Understanding the Similarities and Difference of Oreda and Fmeda Data Analysis

This paper highlights the similarities and differences between the safety parameters which result from OREDA and FMEDA data analysis as these methods are applied to their respective databases.  A sample of the published results from each method is presented and described and, when differences exist, the underlying causes of the differences are discussed.   The fundamental differences between the statistical parameter estimation performed by OREDA (which are based on field failure data from offshore and onshore topside oil exploration and production facilities as well as offshore subsea facilities) and the parameter prediction produced by FMEDA (which derives failure parameters based on validated failure rate and failure mode databases of components that comprise functional safety related devices) are explained.   The similarities and differences in environmental profiles covered by each method are described and compared.  The capabilities of each method for dealing with application specific safety issues are considered; these application issues include the common scenarios of close to trip vs open to trip safety system configurations.  The differences in the methods’ capabilities for analyzing the safety of a specific device vs a generalized subsystem or system are reviewed.    The methods’ capabilities of including the effects of end-user action on safety performance are emphasized because it is the end-user actions that are the most significant source of differences between the two methods’ results for safety related equipment failure rates.   A table comparing these as well as other characteristics is presented.  The relative advantages and disadvantages of each analysis method are discussed and attention is drawn to the complementary nature of the data produced by the two methods.