Developing Maintenance Plans v1

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APPLICATION NOTE

DEVELOPING PREVENTIVE MAINTENANCE PLANS WITH

RCM

Ir. Martin van den Hout, Agidens Consulting & Services

October 2015

ECI Publication No Cu0217

Available from www.leonardo-energy.org



Publication No Cu0217

Issue Date: October 2015

Page i

Document Issue Control Sheet

Document Title: Application Note – Developing preventive maintenance plans

Publication No: Cu0217

Issue: 01

Release: October 2015

Author(s): Martin van den Hout, Egemin Consulting & Services

Reviewer(s): Kari Komonen, Bruno De Wachter, Carol Godfrey (English Upgrade)

Document History

Issue Date Purpose

1 September2015

First publication in the framework of the Good Practice Guide

2

3

4

Disclaimer

While this publication has been prepared with care, European Copper Institute and other contributors provide

no warranty with regards to the content and shall not be liable for any direct, incidental or consequential

damages that may result from the use of the information or the data contained.

Copyright© European Copper Institute.

Reproduction is authorised providing the material is unabridged and the source is acknowledged.





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CONTENTS

Summary ........................................................................................................................................................ 1

Terms and definitions ..................................................................................................................................... 2

Introduction .................................................................................................................................................... 4

What do we mean by maintenance? .............................................................................................................. 5

Preventive maintenance strategies ................................................................................................................. 6

Predetermined maintenance.................................................................................................................................. 6

Condition-based maintenance ............................................................................................................................... 6

Functional testing ...................................................................... .............................................................. ............... 6

Breakdown maintenance ...................................................................................................... .................................. 6

Context: Why does it matter? ......................................................................................................................... 7

Energy and environmental sustainability ............................................................................................................... 7

Availability and quality ........................................................................................................................................... 7

Calamity risk ........................................................................................................................................................... 8

Lifetime ...................... ............................................................... ................................................................. ............ 8

Cost ................................................................ ................................................................ .................................. 8

Setting up preventive maintenance with RCM: general approach .................................................................. 9

History of RCM ..................................................... ................................................................. .................................. 9

What is RCM? ......................................................................................................................................................... 9

The first main steps of an RCM project ......................................................................................................... 11

Initiation ............................................................................................................................................................... 11

Establishing the scope of the analysis ............................................................................... ..................... 12

Awareness of strategical importance .......................................................... ........................................... 12

Selecting team members ........................................................ .............................................................. .. 12

Planning ............................................................ ................................................................. ..................... 12

Demands for the assets .................................................. ................................................................. ..................... 12

Set up master equipment list ................... ................................................................. ........................................... 14

Criticality ranking and choice of type of analysis....................................................... ........................................... 14

Classic RCM analysis ..................................................................................................................................... 15

Functional demands ................................................................. ............................................................... ............. 15

(Functional) failures .............................................................................. .............................................................. .. 15

Failure mechanisms ......................................................................................... ..................................................... 15 Failure effect .............................................................................................................. ........................................... 16





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Failure consequences ................................................................ ................................................................ ........... 16

What should be done to prevent or predict each failure? ................................................................................... 16

Failure patterns ...................................................................................................................................... 17

Task interval ......................................................... ................................................................. ................................ 18

The optimal interval for predetermined maintenance ................................................................ .......... 18

The optimal interval for condition-based maintenance ............................................................... .......... 20

The optimal interval for functional tests ................................................................ ................................ 20

What should be done if a suitable proactive task cannot be found? ......................................................... .......... 21

Industrial RCM analysis ................................................................................................................................. 22

PM (Preventive Maintenance) Set Up ........................................................................................................... 23

Optimizing critical spare parts ...................................................................................................................... 24

Implementation and continuous improvement ............................................................................................ 25

Implementation of the selected maintenance tasks ....................................................................... ..................... 25

Task packaging ....................................................................................................................................... 25

Job plans ........................................................... ................................................................. ..................... 25

Planning the first execution ................................................................................................................... 25

Continuous improvement .......................................................... ................................................................. .......... 26

Conclusion .................................................................................................................................................... 27





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SUMMARY Preventive maintenance has a great impact on performance, risk, costs and energy consumption of assets. It

should be customised for each asset, because every asset works under different circumstances and has

another criticality. One of the major shifts in point of view in preventive maintenance within these last few

decades is that it should be aimed at fulfilling the organisational strategy.

Maintenance involves all the activities needed to keep an asset functioning according to the demands of the

organisation. It includes not only overhauls or exchange of parts, but also calibration, inspection, cleaning,

lubrication, functional tests and more. Simply replacing or restoring components after fixed intervals is called

predetermined maintenance. This is often not an effective strategy, because only a minor part of all failure

modes are time related. Most failure modes do not have a rising probability with rising component age. In

these cases condition monitoring or function test may provide a good solution.

RCM is a good and generally accepted methodology to select preventive maintenance tasks. An RCM analysis

consists of seven basic questions concerning each asset:

1. What are the functional demands for the system?

2. Which failures can occur?

3. Which failure mechanisms can lead to these failures?

4. What effect will each failure have?

5. What consequences will each failure have?

6. Which maintenance tasks should be selected to reduce the risk of failure to an acceptable level?

7. What can be done if an appropriate maintenance task cannot be found?

Because it is too time consuming to answer these questions for every asset in an organisation, faster methods

have been developed, such as Industrial RCM, which uses templates with failure modes and preventivemaintenance actions for standard components.

This Application Note describes how to select the right mix of preventive maintenance tasks for an asset

system, using RCM, Industrial RCM and Preventive Maintenance Set Up (PM Set Up).





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TERMS AND DEFINITIONS In standards and literature about maintenance and related subjects, many definitions are used for all related

topics. The terms and definitions in this section are mainly based on ISO13306 (2001): Maintenance

Terminology.

Asset

Item, thing or entity that has potential or actual value to an organisation.

