fmea/fmeca considerations - jahcon considerartions.pdf · fmea/fmeca considerations copyright©...

Copyright© 2013 Dr. JA Healy

Publisher

JAHCon Physical Asset Management Pty. Ltd.

FMEA/FMECA Considerations

Dr. JA Healy

If you would like additional

information on the topic covered in this

information sheet please contact JAHCon on the

numbers shown on page 2


Copyright© 2013 Dr. JA Healy Page 1

Contents Contact Information .................................................................................................................. 2

Summary .................................................................................................................................... 3

Scope .......................................................................................................................................... 3

Failure Mode and Effects Analysis ............................................................................................ 4

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

FMEA/FMECA Assessment ....................................................................................................... 5

Pre-Analysis and setup ........................................................................................................... 5

Assignment of Accountabilities and Responsibilities ............................................................ 5

Identify the assets to be assessed ....................................................................................... 6

DFMEA: ................................................................................................................................. 6

PFMEA: .................................................................................................................................. 6

Process boundaries ............................................................................................................. 6

Operating phases ................................................................................................................ 6

Team selection .................................................................................................................... 6

Analysis tool ....................................................................................................................... 7

Asset information requirements ........................................................................................ 7

Prompt tables ..................................................................................................................... 7

Prior to the Workshop ............................................................................................................... 8

During the Workshop ................................................................................................................ 8

Lead in .................................................................................................................................... 8

System Hierarchy Breakdown ................................................................................................ 8

Carrying out the assessment .................................................................................................. 9

Step 1: Select the asset to be assessed. ............................................................................... 9

Step 2: Identify the equipment or sub-component. ........................................................... 9

Step 3: Identify the failure modes and associated information. ........................................ 9

Step 4: Risk Priority Number calculation (FMECA only). ................................................ 11

Step 5: Recommended actions .......................................................................................... 11

Repeat the assessments until complete. .............................................................................. 12

Workshop Windup ............................................................................................................... 12

Follow up actions ..................................................................................................................... 12

Reports ..................................................................................................................................... 12

Report format ....................................................................................................................... 13

Summary reports .............................................................................................................. 13

Detailed reports ................................................................................................................ 13

Reviews .................................................................................................................................... 13



Approvals ................................................................................................................................. 13

Documentation control ............................................................................................................ 13

Abbreviations ........................................................................................................................... 14

Contact Information

Copyright© 2013 Dr. JA Healy

Published by JAHCon Physical Asset Management Pty. Ltd.

P.O. Box 766, Everton Park, Brisbane, Qld. Australia 4053

Phone: +61 7 3855 8964

Web: www.jahcon.com.au

Email: [email protected]

Email: [email protected]

http://www.jahcon.com.au/

mailto:[email protected]



Summary This booklet provides an overview of how to conduct a Failure Mode and Effects Analysis

(FMEA) and a Failure Mode, Effects and Criticality Analysis (FMECA).

In this booklet FMEA will be used to refer to both FMEA and FMECA.

The FMEA analysis should include input from support and site staff under the guidance of a

suitably experienced facilitator.

Scope This booklet covers the steps involved in setting up an FMEA workshop, carrying out the

workshop and reporting the workshop findings.

This booklet does not provide a detailed plan for carrying out actions resulting from the

findings of the FMEA workshop.

FMEA assessments are carried out on all critical assets whenever they are introduced into

the organisation, whenever a Management of Change (MOC) procedure requires a re-

assessment of the asset maintenance requirements or whenever an existing FMEA

assessment has reached its review date.



Failure Mode and Effects Analysis

Introduction

This booklet provides an introduction to the basics of carrying out a Failure Mode and

Effects Analysis (FMEA) and Failure Mode, Effects and Criticality Analysis (FMECA).

FMEA and FMECA are related Reliability techniques used to systematically identify the

failure modes of equipment that have unacceptable consequences and to identify appropriate

maintenance tasks to minimise or manage the risks associated with these failures.

FMEA is used in this booklet to denote both FMEA and FMECA. Where the difference is

significant it will be clarified in the text.

A FMEA can be carried out on its own without the criticality analysis component being

completed while an FMECA must include the components of an FMEA before the criticality

analysis can be performed. The Criticality Analysis can therefore be considered as an

extension of the basic FMEA.

FMEA’s can be applied at different stages of the asset life cycle and the level of detail

included in the analysis will depend upon the availability of data.

