FMEA Failure Modes and Effects Analysis

Definition/Purpose:

FMEA (Failure Modes and Effects Analysis) is a systematic, proactive method for evaluating a process to identify where and how it may fail and to assess the relative impact of different failures, in order to identify parts that are most in need of change. Typically, the purpose of FMEA is to identify specific ways a product, process or service might fail. It is designed to prevent tragedy by identifying potential failures. FMEA is useful in the Improve phase. FMEA includes review of the following:

Steps in the process
Failure Modes (What could go wrong?)
Failure Causes (Why would the failure happen?)
Failure effects (What would be the consequences of each failure?)

Definitions:

Potential Failure Mode – What could go wrong? The four main types of process failure modes are too much, too little, missing, or wrong.
Effects – What could be the consequences of each failure?
Severity – How serious would the impact be if the potential failure were to occur?
Potential Causes – What are the drivers of this failure?
Occurrence – How likely is the cause and failure mode to occur?
Current Controls – What safeguards are currently in place?
Detection – How difficult is the cause and failure mode to detect prior to occurrence?
Risk Priority Number (RPN) – Use to prioritize potential failure modes.

RPN = (Occurrence) x (Severity) x (Detection)

Instructions: To use as a template, please save a copy by clicking on the save icon.

Select a process.
Assemble a multi-disciplinary team who knows the process.
The team lists all steps in the process.
Identify high risk process steps.
List the failure modes and effects.
Define occurrence, severity and detection and calculate the RPN score.
Evaluate the results.

Capturing FMEA Information

FMEA Analysis

Project:

Team:

Original Date:

Revised Date:

Item or Process Step

Potential Failure Mode

Potential Effect(s) of Failure

Potential Cause(s)

Current Controls

RecommAction

Responsand Target Date

“After” Action Taken

Risk Priority Number =

“After” Risk Priority Number =

S = Severity, O = Occurrence, D = Detection, R = RPN

Source: https://uihc.org/sites/default/files/documents/asset-3721.doc

Web site to visit: https://uihc.org

Author of the text: indicated on the source document of the above text

FMEA (Failure Modes and Effects Analysis)
FMECA Failure, Modes, Effects and Criticality Analysis / AMDEC (Analyse des Modes de Défaillances, de leurs Effets et de leur Criticité)
SEEA (Software Error Effects Analysis) / AEEL (Analyse des Effets des Erreurs de Logiciel)

What is failure modes and effects analysis?

Identify ways the product or process can fail
Plan how to prevent those failures

Types of FMEA

System FMEA: is used to analyze systems and subsystems in the early concept and design stages. Focuses on potential failure modes associated with the functions of a system caused by design.
Product FMEA (a.k.a. Design FMEA): is used to analyze products before they are released to production.
Process FMEA: is used to analyze manufacturing, assembly and transactional processes.

How Does FMEA Work?

Identify potential failure modes and rate the severity of their effects
Evaluate objectively the probability of occurrence of causes and the ability to detect the cause when it occurs
Evaluating the current design/control plan for preventing these failures from occurring
Prioritizing the actions that should be taken to improve the product/process

FMEA is a table with the following columns:

product part or process step
failure mode
effect
severity of effect 1-5
potential cause/mechanism of failure
probability of failure (occurrence) 1-5
detection and recovery mechanism
probability of detection 1-5
action recommended
who is responsible to perform/drive the action

→ RPN (Risk Priority Number) 1-125

FMEA process for Six Sigma:
Preparation
1. Select Process Team
2. Develop Process Map and Identify Process Steps
3. List Key Process Outputs to Satisfy Internal and External Customer Requirements
4. List Key Process Inputs for Each Process Step
5. Define Matrix Relating Product Outputs to Process Variables
6. Rank Inputs According to Importance
FMEA Process
7. List Ways Process Inputs Can Vary (Causes) and Identify Associated Failure Modes and Effects
8. List Other Causes (Sources of Variability) and Associated FM&Es
9. Assign Severity, Occurrence and Detection Rating to each Cause
10. Calculate Risk Priority Number (RPN) for each Potential Failure Mode Scenario
FMEA Process Improvement
11. Determine Recommended Actions to Reduce RPNs
12. Establish Timeframes for Corrective Actions
13. Create “Waterfall” Graph to Forecast Risk Reductions
14. Take Appropriate Actions
15. Re-calculate All RPNs
16. Put Controls into Place

FMEA is a team job. The responsible system or product leads the FMEA team. The responsible is expected to involve representatives from all affected activities. Team members should include design, manufacturing, assembly, quality, reliability, service, purchasing, testing, supplier, and other subject matter experts as appropriate.