Asset Management

Systematic and coordinated activities and practices through which an organisation optimally and sustainably

manages its assets and asset systems, their associated performance, risks and expenditures over their life

cycles for the purpose of achieving its organisational strategic plan.

Asset system

Set of assets that interact or are interrelated.

Corrective maintenance

Maintenance carried out after fault recognition and intended to put an item into a state in which it can

perform a required function.

Critical spare part

Spare part with a high price and long delivery time, but usually with a small probability of failing. Also

sometimes called insurance part.

Dependability

Collective item used to describe the availability and its influencing factors: reliability, maintainability and

maintenance supportability.

Energy

Electricity, fuel, steam, heat, compressed air, etc.

Industrial RCM

Form of RCM developed to set up a maintenance plan for asset systems with less resources and man hours.

Industrial RCM involves both work by an individual engineer and team sessions.

Maintenance

Combination of all technical, administrative and managerial actions during the life cycle of an item intended toretain it in, or restore it to, a state in which it can perform the required function.

Maintenance management

All activities of management that determine the maintenance objectives, strategies and responsibilities

and implement them by means such as maintenance planning, maintenance control and supervision, and

improvement of methods in the organization including economical aspects.

Maintenance plan

Structured set of tasks that include the activities, procedures, resources and the timescale required to carry

out maintenance.





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Organisation

This includes any type of organisation, ranging from a single person to a multinational corporation or a

government institution. In this application note we use this term for any organisation that wishes to

implement the standards.

Preventive maintenanceMaintenance carried out at predetermined intervals or according to prescribed criteria and intended to

reduce the probability of failure or the degradation of the functioning of an item.

Predetermined maintenance

Preventive maintenance carried out in accordance with established intervals of time or number of units of use

but without previous investigation of condition.

Condition-based maintenance

Preventive maintenance which includes a combination of condition monitoring and/or inspection and/or

testing, analysis and the ensuing maintenance actions.

Preventive Maintenance Set Up (PM Set Up)

Methodology to set up preventive maintenance plans for asset systems by an individual engineer, based on

the approach of Reliability Centered Maintenance.

Reliability Centered Maintenance (RCM)

Method to identify and select failure management policies to efficiently and effectively achieve the required

safety, availability and economy of operation.





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INTRODUCTION Maintenance involves all activities needed to keep an asset functioning according to the demands of the

organisation. It not only includes overhauls or exchange of parts, but also calibration, inspection, cleaning,

lubricating, functional tests and more.

Systems that are not well maintained consume unnecessary energy for various reasons. To ensure that all

systems keep performing at the required level of energy efficiency, preventive maintenance is necessary.

Besides energy consumption, there are other important aspects to consider when deciding which preventive

maintenance tasks are most suitable for an asset, such as availability, quality, cost, risk and sustainability.

Consideration must be given as to which set of preventive maintenance tasks delivers the optimal balance

between all these aspects.

One of the major shifts in point of view in preventive maintenance these last few decades is that preventive

maintenance should be aimed at fulfilling the demands that are necessary to achieve the organisational

strategy. If an organisation considers the reduction of energy consumption very important, it will need a

different kind of maintenance schedule to an organisation for which energy is less crucial. An organisation that

needs one hundred percent availability of its assets requires a different maintenance strategy to an

organisation that doesn’t. This means the preventive maintenance should not just be set up based on the

types of components installed, but based on the impact of failure of these components on the demands of the

organisation. For example, if an organisation has two identical transformers, one supplying highly critical

equipment and the other just supplying some secondary systems, the organisation may choose to spend more

resources on the maintenance of the first transformer.

Reliability Centered Maintenance (RCM) is an internationally accepted standardized methodology to

determine which (preventive) maintenance actions are necessary. RCM is described in several international

standards, such as IEC 60300-3-11 (1999-03) Dependability management - Application guide - Reliability

centred maintenance.

RCM is accepted by all major industries, such as aviation, railways, power industry, product development etc

as the standard for developing maintenance plans.

This application note describes the steps in an RCM analysis and gives a practical example of the

implementation of RCM on an electric motor. It also describes a faster form of RCM, called Industrial RCM,

which is more suitable in situations when a classic RCM analysis would require too many resources.





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WHAT DO WE MEAN BY MAINTENANCE?

For the purpose of this paper we will define maintenance as: all activities an organisation deploys to keep its

existing assets performing as needed to fulfil its organisational strategy .

Selecting the right preventive maintenance tasks is only one of the aspects of maintenance that an

organisation has to carry out to assure optimal functioning of its assets. Maintenance management consists of

several sub-domains, such as:

1. Preventive maintenance

2. Determining what preventive maintenance activities are necessary to keep the asset system

functioning at the desired level

3. Executing the preventive maintenance

4. Breakdown and repair

5. Continuous improvement

6. Managing processes and workflows to make sure all activities are carried out on time and with the

right quality

7. Managing resources such as spare parts, contracts, documentation and workshops

8. Managing the people in the organisation: organisational structure, number of employees, skills and

competences.

This application note focusses on selecting the right preventive maintenance tasks.

Maintenance is a part of asset management. Asset management involves the whole life cycle of assets. It

includes:

Investment decisions: should we build new assets?

Definition of asset solution

Design and engineering: how should these assets function?

Building and installation of the assets

Operations

Maintenance

Continuous improvement

Demolishing or removing the assets.





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PREVENTIVE MAINTENANCE STRATEGIES

There are several preventive maintenance strategies. A good preventive maintenance schedule is usually a mix

of these strategies. Which mix of strategies is best for a specific asset will be discussed further in this

application note.

PREDETERMINED MAINTENANCE

Predetermined maintenance means that components are exchanged or overhauled after a fixed interval. This

interval can be a fixed period of time, but also some other measure, such as the number of kilometres driven

by a car or when a system has run for a certain number of hours.

