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FMECA

 

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What is an FMEA/FMECA?

An FMEA/FMECA is a systematic method of product or process analysis that identifies the potential failures which include the root causes of failures, their subsequent effects on production and so on. It is used to prevent hazards of products and processes from occurring.

Failure Mode and Effects Analysis (FMEA) is defined as:
The study of the potential failures that might occur in any part of a system to determine the probable effect of each on all the other parts of the system and on probable operational success. (BS 4778 17.7)

Failure Mode, Effects, and Criticality Analysis (FMECA) is defined as:
The study of the potential failures that might occur in any part of a system to determine the probable effect of each on all the other parts of the system and on probable operational success, the results of which are ranked in order of seriousness. (BS 4778 17.8)

FMECA is a modified version of FMEA. It is more streamlined than FMEA.

The difference between FMEA and FMECA is that FMECA exercises a ranking system while FMEA does not.

 

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What is the purpose of FMEA / FMECA?

FMEA/FMECA is purposed to prevent process and product failures from occurring. It is suggested to be conducted during the product design or process development. It is because the changes of design and process can be made at these earliest stages and the changes are relatively inexpensive. Therefore, the cost can be reduced.

 

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Types or Levels of FMECA
  • System FMECA: To identify and prevent the potential problems/bottlenecks in larger processes (like production lines) in the early design concept stage.

  • Design FMECA: To eliminate failures of product in the design stage.

  • Process FMECA: To identify and prevent the potential problems which are related to the entire manufacturing or assembling processes.

 

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The FMECA Team

FMECA is a team-based analysis. The leader of the FMECA team which should be the person responsible for coordinating the FMECA process, including:

  • setting up and facilitating meetings,
  • ensuring the team having the necessary resources available,
  • making sure that the team is progressing toward the completion of the FMECA, and
  • producing the analysis in worksheet format.

 

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Assessing the Risk Priority Number

Risk Priority Number (RPN) is a criticality index to indicate the priority for corrective actions. RPN ( range from 1 to 1,000 for each failure mode) is determined for each potential failure mode and effect by multiplying the ratings of the three factors - severity, occurrence and detection.

RPN = Severity x Occurrence x Detection

Factor

Meaning

Scale / Ranking

Severity

the seriousness of the failure effect after it has occurred

Severity

Likelihood/Occurrence

the probability or frequency of the failure occurring

Occurence

Detection

the probability of the failure being detected before the impact of the effect is realized

Detection

 

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The 12 Steps for an FMECA

All design and process FMECAs follow these 12 steps:

Step1: Review the process or examine the product (or a prototype of the product) physically.
- It helps better understanding of the process or product.
Step2: Brainstorm potential failure modes and list all of them.
Step3: List the potential effects of each failure mode.
Step4: List the potential causes of each failure.
Step5: List the current controls.
Step6: Assign a severity rating for each effect.
Step7: Assign an occurrence rating for each failure mode.
Step8: Assign a detection rating for each failure mode and/or effect.
Step9: Calculate the risk priority number (RPN) for each effect.
Step10: Prioritize the failure modes for action according to:
  • Highest numerical scores (RPNs).
  • Any Severity, Occurrence or detection ratings above 8.
Step11: Take corrective actions to eliminate or reduce the high-risk failure modes.
Step12: Calculate the Resulting RPN as the failure modes are reduced or eliminated.
- Resulting RPN which is the new RPN after improvement is determined by reevaluating the Severity, Occurrence, and Detection ratings.

 

 

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Failure Mode, Effects, and Criticality Analysis - FMECA Standard Log Sheet
Session: ____________________________ Reference Materials: ____________________________ Design/System/Process: __________________
Participants: ________________________________________________________________________ Date: ________________________________
Item Components/System Function Failure Mode Causes Effects S L D RPN Recommendations Action/Responsible
                     
                     
                     
                     
                     
                     
                     
                     
                     

A worked example of FMECA Standard Log Sheet:

Internal link : Learning > Worked example - FMECA Standard Log Sheet: A design FMECA for Marker

 

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FMEA/FMECA Related Standards

IEC 60812 : Procedures for Failure Mode and Effect Analysis

BS 5760-5 : Guide to Failure Modes, Effects, and Criticality Analysis

 

Sources:

From the book:

  1. Abbott, H. (1997). Safer by design : a guide to the management and law of designing for product safety. Aldershot, England; Brookfield, Vt: Gower.
  2. McDermott, Robin E., Mikulak, Raymond J., & Beauregard, Michael R. (1996). The basic of FMEA. Portland, OR: Productivity.
  3. Zepf Paul J. (2002). How to do a risk analysis using FMECA. Oakville, Zarpac Inc.

 

Last updated on 7 APR 2010