Recovery of E-SRS With 2 × (2<i>oo</i>2) System Architecture and Its Impact on the Safety Integrity of a Safety Function

All electronic safety-related systems (E-SRS) must undergo qualitative and quantitative evaluation to determine the required safety integrity level (SIL) or similar safety evaluation metrics. Various methods, such as fault tree analysis (FTA) and Markov chain analysis (MC), are available for evaluating system safety parameters. While existing studies extensively document the safety characteristics of electronic safety-related systems, there is a lack of research focusing specifically on the impact of recovery mechanisms in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$ 2 \times (2 oo 2) $ </tex-math></inline-formula> system architectures. This study utilizes homogeneous continuous-time Markov chains (CTMC) to assess the safety and reliability properties of electronic safety-related systems with cold standby. Qualitative and quantitative analyses are performed on the E-SRS architecture, with a focus on identifying potential subsystem failure combinations that could lead the system into a dangerous state. The practical analysis is divided into three parts: first, the safety and reliability of the E-SRS without recovery are evaluated; second, recovery mechanisms are incorporated using different approaches; and third, results from systems with and without recovery are compared. The analysis reveals that recovery mechanisms slightly reduce safety, with a negative impact of 3. 36% observed in the calculations with our parameters compared to system architecture without recovery. However, recovery significantly improves reliability, underscoring its practical advantages despite minor safety trade-offs. The implications of this study can be used to determine the optimal way to employ qualified personnel to perform recovery of the system.