CONDITION-BASED MAINTENANCE

In condition-based maintenance a component is regularly inspected to determine its condition. Are there

indications that the part will fail in the near future, such as signs of wear and tear? The part is exchanged or

overhauled only when such signs are found. The inspections can be done visually, but many advanced

instruments have been developed for inspection purposes. When specialized equipment is used, condition-

based maintenance is also called predictive maintenance. Some of the technologies that are commonly used

are:

Vibration measurements for rotating equipment

Infrared thermography for electrical equipment, insulation or rotating equipment

Ultrasound inspection, for instance to detect air leakages or high voltage corona

Oil analysis

Motor current analysis to establish the quality of electrical circuits

Inspection of the quality of the electrical insulation

Non-destructive testing to test the integrity of static equipment, such as the wall thickness of vessels.

FUNCTIONAL TESTING

Some failures do not have an immediate impact on the functioning of the system as a whole. The main system

fails only when a second failure occurs. These types of failures are called “hidden” failures. Examples of

systems in which they occur are redundant systems, idle equipment and safety circuits. Periodically testing to

determine if a hidden failure has already occurred can keep the risk of failure of the main system at an

acceptable low level.

BREAKDOWN MAINTENANCE

This strategy is also called: “run it till it fails”. This may be a good choice if a failure does not have severeconsequences, does not occur very often or if the maintenance is so expensive that the preventive

maintenance would cost more than the failures over a period of time.





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CONTEXT: WHY DOES IT MATTER?Without maintenance, most assets will not keep performing at the level they were designed for. All kinds of

mechanisms, such as wear, corrosion, fatigue and many others cause degradation of the assets. Maintenance

is required to keep them performing at the required levels.

Maintenance has a direct impact on many areas:

1. Energy and environmental sustainability

2. Availability and quality

3. Calamity risk

4. Life expectancy

5. Cost.

ENERGY AND ENVIRONMENTAL SUSTAINABILITY

Systems that are not well maintained lose energy due to friction, electrical resistance, pollution, corrosion, and

many other causes. In electrical systems wear and improper adjustment lead to increased electrical resistance,higher harmonics and energy loss. In mechanical systems improper adjustment and pollution lead to higher

friction and energy losses.

But it is not just the direct energy consumption of the asset itself, when it is operational, that we need to

consider. The repair of failures and breakdowns can also consume a lot of energy. Finally, the life expectancy

of systems that are maintained correctly is longer, thus reducing consumption of energy and other resources

necessary to produce their replacements.

AVAILABILITY AND QUALITY

One of the main targets of maintenance is to reduce the number of breakdowns. Companies with good

preventive maintenance programs can reduce the amount of breakdowns by 80%.

But even if a system is still functioning, it may be operating at lower capacity than it was designed for.

Maintenance has a direct impact on the capacity of most systems. Systems that are not available when they

are needed cost billions of euros in Europe each year.

A simple calculation shows that if:

a system is available for 90% of the time

during this time it operates at 90% of its maximum capacity

it produces 90% good results

the end result is it only delivers 90% * 90% * 90% = 72.9% of its maximum capacity.

In production plants this figure is called the Overall Equipment Effectiveness (OEE). A decrease of just 2% of

OEE can lead to 50% loss in the profit of a commercial company. But organisations in other sectors also suffer

great losses due to breakdowns. For example, energy suppliers and railway companies have to pay their

customers compensation if their systems are not available for a certain period of time.

Sometimes it can be hard to detect quality problems. If an electrical system is not well maintained, the

electrical current can contain higher harmonic content, which not only causes energy losses, but also issues in

electronics, transformers, capacity batteries, etc.





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CALAMITY RISK

In maintenance management it is necessary to look not only at the performance or output of a system, but

also at the risk of unacceptable events happening, such as the risk of a safety-related incident or an

environmental pollution. Unfortunately there are many examples of catastrophes that have happened because

of inadequate maintenance practices.

One of the best known cases is the accident of the Deepwater Horizon, a semi-submersible oil rig in the

Mexican Gulf in 2010. Eleven people died in this accident and seventeen people were injured. For three

months oil f lowed into the sea, killing thousands of animals. According to the BP website: “BP has spent more

than $14 billion and workers have devoted more than 70 million personnel hours to response and clean-up

activities.”

The damage to the tourism industry is estimated at 23 billion dollars. The cause of this spill: failure of a blow-

out preventer.

LIFETIME In many capital-intensive sectors, the capital costs make up half of the operational expenditure every year. So

the costs of interest and depreciation are just as high as all other operational costs combined. An increase of

10% of lifetime for the average asset has a huge impact on the financial results of an organisation.

Maintenance has an enormous impact on wear and other degradation mechanisms. For example, when an

electrical field is present, insulation of electrical components and wiring degrades. This process starts where

the material is less homogenous. Increase in temperatures can cause degradation in a few minutes that will

normally take years. The strength of the electrical field also has a huge impact. For polyethene insulation, an

electrical field that is twice as strong decreases the life 500 times!

COST

The previous paragraphs described why maintenance is necessary. Lack of proper maintenance can cost an

organisation a lot of money. However, maintenance itself also costs money. In many industries, maintenance

costs rank in the top three of operational expenditures.

In process plants raw materials and energy consumption are costing more money

In some manufacturing plants, such as automotive plants, labour costs and raw materials rank

number one and two

In infrastructure and network companies, maintenance is the number one operational expenditure.

The costs of maintenance that are registered in a company’s financial accounts include direct costs, such as

labour, parts and contracts. Even more expensive, however, may be the costs of taking a system out of servicefor preventive maintenance. Therefore, it can be necessary to develop a preventive maintenance plan that

optimally balances all the aspects discussed in this paragraph.





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SETTING UP PREVENTIVE MAINTENANCE WITH RCM: GENERAL APPROACH

Reliability Centered Maintenance (RCM) is a methodology to set up preventive maintenance for assets. It is the

only methodology that is accepted worldwide by organisations such as the airline industry, railways or defence

organisations.

