9. Glossary

Safe failure fraction (SFF)

Proportion of the overall rate of random hardware failures in a device that results in a safety-related failure or a detected hazardous failure, i.e. detected by a diagnostic test (based on report Ω 10 – INERIS).

Aussi bon que neuf; as good as new (AGAN)

Calculation assumption used in IEC 61508-6. After each periodic test, the PFD(t ) value is assumed to return to its initial value.

Safety Integrity Level; SIL level

IEC 61508 introduces four discrete levels whose function is to specify requirements (qualitative and quantitative) concerning the safety integrity of safety functions. Each SIL level has a corresponding risk reduction factor.

Probabilité de défaillance moyenne à la demande; Average of Probability Failure...