Analysis (FMEA). • A qualitative approach that is intended to: – Recognize and
evaluate the potential failures of a product or process and the effects of that
failure.
An Introduction to Failure Modes Effects and Criticality Analysis FME(C)A Dr Jane Marshall Product Excellence using 6 Sigma Module PEUSS 2011/2012
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Reliability tool and techniques • Methods for fault avoidance • Methods for architectural analysis and assessment
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Methods for fault avoidance • Parts derating and selection – Limiting component stress levels to below specified maxima – Ratio of applied stress to rated maximum stress – Applied stress taken as maximum likely to be applied during worst case operating conditions
• Stress-strength analysis PEUSS 2011/2012
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Methods for architectural analysis and assessment • Bottom-up method – Event tree analysis (ETA) – FME(C)A – Hazard and operability study (HAZOP)
• Top-down method – Fault tree analysis (FTA) – Reliability block diagram (RBD) – Markov analysis PEUSS 2011/2012
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FME(C)A • • • •
What is FME(C)A? Why FME(C)A? How to perform FME(C)A FME(C)A Exercise
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Failure Modes and Effects Analysis (FMEA) • A qualitative approach that is intended to: – Recognize and evaluate the potential failures of a product or process and the effects of that failure – Identify actions which could eliminate or reduce the chance of the potential failure occurring – Document the entire process
• Failure Modes Effects and criticality Analysis (FMECA) – Extends FMEA to include criticality analysis – Quantifies failure effects and severity
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Definition • Failure modes effects and criticality analysis (FMECA) is a step-by-step approach for identifying all possible failures in a design, a manufacturing or assembly process, or a product or service. • “Failure modes” means the ways, or modes, in which something might fail. • “Effects and criticality analysis” refers to studying the consequences of those failures.
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Why is it Important? • Provides a basis for identifying root failure causes and developing effective corrective actions • Identifies reliability/safety critical components • Facilitates investigation of design alternatives at all stages of the design • Provides a foundation for other maintainability, safety, testability, and logistics analyses
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History/Standards The FMEA was originally developed by NASA to improve and verify the reliability of space program hardware. • MIL-STD-785, Reliability Programs for System and Equipment Development and Production-Task 204, sets out the procedures for performing FMECA • MIL-STD-1629 establishes requirements and procedures for performing FMECA • Automotive suppliers may use SAE J1739 FMEAs, or they may use the Automotive Industry Action Group (AIAG FMEA) • QS-9000 standard • IEC 60812 - Analysis techniques for system reliability – Procedure for failure mode and effects analysis (FMEA) PEUSS 2011/2012
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Benefits of FME(C)A • FME(C)A is one of the most important and most widely used tools of reliability analysis. • The FME(C)A facilitates identification of potential design reliability problems • It can help removing causes for failures or developing systems that can mitigate the effects of failures. • Help engineers prioritize and focus on high-risk components/failures
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Benefits of FME(C)A • It provides detailed insight into the systems interrelationships and potentials for failure. • Information and knowledge gained by performing the FME(C)A can also be used as a basis for trouble shooting activities, maintenance manual development and design of effective built-in test techniques.
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Benefits and limitations • • • • • • •
Systematically identifies cause and effect relationships Indicates critical failure modes Identifies outcomes from causes Framework for identifying mitigating actions Output may be large even for simple systems Prioritising may become difficult with competing failure modes May not easily deal with time sequences, environmental conditions and maintenance aspects
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FME(C)A Applications - 1 • To identify failures which, alone or in combination, have undesirable or significant effects; to determine the failure modes which may seriously affect the expected or required quality. • To identify safety hazard and liability problem areas, or non-compliance with regulations. • To focus development testing on areas of greatest need.
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FME(C)A Applications - 2 • To assist the design of Built-in-Test and failure indications. • To assist the preparation of diagnostic flow charts or fault-finding tables. • To assist maintenance planning. • To identify key areas in which to concentrate quality control, inspection and manufacturing controls.
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FME(C)A Applications - 3 • To provide a systematic and rigorous study of the process and its environment. – To support the need for standby or alternative processes or improvements to current processes. – To identify deficiencies in operator and supervisor training and practices.
