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Abstract
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This paper describes a fault tree analysis package that eliminates most of the housekeeping tasks involved in proceeding from the initial construction of a fault tree to the final stage of presenting a reliability analysis in a safety report. It is suitable for designers with relatively little training in reliability analysis and computer operation.
Users can rapidly investigate the reliability implications of various options at the design stage and evolve a system which meets specified reliability objectives. Later independent review is thus unlikely to reveal major shortcomings necessitating modification and project delays.
The package operates interactively, allowing the user to concentrate on the creative task of developing the system fault tree, which may be modified and displayed graphically. For preliminary analysis, system data can be derived automatically from a generic data bank. As the analysis proceeds, improved estimates of critical failure rates and test and maintenance schedules can be inserted.
The computations are standard--identification of minimal cut-sets, estimation of reliability parameters and ranking of the effect of the individual component failure modes and system failure modes on these parameters. The user can vary the fault trees and data on-line and print selected data for preferred systems in a form suitable for inclusion in safety reports.
The programs, which are written in FORTRAN for an IBM 370, can accommodate up to 500 basic faults and 500 gates. Their application to a system with 355 basic faults and 285 gates is described. |