MAINTENANCE MANAGEMENTIM 503

Lecture 14: Reliability Centered M i (RCM)Maintenance (RCM)

D M h d F h dDr Muhammad Fahad

Associate Professor/Director Product Development Centre

Dept of Industrial & ManufacturingDept of Industrial & Manufacturing

NED University of Engineering & Technology

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Maintenance: Evolution

Third GenerationProfit Contributor

Second Generation

Higher plant availability and reliability

Greater safety Better product qualityp

m

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Necessary Evil

Technical Matter

First Generation Fix it when it broke

Higher plant availability Longer equipment life Lower costs

Better product quality No damage to the

environment Greater cost effectiveness

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M

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ecessa y

1940 1950 1960 1970 1980 1990 2000

1st Generation Covers period up to

2nd Generation Mechanization increased

3rd Generation RCM Covers period up to

world war II Low level

mechanization Equipment simple &

d i d

Mechanization increased rapidly

PM techniques became popular

Equipment overhaul done t fi d i t l

RCM Higher demand on plant

availability Greater emphasis and

laws on health, safety & i t lover-designed

Low level technical skill required

at fixed interval Cost of maintenance

increased

environmental protection

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Reliability Centered Maintenance

Definition

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Definition Reliability Centered Maintenance (RCM) is a systematic

process used to determine what has to be accomplished toensure that any physical facility is able to continuously meet itsdesigned functions in its current operating context.

RCM l d t i t th t f ti RCM leads to a maintenance program that focuses preventivemaintenance (PM) on specific failure modes likely to occur.

RCM has been so named to emphasize the role that reliability RCM has been so named to emphasize the role that reliabilitytheory and practice plays in properly focusing (centering)preventive maintenance activities on the retention of

i i h d i li biliequipments inherent design reliability.

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Reliability Centered Maintenance

Goals

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Goals To develop design-associated priorities that can facilitate PM.

To gather information useful for improving the design of items To gather information useful for improving the design of items.

To develop PM-related tasks that can reinstate reliability and safety to their inherent levels in the event of equipment or safety to their inherent levels in the event of equipment or system deterioration.

To achieve the above goals when the total cost is minimal To achieve the above goals when the total cost is minimal.

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Reliability Centered Maintenance

Principals

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Principals RCM is system/equipment focused.

RCM is reliability centered RCM is reliability-centered.

Safety and economics drive RCM.

RCM is function-oriented.

Design limitations are acknowledged by RCM.g g y

An unsatisfactory condition is defined as a failure by RCM.

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Reliability Centered Maintenance

Questions

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Questions Any RCM process should ensure that all of the following

questions are answered effectively as per their sequence: What are the functions and associated expected levels of the

facility performance in its current operating context? How might it fail to meet its assigned functions? How might it fail to meet its assigned functions? What are the reasons for each functional failure or failure mode? What are the effects of each failure? How does each failure matter? What remedial measures should be taken to prevent or predict

each failure?each failure? What measures should be taken in the event of not finding a

suitable proactive task?

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Reliability Centered Maintenance

Steps

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p The basic RCM process consists of the following steps:

Identify important items with respect to maintenancey p p

Obtain appropriate failure data

D l f lt t l i d t Develop fault tree analysis data

Apply decision logic to critical failure modes

Classify maintenance requirements

Implement RCM decisionsp

Apply sustaining-engineering on the basis of field experience

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Reliability Centered Maintenance

Operation Types

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Operation Types

Corrective Maintenance

Preventive Maintenance

RCMRCM Components

PredictiveProactive Predictive Inspection /

Testing

Proactive Maintenance

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Reliability Centered Maintenance

Operation Types

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Operation TypesSpecifications for

New/Rebuilt Equipment

Root Cause Failure Analysis

Reliability Engineering

Equipment

Proactive MaintenanceProactive Maintenance methods to extend

equipment lifeFailed Item AnalysisAge Exploration

Rebuild Verification/

Recurrence Control

Precision Reb ild andVerification/

CertificationControl Rebuild and

Installation

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis

Failure mode and effect analysis (FMEA) is anFailure mode and effect analysis (FMEA) is an

engineering technique used to define, identify, and

li i t k d/ t ti l bleliminate known and/or potential problems, errors,

and so on from the system, design, process, and/or

service before they reach the customer.

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis

FMEA is a systemic methodology intended to

Identify and recognize potential failures including theircauses and effects

E l t d i iti id tifi d f il d i Evaluate and prioritize identified failure modes sincefailures are not created equal

Identify and suggest actions that can eliminate or reduce the Identify and suggest actions that can eliminate or reduce thechance of the potential failures from occurring

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis Ideally, FMEAs are conducted in the product design or process

development stages.

However, conducting them on existing products and processesmay also yield benefits such as in RCM to develop an effectivepreventive maintenance program.

Identifying known and potential failure modes is an important task in FMEA.

