Reliability-Centered Maintenance. An introduction to by JBM

7/26/2011

1

Reliability-Centred Maintenance

“An Introduction to”

Jean-Baptiste MARTIN

Risk, Safety & Reliability Consultant

Content

JBM 2

1. RCM Introduction

2. Maintenance Strategy Review

3. Introduction to Functional Analysis

4. Introduction to FMECA

5. Function selection

6. RCM Tasks evaluation

7. RCM Tasks selection

8. RCM Implementation

9. Feedback

RCM Introduction

Logical and systematic approach to define a routine

maintenance program composed of cost-effective tasks

that preserve important functions

Process to establish the safe minimum levels of

maintenance

Process to determine the maintenance requirements of

any physical asset in its present operating context

JBM 3

“Why” maintenance should be conducted on equipment

instead of “What” maintenance tasks could be done

RCM Introduction

Started in 1960’s – Federal Aviation Administration

(USA) concerned with high crash rate

1978: “Reliability-Centred Maintenance” Report by

United Airlines Engineers (for US Defence)

Basis of Maintenance strategy

Promulgated in 1980s

Used these days (slightly modified) by commercial

aviation industry

4JBM

7/26/2011

2

RCM Introduction

First RCM approach

Frequent overhaul and parts replacement

Costly and did not improved reliability

Why Aviation Industry ?

The “Fix it when it breaks” approach was obviously not

acceptable for airplanes !

Nowadays derivatives of RCM implemented in many

other industries

JBM 5

RCM Introduction

RCM strength

HSE levels are met or exceeded

Increase cost effectiveness

Maximize equipment availability

Reduce repairing time

Set up a new data base

6JBM

Maintenance Cost

Availability

RCM Introduction

RCM weakness

Requires significant effort and focus (labor intensive)

Needs some specific data to be available or assumed

(MTBF etc.)

Yes / No answers are required – but everything is not

always black / white

Where to stop ? Level of details should be defined at the

beginning

7JBM

Maintenance Strategy Review

8JBM

Significant functions selection

FMECA

Functional analysis

RCM task evaluation

RCM task selection

RCM implementation

F

e

e

d

b

a

c

k

7/26/2011

3


On failure

maintenance

Downtime not an

issue

JBM 9

Increased demand of goods

(World war II)

Increased automation

Higher maintenance cost

Scheduled Overhaul

Planning Systems

Computerisation

Stringent economical

environment

Need to reduce operating

& maintenance costs

6 , TPM, RBI, RCM

1930’s 1950’s – 1980’s 2000’s


Different maintenance strategies

On failure: “We need to fix it quickly !”

“Feeling”: “Why not maintaining it tomorrow before

lunch?”

Based on experience: “If some maintenance is good, then

a lot more must be better !” or “We have always done it

that way!”

10JBM

Maintenance is a process NOT an event

Maintenance Strategies Review

Need for MSR

Safety, cost-effective & technical viability

Produce an optimised maintenance programme

Document all information used in making decisions

Identifies important monitoring parameters

Allows for feedback & continuous improvement

Dangers of MSR

Fall into the technology trap

Use inappropriate technology

Fail to set objectives/success criteria

Fail to address cultural issues

Fail to gain management support

JBM 11


12JBM

Functional analysis

7/26/2011

4

Introduction to Functional Analysis

13JBM

Integrated Definition (IDEF0)

Input Output

Mechanism

Control

Function


14JBM


Function: an activity, process, or transformation identified by

a verb or verb phrase that describes what must be

accomplished.

Input

Control

Function

Input: data or consumables that trigger

the activity

Control: commands which guide or

influence the activity


15JBM


Mechanism: means, tools or people used to accomplish

the activity (allocation of activities)

Outputs: data or products that are produced by the

activity

Output

Mechanism

Function


16JBM

7/26/2011

5


17JBM

FMECA

Introduction to FMECA

Failure Modes, Effects and Criticality Analysis

Extension of FMEA

Identification of all possible failures within a system, the

possible effects of these failures and any potential

consequences

Ranking of these potential problems in terms of

“Criticality”

JBM 18


JBM 19

What is the

function ?

What is the function?

Two categories of functions

Primary Functions: usually fairly easy to recognise. Theyare the main reasons why assets have been acquired

Secondary Functions: less obvious than the primary, eventhough their failure can sometimes have more seriousconsequences (Environmental, Safety, Control / Comfort,Appearance, Protection, Economy etc.)