HISTORY OF RCM

RCM was originally developed for setting up preventive maintenance for the Boeing 747 Jumbo Jet.

Investigations showed that some of the accidents happening until then were caused by technical failure. The

response of the airline industry had always been to exchange or restore components more often. However,

this did not lead to a drop in the overall number of accidents. The number of critical hull failures per one

million take-offs only dropped about 10%. This discovery led to the assignment of Maintenance Steering

Groups (MSGs) that aimed to develop a methodology for setting up preventive maintenance for aircraft. In

1978 the third maintenance steering group (MSG3) presented a report called Reliability Centered Maintenance

(RCM). The name of this report became the name that is most commonly used for the methodology it

described.

Because regular industries do not need such an intensive method for detailed analysis of their systems, faster

methodologies have been derived from it, such as Industrial RCM.

WHAT IS RCM?

RCM is a structured methodology to analyse an asset, its functions, failures and the maintenance tasks that

can be selected to mitigate these failures. RCM is developed to be able to determine, in the design stage of a

system, which maintenance tasks have to be performed on an asset. In practice, it is also very often applied to

existing systems.

RCM sets up preventive maintenance schedules, based on the functional demands for an asset system. Thismeans that the result of the RCM analysis, the preventive maintenance schedule, does not only depend on the

type of component that needs maintenance. It is the function of the asset system as a whole and its impact on

the organisational strategy that are the starting point of the analysis.

The results of an RCM analysis are a mix of the following maintenance strategies:

1. Condition-based maintenance

2. Predetermined maintenance

3. Functional testing

4. Breakdown maintenance.

An RCM analysis may also have the outcome that it is mandatory or may be useful to re-engineer the system.

Using RCM to set up preventive maintenance has the advantage that a fully documented trail is produced to

show the relation between, on the one hand, all the risks associated with operating an asset system and, on

the other hand, the maintenance that is being performed. In other words: RCM clearly shows why the

maintenance must be done. Once RCM is implemented, it is relatively easy to adjust the preventive

maintenance if the circumstances or the strategy of the organisation change.

An RCM analysis is performed by a team of people who are familiar with the system from several points of

view.





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RCM answers seven standard questions to determine what maintenance a system needs:

What are the functional demands for the system?

Which failures can occur?

Which causes can lead to these failures?

What effect will each failure cause have? What consequences will each failure have?

Which maintenance tasks should be selected to reduce the risk of failure to an acceptable level?

What can be done if an appropriate maintenance task cannot be found?

These are the core steps in an RCM analysis. Of course, more is involved in preparing the sessions and

implementing the preventive maintenance. The sections below describe the whole process step by step.





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THE FIRST MAIN STEPS OF AN RCM PROJECT

Figure 1 – The typical steps of an RCM program.

The following paragraphs will discuss the steps of the RCM program before the actual analysis.

INITIATION

An RCM analysis usually starts with a kick-off meeting with senior management which has several goals:

1. Establishing the scope of the analysis

2. Awareness of the strategical importance

3. Explaining the methodology

4. Deciding who should be in the team performing the actual analysis.

Criticality ranking

Demands: Output, costs,

safety, environment,

quality, energy.....

Set up Master Equipment List

RCMIndustrial

RCM

PM

Set up

Optimize critical spares

Implement

Continuous improvement





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ESTABLISHING THE SCOPE OF THE ANALYSIS

The first question is: which asset systems must be analysed during the RCM analysis? This question only needs

to be answered at a general level at this time. Senior management may decide to give the order to analyse all

asset systems on site, just one plant or maybe only the utility systems.

AWARENESS OF STRATEGICAL IMPORTANCE

Often senior management considers maintenance to be just an expense. The general thought is that every

asset has a maintenance manual and the technicians should just follow that manual. However, manuals do not

take into account the function of an asset in the organisation. Failure of one valve may lead to a catastrophe,

whereas failure of another, identical, valve may have only minor consequences. Moreover, standard

maintenance manuals cannot take into account the circumstances under which a component is functioning.

Breakdowns do not just happen spontaneously. They have a cause and can be prevented. Using RCM, the

organisation can control the balance between the amount and type of failures it is willing to accept and the

amount of money it is willing to spend on maintenance.

SELECTING TEAM MEMBERS A typical team for industrial maintenance consists of:

1. A maintenance engineer who knows how the system is designed and has the know-how to judge

technical improvements.

2. A technician who has hands-on experience in the maintenance and repair of the system. He knows

what failure modes occur in practice and knows in detail what happens when a failure occurs.

3. An operator of the equipment. He knows the functioning of the equipment on a day-to-day basis and

knows small failures and the behaviour of the equipment before larger breakdowns occur.

4. A production supervisor or manager. He knows which failures are important and knows the impact on

the process and product quality.

5. A facilitator. He is the chairman of the sessions, keeps the records and makes sure the team follows

the methodology correctly.

PLANNING

There are several approaches to the practical planning of sessions. In our experience, the optimal length of a

session is three hours. If it is shorter, the team loses too much time getting started each session. If it is longer,

team members may get tired and lose their focus. The sessions should be held at least once a week. There are

several software tools that can be used to record the results. However, in some cases a simple spreadsheet will

also do. Some of the RCM standards specify exactly the layout of forms that should be used to record the

analysis results. There are some minor differences between the standards. The description in this application

note describes the general approach.

DEMANDS FOR THE ASSETS

Maintenance should be aimed at fulfilling the organisational strategy. Therefore this strategy must be known.

It must be translated into an asset management strategy and concrete demands for the assets and their

related performance, costs and risk. During the management session, management must answer questions

such as:

1. What percentage of uptime, or how much output, must the asset system deliver on average? This is a

very important question, because a breakdown of assets that have more capacity than they need has

much smaller financial consequences than the failure of a system that must operate at full capacity.