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis Using data and knowledge of the process or product, each

potential failure mode and effect is rated in each of the following three factors:

Severity: the consequence of the failure when it happens

Occurrence: the probability or frequency of the failure occurring

Detection: the probability of the failure being detected before the impact of the effect is realizedbefore the impact of the effect is realized

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis Then these three factors are combined in one number called

the risk priority number (RPN) to reflect the priority of the failure modes identified.

Failure Mode

Effects(Severity)

Causes(Occurrence)

Control(Detection)

Priority RPN =SxOxD

S O DS O D

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis Process

Select a high-risk process.

Review the process.

Brainstorm potential failure modes.

Identify the root causes of failure modes. Identify the root causes of failure modes.

List potential effects of each failure mode.

Assign severity, occurrence, and detection ratings for each effect.

C l l h i k i i b (RPN) f h ff Calculate the risk priority number (RPN) for each effect.

Prioritize the failure modes for action using RPN.

Take action to eliminate or reduce the high-risk failure modes.

Calculate the Resulting RPN as the failure modes are reduced or eliminated as a mean of monitoring the redesigned improved product or process.

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis Standards MIL-STD-1629A (1984) BS 5760 (1991) BS EN 60812 (IEC 60812) 2006

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis Severity Rating Scale

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis Occurrence Rating Scale

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis Detection Rating Scale

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis Detection Rating Scale

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis Severity Rating Scale

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis Occurrence Rating Scale

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis Deficiencies of RPN Gaps in the ranges: 88% of the range is empty, only 120 of 1000 numbers

are generated

Duplicate RPNs: for several combinations where different factors lead to thesame RPNN

Sensitivity to small changes: a small change in one factor has a much largereffect when the other factors are larger than when they are small (example:9x9x3 = 243 and 9x9x4 =324 versus 3x4x3 = 36 and 3x4x4=48)9x9x3 = 243, and 9x9x4 =324 versus 3x4x3 = 36 and 3x4x4=48)

Inadequate scaling: the ratios on occurrence table are not proportional orlinear; e.g. the ratio can be 2, 2.5 or 5 between the two consecutive ratings

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Reliability Centered Maintenance

Failure Mode and Effect Analysis

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Failure Mode and Effect Analysis Deficiencies of RPN Inadequate scale of RPN. The differences in RPN number might appear negligible while in fact significant.

An example would be: the values: S = 6, O = 4, D = 2, would produce an RPN = 48,while S = 6, O = 5, and D = 2 would produce RPN = 60.

The second RPN is not twice the first number, while in fact O = 5 is twice the probabilityof occurrence with O = 4.

Therefore the RPN numbers should not be compared linearly.

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Reliability Centered Maintenance

Measurement Indicators

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Measurement Indicators Equipment Availability

Hrp

eaTHHEA =

capacityat run toavailable isequipment ofunit each hours ofNumber Hea =period reporting theduring hours ofnumber Total THrp =

Th b h k fi f hi i i 96%The benchmark figure for this metric is 96%

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Reliability Centered Maintenance

Measurement Indicators

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Measurement Indicators Emergency Percentage Index

jH

w

ej

THH

EP =j bk dhfbT lH jobsemergency on workedhoursofnumber Total Hej =

workedhours ofnumber Total THw =

The benchmark figure for this metric is 10% or Less

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Reliability Centered Maintenance

Measurement Indicators

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Measurement Indicators Maintenance Overtime Percentage Index

TMOHTRMHTMOHPmo =

periodduringhoursovertimeemaintenancofnumber Total TMOH =periodduringhoursemaintenancregular ofnumber Total TRMH =

Th b h k fi f hi i i 5% LThe benchmark figure for this metric is 5% or Less

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Reliability Centered Maintenance

Measurement Indicators

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Measurement Indicators Preventive Maintenance Index

MHPPMHPPMHR

MHPPPpm +=workPM ofhoursman TotalMHPP =

workemaintenancreactive ofhoursman TotalMHR =Th b h k fi f hi i i 70%The benchmark figure for this metric is 70%

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Reliability Centered Maintenance

Measurement Indicators

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Measurement Indicators Reactive Maintenance Index

MHRMHPPMHR

MHRPrm +=workPM ofhoursman TotalMHPP =

workemaintenancreactive ofhoursman TotalMHR =Th b h k fi f hi i i 30%The benchmark figure for this metric is 30%

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Reliability Centered Maintenance

Benefits

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Benefits

Improvement in product quality

Improvement in useful life of products

Improvement in safety/environmental protection

Development of a maintenance database

I t i i t t ff ti Improvement in maintenance cost effectiveness

Higher plant availability and reliability

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Reliability Centered Maintenance

Problems

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Problems

The application was superfluous or hurried

Computers were used to drive the process

Only one individual was assigned to apply RCM

Only maintenance department on its own applied RCM

M f t / d k d t l RCM th i Manufacturers/vendors were asked to apply RCM on their own.