Failure mode and effects analysis by kellena89

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									Failure Mode and Effects Analysis

Prof. Enrico Zio

Politecnico di Milano
Dipartimento di Energia




     Prof. Enrico Zio
FMEA

                • Qualitative
                • Inductive

                       AIM:

  Identification of those component failure
modes which could fail the system (reliability)
 and/or become accident initiators (safety)



                 Prof. Enrico Zio
FMEA: Procedure steps
1. Decompose the system in functionally independent
   subsystems;

2. For each subsystem identify its operation modes
   (start-up, regime, shut-down, maintenance, etc.) and
   configurations (valves open or closed, pumps on or
   off, etc.);

3. For each subsystem in each of its operation modes,
   compile a FMEA table




                    Prof. Enrico Zio
FMEA TABLE

    SUBSYSTEM:
    OPERATION MODE:
component       Failure       Effects on    Effects on       Effects on     Probability*     Criticality+   Detection    Protections   Remarks
                mode             other      subsystem           plant                                       methods          and
                             components                                                                                   mitigation

Description     Failure        Effects of    Effects on      Effects on     Probability of    Criticality   Methods of   Protections    Remarks
                 modes       failure mode        the             the           failure       rank of the     detection      and            and
              relevant for    on adjacent   functionality   functionality    occurrence         failure       of the     measures to   suggestion
                  the        components        of the            and        (sometimes        mode on       occurrence    avoid the     s on the
              operational         and        subsystem       availability    qualitative)     the basis       of the       failure      need to
                 mode        surrounding                    of the entire                        of its       failure    occurrence     consider
               indicated     environment                        plant                        effects and      event                    the failure
                                                                                             probability                                mode as
                                                                                             (qualitative                               accident
                                                                                             estimation                                  initiator
                                                                                               of risk)




  * negligible, rare, likely, very likely
  + safe, marginal, critical, catastrophic




                                                  Prof. Enrico Zio
EXAMPLE: SMALL EXTERNAL POOL
The water of the pool is in re-circulation through pumps that aspire the water of the
compensation tank making it pass through the treatment organs before throw it
again in the pool.




 SYSTEM TO
   FILTER
 THE WATER




  SYSTEM TO
CORRECT WATER
     PH



                                                                   SYSTEM TO
                                                              DISINFECT THE WATER
                              Prof. Enrico Zio
Ex. 1: FMECA
The objective of the FMECA analysis is to identify the possible failure modes
of the different components and their effect to the normal operation that can
             contribute to the reduction of the quality of the water.
                                                                Criticality
                                                                              Frequency
                                                                  class


                                                                 Marginal     Reasonably
                                                                               probable




                                                                 Marginal      Remote




                                                                 Marginal      Probable




                                                                 Critical     Reasonably
                                                                               probable




                                                                 Marginal      Remote




                             Prof. Enrico Zio
FMEA: comments

1. Only single failures, except for standby and
   protection components
2. No common cause failures
3. At system design phase, no components but
   functions
4. Simple and systematic (computer tools available)
5. Subjective (relies on analyst’s expertise)
6. Often used in support to the construction of FT and
   for RCM




                    Prof. Enrico Zio

								
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