2. What are the costs of stopping operation because of a failure of an hour (minute, day….)?

3. What is the maximum amount of time that the system is allowed to be unavailable for operation?





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The senior management must state clearly what level of risk it is willing to accept. No operation can ever be

100% safe. Failures, also combined failures, have a chance of happening. They can have consequences in many

areas, such as:

Safety

Environment Quality

Reliability of delivery

Labour circumstances

Security

Legal requirements

Corporate image

Comfort

Politics.

To visualize what level of risk the senior management is willing to accept, a risk matrix is set up. It shows the

relation between the severity and the frequency of incidents.

Figure 2 – The risk matrix.

The first column of this matrix gives a ranking of 1 to 5 for the impact severity of incidents. The next three

columns define the severity categories, in this case by the impact on cost, safety and quality. The following

columns indicate how often a certain failure is allowed to happen. A green block means the failure is

acceptable. Orange means improvement needs to be planned. Red means the failure is unacceptable andimmediate action is necessary. For example: an organisation determines that a power failure of longer than

four hours will occur less than once every ten years and has a severity score of 3. This means no action is

needed.

Some organisations use the risk matrix also for:

Decisions on replacement investments

Decisions on counter measures after incidents

Designing new asset systems.

Severity Economics Safety Quality

< 1 time/

50 years

< 1 time/

10 years

< 1 time/

year

< 1 time /

month

> 1 time/

month

1 <€ 1000 No impact No impact

2 <€ 5000 First AidMinor

complaint

3 <€ 50.000Lost time

incident

Customer

return

4 <€ 500.000Permanent

disabled

5 > € 500.000 DeathProduct

recall





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SET UP MASTER EQUIPMENT LIST

One common problem when setting up preventive maintenance is that many organisations do not have a

complete and up-to-date asset register. This means that before the analysis can actually start, engineers must

verify the correctness of the asset register. Sometimes they can do this with an “asset walk down” on site.

They go into the facility and check the assets that are actually present against the databases in the systems ofthe organisation. If an asset walk down is not possible, special software can be used for data mining and data

cleaning. This software can be applied on databases from the maintenance department, historical purchase

records, investment databases and the data of the financial department to get an accurate overview of the

installed assets. For example, this approach can be used if the assets are networks of cabling that are spread

out over a large geographical area.

CRITICALITY RANKING AND CHOICE OF TYPE OF ANALYSIS

A full blown RCM analysis can take a lot of time. It is only worth allocating resources to a classic RCM analysis if

failure of an asset has serious consequences. If failure can only have smaller consequences, then faster forms

of RCM, such as Industrial RCM are appropriate. To establish which methodology will be used for each asset, a

criticality ranking is performed. The RCM team starts by assigning scores to every asset in the asset register to

determine what the impact of failure of the asset could be according to the criteria set in the risk matrix.

An organisation might, for example, decide to use RCM only on those assets that could cause a calamity of

category 5 in the risk matrix.

Preventive maintenance schedules for the less critical equipment can be set up using Industrial RCM or PM Set

Up. These methodologies are both derived from classic RCM.

The actual analysis with Classic RCM, Industrial RCM or PM Set UP will be tackled in subsequent sections, as

well as how to optimize critical spare parts, the implementation of the selected maintenance tasks and the

notion of continuous improvement.





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CLASSIC RCM ANALYSIS

FUNCTIONAL DEMANDS

An important principle of RCM is that the goal of maintenance is to keep a system as a whole functioning. The

goal is not to keep every component as good as new. This may seem a trivial principle, but it has major

consequences. A transformer, for example, will lose some of its energy efficiency over time. It is not necessary

or economical to keep every transformer at maximum energy efficiency. The team will have to specify how

much loss of energy efficiency is acceptable to comply with the demands senior management has set. Another

example is paintwork. If the organisation specifies esthetical demands for the paintwork (that it should look

good), another interval between paint jobs is necessary compared to when the paintwork only has to preserve

the material that is painted, but it doesn’t have to look brand new.

A division is made between primary and secondary demands. The primary demands are related to the function

for which the equipment was bought. The transformer should be able to transform a certain amount of

electrical power from X volts to Y volts. Secondary demands are the extra features that are required from the

asset. Examples include energy consumption, safety, quality, environmental demands or aesthetics. The

division between primary and secondary demands does not express any priority of one over the other. It is

rather a methodology to avoid secondary demands being forgotten.

(FUNCTIONAL) FAILURES

The second step in the RCM process is to establish all functional failures. The functional failures follow logically

from the functional demands. Suppose, for example, the demand for a transformer is to transform a certain

amount of electrical power from a high voltage to 400V +/- 5%. The secondary demands are that it should be

safe (avoiding equipment damage and human injuries) and its energy efficiency should be higher than 98%. In

this case the failure modes can be:

1. The transformer cannot transform enough power

2. It cannot transform power at all

3. The output voltage is higher than 420V

4. The output voltage is lower than 380V

5. Its efficiency is lower than 98%

6. It is unsafe.

A functional failure is not a cause. It is just a description of what can go wrong. It is very important to have a

clear list of all functional failures. In the next step the team will investigate potential causes for each functional

failure, one by one. The causes of the failure “the output voltage is higher than 420 volts” may be different

from the causes of the failure “the output current is lower than 380 volts”.

FAILURE MECHANISMS

Another word for failure mechanism is cause. In this step the team starts to analyse all possible causes of the

potential functional failures that it listed in the previous step. This step is the most time consuming of the

analysis. Simple systems can already have dozens of failure modes. It is necessary to find the causes behind the

causes, until the description of a cause is so specific that a counter measure can be selected. A cause of failure

on an electromotor may be, for example, a short circuit in its windings. It is very hard to determine which

preventive maintenance actions can prevent this from happening. There can be many causes leading to the

short circuit, one of which may be damage to the insulation. This may be caused by overheating of the motor.





