unit when it breaks

because it was the cheapest alternative.

%uring and after $orld $ar II at that time when the advances of

engineering and scientific technology developed, people developed other

types of maintenance, which were much cheaper such as preventive

maintenance. In addition, people in this era classified maintenance as a

function of the production system.

owadays, increased awareness of such issues as environment safety,

quality of products and services makes maintenance one of the most

important functions that contribute to the success of the industry. -orldclass companies are in continuous need of a very well organized

maintenance program to compete worldwide.


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Maintenance Objectives

Maintenance ob%ectives should be consistent with and subordinate to

production goals. The relation between maintenance ob/ectives and

production goals is reflected in the action of keeping production machines

and facilities in the best possible condition. These are"

0aximizing production or increasing facilities availability at the

lowest cost and at the highest quality and safety standards.

1educing breakdowns and emergency shutdowns.

2ptimizing resources utilization.

1educing downtime.

Improving spares stock control.

Improving equipment efficiency and reducing scrap rate.

0inimizing energy usage.

2ptimizing the useful life of equipment.

3roviding reliable cost and budgetary control.

Identifying and implementing cost reductions.

Types of Maintenance

Run to &ailure maintenance 'RT&(

)reventive Maintenance ')M(

*orrective Maintenance '*M(

)redictive Maintenance ')dM(

Run to &ailure Maintenance 'RT&(

The required repair, replacement, or restore action performed on a

machine or a facility after the occurrence of a failure in order to bring

this machine or facility to at least its minimum acceptable condition.

It is the oldest type of maintenance. It is subdivided into two types"

Emergency maintenance" it is carried out as fast as possible in

order to bring a failed machine or facility to a safe and

operationally efficient condition.

+reakdown maintenance, it is performed after the occurrence

of an advanced considered failure for which advanced provision


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has been made in the form of repair method, spares, materials,

labor and equipment.

%isadvantages" Its activities are expensive in terms of both direct and indirect

cost.

4sing this type of maintenance, the occurrence of a failure in a

component can cause failures in other components in the same

equipment, which leads to low production availability.

Its activities are very difficult to plan and schedule in advance.

This type of maintenance is useful in the following situations"

The failure of a component in a system is unpredictable.

The cost of performing run to failure maintenance activities is

lower than performing other activities of other types ofmaintenance.

The equipment failure priority is too low in order to include the

activities of preventing it within the planned maintenance

budget.


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)reventive Maintenance')M(

)reventive maintenance, where equipment is maintained before break

down occurs. This type of maintenance has many different variations

and is sub/ect of various researches to determine best and most

efficient way to maintain equipment. 1ecent studies have shown that

)reventive maintenance is effective in preventing age related

failures of the equipment.5or random failure patterns which amount

to 678 of the failure patterns, condition monitoring proves to beeffective.

ritish Standard !lossary of terms definedpreventive maintenanceas"

The maintenance carried out at predetermined intervals or according to

prescribed criteria and intended to reduce the probability of failure or the

degradation of the functioning and the effects limited!"

The advantages of applying preventive maintenance activities are to

satisfy most of maintenance ob/ectives.

The factors that affect the efficiency of this type of maintenance"

The need for an adequate number of staff in the maintenance

department in order to perform this type of maintenance.

The right choice of production equipment and machinery that is

suitable for the working environment and that can tolerate the

workload of this environment.


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The required staff qualifications and skills, which can be gained

through training.

The support and commitment from executive management to

the 30 program.

The proper planning and scheduling of 30 program.

The ability to properly apply the 30 program.

It is good for those machines and facilities which their failure

would cause serious production losses.

Its aim is to maintain machines and facilities in such a condition

that breakdowns and emergency repairs are minimized.

Its activities include replacements, ad/ustments, ma/or overhauls,

inspections and lubrications.

The effectiveness of a preventive maintenance schedule depends on the1'0 9Reliability *entered -nalysis: analysis which it was based on, and

the ground rules used for costaffectivity.

Reliability *entered Maintenance'R*M(is a process to ensure that assets

continue to do what their users require in their present operating context.

It is generally used to achieve improvements in fields such as the

establishment of safe minimum levels of maintenance, changes to operating

procedures and strategies and the establishment of capital maintenanceregimes and plans. Successful implementation ofR*M will lead to increase

in cost effectiveness, machine uptime, and a greater understanding of the

level of risk that the organization is managing.

1eliability centered maintenance is an engineering framework that enables

the definition of a complete maintenance regime. It regards maintenance as

the means to maintain the functions a user may require of machinery in a

defined operating context. #s a discipline it enables machinery stakeholders

to monitor, assess, predict and generally understand the working of their

physical assets.

R*M can be used to create a costeffective maintenance strategy to address

dominant causes of equipment failure. It is a systematic approach to defining

a routine maintenance program composed of costeffective tasks that

preserve important functions.


