M21US 2008 Summary

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Copyright Ivara Corporation. All rights res

Reliability-centered Maintenance

RCM2

Introductory Course

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Reliabil ity-centered Maintenance

RCM2

The Business Case for Reliability

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The Changing World of Maintenance

Growing expectations

Changing understanding

New maintenance techniques

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Growing Expectations of Maintenance

1st Generation

Fix it when it breaks

2nd GenerationHigher availability

Lower costs

Longer asset life

3rd Generation

Higher availability andreliability

Greater cost-effectiveness

Greater safety

Better product quality

No damage to theenvironment

Longer asset life

1930 1940 1950 1960 1970 1980 1990 2000 ..

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Changing

understanding

Condition monitoring

Predictive technologies

Reliability systems

Design for reliability andmaintainability

Risk based strategies

Consequence mitigation

Participation/flexibility/multi skill/teamwork

Higher availability and

reliability Greater cost-effectiveness

Greater safety

Better product quality

No damage to the

environment Longer asset life

Changing World: 3rd Generation and RCM2

Growing

expectations

New maintenance

techniques

WithRCM2

We discussed the changing world of maintenance in terms of:

How do we respond to the changing world of maintenance?

RCM2:

Helps determine the maintenance requirements of each physical asset in its operating

context in order to meet the growing organizational and social expectations Is based on our changing understanding of failure

Encourages the use of new reliability techniques in the development of reliability and

asset care strategies

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Reliabil ity-centered Maintenance

RCM2

The RCM2 Process

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The RCM2 Process: Definition of Maintain

We have been discussing the changing world ofmaintenance. What is the definition of the word maintain?

Oxford Dictionary:

to cause or enable to continue

Webster Dictionary:

to keep in an existing state

to cause or enable (what?) to continue (to dowhat?)

to cause any physical asset to continue to dowhatever

its users want it to do

and RCM2 is:

A process used to determine what must be done toensure that any physical asset continues to do whatits users want it to do in i ts present operatingcontext

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The RCM2 Process: Can and Want

Maintenance must causethe asset to continue

to function in this zone

Maintenance cannot raisethe performance of the assetbeyond its built-in capability

(or inherent reliability)

Desired performance(what the user wants it to do)

Built-in capability(what the asset can do)

If we are to apply a processused to determine what must be

done to ensure that a physical

asset continues to do whatever

its users want it to do in itspresent operating context we

need to:

Know exactly what its users

want it to do

Be certain that the asset is

capable of doing what its

users want from the start

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Recording Failed States

The failed states that apply to each function are recorded in the secondcolumn of the RCM2 Information Worksheet

1 To enable aperson to chop

through an 8inch pine log in a

maximum of 8

strokes

FAILURE EFFECTFAILURE MODEFUNCTIONAL

FAILURE

FUNCTION

Unable to chop

wood at all

Takes more

than 8 strokes

to chop

through an 8

inch pine log

A

B

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How Maintenance Works

We have seen that:

The goal of maintenance is to cause systems to continue todo what their users want them to do

So how does maintenance achieve its objective?

By focusing on what prevents the equipment from doingwhat the users want it to do

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How Maintenance Works

How do we deal with equipment that does not do what theusers want it to do?

This is known as thecause of failureor the failure mode

It depends on:

The component or sub-system that causes the system

to fail

The way in which the component or sub-system fails

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Recording Failure Modes

Defining failure modes (causes) is the third step of the RCM process.Failure Modes are recorded on the RCM2 Information Worksheet

1 To enable a

person to chop

through an 8inch pine log in a

maximum of 8

strokes

FAILURE EFFECTFAILURE MODEFUNCTIONAL

FAILURE

FUNCTION

Unable to

chop wood atall

Takes more

than 8 strokesto chop

through an 8

inch pine log

A

B

Axe head wedge

loosened from

repeated impact

Handle broken from

fatigue

Blade worn

Blade corroded

Blade comes in

contact with a rock

1

2

1

2

3

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Identifying Failure Modes

How do we decide what failure modes (causes) to include?

This depends on both:

How likely the failure mode is to occur

How and to what extent the failure mode matters if itdoes occur

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Failure Effects

Before we can decide with confidence how and to whatextent each failure mode matters we must understandwhat

happenswhen it occurs

What happens when failure modes occur is known as

failure effects

Defining the effects of these failures is the fourth stepof the RCM2 process

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Failure Effects

1 To enable a personto chop through an

8 inch pine log in a

maximum of 8

strokes

FAILURE EFFECTFAILURE MODEFUNCTIONALFAILURE

FUNCTION

Unable to chop

wood at all

Takes more than

8 strokes to

chop through an

8 inch pine log

A

B

The wedge loosens with repeated impact,

which loosens the head. Eventually the head

falls off. If the head falls off while the axe is

moving it could hit someone. Without the head

the axe will be unable to chop wood. Time to

reassemble the axe: 1 hour.