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This may be caused by a too high ambient temperature, by electrical overload, by a broken cooling fan or by

dust on the outside of the motor. The team should make the analysis up to this level of detail, before it can

select an appropriate action, such as periodic cleaning of the motor.

FAILURE EFFECT

A failure effect describes exactly what is happening when the failure occurs. Effects can be macro or micro.

Macro effects are the scenario of what happens when the failure occurs. If, for instance, the electric motor

fails, a cooling pump stops running and an alarm sounds in the control room. Micro effects describe local

events, inside the device concerned, or directly related to it. Dust gathers on the motor, this can be seen.

Slowly the temperature of the motor rises. This could be detected. Subsequently, the resistance of the

windings starts to drop and eventually the motor fails.

The macro effects describe the events that happen outside the device concerned. They lead directly to the

failure consequences. The micro effects give an indication of how a failure can be detected before it occurs.

FAILURE CONSEQUENCES A failure consequence describes what the impact of the failure is. Is safety at risk? Does the environment get

polluted? Does the organisation lose money? There are two main reasons to determine the consequences of

the failures.

The first is to be able to judge if a counter measure is desirable. If a failure has no severe consequences and it

will take a lot of resources to prevent it, prevention may not be desirable from an economic point of view.

The other reason is that RCM makes a difference between hidden failures and evident failures. This is an

important concept in RCM. Hidden failures do not have any consequences until a second failure occurs. So, in

principle, the failure can be present for all eternity without any consequences. Hidden failures are most

commonly found in safety devices, idle items and redundant systems. We can keep the risk of system failure atan acceptable low level by testing the safety devices and redundant equipment on a regular basis. Simply put:

it is acceptable if they fail, provided we can detect and repair it fast enough. For an evident failure, periodic

functional testing is not an option. If an evident failure occurs, this will lead directly to a failure of the entire

system. Therefore, evident failures should be prevented.

WHAT SHOULD BE DONE TO PREVENT OR PREDICT EACH FAILURE?

To determine what the best action is to prevent or predict a failure, RCM uses decision diagrams. Their

outcome can be one of the following strategies:

Predetermined maintenance Condition-based maintenance

Functional testing

Breakdown maintenance

Re-engineering.

The RCM decision diagrams first divide the failure modes into three different categories:

1. The hidden failures. Functional testing to detect hidden failures can be a good option to prevent the

asset as a whole of losing its function.

2. Evident (non-hidden) failures with only economic consequences. For these failures:

a. If suitable maintenance tasks can be found, they should only be executed if they cost lessthan the potential failures during a certain period of time





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b. If no suitable maintenance tasks can be found, breakdown maintenance is an option and re-

engineering might be useful

3. Evident failures that have unacceptable consequences according to the risk matrix. If no suitable

maintenance tasks can be found, re-engineering is mandatory. If suitable tasks can be found, they

must be executed, even if they are expensive.

Within each of the above categories, RCM uses questions that look much the same for each category to

determine which kind of preventive task is suitable:

1. Is condition-based maintenance possible? This question can be answered positively if there are

physical or chemical phenomena that can be observed or measured before the failure occurs. This

phenomenon can be a variety of things, such as wear, vibration, noise, pollution, reduced wall

thickness etc. If such a phenomenon can be observed or measured to predict the failure, it is the first

preference of RCM. In general, this requires the least amount of time and money. More importantly,

inspections are less intrusive then overhauls. Every time a system is overhauled, or a component is

replaced, there is a risk of causing new failures. Condition-based maintenance has a lower risk of

these maintenance-induced failures.2. If condition-based maintenance is not possible, is an interval-based maintenance action practically

and economically feasible instead? If this is the case, a periodic overhaul or exchange of parts is the

preferred choice of RCM.

FAILURE PATTERNS

Answering the questions above requires a thorough knowledge of the ways failures occur and how they can be

detected. A graph can be drawn comparing the chance that a failure may occur in the coming period versus

the age of a component. In the airline industry, for example, the following six patterns can be found:

Figure 3 – Example of typical failure patterns (airline industry).

It is commonly believed that failures behave according to failure pattern B but, as we can see, this is only valid

for 2% of the failure modes. Altogether, only 11% of the failure modes occur more often with increasing age.

Only for these 11% can interval-based maintenance be a good strategy. For the other 89% of the failure cases,

interval-based maintenance will be counterproductive.

Pattern A = 4%

Pattern B = 2%

Pattern C = 5%

Pattern D = 7%

Pattern E = 14%

Pattern F = 68%

Age dependent = 11% Random= 89%

time time





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Figures from other industries show a similar trend: only 8% to 23% of the failures are age dependent, while the

other 77% to 92% are random.

TASK INTERVAL

The previous sections describe how the RCM methodology can determine which mix of maintenance tasks

should be selected for an asset. RCM does not include a step to determine how often these tasks should be

executed, even though this is of course an important question. The answer depends on the type of

maintenance strategy that has been selected.

THE OPTIMAL INTERVAL FOR PREDETERMINED MAINTENANCE

As discussed earlier, predetermined maintenance is useful when the risk of failure rises in time. This is true for

the small number of failure causes that fit into pattern A, B or C. If the probability of failure rises over time, the

average cost of failures during the specific year rises as well.

Figure 4 – The cost of failure.

The graph above shows that, if preventive maintenance is postponed, the costs of failures become higher. On

the other hand, the annual cost of preventive maintenance is halved when doubling the task interval.





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Figure 5 – The cost of preventive maintenance at different intervals.

The optimal interval for preventive maintenance is the one at which the aggregated cost of preventive

maintenance and failures goes through a minimum. Not only should the cost of maintenance itself be taken

into account in this calculation, but also that of lost output, which may be much higher than the cost of

maintenance and repair itself.

Figure 6–

Total costs





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To predict the number of future failures is a complex matter. Some ways to estimate this figure are:

1. Using standard tables with historical data for components. This is not very accurate, because the

failure rate of a component strongly depends on its quality, its application and the operational

circumstances in which it is being used.