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The important functions of a piece of equipment to preserve with routine

maintenance are identified, their dominant failure modes and causes

determined and the consequences of failure ascertained. *evels of criticality

are assigned to the consequences of failure. Some functions are not critical

and are left to ;run to failure; while other functions must be preserved at all

cost. 0aintenance tasks are selected that address the dominant failure

causes. This process directly addresses maintenance preventable failures.

1'0 emphasizes the use of )redictive Maintenance93d0: techniques in

addition to traditional preventive measures.

Reliability centered maintenanceis an engineering framework that enables

the definition of a complete maintenance regime. It regards maintenance as

the means to maintain the functions a user may require of machinery in a

defined operating context. #s a discipline it enables machinery stakeholdersto monitor, assess, predict and generally understand the working of their

physical assets. R*M is kept live throughout the ;inservice; life of

machinery, where the effectiveness of the maintenance is kept under

constant review and ad/usted in light of the experience gained.

)reventive maintenance')M(has the following meanings"

$. The care and servicing by personnel for the purpose of maintaining

equipment and facilities in satisfactory operating condition by

providing for systematic inspection, detection, and correction ofincipient failures either before they occur or before they develop into

ma/or defects.

&. 0aintenance, including tests, measurements, ad/ustments, and parts

replacement, performed specifically to prevent faults from occurring.

The primary goal of maintenance is to avoid or mitigate the consequences of

failure of equipment. This may be by preventing the failure before it actually

occur which 3lanned 0aintenance and 'ondition ased 0aintenance help

to achieve. It is designed to preserve and restore equipment reliability by

replacing worn components before they actually fail. 3reventive

maintenance activities include partial or complete overhauls at specified

periods, oil changes, lubrication and so on. In addition, workers can record

equipment deterioration so they know to replace or repair worn parts before

they cause system failure. The ideal preventive maintenance program would

prevent all equipment failure before it occurs.


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3reventive maintenance can be described as maintenance of equipment or

systems before fault occurs. It can be divided into two subgroups"

3lanned maintenance and

'onditionbased maintenance.

The main difference of subgroups is determination of maintenance time, or

determination of moment when maintenance should be performed.

-hile preventive maintenance is generally considered to be worthwhile,

there are risks such as equipment failure or human error involved when

performing preventive maintenance, /ust as in any maintenance operation.

3reventive maintenance as scheduled overhaul or scheduled replacement

provides two of the three proactive failure management policies available to

the maintenance engineer. 'ommon methods of determining what3reventive 9or other: failure management policies should be applied ares already done to similar equipment, and most important measured

values and performance indications.

In a nutshell"

3reventive maintenance is conducted to keep equipment working

and?or extend the life of the equipment. 'orrective maintenance, sometimes called ;repair,; is conducted to

get equipment working again.

*orrective Maintenance '*M(

*orrective maintenance, where equipment is maintained after break down.

This maintenance is often most expensive because worn equipment can

damage other parts and cause multiple damages.

*orrective maintenanceis probably the most commonly used approach, butit is easy to see its limitations. -hen equipment fails, it often leads to

downtime in production. In most cases, this is costly business. #lso, if the

equipment needs to be replaced, the cost of replacing it alone can be

substantial. It is also important to consider health, safety and environment

9@S=: issues related to malfunctioning equipment.


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'orrective maintenance can be defined as the maintenance which is required

when an item has failed or worn out, to bring it back to working order.

'orrective maintenance is carried out on all items where the consequences

of failure or wearing out are not significant and the cost of this maintenance

is much greater than preventive maintenance.

'orrective maintenance is the program focused on the regular task that will

maintain all the critical machinery and the system in optimum operating

conditions. The ma/or ob/ectives of the program are to"

$. =liminating breakdown,

&. =liminating deviation,

(. =liminating unnecessary repairs,

). 2ptimize all the critical planned system.


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)redictive Maintenance ')M(


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Condition Monitorin

Introduction

*ondition Monitoring (*M) is the process of monitoring a parameter of

condition in machinery 9vibration, temperature etc.:, in order to identify a

significant change which is indicative of a developing fault. It is a ma/or

component of )redictive Maintenance ')dM(" The use of conditional

monitoring allows maintenance to be scheduled, or other actions to be taken

to prevent failure and avoid its consequences. 'ondition monitoring has a

unique benefit in that conditions that would shorten normal lifespan can be

addressed before they develop into a ma/or failure. *ondition monitoring

techniques are normally used on rotating equipment and other machinery

9pumps, electric motors, internal combustion engines, and presses:, while

periodic inspection using nondestructive testing techniques and fit forservice 955S: evaluation are used for stationary plant equipment such as

steam boilers, piping and heat exchangers.


