BS IEC 61703 : 2001 AMD 13690

FOREWORD
INTRODUCTION
1 Scope
2 Normative references
3 Definition
4 Glossary of symbols and abbreviations
   4.1 Non-repaired items
   4.2 Repaired items with zero time to restoration
   4.3 Repaired items with non-zero time to restoration
5 Assumptions
   5.1 General remarks
   5.2 Assumptions for non-repaired items
   5.3 Assumptions for repaired items
6 Mathematical expressions
   6.1 Non-repaired items
        6.1.1 Presentation
        6.1.2 Reliability [191-12-01]
        6.1.3 Instantaneous failure rate [191-12-02]
        6.1.4 Mean failure rate [191-12-03]
        6.1.5 Mean time to failure [191-12-07]
   6.2 Repaired items with zero time to restoration
        6.2.1 Presentation
        6.2.2 Reliability [191-12-01]
        6.2.3 Instantaneous failure intensity [191-12-04]
        6.2.4 Mean failure intensity [191-12-05]
        6.2.5 Mean time to failure [191-12-07]
        6.2.6 Mean time between failures [191-12-08]
        6.2.7 Mean operating time between failures
               [191-12-09]
        6.2.8 Mean up time [191-11-11]
   6.3 Repaired items with non-zero time to restoration
        6.3.1 Presentation
        6.3.2 Reliability [191-12-01]
        6.3.3 Instantaneous failure intensity [191-12-04]
        6.3.4 Mean failure intensity [191-12-05]
        6.3.5 Mean time to failure [191-12-07]
        6.3.6 Mean time between failures [191-12-08]
        6.3.7 Mean operating time between failures
               [191-12-09]
        6.3.8 Instantaneous availability [191-11-01]
        6.3.9 Instantaneous unavailability [191-11-02]
        6.3.10 Mean availability [191-11-03]
        6.3.11 Mean unavailability [191-11-04]
        6.3.12 Asymptotic availability [191-11-05]
        6.3.13 Asymptotic unavailability [191-11-07]
        6.3.14 Mean up time [191-11-11]
        6.3.15 Mean down time [191-11-12]
        6.3.16 Maintainability [191-13-01]
        6.3.17 Mean repair rate [191-13-03]
        6.3.18 Mean repair time [191-13-05]
        6.3.19 Mean active corrective maintenance time
               [191-13-07]
        6.3.20 Mean time to restoration [191-13-08]
        6.3.21 Mean administrative delay [191-13-11]
        6.3.22 Mean logistic delay [191-13-13]
Annex A (informative) Performance aspects and descriptors
Annex B (informative) Summary of measures related to time
         to failure
Annex C (informative) Comparison of some dependability
         measures for continuously operating items
Annex D (informative) Software dependability aspects
Bibliography
Figures
Tables

Gives mathematical expressions for reliability, availability, maintainability and maintenance support measures defined in IEC 60050-191. The following classes of items are considered separately in this standard: - non-repaired items; - repaired items with zero time to restoration; - repaired items with non-zero time to restoration. In order to keep the mathematical formulae as simple as possible, the following basic mathematical models are used to quantify dependability measures: - random variable (time to failure) for non-repaired items; - simple (ordinary) renewal process for repaired items with zero time to restoration; - simple (ordinary) alternating renewal process for repaired items with non-zero time to restoration.