Design FMEA’s (DFMEA) are usually carried out during the early stages of the project to determine the risks associated with the proposed equipment. At this stage the equipment class must have been identified but the specific size, make and models may not be known. In this case the FMEA focuses on the functional failures of the proposed assets as failure mode level data is not available.

Process FMEA’s (PFMEA) are carried out on in-service equipment which usually will have some operating history available and some records of failure modes and causes. At this stage of the asset life cycle, the equipment make, model and size is known as are the components and at least some of their failure modes. While the failure mode data may not necessarily be complete, it does provide guidance for the FMEA and therefore the analysis can focus on the failure mode level.

The criticality of an item as listed in the CMMS is usually determined by a separate

procedure and assigned to the item before the FMEA is undertaken. In this way, the most

critical items are identified first and the more stringent analysis afforded by FMEA is only

applied to those items with a known high criticality ranking.

The failure mode level criticality ranking developed during the FMECA is known as a Rank

Priority Number (RPN) and strictly speaking is not a criticality ranking as it includes a

weighting for ‘Detectability’. The product of the ‘Occurrence’ and ‘Severity’ could be used to

represent criticality if no separate criticality ranking is available. The problem with using this

approach to ranking criticality is that the FMECA process would have to be applied to all

equipment in the scope of the project to determine the criticality of the various assets with its

associated high cost and resource requirement.

Techniques for carrying out a Criticality analysis are discussed in a separate paper

available from the JAHCon website.



FMEA/FMECA Assessment FMEA’s are carried out in a structured and systematic manner that maximises the likelihood

that all significant failure modes will be identified and assessed while minimising the

resources and costs required for the analysis.

The process used to carry out an FMEA will vary somewhat between practitioners and

between whatever software tools (if any) are used to support the analysis. This variability

does not represent a problem so long as the methodology used adheres to the underlying

principles set out in the various recognised standards for conducting an FMEA/FMECA. In

fact, some variation in approach helps to develop improvements to the original methodology

outlined in the various standards and helps to keep FMEA’s relevant as industrial

requirements evolve over time.

Broadly speaking FMEA has three stages including:

1. Pre-analysis and setup.

2. Carrying out the workshop.

3. Post workshop reporting and follow-up.

Pre-Analysis and setup

Pre-analysis and setup deals with identification of the assets to be assessed using FMEA,

identifying and assigning the required resources, planning and scheduling the workshop’s

and determining the reporting and follow-up actions required.

The FMEA workshop requires specific asset information and resources to support the

assessments such as experienced personnel, information on operating context, current

operating conditions, known failure history, etc. Any information that can be provided prior

to the workshop will reduce the workshop time required and improve the efficiency of the

workshop.

The pre-analysis process involves several steps which are required to ensure adequate

information is available to support the workshop.

Assignment of Accountabilities and Responsibilities

The manager responsible for carrying out the FMEA workshop should also have

responsibility for the pre-analysis.

The manager will be responsible for the following actions in relation to the pre-analysis:

• Assign a suitable facilitator.

• Authorise time and expenditures for the pre-analysis and the workshop.

• Review the pre-analysis results prior to authorising the workshop to ensure that adequate pre-analysis has been undertaken and that the available information and resources are adequate to support the workshop.



Identify the assets to be assessed

The FMEA workshop should be focused on one or more assets, with a logical association to

others within the scope. The scope of the workshop can be based upon a number of criteria,

with the following being examples:

• Assets from one site.

• Assets common to a process stream.

• Assets of a particular equipment type, class, skid etc.

It is the responsibility of the manager to determine the scope of the workshop and to

communicate the scope to the facilitator.

The facilitator should obtain an up-to-date listing of the asset hierarchy to be assessed in the

workshop and the pre-analysis.

The facilitator should gather the necessary information on all assets within the scope

identified by the manager.

DFMEA:

If the workshop is to be carried out at a pre-project or early project phase, (i.e. a DFMEA)

specific equipment information may not be available and therefore functional failures of the

proposed equipment will have to be assessed rather than specific failure modes. To support a

DFMEA there must be a clear understanding of the equipment ‘classes’ to be used, their

operating requirements and the interaction and dependencies between the individual

equipment and systems.

PFMEA:

If the workshop is to be carried out on existing equipment then some operating and

maintenance experience and history will be available and the PFMEA will focus on the

failure modes of the known equipment parts. To support a PFMEA there must be a list of

equipment, their makes, models and sizes along with information on the components and

parts making up that equipment. A clear understanding of the equipment operating

requirements, interactions and dependencies is also required.

