six sigma black belt week 3 - institute of industrial and ... · point for your fmea. fmeas are not...

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© 2011 Institute of Industrial Engineers 3-6-1

Chapter 3-6

FMEA

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FMEA Definition

A procedure by which each potential failure mode in a system is analyzed to determine the results of effects thereof on the system and to classify each potential failure mode according to its severity, the likelihood of it occurring, and the ability of the system to prevent it from occurring.

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Stated Another Way

A methodology to analyze and discover:

(1) all potential failure modes of a system,

(2) the effects these failures have on the system and

(3) how to correct and or mitigate the failures or effects on the system. [The correction and mitigation is usually based on a ranking of the severity and probability of the failure.]

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What is FMEA?

• FMEA is an acronym that stands for Failure Modes and Effects Analysis

• Methodology of FMEA:

– Identify the potential failure of a system and its effects

– Assess the failures to determine actions that would eliminate the chance of occurrence

– Document the potential failures

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What is an FMEA?

An advanced planning tool used to evaluate potential failure modes and their causes.

• Prioritizes potential failures according to their risk and drives actions to eliminate or reduce their likelihood of occurrence.

• Provides a discipline/methodology for documenting this analysis for future use and continuous process improvement.

• Used in combination with other problem solving tools.

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FMEA

• Identifies possible faults (failure modes) in a system (including their causes –ask the 5 Whys)

• Evaluates the effects of the fault on the operational status of the system

• Determines the risk priority of the failure (based on severity, probability of occurrence, and probability of detecting and avoiding the failure

• Recommends corrective actions for high risk items• Implements corrective actions until risk is reduced• Documents the design process and allows for efficient

review and communication with respect to system safety

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Why FMEA?

FMEA is one of the most important tools of reliability analysis. If undertaken early enough in the design process by senior level personnel it can have a tremendous impact on removing causes for failures or of developing systems that can mitigate the effects of failures. It provides detailed insight into the systems interrelationships and potentials for failure.

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Background

The failure mode and effects analysis (FMEA)

is the most widely used analysis procedure in

practice at the initial stages of system

development.

The FMEA is usually performed during the

conceptual and initial design phases of the

system in order to assure that all possible

failure modes have been considered and that

proper provisions have been made to

eliminate all the potential failures.

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What Is An FMEA?

– Opportunity to Defeat Murphy’s Law

– Focus on Prevention

– Failure Mode And Effects Analysis is• An assessment of Risk

– Safety

– Regulatory

– Customer Satisfaction

– Program

• Coordinated/Documented team effort– To determine what can go wrong

• A method to determine the need and priority of actions

• It is not designed to record previously designed elements

MURPHY’S

LAW

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History of FMEA

• Created by the aerospace industry in the 1960s.

• Ford began using FMEA in 1972.

• Incorporated by the “Big Three” in 1988.

• Automotive Industry Action Group and American Society for Quality Control copyright standards in 1993.

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FMEA Deployment

– A layered approach is highly recommended as FMEAs can get complex.

– FMEAs are like ONIONS/LAYERS.

• Each layer is closer to the root cause

• Each layer is more detailed

• The closer to core the more detail– Core gets to the root cause

– Do too many and you will cry.

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FMEA - Used in all Product Steps

Product

Planning

Product

Design

Process

Design

Production

Quality Planning

Services

Product FMEA

(Design FMEA)

Product FMEA

(Design FMEA)

Process FMEA

(Manufacturing FMEA)

Process FMEA

(Manufacturing FMEA)

Service FMEA

(Transactional FMEA)

Product Goal Setting

• Performance

• Reliability

• Cost

• Life

Design Optimization

Process Sequencing &

Flow Study

Quality Plans

• Manufacturing

• Suppliers

Field Service Goal Setting

• Maintainability

• Serviceability

• Spare Part Availability

Others ?

