The fast beam interlock system (FBIS) for the ESS accelerator was developed and built in-house by the safety critical systems (SKS) group at the Zurich University of Applied Sciences (ZHAW), in close collaboration with the ESS machine protection (MPS) group. The FBIS plays an essential role in ESS machine protection and is the logic solver element of most protection functions. In order to ensure high reliability of the FBIS, a reliability analysis is performed following the IEC 61508 functional safety standard for the assessment of hardware integrity.
The presentation shows the various steps needed to verify the hardware integrity.
This includes the calculation of the Probability of dangerous Failure per Hour (PFH) and the evaluation of the architectural constraints by calculating the Safe Failure Fraction (SFF) and the Hardware Fault Tolerance (HFT) of the system. These calculations are based on failure rate predictions using the Siemens SN 29500 standard and a detailed Failure Modes, Effects and Diagnostic Analysis (FMEDA).
The current results of the FBIS reliability analysis are presented and compared with the corresponding hardware integrity requirements. In addition, an example reliability analysis of a complete ESS machine protection function containing a senor system and actuators is shown.