Process boundaries

The facilitator must identify the process boundaries and the effect of any assets outside the

scope that might impact upon the assessment of those assets within the scope.

Where an asset outside the workshop scope directly impacts upon an asset within the scope,

failure of the external asset will be treated as a functional failure and its impact upon the

asset being assessed determined in the normal way (e.g. loss of electrical power supply,

instrument or general air supply, water supply, etc.).

Operating phases

If the plant has more than one operating phase each phase must be identified. The failure

modes significant to each operating phase must be determined and documented.

Team selection

The subject matter experts required for the FMEA workshop may be required to contribute

to the pre-analysis. Their contribution is likely to be limited to providing information to the

facilitator.



Analysis tool

Various proprietary software tools are available to aid in recording the data generated during

the analysis. Whatever tool is chosen it should suit the approach being taken by the team

rather than dictating the approach and it should help streamline the data entry and

reporting.

A spreadsheet based tool is often the most appropriate for use in carrying out the workshop

assessment due to its familiarity to most users and its ease of data manipulation. If a

spreadsheet tool is used it should be set up by the facilitator prior to each workshop.

Spreadsheet set-up involves uploading the equipment list; setting the scoring parameters

and verifying the spreadsheet formula are working correctly.

Asset information requirements

Once the asset hierarchy has been loaded into the tool and any operating constraints

identified, the information required to support the FMEA workshop is collected.

Fill in the relevant data for the following fields:

• System name – the name of the system being assessed.

• Date of the assessment.

• Compiled by (Facilitator) name.

• Attendee list.

• Venue at which the assessment will be carried out.

Additional information requirements can vary depending upon the asset type and the

operating context but typically will include the following:

• Operating constraints.

• Operating history.

• Available operating and maintenance resources.

• Maintenance history and failure reports.

• List of known problem equipment, failure modes and causes.

• Documentation and drawings, P&ID’s etc.

In some instances this information will be provided by the workshop participants during the

workshop.

Prompt tables

Prompt tables for Severity (S), Occurrence (O) and Detection (D) are required for FMECA

workshop assessments and must be available when the workshop begins. Prompt tables are

only required for generating the RPN and therefore apply only to an FMECA assessments.

The ‘Severity’, ‘Occurrence’ and ‘Detection’ tables should be generated and approved before

the workshop and provided as handouts to all participants.

Prompt tables help to ensure a consistent approach is taken to the RPN assessments. A

common set of prompt tables should be used for all FMEA workshops where the RPN

calculation is required.

Copies of the prompt sheets used for the assessment must be included with the worksheets

and with all reports of the assessment.



Prior to the Workshop Attendees should receive a copy of all relevant information prior to the workshop and should

review these documents and make relevant comments prior to the workshop. If prospective

attendees have any questions prior to the workshop they should contact the facilitator for

clarification or assistance.

Typical information provided prior to the workshop will include:

• Workshop date, time and venue.

• List of equipment to be assessed.

• List of the types of information likely to be required at the workshop, including:

o Maintenance history.

o Known failure modes and causes.

o Chronic failure history if any.

o Printout of reactive W/O’s from the CMMS for known problem equipment.

o RCA reports for known problem equipment where available.

o Operating history.

o Operating constraints and limitations.

o Safety and environmental incidents associated with specific equipment.

o Cost issues associate with specific equipment, and the like.

The facilitator should upload the list of equipment to be assessed into the FMEA tool prior to

the workshop. The facilitator must verify the data upload is correct prior to the workshop.

Sometimes FMEA data is available from earlier workshops or other sources that is applicable

to the assets to be assessed. When available, this data should be uploaded to the FMEA tool.

Any initial FMEA data entered prior to the workshop is included to:

• Promote the transfer of knowledge and experience between sites.

• Guide participants when considering Severity (S), Occurrence (O) and Detection (D).

• Reduce the amount of data entry needed during the workshop.

During the Workshop The workshop should be conducted in a professional, timely and organised manner to ensure

the efficient use of resources and to maximise the likelihood that all critical issues are

addressed. The major steps to be followed include:

Lead in

This step mainly deals with organisational issues such as introductions by participants, an

overview of the process to be used, access to facilities, safety talks etc.

System Hierarchy Breakdown

This step deals with identifying the logical boundaries between individual assets and

equipment. The workshop participants are often the best people to identify the natural



boundaries between items that can be difficult to determine by those not familiar with the

layout or operation of the plant.