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Types of FMEA

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Benefits

o Encourages Simultaneous Engineering

o Identifies Where Early Redesign will often Prevent Process Problems from going into Production

o Identifies Areas that Require Concurrent Engineering in a Product’s Evolution

o Identifies Road Blocks

o Provides Record for Future Development

o Identifies where Controls can be Effectively Implemented

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For FMEA to Work

• Commitment of top management• Knowledgeable individuals, i.e. Expertise in:

– Design– Manufacturing– Assembly– Service– Quality– Reliability

• Individuals attentive to FMEA timeliness, i.e. Achieve greatest value: before a design or process failure mode has been unknowingly designed into the product

• People resources may be internal or external to the business, or a combination thereof

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FMEA Process

FMEA is usually performed by a team of people who are knowledgeable about the process and product and have allocated

Time

Authority

Skill

In the required technical disciplines to perform an FMEA process and implement corrective actions.

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FMEA Flow Chart

Assign a label to each process or system component

List the function of each component

List potential failure modes

Describe effects of the failures

Determine failure severity

Determine probability of failure

Determine detection rate of failure

Assign RPN

Take action to reduce the highest risk

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General Steps of FMEA

1. Compile Information about the System to be Analyzed.

2. Translate Complex Systems into a Set of Distinct Components or Processes and set Scope.

Construct a Flow Chart

3. Determine Function..

4. Determine Potential Failure Modes.

5. Determine Potential Effects of Each Failure Mode.

6. Determine Potential Causes of Each Failure Mode.

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Steps in FMEA

7. Assign a Severity Rating

for each effect. (see

Severity Rating Scale)

8. Assign an Occurrence

Rating for each failure.

(see Occurrence Rating

Scale)

9. Determine the ability to

detect the failure mode.

10. Calculate and prioritize a

Risk Priority Number

(RPN) for each failure.

11. Review the process.

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Steps in FMEA

12. Take action to eliminate

or reduce the Risk

Priority Number.

13. Recalculate the resulting

RPN as the failure modes

are reduced or

eliminated.

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1. Process FMEA Information Gathering

• Flow Process Diagrams

• Engineering Drawings

• Engineering Specifications

• Completed Problem Solving Analyses

• Machine Operation Descriptions

• Gage Plan Descriptions

• Process Illustration Sheets

• ISO 9000 Information

• Machine Operation Sheets

• Manufacturing Plans

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2. Preliminary Analysis – Flow Chart

1. Identify the sequence and steps.2. Construct the chart.3. Draw a flowchart4. Look for areas for improvement

• Is the process standardized?• Are steps repeated or out of sequence?• Are there steps that do not add value?• Are there steps where errors occur frequently?• Are there rework loops?

5. Analyze the results.

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Flow Chart

Draft an initial, “high-level” flowchart of the process being examined. One way to achieve this would be to collect and compile information on the process from the team members and flowchart it for the first meeting. Another way is to work with the team leader to draft the flowchart. This initial flowchart will assist the team in determining if they need to narrow the scope of the process.

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Scope

• This part of the FMEA process is truly a make or break point for your FMEA. FMEAs are not a tool that will “save the world” and fix all the failure points in your MTF at one time.

• Choose a manageable and focused process or specific part of the process (sub-process) that allows the team to conduct an effective FMEA that will find and fix all the critical failure modes within those process boundaries.

• FMEAs are already challenging and when a process scope is too large it becomes extremely difficult to conduct a thorough analysis.

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3. Determine Function

• Determine what the system or process is supposed to do before analyzing for potential failures.

• Functions are tasks that a system is intended to perform. These are sometimes known as primary functions. There are also tasks that a system also performs even if not intended. These are known as secondary functions or possibly effects of failure modes.

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Defining A Purpose

All purposes must be defined using two words, a verb and a noun. Stating purposes this way helps simplify the product.

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Defining A Purpose - Examples

Product

Electric Motor

Light Bulb

Fuel Tank

Purpose

Produces Torque

Generates Light

Contains Fuel

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Defining a Purpose

A product usually has only one primary function. This is the function which the product was specifically designed to perform. An overhead projector's positive function is to project images, its secondary function are those which could have adverse effects. Some of these could be generate heat or consume power. In this case, the secondary functions could be viewed as negative.