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FMEA -- Types System Concept FMEA
Design FMEA
Sub-System Component System
Assembly
Process FMEA
Sub-System Component System
Manufacturing
Sub-System Component
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Design FMEA -- Team
Representatives from: Support Team • Customer Service Design Engineer Manufacturing / Process Engineer
• Suppliers
CORE Team
• Global Test Operations • Corporate Quality
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FMEA Process
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FMEA Procedure • Identify all potential item failure modes and define their effects on the immediate function or item, on the system, and on the mission to be performed • Evaluate each failure mode in terms of the worst potential consequence, which may rank severity classification • Identify failure detection methods and compensating provision for each failure mode • Identify corrective design or other actions required to eliminate the failure or control the risk • Document the analysis and identify the problems, which could not be corrected by design PEUSS 2011/2012
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Setting The Level Of Analysis
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How is it Done? What are the effects of box failures on the system?
What are the effects of board failures on the box?
What are the effects of part failures on the board?
Note: This is a bottom up example. Top down examples are possible. PEUSS 2011/2012
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FMEA Cascade - General System
Sub-System
Component
Process
Effect Failure mode Cause
Effect Failure mode Cause
Effect Failure mode
Effect
Cause
Failure mode Cause
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FMEA Cascade - Flipchart Stand Flip Chart Stand (System)
Clamp (Sub-System)
Screw Assembly (Assembly)
Screw (Component)
Effect
Embarrass Presenter
Failure mode
Paper falls out
Effect
Cause
Insufficient clamping force
Failure Insufficient clamping mode
Effect
Insufficient clamping force
Cause
Failure mode
Screw failure
Effect
Screw failure
Cause
Thread failure
Failure
Thread failure
Paper falls out
force
Screw failure
mode Cause
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Bonnet Release Example • What can go wrong with the bonnet release on your car?
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BONNET RELEASE SYSTEM FMEA FUNCTION •To release Bonnet for opening when required
FAILURE MODE
CAUSE
•Cannot release bonnet
EFFECT
1.Cannot operate lever
•Customer annoyance •Cancelled journey •Curtailed journey
1.R.H. or L.H. does not release respective plunger 1.Secondary catch does not operate •Difficult to release bonnet
•Difficult to operate lever
1.Customer annoyance
1.Secondary catch difficult to operate •To prevent Bonnet releasing or opening when not required to open
1.Bonnet opens when not required to open
1.Bonnet liner detaches from bonnet
•Safety (accident – loss of vision)
1.Primary & secondary catch failure
•To retain Bonnet in required closed position (shut lines, aesthetics) without vibration or flexing
1.Bonnet releases to safety catch when not required
1.Primary catch failure
1.Bonnet vibrates
1.L.H. or R.H. plunger not fully engaged in receptacle
•Hazard (reduced safety) •Vibration or flexing
1.Inadvertent operation of lever
•High customer annoyance
1.L.H. or R.H. plunger detaches from liner 1.L.H. or R.H. plunger can move in receptacle 1.Bonnet flexes
•As 3.1
1.Customer dis-satisfaction
1.Looks awful
1.Incorrect location of L.H. and R.H. plunger
1.High customer annoyance
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BONNET RELEASE SYSTEM FMEA FUNCTION
FAILURE MODE
CAUSE
EFFECT
1.To prevent Bonnet being opened by external means
1.Bonnet can be opened externally
1.External access to primary release mechanism
•High customer annoyance •Theft
1.To enable Bonnet to close and lock in required position using minimal force
•Cannot close bonnet
1.Plunger cannot enter receptacle
1.Cancelled journey
1.Secondary catch cannot enter secondary receptacle •Cannot close bonnet in required position
1.R.H. and/or L.H. plungers incorrectly adjusted
1.Customer annoyance
•Cannot lock bonnet
1.R.H. and/or L.H. plungers incorrectly adjusted (length)
•Cancelled journey
1.R.H. and/or L.H. receptacle failure •Difficult to close bonnet
•R.H. and/or L.H. plungers incorrectly adjusted
1.High customer annoyance
•Incorrect plunger spring fitted •Receptacle stiff to operate •Difficult to lock bonnet
1.R.H. and/or L.H. plungers incorrectly adjusted
•Customer dis-satisfaction
1.Receptacle fails open (intermittent)
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FMECA Techniques • The FMEA can be implemented using a hardware or functional approach, and often due to system complexity, be performed as a combination of the two methods. • Hardware Approach : – Firstly this method lists individual hardware items analyzes their possible failure modes. – This method is used when hardware items can be uniquely identified from the design schematics and other engineering data. – The hardware approach is normally used in a bottom-up manner.