2. Using historical data of the actual component on site. To extrapolate historical data to the future,Weibull analysis can be used.

3. Using expert opinions.

THE OPTIMAL INTERVAL FOR CONDITION-BASED MAINTENANCE

Condition-based maintenance can also be used when the amount of failures does not increase with time. This

means the calculation above will not work, because corrective costs do not rise. To determine the optimal

interval for an inspection, the key question is: how long in advance is it possible to predict a failure?

The curve below explains this. The curve shows the condition of the equipment evolving in time. At first the

equipment is in good condition. At a certain point, the condition starts to drop slightly. This is indicated where

the colour of the graph starts to change from green to red. However, at this point the change is too small tomeasure. At point P, the deviation has become so large it can be detected. P stands for “potential failure”. The

condition of the asset will deteriorate further until it fails at point F.

The interval between inspections should be shorter than the interval between P and F, which is called the P-F

interval. If doing maintenance at this interval is not economically feasible, it is no use doing the inspections less

frequently. The P-F interval strongly depends on the particular nature of the failure and on the technology

used to detect it.

Figure 7 – The P-F curve for inspection intervals.

THE OPTIMAL INTERVAL FOR FUNCTIONAL TESTS

Determining the optimal interval for functional tests follows a completely different logic to the calculation for

interval- based or condition-based maintenance.

A functional test is only useful to prevent a hidden failure. The test determines if the failure has already

occurred.

The figure below explains this.

C o n d i t i e

Time

P

F

C o n d i t i o n

P





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Figure 8 – Functional testing.

If the main system fails at moment A, the safety system protects its function and the system keeps functioning.

If the safety system fails it is only a problem at the moment the main system fails. It should therefore be

checked so often that the chance of them failing at the same time is acceptable.

The testing interval can be calculated with this formula:

MTBFs * MTBFm * 2 = T (FT)

Ta

With:

MTBFs = the mean time between failures of the safety system

MTBFm = the mean time between failure of the main system

Ta = the acceptable minimal time between (two) failures of the entire system

T (FT) = the interval between two functional tests

Suppose the organisation accepts a failure of its power supply once per 100 years.

The relays of the emergency generator have an MTBF of 10 years.

The public power net has an MTBF of 3 years.

This will lead to an inspection interval of:

T(FT) = 10 * 3 * 2 = 0,6 year

100

WHAT SHOULD BE DONE IF A SUITABLE PROACTIVE TASK CANNOT BE FOUND? This is an important question in RCM. There are many failures that cannot be prevented by preventive

maintenance. Their frequency can often be reduced, but they can still occur. What should be done? RCM has

two different answers to this question:

1. If a failure can lead to consequences that are not acceptable according to the risk matrix and

preventive maintenance cannot reduce the risk to an acceptable level, in this case, re-engineering is

mandatory. This may mean changing the design of the system, but it can also relate to the way the

system is operated.

2. If a failure is acceptable, because it has only a minor impact and/or does not happen very often, re-

engineering still might be useful. However, the first outcome of RCM in this case is “run it till it fails”.

Simply do nothing and fix it when it breaks.

Main system

Safety device

A

Time





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INDUSTRIAL RCM ANALYSIS

Classic RCM was originally developed by the airline industries, where failure can have very serious

consequences and aircraft are built in series of several hundreds. This makes it worth investing time in a full-

blown RCM analysis. For many other industries, consequences are less severe and the diversity of equipment is

much greater, which sometimes akes RCM too time consuming.

For these industries Industrial RCM (iRCM) has been developed. It takes away the most time consuming step of

an RCM analysis, namely the analysis of failure mechanisms. During an Industrial RCM analysis, an engineer

uses a database with failure causes and suitable maintenance tasks of standard components. This part of the

RCM analysis is stored as a template for each type of component.

In the next step he determines which failure causes are suitable for the equipment he is analysing. Typically

the engineer will use three versions of the template for each component:

1. For very critical equipment he may select all (or most of) the maintenance tasks in the template - in

other words, all the maintenance tasks that are useful from a technical point of view.

2. For medium critical equipment he may choose to do the most common maintenance tasks.

3. For non-critical equipment he may choose to do only the maintenance that is necessary to make sure

the component does not wear faster, such as cleaning or lubricating.

The next step in the Industrial RCM consists of sessions where the maintenance engineer acts as a facilitator

and discusses with a team:

1. His proposal for preventive maintenance

2. Special situations where templates are not applicable

3. If the staff of the organisation have enough knowledge to perform maintenance and repairs

4. Which critical spare parts are needed

5. If extra measures are necessary to make the preventive maintenance or repairs possible, such asimproving access to the equipment or installing hoisting beams or safety switches.

6. Who will do the maintenance: technicians from the organisation itself, contractors or operators?

The team has the same type of members as a team performing a RCM analysis.

An important purpose of the sessions is to receive buy-in and acceptance from the maintenance and

operations departments. This will make implementation of the maintenance plan a lot easier.

Apart from the speed, an advantage of iRCM above RCM is that the templates comprise the knowledge of

several teams and experts. During a classic RCM, the team has to gather this data itself.

The advantage of RCM over iRCM is that it critically analyses the components in the way they are used in the

particular system. Design errors and operator mistakes will also be discussed by the team. Industrial RCM

assumes the quality of the design is good enough for its purpose.

An example of an Industrial RCM analysis is an energy network company that maintains 500 high voltage

transformers and 40.000 medium voltage transformers. The rules of classic RCM would imply that each

transformer should be analysed separately. Industrial RCM analyses one of each and copies the results of this

analysis to all the others. Of course this copying can only be done by experts who know what they are doing

and can judge if two systems are really identical.