Carrying out the assessment

The assessment follows the steps shown here and are also displayed in figure 1.

Step 1: Select the asset to be assessed.

• Select the asset from the hierarchy level (e.g. TEG, Boiler, crusher, conveyor, etc.).

• Enter the item identification number as it appears in the CMMS.

• Enter the description of the item as it appears in the CMMS.

Step 2: Identify the equipment or sub-component.

• Select the sub-system or component from the hierarchy level (e.g. Grate drive, motor, pump, fan, etc.).

• Enter the sub-system or component identification number as it appears in the CMMS.

• Enter the sub-system or component description of the item as it appears in the CMMS.

Step 3: Identify the failure modes and associated information.

Failure modes are a description of the way in which an item fails, or is perceived to fail under

specified operating conditions. In practice, a failure or loss of performance can arise in two

ways.

• Item failure - complete loss of the function provided by the item due to wear, corrosion, fracture, buckling etc. leading to a loss of integrity of the component involved.

• Functional failure - partial loss of function where the item can no longer meet the operating requirements even though the item may still be operating and there is no loss of integrity of the component involved.

Once the failure mode has been identified it must be recorded in the FMEA tool.

Failure causes - For each failure mode record the likely cause or causes for the failure

mode occurring. Failure causes are the physical or chemical processes, design weaknesses,

quality defects etc. that lead to the failure mode occurring under operating conditions.

Failure mode causes are important as they influence the type of maintenance or other actions taken to manage or eliminate the failure mode.

Effects – For each failure mode record the effects of the failure at different levels of the

system hierarchy.

1. Local effects – are those effects that manifest themselves as changes in the item or equipment operation or performance as a direct result of the failure mode occurring. E.g. pump bearing seizes due to inadequate lubrication.

2. Next level effects – are those effects that manifest themselves as changes in the machine or system operation or performance as a direct result of the failure mode occurring. E.g. pump trips on overload as a result of the seized bearing.



3. End level effects – are those effects that manifest themselves as changes in the asset, system, skid operation or performance as a direct result of the failure mode. E.g. system shuts down due to loss of pump.

Figure 1 FMECA logic flowchart



Step 4: Risk Priority Number calculation (FMECA only).

The RPN is used only when a FMECA is being performed and therefore if the RPN

calculation is not required this step can be omitted.

Severity (S): Assess the Severity of the FM.

Identify the description in the Severity prompt table that best describes the Severity (Consequences) of the failure mode.

Occurrence (O): Assess the failure mode Occurrence.

Identify the description in the Occurrence prompt table that best describes the Occurrence (Likelihood) of the failure mode.

Detection (D): Assess the failure mode Detectability.

Identify the description in the Detection prompt table that best describes the Detection (Detectability) of the failure mode.

‘Detection’ in this context refers to the ability of the operator to detect that failure once it has occurred without having to carry out any special tests or remove panels or covers etc. This measure is used to identify ‘Hidden failures’ rather than as an indication

of the predictability of a fault before it occurs.

The FMEA tool should be configured to automatically calculate the RPN on entry of the

component scores.

Step 5: Recommended actions

The following items relate to supporting information and recommended actions that could

be implemented to reduce the likelihood or consequences of the failure mode or improve the

detection of the incipient or actual failure.

Notes:

Make any notes necessary to provide clarifying information for the failure mode. These notes should be used to clarify the assumptions and conditions used to establish the scores presented.

Failure detection methods:

Record any recommended failure detection methods identified during the workshop.

If the failure mode is a hidden failure the detection method should address how the failure would be discovered after it occurs.

Compensating provisions:

Record any compensating actions the operator can take to bypass the failed item to reduce the negative impact of the failure or other actions that can be taken to reduce safety or financial risks associated with the failure mode.

Comments:

Any comments that are needed to support the ‘Detection Methods’ recommendations or the ‘Compensating Provisions’ should be recorded.



Current PM’s:

If the item is currently subject to scheduled maintenance activities (i.e. PM’s) these PM’s should be listed where possible.

It does not necessarily follow that just because PM’s are currently listed against the item that they are being carried out, or that they address the relevant failure modes.

Proposed PM’s:

Record any new PM’s, or changes to existing PM's, that are proposed as a result of this FMEA.

Repeat the assessments until complete.