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FMECA Techniques • Functional Approach : – This approach considers the function of each item. Each function can be classified and described in terms of having any number of associated output failure modes. – The functional method is used when hardware items cannot uniquely identified. – Basically, this method should be applied to when the design process has developed a functional block diagram of the system, but not yet identified specific hardware to be used.
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Functional Block Diagram • A functional block diagram is used to show how the different parts of the system interact with one another to verify the critical path. • It is recommended to break the system down to different levels. • Review schematics and/or other engineering drawings of the system to show how different parts interface with one another by their critical support systems to understand the normal functional flow requirements. • A list of all functions of the equipment is prepared before examining the potential failure modes of each of those functions. • Operating conditions (such as; temperature, loads, and pressure), and environmental conditions may be included in the components list. PEUSS 2011/2012
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Typical FME(C)A Worksheet Item Potential Failure Mode
Potential Effect(s) of Failure
Function
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C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
FMEA
D e t e c
Action Results R P N
Recommended Actions
Response & Traget Target Complete Date
Action Taken
S E V
O C C
D E T
R P N
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Failure Definitions • Failure Mode & Cause – Potential failure modes, for each function, are determined by examination of the functional outputs contained on the system functional block diagram. A bottoms-up approach is used where by analysis begins at the component level, followed by analysis of subsequent or higher system levels • Failure Effects – The consequences of each postulated failure mode is identified, evaluated, and recorded on the FMEA worksheets.
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General Item Potential Failure Mode
Potential Effect(s) of Failure
Function
• • • •
S e v
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
Action Taken
S E V
O C C
D E T
R P N
Assumptions should be included in the header. Product/part names and numbers must be detailed in the header All team members must be listed in the header Revision date, as appropriate, must be documented in the header
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Function Item Potential Failure Mode
Potential Effect(s) of Failure
S e v
Function
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
S E V
Action Taken
O C C
D E T
R P N
• Function should be written clearly and must be precise so there is no change of misinterpretation. • Each function must have an associated measurable metric.
• EXAMPLES – HVAC system must defog windows and heat or cool cabin to 70 degrees in all operating conditions (-40 degrees to 100 degrees)
• •
within 3 to 5 minutes As specified in functional spec #_______; rev. date_________
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Failure Mode Item Potential Failure Mode
Potential Effect(s) of Failure
Function
S e v
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
Action Taken
S E V
O C C
D E T
R P N
• Failure modes be written clearly and must be precise so there is no change of misinterpretation. • There are 5 types of failure modes: – – – – –
complete failure, partial failure, intermittent failure, function out of specification unintended function
• EXAMPLES – HVAC system does not heat vehicle or defog windows – HVAC system takes more than 5 minutes to heat vehicle – HVAC system does heat cabin to 70 degrees in below zero temperatures – HVAC system cools cabin to 50 degrees – HVAC system activates rear window defogger PEUSS 2011/2012 FMEA
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Effect(s) of Failure Item Potential Failure Mode
Potential Effect(s) of Failure
Function
S e v
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
Action Taken
S E V
O C C
D E T
R P N
• Effects must be listed in a manner customer would describe them • Effects must include (as appropriate) safety / regulatory body, end user, internal customers – manufacturing, assembly, service • EXAMPLES – – – –
Cannot see out of front window Air conditioner makes cab too cold Does not get warm enough Takes too long to heat up
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Severity Classification • A qualitative measure of the worst potential consequences resulting from the item/function failure. • It is rated relatively scaled from 1-10.
