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Development of Quantitative ReliabilityCentered Maintenance Method

April 　 27-28,1999

ｂｙShinya Kamata (Mitsubishi Heavy Industries, Ltd)

　　　　 Hiroshi Sakuda (Kansai Electric Power Co., Inc)

at 5TH KOREA-JAPAN PSA WORKSHOP, SEOUL 　

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Contents

1. Overview of RCM

2. RCM evaluation procedure

3. Approaches with consideration of aging effects

4. Maintenance selection logic

5. Trial evaluation

6. Conclusion

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1. Overview of RCM

　

• Increase of plant operation time

• Increase of PM cost• Lack of maintenance staffs 　

Failureexperiences

Sys. Reliability Analysis

PSAinformation

RCM

Optimizationof PM

Expertjudgment

PM : Preventive Maintenance

RCM : Reliability Centered Maintenance

Background

Reduction of PM cost

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1. Overview of RCM

Basic concept

Optimize maintenance task selection based on system reliability and plant safety

Reflect the aging effects and failure experiences of components

Reduce maintenance tasks and cost

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　2. RCM evaluation procedure

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Selection ofSystem

Evaluation of Sys. Reliability PSA

ComponentImportance

Selection of PM strategy

MaintenanceFailure

Experiences

Re-evaluation of Sys. Reliability

Alteration of PM strategy

Alteration of PM strategy

NoNew

Strategy 　 isAcceptedYes

TargetSatisfied?

TargetSatisfied?No Yes

CostEvaluation

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2. RCM evaluation procedure

The difference between EPRI RCM and Quantitative RCM

　 　 　 method items EPRI RCM Quantitative RCM

Reliabilityanalysis FMEA (FTA)

　 FTA, F-V importance,　 PSA information

Optimizationof PM interval Expert judgment

Evaluation of Sys. unavailability change based on alteration of PM interval

Reflectionof failure

experiences

Expert judgmentbased on critical

failures experiences

　 　 Aging Model based on　 　 Weibull function

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3. Approaches with consideration of aging effects

　

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Survey of aging failureex.,erosion,corrosion,leak,crack…..

FailureDB

　　　　　　　　　　　　　　　　

Occurrence history ofcomponent failures

Fitting curve by Weibull functionWeibull chart

Cumulativefailurefrequency

　　　　1　 lnln　　　 R(t)

F(t)

time(lnt) time

　　　　　　　 tm

F(t)=1-exp -　　　　　　　 t0

F(t) : Failure distribution　　 functionm : shape parametert0 : scale parameter

･････

･ ･

･････

･

Aging model

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3. Approaches with consideration of aging effects 　

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Establishment ofF(t) in a failure mode　　　　　　　　 tm

F(t)=1-exp - 　　　　　　　　　　 t0

λ0→Q0 　 λN→QN

ΔQ=QN-Q0

ΔQ:Sys. unavailability　　 changeΔQ<εor ΔQ>ε

λ(T)=F(t)/ 　 (1-F(t))dt a=λ(TN)/ λ(T0)λN=aλ0(failure rate for new　　　　　 interval)

λ(t) 　　　　　　 F(t)λ(T)=　　　　　　 (1-F(t))dt

T0 TN time

Q : Sys. unavailabilityε : permitted value of ΔQ

λ0 : Basic failure rate T : Replacement interval

Failure rate model

T∫ 0

T∫ 0

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4. Maintenance selection logic

Rank C

CD

Rank A,B CD ? TD ?

Rank DRe-evaluation

of Q

Survey ofinterval

extension

Survey forrepeal of PM

ΔQ<ε keepinginterval

･ New interval ･ Repeal of PM

･ Facilities 　 improvement ･ FFT

No No

Yes Yes

No

Yes

A ～ D component importance　　　 rank

CD : Condition Directed PM TD : Time Directed PMFFT : Failure Finding Task

Logic tree analysis

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Example of RCM Results for PWR plant

Evaluate the effect of the alteration of the replacement　　 interval on system reliability in Residual Heat

Removal　　 system (main 12 components)

　　　　 case1 ： RHR pump (2years 5years)　　　　　　　　　 MOV (10years 15years),AOV(4years

6years)　　　　 case2 ： RHR pump (2years 5years)　　　　　　　　　 MOV (10years 20years),AOV(4years

8years)

　　　　　　　

5.Trial evaluation

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• Sys. Reliability : Not meaningful change• Cost reduction : Effective 　　　　　　　　　　

Results

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5. Trial evaluation

　

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• Visual information of ΔQ and ΔC • Survey for several PM programs• Ground for PM mitigation and cost optimization• Reduction of PM management

ΔQ : Sys. Unavailability changeΔC : Cost change ε 　 : Permitted valve of ΔQ

• Advantages of RCM-proto type system

ΔQ(%)

ε

0.0

-3.00.0 ΔC(%)

3.0

-50.0 50.0

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5. Trial evaluation

　 Output image for Logic Ｔｒｅｅ Analysis

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5. Trial evaluation

Output image for the relation betweenΔQ and ΔC

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6. Conclusion

1. Development of quantitative RCM method　・ Approaches with consideration of aging effects　・ RCM procedure based on Sys.reliability and pl

ant　　 safety　・ Trial application of the method to PM programs 2. Future subjects　・ Development of component failure DB　・ Combination with deterministic information (ex, service life,and operation environment of the component)

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