5. Glossary

Aussi bon que neuf; As Good As New (AGAN)

Calculation assumption used in IEC 61508-6. After each periodic test, the PFD(t) curve 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 of Failure on Demand

Average value of the probability of failure on demand PFD(t) over the time interval between two function tests.

Redundancy; Redondance

Existence, in an entity, of more than one means to accomplish a...