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Mil-Std-1629 Severity Levels •
Category I - Catastrophic: A failure which may cause death or weapon system loss (i.e., aircraft, tank, missile, ship, etc...) Category II - Critical: A failure which may cause severe injury, major property damage, or major system damage which will result in mission loss. Category III - Marginal: A failure which may cause minor injury, minor property damage, or minor system damage which will result in delay or loss of availability or mission degradation. Category IV - Minor: A failure not serious enough to cause injury, property damage or system damage, but which will result in unscheduled maintenance or repair.
• •
•
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Severity Item Potential Failure Mode
Potential Effect(s) of Failure
Function
S e v
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
Action Taken
S E V
O C C
D E T
R P N
• Severity values should correspond with AIAG, SAE, etc. • If severity is based upon internally defined criteria or is based upon standard with specification modifications, a reference to rating tables with explanation for use must be included in FMEA • EXAMPLES – – – –
Cannot see out of front window – severity 9 Air conditioner makes cab too cold – severity 5 Does not get warm enough – severity 5 Takes too long to heat up – severity 4
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Classification Item Potential Failure Mode
Potential Effect(s) of Failure
S e v
Function
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
Action Taken
S E V
O C C
D E T
R P N
• Classification should be used to define potential critical and significant characteristics • Critical characteristics (9 or 10 in severity with 2 or more in occurrence suggested) must have associated recommended actions • Significant characteristics (4 thru 8 in severity with 4 or more in occurrence suggested) should have associated recommended actions • Classification should have defined criteria for application • EXAMPLES – Cannot see out of front window – severity 9 – incorrect vent location – occurrence 2 – Air conditioner makes cab too cold – severity 5 - Incorrect routing of vent hoses (too close to heat source) – occurrence 6 PEUSS 2011/2012
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Cause(s) of Failure Item Potential Failure Mode
Potential Effect(s) of Failure
Function
S e v
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
Action Taken
S E V
O C C
D E T
R P N
• Causes should be limited to design concerns • Analysis must stay within the defined scope (applicable system and interfaces to adjacent systems) • Causes at component level analysis should be identified as part or system characteristic (a feature that can be controlled at process) • There is usually more than one cause of failure for each failure mode • Causes must be identified for a failure mode, not an individual effect • EXAMPLE – – –
Incorrect location of vents Incorrect routing of vent hoses (too close to heat source) Inadequate coolant capacity for application
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Occurrence Classification Description
10 >= 50% (1 in two) 9 >= 25% (1 in four) 8 >= 10% (1 in ten) 7 >= 5% (1 in 20) 6 >= 2% (1 in 50) 5 >= 1% (1 in 100) 4 >= 0.1% (1 in 1,000) 3 >= 0.01% (1 in 10,000) 2 >= 0.001% (1 in 100,000) 1 Almost Never PEUSS 2011/2012
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Occurrence Item Potential Failure Mode
Potential Effect(s) of Failure
Function
S e v
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
Action Taken
S E V
O C C
D E T
R P N
• Occurrence values should correspond with AIAG, SAE • If occurrence values are based upon internally defined criteria, a reference must be included in FMEA to rating table with explanation for use • Occurrence ratings for design FMEA are based upon the likelihood that a cause may occur, based upon past failures, performance of similar systems in similar applications, or percent new content • Occurrence values of 1 must have objective data to provide justification, data or source of data must be identified in Recommended Actions column • EXAMPLES – – –
Incorrect location of vents – occurrence 3 Incorrect routing of vent hoses (too close to heat source) – occurrence 6 Inadequate coolant capacity for application – occurrence 2
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Current Design Controls Item Potential Failure Mode
Potential Effect(s) of Failure
Function
S e v
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
Action Taken
S E V
O C C
D E T
R P N
• Preventive controls are those that help reduce the likelihood that a failure mode or cause will occur – affects occurrence value • Detective controls are those that find problems that have been designed into the product – assigned detection value • If detective and preventive controls are not listed in separate columns, they must include an indication of the type of control • EXAMPLES – – – –
Engineering specifications (P) – preventive control Historical data (P) – preventive control Functional testing (D) – detective control General vehicle durability (D) – detective control
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Detection rating • A numerical ranking based on an assessment of the probability that the failure mode will be detected given the controls that are in place. • It is rated relatively scaled from 1-10.