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PM (PREVENTIVE MAINTENANCE) SET UP

Although Industrial RCM takes much less time than classic RCM, it may still cause too much workload for an

organisation to hold iRCM sessions for each asset system. “PM Set Up” is a methodology for a maintenance

engineer to set up preventive maintenance individually, without consulting a team. He will use the same

approach as the engineer performing iRCM, except that no team sessions are held.





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OPTIMIZING CRITICAL SPARE PARTS

During the process of an RCM analysis, the spare parts should be selected that need to be kept in stock at all

times.

Spare parts with a low cost but a long delivery time could best be kept in stock.

The ones with a low cost, but short delivery time, do not need to be kept in stock but it could be

sensible.

The ones with a high cost and short delivery time are probably not worth having in stock.

Critical spare parts are the ones with a long delivery time and a high price.

If the chance they will ever be needed is small, it is a complex decision whether or not an organisation should

buy critical parts to keep them in stock. This is especially true if there is only a small chance they will ever be

needed. The RCM analysis should show insight in which failure modes they may be needed and what the

chances are of these failure modes actually occurring.





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IMPLEMENTATION AND CONTINUOUS IMPROVEMENT

IMPLEMENTATION OF THE SELECTED MAINTENANCE TASKS

The implementation of preventive maintenance consists of several activities;

1. Personnel need to be trained

2. Contracts with external partners need to be closed

3. Some processes and procedures need to be developed. For example, if operators are to do routine

checks, it is very important to have a clear procedure for planning their checks, reporting findings and

giving feedback to the operators.

4. When re-engineering has been executed, the impact on reliability and costs should be thoroughly

examined. One should be careful not to introduce new faults while trying to fix an existing one.

5. The results of the RCM analysis should be used as input for future designs.

These are just some of the activities during the implementation stage. In the next two sub-sections we will

describe task packaging and job plans in more detail.

TASK PACKAGING

Tasks have to be combined into work orders that can be managed through a planning system. The result of an

RCM analysis is a long list of separate tasks. They should be grouped according to their frequency, so the assets

do not have to stop more than necessary. Tasks that must be performed by specialized contractors must be

grouped together so travel times are reduced to a minimum. As many external tasks as possible should be

covered by one contract to save administrative costs.

JOB PLANS

A good preventive maintenance schedule only has value if it is being executed the correct way. Maintenance

tasks have to be described in job plans to the appropriate level of detail. An experienced technician may only

need a brief description of a standard task, such as checking a V-belt. An inexperienced operator will need a

longer description. What is a V-belt? What does it look like when it is in good condition and what are the signs

that it is deteriorating? How to check the belt pulley? How to check the tension? If the description is not

detailed enough, the person cannot execute the tasks correctly. If the description is too detailed, the person

will not read it, because he thinks he already knows everything that is in the work instruction. A job plan

contains information such as:

a. The most important steps in the task

b. Special points of attention

c. Quality criteria to judge if the quality of the component and the work are OK

d. The amount of time needed

e. The amount of people needed and their skills

f. Safety precautions

g. Materials to be used and special tools needed.

PLANNING THE FIRST EXECUTION

During the implementation stage, special care has to be taken not to increase the workload too much. Good

preventive maintenance practices will lead to less workload and better planning in the end, but initially the

workload is likely to increase. At first the amount of preventive maintenance will increase, before the amount

of corrective maintenance will drop. Moreover, each job needs special attention the first time it is being

executed. This should be discussed with the persons performing the task. Maybe the descriptions are not





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accurate, maybe the time planning is not realistic, or maybe some tools are missing. These are the kind of

points that need fine tuning. Asking for feedback will greatly increase the level of acceptance by the crew.

CONTINUOUS IMPROVEMENT

RCM was originally developed to be used during the design stage of a system. During operation it will become

clear if the analysis needs fine tuning. Usually there are some points that can be improved. They consist of

different types:

• Failure modes occur that were not foreseen. This is what people fear the most, but it does not

happen very often. A good analysis will find most of the failure modes.

• The frequency of the failure modes was not estimated accurately. This is almost inevitable,

because every system operates under different circumstances and often uses the newest model

of some component that will behave differently from all previous models. Therefore it is

necessary to record all failures and analyse them periodically to see if the preventive

maintenance intervals need adjustment.

• Failures occur that cannot be prevented by maintenance. Often failures occur due to causes suchas wrong adjustment, operator error, external damage, changes in raw materials etc. To reduce

this type of failures, a continuous improvement program is necessary. Again this starts with

recording all failures and losses to determine their impact and cause. The next step is to select

the most important problems to work on. Most organisations do not have the budget or

manpower to work on every problem that occurs. Therefore setting priority is necessary. A

Pareto-diagram usually shows that 80% of the failures is caused by 20% of the causes.

Organisations should focus on this 20% and on the causes that can lead to unacceptable

consequences according to their risk matrix. Subsequently a method like Root Cause Analysis can

be used to determine the deeper causes of the problem and to find solutions.

• The maintenance task was selected correctly, but the description of how the task should be

executed needs to be improved. There should be enough space on the work orders fortechnicians to give remarks for improvement if, for example, some parts or tools are missing.

It is important that all the points above are embedded in the processes, procedures and communication flows

of the organisation to ensure that it continues to receive sufficient attention.



CONCLUSION

Preventive maintenance has a great impact on performance, risk, costs and energy consumption of assets. It

should be customised for each asset, because every asset works under different circumstances and has

another criticality. This means that two identical components may have different maintenance strategies. RCM

is a good and generally accepted methodology to select preventive maintenance tasks. However, it is very timeconsuming. If assets are less critical, Industrial RCM or PM Set Up may be good alternatives.

Simply replacing or restoring components after fixed intervals is called predetermined maintenance. This is

often not a good strategy, because only some of all failure modes are time related. The others do not have a

rising probability with rising component age. In these cases condition monitoring or function tests may provide

a good solution.

How the optimal interval for maintenance should be determined depends on the type of prevention strategy.

Developing Maintenance Plans v1

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