introduction to fmea/fmeca

Michael Herman

August 31, 2013

Introduction to FMEA/FMECA

http://www.fmea-fmeca.com

http://www.fmea-fmeca.com/

FMEA and FMECA

• What is it?– A systematic analysis technique which

facilitates the identification of potential problems by examining the effects of lower level failure modes on system operation.

2 Introduction to FMEA/FMECAwww.fmea-fmeca.com


Acronyms

• FMECA - Failure Mode, Effects, and Criticality Analysis.

• FMEA - Failure Mode and Effects Analysis.• CIL – Critical Items/Issues List

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Why is FMEA / FMECA 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 maintainability, safety,

testability, and logistics analyses• FMECA and CIL (Critical Items List) evaluations

cross check the completeness of the safety hazard analysis.

• Serves as a formal record of the analysis performed. Could be used as evidence in court (e.g. product safety).

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Background / History• Originally part of risk management techniques

developed for defense and nuclear industries in the 1940’s.

• An offshoot of Military Procedure MIL-P-1629, titled Procedures for Performing a Failure Mode, Effects and Criticality Analysis, dated November 9, 1949.

• Used as a reliability evaluation technique to determine the effect of system and equipment failures. Failures were classified according to their impact on mission success and personnel/equipment safety.

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Background / History• Formally developed and applied by NASA in the

1960’s to improve and verify reliability of space program hardware.

• Early adopters were the aerospace, petroleum, chemical, and automotive industries.

• In the 1990’s the medical devices industry began using FMECA in response to new FDA regulations / guidelines.



FMECA Standards/Guidelines• The procedures called out in MIL-STD-1629A are

probably the most widely accepted methods throughout the military and commercial industry.

• SAE J-1739 is a prevalent FMEA standard in the automotive industry.

• SAE ARP5580 - FMECA for Non-Automotive applications. Provides some upgrades to MIL-STD-1629A.

• Army TM 5-698-4 – FMECA for C4ISR Facilities• MIL-STD-882D – Helpful in assessing safety issues

and identifying critical items.

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Definitions• Failure Cause: The physical or chemical processes,

design defects, quality defects, part misapplication or other processes which are the basic reason for failure or which can initiate the physical process by which deterioration proceeds to failure. Why does it fail? (Past)

• Failure Mode: The way in which a failure is observed, describes the way the failure occurs, and its impact on equipment operation. How does it fail? (Present)

• Failure Effect: The consequence a failure mode has upon the operation, function or status of a system or equipment. What happens when it fails? (Future)



Definitions

• Local Effect: The consequence a failure mode has on the operation, function or status of the specific item being analyzed.

• Next Higher Effect: The consequence a failure mode has upon the operation, function, or status at the next higher level of assembly.

• End Effect: The consequence a failure mode has upon the operation, function, or status at the highest level of indenture. Sometimes referred to as a System Effect.

Types of Failure Effects:

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Definitions• Severity: Considers the worst possible consequence of a

failure classified by the degree of injury, property damage, system damage and mission loss that could occur.

• Criticality: A relative measure of the consequences of a failure mode and its frequency of occurrence.

• Failure Mode Ratio: The probability of occurrence of a failure mode. The sum of the failure mode ratios for an item should equal 1.0. Sometimes referred to as alpha (α).

• Failure Effect Probability: Often referred to as the End Effect Conditional Probability or beta (β). Represents the probability that a particular failure effect will result, given that a certain failure mode occurs.



Types of FMEA/FMECA• There are many different flavors or types of FMECA.• Both qualitative and quantitative approaches may be

used.• Some examples are: Concept, Design, Process,

Hardware, Functional, Software, Interface, Healthcare, Machinery, Environmental, etc…

• The technique is basically the same when completing each type of FMECA, but the criteria used in determining failure modes, effects, severity levels and other aspects of the FMECA may be tailored for each specific use.



Conceptual ValidationEngineering Development

Engineering PrototypeProduction / Deployment

Design Process

FMECA

Design Reviews

ACQUISITION PROGRAM

Functional HardwareUpdates Updates

PDR CDR PRDR FACI

PDR - Preliminary Design Review CDR - Critical Design Review PRDR - Preproduction Design Review FACI - First Article Configuration Inspection

FMECA Timeline – Aerospace Industry



• Design FMECA– Start early in process. Complete by the time preliminary drawings are done, but

before any tooling is initiated.

• Process FMECA– Start as soon as basic manufacturing methods have been discussed. Complete prior

to finalizing production plans and releasing for production

Concept Prototype Build

Design Go-Ahead

Production Start

Eng./Mfg. Sign Off

Design Completion

Design FMEA Process FMEA

FMECA Timeline – Automotive Industry



How is FMECA Done?Bottom-Up Analysis Top-Down Analysis

Determine failure modes of lower level items.

Work upward and determine effects.

Pick upper level failure modes.

Work downward and flow down causes.



The FMECA Analysis Process1. Define the system2. Define ground rules and assumptions3. Construct system block diagrams4. Identify failure modes5. Analyze failure effects / causes6. Feed results back into design process7. Classify failure effects by severity8. Perform criticality calculations9. Rank failure mode criticality10. Determine critical items11. Feed results back into design process12. Identify means of failure detection, isolation and compensating provisions13. Document the analysis. Summarize uncorrectable design areas, identify special

controls necessary to mitigate risk.14. Make recommendations15. Follow up on corrective action implementation / effectiveness

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