PFD
avg
T
P
roof
=
1
year
T
P
roof
=
5
years
T
P
roof
=
10
years
<
0
.
044
x
10
-
2
<
0
.
218
x
10
-
2
<
0
.
436
x
10
-
2
PFH
<
0
.
1
x
10
-
6
/
h
D
ouble channel architecture
I
f the measuring instrument is used in a double channel
architecture
,
the safety
-
relevant characteristics of the selected
structure of the measuring chain must be calculated acc
.
to the
above failure rates
(
especially for the selected application
).
A
C
ommon
C
ause
F
actor must be taken into account which is in
the worst case
10
%
.
T
he following is applicable
:
SIL
3
(
S
afety
I
ntegrity
L
evel
)
HFT
=
1
(
H
ardware
F
ault
T
olerance
)
T
he time
-
dependent process of
PFD
avg
reacts in the time
period up to
10
years virtually linear to the operating time
.
T
he
above values only apply to the
T
P
roof
interval
,
after which a
recurring function test must be carried out
.
1
5
10
T
Proof
PFD
avg
1
2
3
4
F
ig
.
9
:
T
ime
-
dependent process of
PFD
avg
2
)
1
PFD
avg
=
0
2
PFD
avg
after
1
year
3
PFD
avg
after
5
years
4
PFD
avg
after
10
years
2
)
N
umbers see in the above charts
.
A
rchitecture
1
oo
1
D
T
ime
-
dependent process of
PFD
avg
30
SU
501
E
x
-
S
ignal conditioning instrument
F
unctional safety
27953
-
EN
-
050616