Function description: “To be capable of”, “To provide”

Example: Pump

Primary function: To pump oil from well to refinery

Secondary function: To contain the fluid

20JBM

7/26/2011

6


Operational mode – Example is Airplane

Taxi

Take-off

Climb

Cruise

Descent

Approach

Flare-out

Roll

JBM 21


Performance standards

Performance standards specify the boundary between

satisfactory performance and failure

Performance standards describe the minimum acceptable

performance requirement associated with functions rather

than the item design capability

Some performance standards can be drawn directly from

the operating context

22JBM


“What are the items supposed to do …” Define The Primary Function “What It Is Required To Do”

- Not The Design

Define The Performance Standards “Quantitative ratherthan Qualitative”

Define The Tolerances On The Performance Standard“Minimum, Maximum, Nominal Etc.”

JBM 23


JBM 24

In what

way can

it fails?

http://www1.free-clipart.net/cgi-bin/clipart/directory.cgi?action=view&link=clipart/Business/General&image=Profit.jpg&img=30

7/26/2011

7

In what way can it fails?

Functional Failure: inability of an asset to fulfil afunction with an acceptable level of performance forthe user

Covers Complete loss of function

Situations where the asset still functions but performsoutside acceptable limits

Described as “Fails to be capable of …”

JBM 25

In what way can it fails?

• Most common

When capability drops below desired performance after the asset commissioned

When desired user performance raises above capability after the asset commissioned

When the asset is not capable of doing what is wanted from the beginning

JBM 26


JBM 27

What are the failure

modes?

What’s the failure modes ?

A failure mode is any event which could cause afunctional failure - past, future & currently prevented

All failure modes which are reasonably likely to causea functional failure should be identified

The root cause of failure modes should be identified

Black boxing is acceptable under certaincircumstances

JBM 28

7/26/2011

8

What’s the failure modes ?

Failure detection: the means by which functionalfailures become evident and how their failure Evident: lights, buzzers, smoke etc.

Hidden: detectable by maintenance only

Example: the failure mode “fail to start” of a pump withoperational mode “standby” is an example of a hiddenfailure.

JBM 29


JBM 30

What

are the

effects

of

failure?

What the effects of failure?

Effect identification should describe The effects on safety or the environment

The effect on production/operation (economic or servicelevel)

Potential secondary damage to other equipment

Downtime or repair actions with estimated time (loss offunction to the restoration of function)

JBM 31

FMECA

JBM 32

Does it matter?

7/26/2011

9

Does it matter?

Severity categories (examples) Hidden or evident under normal conditions

Safety or environmental

Operational (economic or service level)

Non-operational

Etc.

JBM 33

Does it matter?

Ranking of Risk Priority Number (RPN) O = the rank of the occurrence of the failure mode

S = the rank of the severity of the failure mode

D = the rank of the likelihood the failure will be detectedbefore the system reaches the end-user/customer

The smaller the RPN the better – and – the larger theworse

RPN = S x O x D

JBM 34

Does it matter?

Severity Ranking Example

JBM 35

Does it matter?

Occurrence Ranking Example

JBM 36

7/26/2011

10

Does it matter?

Detection Ranking Example

JBM 37


38JBM

Significant functions selection

Functions Selection

Function selection Significant Function (SF) – A function whose failure will

result in adverse consequences with respect to safety, theenvironment, operations, or economics

Non-significant Function (NSF) – A function whose failurewill have no adverse safety, environmental, operational,or economic consequences

SF Selection Logic diagram

Apply to every function that has the potential of beingsignificant

First question in the logic flow that evokes a “YES”answer dictates that the function is significant

39JBM

Functions Selection

JBM 40

7/26/2011

11


41JBM

RCM task evaluation

RCM decision logic

JBM 42

√ = Optional

M = Mandatory

RCM task evaluation

Task evaluation: process used to determine which ofseveral options is best suited to

Prevent a failure mode from occurring

Reduce the consequence of its failure to a level that is

acceptable

Each option has unique criteria that determine if the task isappropriate for the failure mode

43JBM

RCM task evaluation - OC

On Condition task (predictive)

To detect potential failure

And then take action to prevent the functional failure or to

avoid the consequences (outside of RCM scope)

44JBM

7/26/2011

12

RCM task evaluation - OC

Development of OC task

Do we have any prior warning of the failure?

What is this warning?

How long will it take to fail from the prior warning?

Is It consistent in time?

Will it give us enough time to respond appropriately?

45JBM

If YES to ALL: OC is technically feasible

RCM task evaluation - SR

Scheduled Replacement

Removes or restores the item at a predetermined age

regardless of whether or not failure is impending

SR development

Do we have a reliable age projection (Wear Out)?

Will most items reach this age?

Can a task interval be developed that reduces the

probability of failure to an acceptable level?

