Spurious activation and operational integrity evaluation of redundant safety instrumented systems

Meng Qi, Yufeng Kan, Xun Li, Xiaoying Wang, Dongfeng Zhao, Il Moon

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


Safety instrumented systems (SISs) used in various industries are designed to perform specific safety functions to prevent possible accident scenarios. However, spurious activation occurs when a SIS is activated in an untimely manner, potentially resulting in production interruption, economic loss as well as risk to present during the system restoration. Therefore, it is necessary to quantify the spurious activation rate to reduce the number of spurious activations and achieve the highest overall level of risk reduction. This study analyzes possible scenarios leading to a spurious trip in SIS subsystems and presents a further development of existing analytical formulas to calculate the spurious trip rate (STR) for any KooN configuration. The proposed formulas are compared to the existing ones to evidence the improvements and are applied in numerical calculations to investigate the operational integrity of SIS subsystems. Results indicate that common cause failure contributes to most of the STR in input elements and logic solvers, and optimal configurations with both lower PFDavg and lower STR are identified in each subsystem. The overall approach is illustrated via a simple case study and some conclusions are drawn.

Original languageEnglish
Article number106785
JournalReliability Engineering and System Safety
Publication statusPublished - 2020 May

Bibliographical note

Funding Information:
We express our sincere thanks to the anonymous reviewers for their constructive comments and useful suggestions on the original manuscript, which led to this improved version. The authors gratefully acknowledge the financial support provided by the Key R&D Program of Shandong Province, China , in 2019 (Major Scientific and Technological Innovation Project) ( 2019JZZY020502 ).

Publisher Copyright:
© 2019 Elsevier Ltd

All Science Journal Classification (ASJC) codes

  • Safety, Risk, Reliability and Quality
  • Industrial and Manufacturing Engineering


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