The technique of brainstorming has often proven to be a useful method for finding failures modes.

Cause and effect diagrams can be used to determine the effects and causes of potential failures.

The FMEA must be updated during the project life, whenever a change is being considered to a product’s design, application, environment, material, or to any process.

Setting the right granularity level is a crucial success factor, considering more than 7-10 entities will generally lead to difficulties
For software, UML collaborations and state diagrams give good support when analyzing the failure modes related to a use case.
FMEA only permits Single Point Failure Analysis (use FTA for analysis of simultaneous failures at several points).

GEMS safety FMEA
diagram with numbered entities (the entities may be modules, classes, processing steps...)
followed by a table:

entity number
entity name
function (there may be several functions for a given entity, in this case, the entity will be factorized on several lines)
failure mode (there may be several failure modes for a given function)
failure cause (there may be several causes for a failure mode)
local effect
final effect
severity level (negligible, medium, high)
dormant issue
detection at system level
compensation for safe state recovery
probability level
risk level
single point validation plan
safety evaluation minimum requirements
status

IEC 60812 -- Analysis techniques for system reliability - Procedure for failure mode and effects analysis (FMEA)
this standard gives guidance as to how the following objectives could be achieved when using FMEA/FMECA as risk analysis tools including:

Procedural steps necessary to perform an analysis
Identification of appropriate terms, assumptions, criticality measures, failure modes
Determining basic principles
Form for documenting FMEA/FMECA
Criticality grid to evaluate failure effects

Examples of ratings

Severity Ratings
Example 1

Critical	Safety hazard. Causes or can cause injury or death.
Major	Requires immediate attention. System is non-operational.
Minor	Requires attention in the near future or as soon as possible. System performance is degraded but operation can continue.
Insignificant	No immediate effect on system performance.

Example 2

1	None	Effect will be undetected by customer or regarded as insignificant.
2	Very minor	A few customers may notice effect and may be annoyed.
3	Minor	Average customer will notice effect.
4	Very low	Effect recognised by most customers.
5	Low	Product is operable, however performance of comfort or convenience items is reduced.
6	Moderate	Products operable, however comfort or convenience items are inoperable.
7	High	Product is operable at reduced level of performance. High degree of customer dissatisfaction.
8	Very high	Loss of primary function renders product inoperable. Intolerable effects apparent to customer. May violate non-safety related governmental regulations. Repairs lengthy and costly.
9	Hazardous – with warning	Unsafe operation with warning before failure or non-conformance with government regulations. Risk of injury or fatality.
10	Hazardous – without warning	Unsafe operation without warning before failure or non-conformance with government regulations. Risk of injury or fatality.

Probability of Occurrence Ratings

1	Unlikely	≤ 1 in 1.5 million (≤.0001%)
2	Low (few failures)	1 in 150,000 (.001%)
3	Low (few failures)	1 in 15,000 (.01%)
4	Moderate (occasional failures)	1 in 2,000 (0.05%)
5		1 in 400 (0.25%)
6		1 in 80 (1.25%)
7	High (repeated failure)	1 in 20 (5%)
8	High (repeated failure)	1 in 8 (12.5%)
9	Very high (relatively consistent failure)	1 in 3 (33%)
10	Very high (relatively consistent failure)	≥ 1 in 2 (50%)

Control Effectiveness Ratings

1	Excellent; control mechanisms are foolproof.
2	Very high; some question about effectiveness of control.
3	High; unlikely cause or failure will go undetected.
4	Moderately high
5	Moderate; control effective under certain conditions.
6	Low
7	Very low
8	Poor; control is insufficient and causes or failures extremely unlikely to be prevented or detected.
9	Very poor
10	Ineffective; causes or failures almost certainly not prevented or detected.

Source: http://mazure.fr/quality/fmea.doc

Web site to visit: http://mazure.fr/

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FMEA Failure Modes and Effects Analysis

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