Following completion of steps 1 to 5 for the previous item, make the following checks:

1. If there is another failure mode to be assessed repeat steps 3 to 5 until all failure modes, have been completed.

2. If there is another sub-system to be assessed repeat steps 2 to 5 until all subsystems have been completed.

3. If there is another asset to be assessed repeat steps 1 to 5 until all assets have been completed.

4. If all items have been completed commence the workshop wind-up phase.

Workshop Windup

On completion of all items, the following actions should be taken:

1. Identify any outstanding information required to complete a particular item assessment not completed during the workshop.

2. Agree who will follow up on outstanding data and when it will be provided to the facilitator.

3. Organise future meetings if necessary to complete this workshop or to kick off the assessment of a different group of items.

Follow up actions Any follow up action to obtain data or similar information should be completed as soon as

possible following the workshop and the data provided to the facilitator for inclusion in the

draft and final reports.

Reports

A draft report of the workshop findings, including a list of participants, major findings, RPN

scores (if applicable), copies of prompt sheets used etc. should be prepared by the facilitator

and circulated for review as soon as possible following receipt of any outstanding data from

the workshop.



Report format

FMEA reports must contain sufficient information such that the reader can understand how

scores were assigned and the context of the scoring. Depending upon the audience for the

FMEA report at least two levels of report detail should be available.

Summary reports

Summary reports should be provided for senior management review and monitoring.

Summary reports should highlight any areas of concern including the highest risks

identified.

Detailed reports

Detailed report should be provided to area engineers and managers to allow them to review

the detail analysis process and the appropriateness of the assumptions and scores. Detailed

reports should include all data and associated information used to carry out the assessment.

Reviews The draft workshop report should be submitted to the workshop manager and the Technical

Authority (TA) for formal review and any comments relayed to the workshop facilitator for

follow up. Additional reviewers can be added at the discretion of the workshop manager or

the TA.

Approvals The reviewed workshop report should be signed off by the workshop manager and the

Engineering manager and released for circulation in accordance with normal company

policy.

Documentation control As an FMEA represents a significant financial and resource commitment on the part of the

organisation, its findings should be made available to all interested parties. Appropriate

document management procedures should be used to ensure that all documents relating to

the FMEA are recorded, identified and stored to facilitate retrieval and review in the future.

The procedure used for document management will depend upon the practices of the

individual organisation but must be adequate to identify and link the many different

documents that contribute to the FMEA and not just the final report. Failure to employ

professional document management practices can mean that corporate or regulatory

compliance is not achieved or that an audit trail cannot be maintained of the assessment for

future review and update purposes.



Abbreviations

ABBREVIATION DESCRIPTION

Asset class A group or type of equipment having common components and common failure modes. (E.g. centrifugal pumps, AC electric motors, etc.).

Criticality A measure of the relative or absolute importance of the item to the organisation under specified operating criteria. Equivalent to the product of the Occurrence (O) and the Severity (S).

Detection (D) The means by which a failure can be discovered by an operator under normal operating conditions or by the maintenance group using test or diagnostic techniques (MIL-STD-1629A)

DFMEA Design FMEA - An FMEA assessment carried out on the functional failures of equipment not yet finalised as part of a project design phase.

Failure Mode (FM)

A specific mechanism by which a particular part can be said to have failed or deteriorated.

Failure Event (FE)

Events which lead to the item failing to meet its design performance standard (may include multiple failure modes).

FMEA Failure Mode and Effects Analysis

FMECA Failure Mode, Effects and Criticality Analysis

Functional failure

Partial loss of function where the item can no longer meet the operating requirements even though the item may still operate and there is no loss of integrity of the component.

Hidden Failure A failure that would not be apparent to the operator under normal operating conditions without conducting specific tests, inspection requiring the removal of access panels etc.

Item failure Complete loss of the function provided by the item due to wear, corrosion, fracture, buckling etc. leading to a loss of integrity of the component.

Item integrity Wholeness or completeness

MTBF Mean Time Between Failure

Occurrence (O) The likelihood of the failure mode occurring

OEM Original Equipment Manufacturer

PFMEA Process FMEA - An FMEA carried out on existing assets where in-service experience and operating and maintenance history is available

Priority The urgency with which an action or task must be undertaken.

RCA Root Cause Analysis

Risk Priority Number (RPN)

The calculated risk score for the failure mode based upon the product of the Severity (S), Occurrence (O) and Detection (D) scores

Severity (S) The worst consequences of a failure mode occurring (MIL-STD-1629A)

TA Technical Authority. The final arbitrator in technical matters relating to a specific asset class.

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