Taxomomy of Deviations to Prevent Safety-Related Oversights

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System failures occur when functional units deviate from normalcy. These failures can be decreased if system designers can enumerate potential deviations of functional units. Some deviations can be neglected based on possibility and seriousness. and others should be coped with by design modifications. This study classifies safety-related deviations to facilitate discovery of the deviations.The 1998 study uses labels for characterization of system elements. For instance, a blade of a fan can be labeled as a "rotating part" from which inadvertent stoppage and abnormal rotation rate can be found. A total of 35 labels are listed. An interactive computer program is developed to aid the discovery.The 1999 study focuses on materials and functions. The materials are grouped into raw materials. products. service materials and storage materials. The functions are classified into constraint. transformation. and generation. Functional deviations include execution failure and failure to achieve specifications. Material failures are classified from points of view of stressors such as force. torque. heat. temperature. and pressure. An after-burning deviation can be found for automobiles.