With a broken handle the axe cannot be used

to chop wood. If the axe is used with a

damaged handle the handle may fall apart and

the head fly off possibly hitting someone.

Finding and fitting a new handle takes up to 4

hours.

With usage the blade wears, loses its

sharpness and it progressively takes more and

more strokes to cut through an 8 inch pine log.

Time to sharpen the blade: 1 hour.

Axe head wedge

loosened from repeated

impact

Handle broken from

fatigue

Blade worn

Blade corroded

1

2

1

2

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Failure Consequences

The term failure consequences is used to describe how andto what extent a failure mode matters

Assessing the consequences of these failures is the fifthstepof the RCM2 process

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Failure Consequences

Failure mode 1 is a safety

hazard as the axe head

could injure someone

Failure mode 2 affects

operations (causes

downtime) but is unlikely

to hurt anyone

The wedge loosens w ith repeated impact,

which loosens the head. Eventually the head

falls off. If the head falls off while the axe is

moving it could hit someone. Without the head

the axe will be unable to chop wood . Time to

reassemble the axe: 1 hour.

With usage the blade wears, loses its

sharpness and it progressively takes more and

more strokes to cut through an 8 inch pine log.

Time to sharpen the blade: 1 hour.

Axe head wedge

loosened from

repeated impact

Blade worn

1

2

FAILURE EFFECTFAILURE MODE

Which of these two failure modes is more serious?

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Failure Consequences: Categories

There are four categories of failure consequences:1. Hidden Failures

Failures occur in such a way that in normal conditions no-one knows that theyare in a failed state

2. Safety or Environmental Consequences

Someone could get injured or killed, or an environmental standard or regulationcould be breached

3. Operational consequences Affect output, product quality, customer service and/or operating costs in

addition to the costs of repair

4. Non-operational consequences

Repair only

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Failure Management Strategies

Once we have: Determined what failure modes (causes) are reasonably

likely to prevent the equipment from doing what the users

want it to do

Identified the effect of each failure mode

Assessed the consequences of each failure mode

We are in a position to identify the failure management

strategy that deals most effectively with the consequences

of each cause of failure (failure mode)

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These include: Predictive or condition-based maintenance

Preventive maintenance - fixed interval restorations

Preventive maintenance - fixed interval replacements Failure finding tasks

No scheduled maintenance

One time changes to the physical configuration of the system orthe way it is operated and maintained

RCM2 recognizes and can define ALL of these failure

management strategies

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The RCM2 Decision Diagram provides a rigorous process for deciding:

Hidden FailureConsequences

Safety and EnvironmentalConsequences

OperationalConsequences

Non-operationalConsequences

Will the loss of functioncaused by this failure modeonits own become evident to theoperating crew under normal

circumstances?

H Does this failuremode cause a

loss of function orother damage which

could injure or killsomeone?

Does this failuremode cause a loss of

function or other damagewhich could breach anyknown environmental

standard or regulation?

S E Does this failure mode have adirect adverse effect on

operational capability (output,product quality, customer service

or operating costs in addition to

the direct cost of repair)?

O

Is an on-condition task technically feasibleand worth doing?

Is there a clear potential failurecondition? Whatis it? Whatis the

P-F interval? Is the P-F interval long

enoughto be of anyuse? Is itconsistent? Can the taskbe done at

intervals less thanthe P-F interval?

Does this tasksecure theavailabilityneeded to reduce

the probabilityof a multiple

failure to a tolerable level?

H1 Is an on-condition task technically feasibleand worth doing?Is there a clear potential failure

condition? Whatis it? What is the P-

F interval? Is the P-F interval long

enoughto be of anyuse? Is itconsistent? Can the taskbe done at


Does this taskreduce the riskof failure to a tolerable level?

S1 Is an on-condition task technically feasableand worth doing?Is there a clear potential failure

condition? Whatis it? Whatis the

P-F interval? Is the P-F interval longenoughto be of anyuse? Is it

consistent? Can the task be done atintervals less thanthe P-F interval?

Overa period of time, will this

taskcost less thanthe costof

the operational consequencesplus repairof the failures which

itis meant to prevent?

O1 Is an on-condition task technically feasibleand worth doing?Is there a clear potential failure

condition? Whatis it? What is the P-F

interval? Is the P- F interval long

enoughto be of anyuse? Is itconsistent? Can the task be done at


Overa period of time, will costof doingthis taskbe less than

the costof repairing the failures

whichit is meantto prevent?

