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The Quality Improvement Process
Published in Marlin U. Thomas, Reliability and Warranties: Methods for Product Development and Quality Improvement, 2006
Quality feedback from customer and warranty sources provides indications of problems, but further analysis is necessary to identify the actual causes of failures and malfunctions. For complex products and production systems, this can require extensive trouble-shooting and diagnostic studies. The most common techniques for examining failures are Failure Mode and Effect Analysis (FMEA); its extension, Failure Mode, Effect, and Criticality Analysis (FMECA); and Fault Tree Analysis (FTA). FMEA is a systematic procedure for decomposing a product or part into its most basic elements for determining the source of failure. It is the required process by any supplier to companies that subscribe to QS-9000, the quality standard that supplements ISO-9000. FMECA has the further purpose of estimating the risk associated with the failure modes. The procedure for performing FMECA is maintained by MIL-STD-1629A. FTA is a graphical technique for determining the root cause of undesirable events that is generally conducted in conjunction with FMECA.
Safety Criteria and Dependability Management Practices: A Case Study with I&C Systems of Prototype Fast Breeder Reactor
Published in Nuclear Technology, 2018
Srikantam Sravanthi, R. Dheenadhayalan, K. Madhusoodanan, K. Devan
All scram processing electronics are deployed with online self-diagnostics and subsequent fail-safe outputs in case of faults. Only one of the two voting logic circuits uses an inherently fail-safe design (PCSL). Inherently, fail-safe systems will automatically lead to a safe state in case of failures in the system. It does not require an additional diagnostic circuit. So these circuits have a lower unsafe failure probability since the periodicity of self-test is tending to zero and the issues arising out of failures in diagnostic circuitry do not exist. A failure mode effect analysis (FMEA) has to be used to assess the effects of each potential component failure on the system. This is performed by analyzing each component with all dominant failure modes as listed in Failure Mode/Mechanism Distributions in Ref. 21 and consequences of such failures on the system. IEC 60812 is the recommended standard for carrying out FMEA (Ref. 22).