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Criteria for SC-CC parameters

Discussion in 'FMEA - Failure Modes and Effects Analysis' started by Aalekh Prajapati, Nov 26, 2019.

  1. Aalekh Prajapati

    Aalekh Prajapati Member

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    In order to classify any parameter as SC or CC, i understand that there is criteria for severity and occurrence, which is as follows (SC criteria may differ companywise).

    Severity:
    CC: Severity 9-10; since it refers to regulations and safety requirements.
    SC: Severity 5-8; since it refers to functional requirement. There is no degradation or loss of function below severity 5 according to FMEA AIAG-VDA manual.

    Occurrence:
    CC: No criteria
    SC: Occurrence 4 or higher.

    Most of the companies have adopted the criteria of occurrence for SC.

    I am in middle of defining criteria for SC-CC in my organization. Management is asking for explanation behind occurrence criteria.
    I would like to understand why there is a need to define criteria of occurrence, to define a parameter as SC ?

    Any answers / explanations / leads will be highly appreciated.
    Thanks in advance.

    Regards,
    Aalekh Prajapati
     
  2. Bev D

    Bev D Moderator Staff Member

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    There should be no occurence rating - even though it might be popular there is NO scientific basis for assigning it other than actual testing at the apporapriate sample sizes and variation in conditions and inputs.

    NO ONE can assess occurence appropriately without data. Without data it’s just guessing.
    I can look at any of our products over time and see a lot of variation in defect rates low to high and back again as inputs and conditions vary.

    We use only severity.
    Occurence is an output of risk assessment not an input.
     
  3. Bev D

    Bev D Moderator Staff Member

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    Some references:

    Wheeler, Donald, “Problem with Risk Priority Numbers, More Mathematical Jabberwocky”, Quality Digest, June 2011. http://www.qualitydigest.com/inside/quality-insider-article/problems-risk-priority-numbers.html

    Youssef, Nataly F. and Hyman, William A., “Analysis of Risk: Are Current Methods Theoretically Sound? Applying risk assessment may not give manufacturers the answers they think they are getting”, Medical Device & Diagnostic Industry, October 2009
    http://www.mddionline.com/article/analysis-risk-are-current-methods-theoretically-sound

    Flag, John, “Rethinking Failure Mode and Effects Analysis”, Quality Digest, June 2015

    https://www.qualitydigest.com/insid...inking-failure-mode-and-effects-analysis.html

    Crosby, David, “Words that Kill Quality and Spill Oil”, Quality Digest, July, 2010
    https://www.qualitydigest.com/inside/twitter-ed/words-kill-quality-and-spill-oil.html

    Imran, Muhammad, “The Failure of Risk Management and How to Fix It”, Book Review, Journal of Strategy & Performance Management, 2(4), 2014 pp. 162-165
    http://jspm.firstpromethean.com/documents/162-165.pdf

    “United Airlines Flight 232 FAA Lessons Learned”
    https://lessonslearned.faa.gov/ll_main.cfm?TabID=3&LLID=17&LLTypeID=2



    Books:

    Hubbard, Douglas W., The Failure of Risk Management; Why It’s Broken and How to Fix It, John Wiley and Sons, 2009

    Taleb, Nassim Nicholas, The Black Swan: The Impact of the Highly Improbable, Random House Trade Paperbacks, May 2010
     
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