IEC 61508 Functional Safety Assessment Rosemount Inc. - Exida

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6 Terms and DefinitionsFault toleranceFITFMEDAHFTLow demand modePFD AVGSFFSIFSILSISType A (sub)systemType B (sub)systemAbility of a functional unit to continue to perform a required function in thepresence of faults or errors (IEC 61508-4, 3.6.3)Failure In Time (1x10 -9 failures per hour)Failure Mode Effect and Diagnostic AnalysisHardware Fault ToleranceMode, where the frequency of demands for operation made on a safetyrelatedsystem is no greater than twice the proof test frequency.Average Probability of Failure on DemandSafe Failure Fraction summarizes the fraction of failures, which lead to asafe state and the fraction of failures which will be detected by diagnosticmeasures and lead to a defined safety action.Safety Instrumented FunctionSafety Integrity LevelSafety Instrumented System – Implementation of one or more SafetyInstrumented Functions. A SIS is composed of any combination ofsensor(s), logic solver(s), and final element(s).“Non-Complex” (sub)system (using discrete elements); for details see7.4.3.1.2 of IEC 61508-2“Complex” (sub)system (using micro controllers or programmable logic); fordetails see 7.4.3.1.3 of IEC 61508-2© exida Certification rosemount 11-07-062 r007 v1 r1 iec 61508 assessment.docx, 3/8/2012Michael Medoff Page 20 of 21
7 Status of the document7.1 Liabilityexida prepares reports based on methods advocated in International standards. Failure rates areobtained from a collection of industrial databases. exida accepts no liability whatsoever for the useof these numbers or for the correctness of the standards on which the general calculation methodsare based.7.2 ReleasesVersion: V1Revision: R1Version History: V1, R1: Updated based on review comments; March 8, 2012V0, R1: Draft; March 7, 2012Authors: Michael MedoffReview: V1, R1: John Yozallinas & Jessica Lo; March 8, 2012Release status: Released.7.3 Future EnhancementsAt request of client.7.4 Release SignaturesJohn Yozallinas, Evaluating AssessorMichael Medoff, Certifying Assessor© exida Certification rosemount 11-07-062 r007 v1 r1 iec 61508 assessment.docx, 3/8/2012Michael Medoff Page 21 of 21
Page 1 and 2: IEC 61508 Functional Safety Assessm
Page 3 and 4: Table of ContentsManagement summary
Page 5 and 6: 2 Project management2.1 exidaexida
Page 7 and 8: [D189] exida Modification Phase Ver
Page 9 and 10: [D97] Software DVT Test Plan B.2;11
Page 11 and 12: 3 Product DescriptionThe Rosemount
Page 13 and 14: 4 IEC 61508 Functional Safety Asses
Page 15 and 16: 5.1.2 Safety Requirements Specifica
Page 17 and 18: Requirements from IEC 61508-3, Tabl
Page 19: These results must be considered in

IEC 61508 Functional Safety Assessment Rosemount Inc. - Exida

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