PREVENTIVE MAINTENANCE. Does your system have a preventive maintenance plan ?
Preventive Maintenance Part I
Transcript of 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.