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PFU 780 · Edition 02.12
63
Technical data
9 .1 Safety-specific characteristic values
In the case of ionization
control, suitable for Safety
Integrity Level
SIL 3
Diagnostic coverage DC
97.9%
Type of subsystem
Type B to EN 61508-2,
7.4.3.1.4
Mode of operation
High demand mode pursu-
ant to EN 61508-4, 3.5.12
Mean probability of dange-
rous failure PFH
D
1.34 x 10
-8
l/h
Mean time to dangerous
failure MTTF
d
Safe failure fraction SFF
99.2%
The specified values apply for the combination with ionization
electrode (sensor) and PFU 780 (logic).
Relationship between the Performance Level (PL) and the
Safety Integrity Level (SIL)
PL
SIL
a
–
b
1
c
1
d
2
e
3
Pursuant to EN ISO 13849-1:2006, Table 4, the PFU can be
used up to PL e.
Max. service life under operating conditions:
20 years after date of production, plus max. 1/2 year in stor-
age prior to first use.
For a glossary of terms, see page 67 (Glossary).