Strategy for defense against failures

The underlying strategy for defenses against systematic, random, and common-cause failures involves improving three fundamental aspects of an installation 

The overall quality refers to the precautions taken to guard against systematic failures. Specification errors, equipment errors, and software errors can easily occur during normal maintenance activities. Improving the overall quality involves careful thought and planning at every step of the lifecycle process. The use of an approved quality management system is recommended. 

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The architecture refers to the way in which the SIF devices are arranged and the arrangement of the SIS reiative to other protection layers. Fault tolerant architectures supplemented with the careful use of diversity reduce the risk of random failures, as well as systematic failures. ISA-TR 84-00-04, Annex K, provides guidance on minimum fault tolerance requirements. 

ANSI/ISA-84.00.01-2004-1, Clauses 16.2.2 and 16.3.3, identifies the data to be maintained on the SIS/SIF by Operations and Maintenance respectively. The IPRDS provides data to determine process demand frequencies and device failures, as described in ANSI/ISA-84.00.01-2004-1, Clauses 16.3.1.5. It also provides failure mode information that can be used to develop diagnostic techniques and to serve as the basis for device checklists, revealing a greater percentage of the dangerous failures. ANSI/ISA- 

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Inspection and testing to identify potential problems affecting muitipie devices G.8 Strategy for defense against failures... 

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