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4. Determine Failure Modes

o How might a process fail or produce a product that is unacceptable?

o The likelihood of each mode occurring is also considered.

o Ways in which a part/assembly/system could potentially fail to meet the design intent.

o Assumption is made that the failure could occur but will not necessarily occur.

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Design Failure Cause Examples

• Improper tolerancing

• Incorrect stress calculation

• Wrong assumptions

• Wrong material call out

• Lower grade component

• Lack of design standards

• Improper heat treatment

• Improper torque call out

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Process Failure Cause Examples

• Omitted processing• Processing errors• Errors setting up• Missing parts• Wrong parts• Processing wrong part• Mis-operation• Adjustment error• Tools/fixtures improperly

prepared

• Poor control procedures• Improper maintenance• Bad recipe• Fatigue• Safety• Hardware failure• Environment• Stress

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Potential Failure Modes

Potential failure modes that would only occur under certain operating conditions should be considered.

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5. Potential Effects of Failure

• The effects of the failure mode on the customer.

• Describe the effects of the failure in terms of what the customer might notice or experience.

• Always stated in terms of system performance.

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Typical Failure Effects

• Noise

• Unstable

• Impaired

• Draft

• Erratic Operation

• Intermittent

• Rough

• Appearance

• Inoperative

• Vehicle Control

• Odor

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Potential Causes Of Failure - Failure Occurrences

• A potential cause of failure is defined as an indication of a design or process weakness, the consequence of which is the failure mode.

• The causes should be listed as concisely and completely as possible so that remedial efforts can be aimed at pertinent causes.

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Potential Causes of Failure

• Incorrect material specified

• Incorrect Assembly instructions

• Insufficient lubrication

• Poor mold form

• Handling damage

• Inadequate clamping

• Improper surface prep

• Improper tool setup

• Incorrect material thickness specified

• Inappropriate material specified

• Improper heat treatment

• Inaccurate gauging

• Incorrect feeds, speeds

• Worn tooling

Typical Manufacturing Failure Causes

could be:

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7. Severity

• An assessment of the seriousness of the effect of the potential failure mode to the next assembly or to the customer.

• Severity applies to the effect and the effect only.

• A reduction in severity ranking index can be affected only through a design change for the part or the process.

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Severity

The FMEA process normally ranks the severity. A typical scale will rank the severity from 1 (least severe) to 10 (most severe.)

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FMEA - Severity

Effect SEVERITY of Effect Ranking

Hazardous without warning Very high severity ranking when a potential failure mode affects safe system operation without warning 10

Hazardous with warning Very high severity ranking when a potential failure mode affects safe system operation with warning 9

Very High System inoperable with destructive failure without compromising safety 8

High System inoperable with equipment damage 7

Moderate System inoperable with minor damage 6

Low System inoperable without damage 5

Very Low System operable with significant degradation of performance 4

Minor System operable with some degradation of performance 3

Very Minor System operable with minimal interference 2

None No effect 1

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Severity

Critical characteristics affecting regulatory compliance or safe product function are those product or process requirements which require special supplier, manufacturing, assembly, shipping, monitoring and/or inspection actions.

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8. Failure Occurrence

• How frequently the failure mode is projected to occur as a result of a specific cause.

• The occurrence ranking number has a meaning rather than a value

• We need to estimate the likelihood of the occurrence of potential failure modes on a "1 to 10" scale.

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Failure Occurrence

• Only methods intended to prevent the cause of failure from occurring should be considered for this ranking.

• Refer to the occurrence ranking system on the next page.

• The occurrence ranking system should be used for consistency.

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FMEA - Probability

PROBABILITY of Failure Failure Prob Ranking

Very High: Failure is almost inevitable >1 in 2 10

1 in 3 9

High: Repeated failures 1 in 8 8

1 in 20 7

Moderate: Occasional failures 1 in 80 6

1 in 400 5

1 in 2,000 4

Low: Relatively few failures 1 in 15,000 3

1 in 150,000 2

Remote: Failure is unlikely <1 in 1,500,000 1

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9. Detection

Detection is an assessment of the ability of the proposed process verification to identify a potential process weakness or failure mode before the part or assembly is released for production.

