Analysis of the operator´s error influence on the safety of the controlled process

The demonstration of the safety of safety related control systems (SRCS) is a necessary condition for their putting in operation. An assessment of faults influence on safety of the SRCS is an important activity during demonstration of the safety. If the safety assessment is expected to be objective, it should be based on the use of quantitative methods and the real estimates of reliability characteristics. Very difficult is to objectively assess the impact of human errors on the safety of the SRCS. Human errors may occur before putting the SRCS into service (there means errors during the development of SRCS and its implementation, which may cause the occurrence of systemic failures of the SRCS) or during the SRCS operation (there means the use of safety-critical commands in case of the partial or total failure of the SRCS). This contribution deals with the issue of the safety assessment of the operator effect on the safety of the controlled process.