Squeezing every last drop: life extension of the LHC and PS access safety systems

The LHC Access Safety System (LASS) was commissioned in 2008 for the initial launch of the LHC, while the current PS Access Safety System (PASS) entered in operation in 2015 after a full multi-year revision. By the end of the upcoming LHC Long Shutdown 3 in 2030, LASS will have accumulated over 20 years of service and PASS 15 years. Both systems are based on Siemens series 400 safety PLCs, a product line that is being progressively phased out by the vendor. After evaluating several consolidation strategies to ensure the smoothest possible continuity of operation of both LHC and PS, we have opted for a life extension of both current access safety systems. This strategy retains the existing systems but introduces a number of architectural enhancements to mitigate current limitations that could impact accelerator availability. The objective is to secure reliable long-term operation of both safety systems, while also improving operational autonomy, maintenance capabilities, and resilience to vendor product life cycles. This paper outlines the rationale behind the selected approach, the external factors influencing our decision, and the key steps planned to implement this consolidation effectively.