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Detection

• Assume the failure has occurred and then assess the capabilities of all current controls to prevent shipment of the part having this failure mode or defect.

• Do not automatically presume that the detection ranking is low because the occurrence is low, but do assess the ability of the process controls to detect low frequency failure modes or prevent them from going further in the process.

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Detection

This system assigns a ranking showing the likelihood that the existence of a defect will be detected by controls before the next or subsequent process, or before the part or component leaves the manufacturing or assembly location.

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FMEA - Detection

Detection Likelihood of DETECTION by Design Control Ranking

Absolute Uncertainty Design control cannot detect potential cause/mechanism and subsequent failure mode 10

Very Remote Very remote chance the design control will detect potential cause/mechanism and subsequent failure mode 9

Remote Remote chance the design control will detect potential cause/mechanism and subsequent failure mode 8

Very Low Very low chance the design control will detect potential cause/mechanism and subsequent failure mode 7

Low Low chance the design control will detect potential cause/mechanism and subsequent failure mode 6

Moderate Moderate chance the design control will detect potential cause/mechanism and subsequent failure mode 5

Moderately High Moderately High chance the design control will detect potential cause/mechanism and subsequent failure mode

4

High High chance the design control will detect potential cause/mechanism and subsequent failure mode 3

Very High Very high chance the design control will detect potential cause/mechanism and subsequent failure mode 2

Almost Certain Design control will detect potential cause/mechanism and subsequent failure mode 1

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10. Risk Priority Number

The risk priority number, RPN, is the product of the Occurrence, Severity, and Detection rankings. This value should be used to rank order the concerns in the design.

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FMEA Form

Process FMECA

Part/Process Water Test Suppliers Affected: Prepared by:

Manufacturing Model Year: FMEA Date:

Reponsibility:

Other Areas: Release Date: Key ProductionDate:

Process Purpose Potential Potential Severity Class Potential Occur Current Detect RPN Recom Respon Actions Severity Occur Detect

Conformity Failure Effects Cause Controls Actions

Mode

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11. Review

Check the steps and document progress beforemoving on:

• Were potential causes determined for eachfailure mode?

• Were potential causes prioritized?

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12. Corrective Action

• The intent of any recommended action is to reduce any one or all of the Occurrence, Severity, and/or Detection rankings.

• Corrective action should be first directed at the HIGHEST ranked concerns and at CRITICAL items.

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Corrective Action

• To reduce probability of Occurrence, process and/or design revisions are required.

• To increase possibility of detection, process and/or design revisions are required.

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Corrective Action

The need for taking specific, positive corrective actions with quantifiable benefits, recommending actions to other activities, and following up all recommendations cannot be overemphasized.

A thoroughly thought out and well developed Process FMEA will be of limited value without positive activities to implement effective follow up programs to address all recommendations.

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Corrective Action

Corrective actions must be identified by the FMEA team.

– The area responsible for the recommended action.

– The individual responsible for the recommended action

– The target date for completion of the recommended action.

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Follow Up

• The FMEA leader is responsible for assuring that all actions recommended have been implemented or adequately addressed.

• The FMEA is a living document and should always reflect the latest design level, as well as the latest relevant actions.

• After the changes have occurred, the occurrence ranking, the severity ranking, and the detection ranking need to be reevaluated and the risk priority numbers need to be recalculated.

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Summary - Steps Required to Perform a Process FMEA.

1) Identify the part or process name and number.

2) Identify processing responsibility.

3) Identify other areas involved.

4) Identify suppliers affected.

5) Identify engineering release data.

6) Identify key production dates.

7) Assign responsibility for FMEA preparation.

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Summary - Steps Required to Perform A Process FMEA

8) Show FMEA dates.

9) Prepare process description and purpose.

10) Identify potential failure modes.

11) Identify potential effects of failure.

12) Identify severity.

13) Identify critical characteristics.

14) Identify potential causes of failure.

