An improved FMEA methodology

The application and use of process and design FMEA (failure mode and effects analysis) in the British rail and automotive industries are considered. Guidelines from BS.5760 standard are reviewed, and associated problem areas discussed. These guidelines are based on risk priority numbers (RPNs) which are calculated for every recorded cause of failure. Since these guidelines do not address themselves to the computation of RPNs for all modes of failure for each item and module of the system, a methodology based on probability theory is developed to calculate RPNs for every recorded failure cause. The probabilistic approach presented is extended to calculate priority indices for every recorded failure mode, component, and for the total system. The authors introduce the idea of an ordered matrix FMEA where all qualitative and quantitative information recorded is stored in a pictorial and convenient way. The probabilistic and matrix approaches have been incorporated in a computer program implemented on an IBM PC. The program developed is used to identify efficiently all potential causes of failure. An illustrative example of its use is given