N1

Is a scheduled restoration task technicallyfeasible and worth doing?

Is there anage atwhich there is a

rapidincrease in the conditional

probabilityof failure? What is it? Domostfailures occurafter this age?

Will the restorationtaskrestore the

original resistance to failure?

Does this tasksecure the

availabilityneeded to reduce

the probabilityof a multiplefailure to a tolerable level?

H2

Is a scheduled discard task technicallyfeasible and worth doing?

Is there anage atwhich there is arapidincrease in the conditionalprobabilityof failure? What is it? Do

mostfailures occurafter this age?

Does this tasksecure theavailabilityneeded to reducethe probabilityof a multiple


H3

Is a scheduled failure-finding tasktechnically feasible and worth doing?

Is itpossible to checkif the itemhas

failed? I s itpractical to do the taskatthe requiredintervals?

Does this tasksecure the

availabilityneeded to reducethe probabilityof a multiple


H4



rapidincrease in the conditional

probabilityof failure? What is it? Doall failures occurafter this age? Will

the restorationtaskrestore the


Does this taskreduce the risk

of failure to a tolerable level?

S2


Is there anage atwhich there is arapidincrease in the conditional

probabilityof failure? What is it? Do

all failures occurafterthis age?

Does this taskreduce the riskof failure to a tolerable level?

S3




mostfailures occurafterthis age?Will the restorationtaskrestore the


Overa period of time, will thistaskcost less thanthe costof

the operational consequences

plus repairof the failures whichitis meant to prevent?

O2





Overa periodof time, will thistaskcost less thanthe costofthe operational consequences

plus repairof the failures which

itis meant to prevent?

O3



rapidincrease in the conditionalprobabilityof failure? What is it? Do

mostfailures occurafterthis age? Will

the restorationtaskrestore the originalresistance to failure?

Overa period of time, will cost

of doingthis taskbe less thanthe costof repairingthe failures


N2





Overa periodof time, will costof doingthis taskbe less than

the costof repairing the failures


N3

Is a combination of the above taskstechnically feasible and worth doing?

S4

Could the multiplefailure affect safety orthe environment?

H5

Do the scheduled restoration task


Do the on-condition task Do the on-condition task Do the on-condition task Do the on-condition task

Do the scheduled restoration task Do the scheduled res toration task Do the scheduled res toration tas k

Do the scheduled discard task Do the scheduled discard task Do the scheduled discard task Do the scheduled discard task

Redesign may be desirable


Redesign may be desirable

Do the scheduled failure-finding task

Redesign is compulsory No scheduled maintenance Redesign may be desirable

Combination of tasks

Redesign is compulsory

The RCM2 DECISION DIAGRAM

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No

Yes No

No

No

No

Yes

Yes

Yes

Yes

No

Yes

Yes Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Yes Yes

Yes

Yes

No No No

No

No

No

No

No

No

No No

No

No

When it is appropriateto apply any particularstrategy ensuring that

it is technically feasibleand worth doing

How often routinetasks should be done

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Recording Decisions

The RCM2 Decision Diagram guides us through a series ofquestions in order to develop a maintenance program. Our

answers are recorded on an RCM2 Decision Worksheet

F F

F

F

M

H S E O 1 2 3 H

4

H

5

S

4

Proposed Task InitialInterval

Can bedone by

1 A 1 Y Y Y Visual inspection of the axe head wedge toensure that it is properly anchored. Fix or

replace as needed.

3 months Operator

1 A 2 Y Y YVisual inspection of the axe handle for cracks.

Replace as needed.

6 months Operator

1 B 1 Y N N Y Y Inspect the axe heads blade to ensure that it issharp. Have the head sharpened as needed.

Monthly Mechanic

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Conclusion: the RCM2 Process

RCM2 is a process used to determine what must be done to ensure thatany physical asset continues to do what its users want it to do in itspresent operating context.

It asks the following questions:

What are its functions (what do its users want it to do)?

In what ways can it fail (functional failures)?

What causes it to fail (failure modes)?

What happens when it fails (failure effects)? Does it matter if it fails (consequences of failure)?

Can anything be done to predict or prevent the failure?

What do we do if we cannot predict or prevent the failure?

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Agenda

It asks the following questions:

What are its functions (what do its users want it to do)?

In what ways can it fail (functional failures)?

What causes it to fail (failure modes)?

What happens when it fails (failure effects)? Does it matter if it fails (consequences of failure)?

Can anything be done to predict or prevent the failure?

Whatdowedo ifwecannotpredictorprevent the failure?

During the remainder of the course we will explore the sevenquestions of RCM2 and apply these to a case study.

M21US 2008 Summary

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