46JBM

If YES to ALL: SR is technically feasible

RCM task evaluation - SR

Wear out

Increase in the conditional probability of failure with age

Life limit

Safe Life Limit (SLL)

Economic Life Limit (ELL)

47JBM

SLLELL

RCM task evaluation - FF

Failure Finding task

Objective: prevent or at least reduce the probability of the

associated multiple failure

Check a hidden function at regular intervals to find out

whether it has failed

Multiple failure is when the protected function fails and

the protective device is also in a failed state

FF task should avoid dismantling protective devices orotherwise disturbing them

48JBM

7/26/2011

13

RCM task evaluation - FF

Failure Finding Interval

MTBF of protective device

Desired availability of the device

49JBM

Availability (%) 99.99 99.95 99.90 99.50 99.00 98.00 95.00

Interval (% of

MTBF)

0.02 0.10 0.20 1 2 4 10

RCM task evaluation - OFM

On Failure Maintenance task valid only if:

A suitable proactive or failure-finding task cannot be

found for a hidden failure, and the associated multiple

failure does not have safety or environmental

consequences

A cost-effective proactive task cannot be found for evident

failures which have operational or non-operational

consequences

50JBM

RCM task evaluation - RD

Re-Design definition

A change in the physical configuration of an asset or

system

A change to a process or operating procedure

A change to the capability of a person, usually by training

Re-Design if only

The multiple failure could affect safety or the environment

If the multiple failure does not affect safety or theenvironment but RD economically justified

51JBM


52JBM

RCM task selection

7/26/2011

14

RCM Task selection

Three types of outputs depending on the option

Perform PM tasks (OC, FF, SR)

Allow the failure mode to occur, then take correctiveaction (OFM)

Take some other action, such as redesigning the item(RD)

BEST solution: comparing each of the available options

with the others

How to define which one is the BEST ?

JBM 53

RCM Task selection

Cost

Cost of options are typically compared by normalizingthem to a common unit such as cost per unit operatinghour, cost per hour, or cost per cycle

Operational consequences

If the operational impact is considered more important,the more expensive task should be chosen

JBM 54


55JBM

RCM implementation

RCM implementation

Build RCM Team RCM Facilitator

Production

Maintainers

HSE

Ensure RCM methodology is followed

Keep the review at the right level

Document all the RCM information

Chair and manage the meetings / workshops (ensuretime aspects and involvement of all members etc.)

JBM 56

7/26/2011

15

RCM implementation

Make documents available

Plant overall plot plan ; layouts

Process flow Diagram

Operating & Maintenance manuals

Existing maintenance strategy

Maintenance history record

Define context : objectives Process / product affected

Applicable HSE regulations

Process availability requirements

Business risk & reliability

DownTime economics

JBM 57

RCM implementation

Align tasks for effective resources and production use

Schedule routine maintenance

Incorporate into SAP

58JBM

RCM implementation

Alternative to detailed RCM (medium criticality

functions): Generic RCM

Define equipment type (pump, filter etc.)

Define failure modes from previous experience

Define failure consequences

Define failure characteristics

Determine task or strategy most applicable

Apply task routines to medium criticality equipment

generically

Ensure consequences are still applicable

59JBM

RCM implementation

Alternative to detailed RCM (Low criticality functions):MS Review

Analyse vendors recommendations

Define failure modes from previous experience

Define failure consequences

Compare existing vendor tasks with failure modes

Determine if task is

(R) retained

(U) updated

(C) changed or

(D) deleted

60JBM

7/26/2011

16


61JBM

Feedback

Feedback

RCM analysis will never be perfect because

Numerous decisions have to be made on the basis of

incomplete or non-existent hard data

The assets, and the processes of which they form part,

will be subject to continuous change

The perspectives, attitudes and priorities of people will

be changing continuously

Technological advancements may affect / invalidate

analysis decisions

62JBM

Feedback

The RCM should be periodically reviewed

Collect data on the effectiveness of the maintenance

program through in-service equipment performance

To investigate and correct maintenance related problems

To identify hardware design and manufacturing

deficiencies

To document specific resource savings that are achieved

through the RCM process

63JBM

Compare cost, manpower, and readiness levels achieved by

previous maintenance approach to the revised RCM strategy

Conclusion

RCM

Is an effective mean of improving production availability

and reducing maintenance cost

But has some weaknesses …

A strong RCM team is needed

Management willingness and support is required

Close cooperation between maintenance and production

Basics equipment information required as a starting point

JBM 64

Let’s implement RCM on a pilot system !

Reliability-Centered Maintenance. An introduction to by JBM

Documents

Transcript of Reliability-Centered Maintenance. An introduction to by JBM