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Detection Item Potential Failure Mode
Potential Effect(s) of Failure
Function
S e v
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
Action Taken
S E V
O C C
D E T
R P N
• Detection values should correspond with AIAG, SAE • If detection values are based upon internally defined criteria, a reference must be included to rating table with explanation for use • Detection is the value assigned to each of the detective controls • Detection values of 1 must eliminate the potential for failures due to design deficiency • EXAMPLE: – – – –
Engineering specifications – no detection value Historical data – no detection value Functional testing – detection 3 General vehicle durability – detection 5
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Rate the Risks Relatively • A systematic methodology is used to rate the risks relative to each other. The RPN is the critical indicator for each failure mode. The RPN is a function of three factors: The Severity of the effect, the frequency of Occurrence of the cause of the failure, and the ability to Detect (or prevent) the failure or effect. • RPN = Severity rating X Occurrence rating X Detection rating – The RPN can range from a low of 1 to a high of 1,000 – Higher RPN higher priority to be improved.
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RPN (Risk Priority Number) Item Potential Failure Mode
Potential Effect(s) of Failure
S e v
Function
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
S E V
Action Taken
O C C
D E T
R P N
• Risk Priority Number is a multiplication of the severity, occurrence and detection ratings • Lowest detection rating is used to determine RPN • RPN threshold should not be used as the primary trigger for definition of recommended actions • EXAMPLE – – – –
Cannot see out of front window – severity 9, incorrect vent location – occurrence 2, Functional testing – detection 3, RPN - 54
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Recommended Actions Item Potential Failure Mode
Potential Effect(s) of Failure
Function
S e v
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
Action Taken
S E V
O C C
D E T
R P N
• All critical or significant characteristics must have recommended actions associated with them • Recommended actions should be focused on design, and directed toward mitigating the cause of failure, or eliminating the failure mode • If recommended actions cannot mitigate or eliminate the potential for failure, recommended actions must force characteristics to be forwarded to process FMEA for process mitigation
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Responsibility & Target Completion Date Item Potential Failure Mode
Potential Effect(s) of Failure
S e v
Function
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
Action Taken
S E V
O C C
D E T
R P N
• All recommended actions must have a person assigned responsibility for completion of the action • Responsibility should be a name, not a title • Person listed as responsible for an action must also be listed as a team member • There must be a completion date accompanying each recommended action
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Action Results Item Potential Failure Mode
Potential Effect(s) of Failure
Function
S e v
C l a s s
Potential Cause(s)/ Mechanism(s) Of Failure
O c c u r
Current Design Controls Prevent Detect
D e t e c
Action Results R P N
Recommended Actions
Response & Target Complete Date
Action Taken
S E V
O C C
D E T
R P N
• Action taken must detail what actions occurred, and the results of those actions • Actions must be completed by the target completion date • Unless the failure mode has been eliminated, severity should not change • Occurrence may or may not be lowered based upon the results of actions • Detection may or may not be lowered based upon the results of actions • If severity, occurrence or detection ratings are not improved, additional recommended actions must to be defined
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Criticality – Mil-Std-1629 Approach • Occurrence is a measure of the frequency of an event. – May be based on qualitative judgment or – May be based on failure rate data (most common)
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Criticality Analysis • Qualitative analysis: – Used when specific part or item failure rates are not available.
• Quantitative analysis: – Used when sufficient failure rate data is available to calculate criticality numbers.
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Quantitative Criticality Analysis • Define the reliability/unreliability for each item, at a given operating time. • Identify the portion of the items unreliability that can be attributed to each potential failure mode. • Rate the probability of loss (or severity) that will result from each failure mode that may occur.
