Challenges related to surveillance of safety functions

摘要

One of the main principles for the safety work in high-risk industries such as the nuclear and process industry, is the principle of defence-in-depth that imply use of multiple safety barriers or safety functions in order to control the risk. Traditionally, there has been a strong focus on the design of safety functions. However, recent standards and regulations focus on the entire life cycle of safety functions, and this paper focuses on the surveillance of safety functions during operations and maintenance. The paper presents main characteristics of safety functions, factors influencing the performance, a failure category classification scheme, and finally a discussion of challenges related to the surveillance of safety functions during operations and maintenance. The discussion is based on experiences from the Norwegian petroleum industry and results from a research project concerning the reliability and availability of computerized safety systems. The main message is that there should be an integrated approach for surveillance of safety functions that incorporates hardware, software and human/organizational factors, and all failure categories should be systematically analyzed to (1) monitor the actual performance of the safety functions and (2) systematically analyze the failure causes in order to improve the functionality, reliability and robustness of the safety functions.