FCU 500, FCU 505 · Edition 02.17
147
Glossary
21 .8 Safe failure fraction SFF
Fraction of safe failures related to all failures, which are
assumed to appear
from EN 13611/A2:2011
21 .9 Probability of dangerous failure PFH
D
Value describing the likelihood of dangerous failure per
hour of a component for high demand mode or con-
tinuous mode. Unit: 1/h.
from EN 13611/A2:2011
21 .10 Mean time to dangerous failure
MTTF
d
Expectation of the mean time to dangerous failure
from EN ISO 13849-1:2008