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*ondition Monitoring within a Reliability *onte.t! -here condition

monitoring is used as a proactive defect elimination strategy to drive failure

prevention the benefits really add up with improved reliability giving

extended Mean Time between &ailures and additional 3lant #vailability.

There have been recorded instances where the gains in improved plant

uptime have lead to deferment of expensive plant expansion.

/efinition of *ondition Monitoring" The process of systematic data

collection and evaluation to identify changes in performance or condition

of a system, or its components, such that remedial action may be planned in

a cost effective manner to maintain reliability. -hile the basic definition of

'ondition 0onitoring 9'0: may have general application across many

industries, the ob/ectives for *ondition +ased Maintenance '*+M( may

vary greatly. CM uses se"ected measurements to detect chanes in operatin

conditions! 0any failure modes have measurable responses and

develop over periods of time. These are the ideal applications for

*+M. Sampling may be continuous, 9e.g. turbomachinery: or

periodic 9e.g. monthly survey on conveyor drive:.


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CM ives ear"y warnin of potentia" fai"ure!

If the measured parameters are well chosen and properly measured

and analyzed, there will be valuable information gained for

maintenance planning purposes. It is essential that what defines

AnormalB is understood and documented so that the severity of

variations can be measured.

CM ives information about the nature of the fai"ure!

5rom this a prognosis should be able to be determined. The rate of

sampling and access to maintenance history on the machine may

have an influence on the quality of the final decisions made.

CM a""ows manaement of fai"ure to fu"" "ife potentia"!

Identification of a failure mode does not necessarily mean that an

immediate maintenance action is needed. Cust when maintenance

action must be taken is the toughest part of managing a *+Mprogram. Dour reputation may depend on it. The best course is to

involve as many informed people in the decision making process.

CM eva"uates corrective action! Immediately after a machine has

been repaired it should be sub/ect to condition monitoring testing.

This will potentially identify assembly or installation faults that

may lead to early failure 9infant mortality: or affirm the quality of

improvement achieved through the application of improved work

practices or maintenance standards.

Trends for *ondition Monitoring in the 01st *entury,

The development of smart sensors, and other lowcost online

monitoring systems that will permit the costeffective continuous

monitoring of key equipment items.

The increasing provision of builtin vibration sensors as standard

features in large motors, pumps, turbines and other large equipment

items

Increasingly sophisticated condition monitoring software, with rapidlydeveloping ;expert; diagnosis capabilities

The acceptance of 'ondition 0onitoring within the ;mainstream; of

2perations and 0aintenance, with 3roduction operators increasingly

utilising 'ondition 0onitoring technologies as part of their daytoday

duties


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Increasing integration, and acceptance of common standards for

interfacing 'ondition 0onitoring software with '00S and 3rocess

'ontrol software

#n increasing focus on the business implications and applications of

'ondition 0onitoring technologies, leading to the utilisation of

'ondition 0onitoring technologies to improve equipment reliability

and performance, rather than to merely predict component failure.

# reduction in the costperpoint of applying 'ondition 0onitoring

technologies possibly leading to more widespread use of these

technologies.

How to view PM #Preventive maintenance$ and PdM #Predictive

maintenance$

=ffective 30 or 3d0 is like a skyscraper with four sides. 30 initiative

commonly fails to meet expectations or /ust gradually fade out of existence

when one side is neglected. If the program is to be successful it needs to

have structural integrity in all four areas"

$. %nineerin!#nalysis of statistics of failure, uptime, and repair is

included in the engineering pillar of 30.

&. %conomic!The task must be EworthF doing. This economic question

is critical.

(. Peop"e& Psycho"oica"" The people doing the 30 have to be

motivated to the extent that they actually do the designated tasksproperly.

). Manaement" 30 has to be built into the systems and procedures

that control the business and these systems must be designated so that

good 30 results.

'hat is the Mission of Maintenance(

The 0ission definitions ranged from quick reaction times in fixing

breakdowns to serving the customer more efficiently. Some firma are intenton reducing downtimes and other focus on cost control or quality. # few

focus on safety or environmental security. #ll these missions are good,

useful, and important.

In todayBs organizations the creed is that everyone must add value to the

product. =very one and everything is expendable, outsource able. There is a


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conflict between the old mission statements and the new culture. The new

mission is" The mission of the maintenance department is to provide

reliable physical assets and e.cellent support for its customers by reducing

and eventually eliminating the need for maintenance services!"

)ew ro"e!

The new mission requires a rethinking of traditional roes. 2n one side

maintenance must merge with machine, building and tool design to

integrate maintainability improvements into designs on an ongoing basis.

The accumulated knowledge and lessons of maintenance will be merged

immediately into the design professions. There will be a revolving door

between the people who design and the people who maintain. 2n the

other side, routine maintenance activity will be merged increasingly into

operations.

preventive maintenance part i

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