• •
– Calculate the criticality for each potential failure mode by obtaining the product of the three factors: – Mode Criticality = Item Unreliability x Mode Ratio of Unreliability x Probability of Loss Calculate the criticality for each item by obtaining the sum of the criticalities for each failure mode that has been identified for the item. Item Criticality = SUM of Mode Criticalities
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Quantitative Analysis • Calculate the expected number of occurrences over a specific time interval. • Many different methods are used – Use handbook reliability data – Use past experience – Uses various Bayesian combinations of past experience data and expert judgement – Uses other analysis methods (RBD, FTA etc.) PEUSS 2011/2012
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Qualitative criticality analysis • To use the method to evaluate risk and prioritize corrective actions, the analysis team must: – Rate the severity of the potential effects of failure. – Rate the likelihood of occurrence for each potential failure mode. – Compare failure modes via a Criticality Matrix, which identifies severity on the horizontal axis and occurrence on the vertical axis.
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Qualitative Analysis • •
•
Because failure rate data is not available, failure mode ratios and failure mode probability are not used. The probability of occurrence of each failure is grouped into discrete levels that establish the qualitative failure probability level for each entry based on the judgment of the analyst. The failure mode probability levels of occurrence are: – – – – –
Level A - Frequent Level B - Probable Level C - Occasional Level D - Remote Level E - Extremely Unlikely
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FME(C)A Checklist • • • • • • • •
System description/specification Ground rules Block Diagram Identify failure modes Failure effect analysis Worksheet (RPN ranking) Recommendations (Corrective action) Reporting
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The results of the FME(C)A • Highlight single point failures requiring corrective action • Rank each failure mode. • Identify reliability, safety critical components • FMECA is a living document
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Integrated FMECA • FMECAs are often used by other functions such as Maintainability, Safety, Testability, and Logistics. – Coordinate effort with other functions up front – Integrate as many other tasks into the FMECA as possible and as make sense (Testability, Safety, Maintainability, etc.) • Integrating in this way can save considerable cost over doing the efforts separately and will usually produce a better product. • If possible, use the same analyst to accomplish these tasks for the same piece of hardware. This can be a huge cost saver.
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FMECA Facts and Tips • FMECAs should begin as early as possible – This allows the analyst to affect the design before it is set in stone. – If you start early (as you should) expect to have to redo portions as the design is modified. • FMECAs take a lot of time to complete. • FMECAs require considerable knowledge of system operation necessitating extensive discussions with software/hardware Design Engineering and System Engineering. • Spend time developing ground rules with your customer up front.
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Exercise : Flashlight This flashlight is for use by fire and rescue operative involved in
emergency operation to rescue people from fires, floods and other disasters. Perform an FMECA on the torch.
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Flashlight (cont.) How can it fail? What is the effect? Note that Next Higher Effect = End Effect in this case.
Part Item
Failure Mode
End Effect
bulb
dim light no light
flashlight output dim no flashlight output
switch
stuck closed stuck open interm ittent
constant flashlight output no flashlight output flashlight sometimes will not turn on
contact
poor contact no contact interm ittent
flashlight output dim no flashlight output flashlight sometimes will not turn on
battery
low power no power
flashlight output dim no flashlight output
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Simple Example: Flashlight (cont.) • Severity – Severity I – Severity II – Severity III – Severity IV
Light stuck in the “on” condition Light will not turn on Degraded operation No effect
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Simple Example: Flashlight (cont.) Item
Failure Mode
End Effect
bulb
dim light no light
flashlight output dim no flashlight output
III II
switch
stuck closed stuck open interm ittent
constant flashlight output no flashlight output flashlight sometimes will not turn on
I II III
contact
poor contact no contact interm ittent
flashlight output dim no flashlight output flashlight sometimes will not turn on
III II III
battery
low power no power
flashlight output dim no flashlight output
III II
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Severity
FMEA
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Simple Example: Flashlight (cont.)
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FMEA
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Simple Example: Flashlight (cont.)
Can circled items be designed out or mitigated? (There may be others that need to addressed also.) PEUSS 2011/2012
FMEA
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Summary • • • •
Defined FMEA Difference between FMEA and FMECA Standard approach and pro-forma Applications
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