15) Identify occurrence.

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Summary - Steps Required to Perform A Process FMEA

16) Identify current controls.

17) Perform detection.

18) Calculate RPN.

19) Identify Responsibility for and Perform corrective actions.

20) Revise RPN.

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Failure Modes for FMEA’s

• The team developing the FMEA turns out to be one individual.

• Is created to satisfy a customer or third party requirement– NOT to improve the process.

• Is developed too late in the process and does not improve the product/process development cycle.

• Is not reviewed and revised during the life of the product.

• Is perceived either as too complicated or as taking too much time.

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Tracking FormProcess FMEA

Part/Process Suppliers Affected: Prepared by:

Name:

Manufacturing Model Year: FMEA Date:

Reponsibility:

Other Areas: Release Date: Key ProductionDate:

Process Purpose Potential Potential Severity Class Potential Occur Current Detect RPN Recom Respon Actions

Failure Effects Cause Controls Actions

Mode

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Case Study

The case study takes place in a slimming and convalescence medical clinic. The clinic restaurants were selected for the study since the meals and the way they are served are extremely critical for the success of the treatment and the customer satisfaction.

On the following page is a flow chart for the system. Two lines are identified: the Front Office where the customer experiences the service and the Backroom where the support activities for the front office are carried out.

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BACKROOM FRONT OFFICE

Deliver Drug A1 1 Take Drug with Nurse

Deliver Ticket A2 2 Take Ticket with Dietician

3 Help yourself to Drinks

4 Help yourself to Sauces

5 Choose table and Sit Down

6 Choose salads

Receive Ticket A7 7 Hand ticket to Attendant

Take Meal A8 8 Wait

Serve Meal A9 9 Receive Meal

10 Eat

11 Drink Coffee

12 Leave Dining Room

Take Utensils A12

Clean Table

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Perform the FMEA

• Function

• Failure Modes

• Failure Effects

• Severity

• Controls

• RPN

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RATING DEGREE OF SEVERITY LIKELIHOOD OF OCCURRENCE ABILITY TO DETECT

1 Customer will not notice the adverse effect or it is insignificant. Likelihood of occurrence is remote. Sure that the potential failure will be found or prevented before reaching the next customer.

2 Customer will probably experience slight annoyance. Low failure rate with supporting documentation.

Almost certain that the potential failure will be found or prevented before reaching the next customer.

3 Customer will experience annoyance due to slight degradation of performance.

Low failure rate without supporting documentation.

Low likelihood that the potential failure will reach the next customer undetected.

4 Customer dissatisfaction due to reduced performance. Occasional failures. Controls may not detect or prevent the potential failure from reaching the next customer.

5 Customer is made uncomfortable or their productivity is reduced by the continued degradation of the effect.

Relatively moderate failure rate with supporting documentation.

Moderate likelihood that the potential failure will reach the next customer.

6 Warranty repair or significant manufacturing or assembly complaint.

Moderate failure rate without supporting documentation.

Controls are unlikely to detect or prevent the potential failure from reaching the next customer.

7 High degree of customer dissatisfaction due to component failure without complete loss of function. Productivity impacted by high scrap or rework levels.

Relatively high failure rate with supporting documentation.

Poor likelihood that the potential failure will be detected or prevented before reaching the next customer.

8 Very high degree of dissatisfaction due to the loss of function without a negative impact on safety or governmental regulations.

High failure rate without supporting documentation.

Very poor likelihood that the potential failure will be detected or prevented before reaching the next customer.

9 Customer endangered due to the adverse effect on safe system performance with warning before failure or violation of governmental regulations.

Failure is almost certain based on warranty data or significant DV testing.

Current controls probably will not even detect the potential failure.

10 Customer endangered due to the adverse effect on safe system performance without warning before failure or violation of governmental regulations.

Assured of failure based on warranty data or significant DV testing

Absolute certainty that the current controls will not detect the potential failure.

FMEA Standardized Rating System1 < RPN = (Degree of Severity)*(Likelihood of Occurrence)*(Ability to Detect) < 1000