Vega VEGAPULS 61, Руководство по безопасности

Страница: 4 / 16

λ
dd
R ate for dangerous detected failure
λ
du
R ate for dangerous undetected failure
DC
S
D iagnostic C overage of safe failures ; DC
S
= λ
sd
/(λ
sd
+ λ
su
)
DC
D
D iagnostic C overage of dangerous failures ; DC
D
= λ
dd
/(λ
dd
+ λ
du
)
FIT F ailure I n T ime (
1
FIT
=
1
failure /
10
9
h )
MTBF M ean T ime B etween F ailure
MTTF M
ean
T
ime
T
o
F
ailure
MTTR M ean T ime T o R epair
l
IEC
61508
(
also available as
DIN EN )
-
F
unctional safety of electrical
/
electronic
/
programmable
electronic safety - related systems
l
IEC
61511
-
1
-
F unctional safety - safety instrumented systems for the
process industry sector
- P
art
1
: F
ramework
,
de fi ni
-
tions , system , hardware and software requirements
F ailure limit values for a safety function , depending on the SIL
class
(
of
IEC
61508
-
1
,
7
.
6
.
2
)
S
afety integrity level
L
ow demand mode
H
igh demand mode
SIL PFD
avg
PFH
4
≥
10
-
5
… <
10
-
4
≥
10
-
9
… <
10
-
8
3
≥
10
-
4
… <
10
-
3
≥
10
-
8
… <
10
-
7
2 ≥ 10
- 3
… < 10
- 2
≥ 10
- 7
… < 10
- 6
1
≥
10
-
2
… <
10
-
1
≥
10
-
6
… <
10
-
5
S
afety integrity of hardware for safety
-
related subsystems of
type B ( IEC
61508
-
2
,
7
.
4
.
3
)
S afe failure fraction H ardware fault
tolerance
SFF HFT = 0 HFT = 1 ( 0 ) HFT = 2
<
60
% not permitted SIL
1
SIL
2
60 % … < 90 % SIL
1
SIL 2 SIL
3
90
% … <
99
% SIL
2
SIL
3
( SIL
4
)
≥
99
% SIL
3
( SIL
4
) ( SIL
4
)
R elevant standards
S afety requirements
4
VEGAPULS series
60
-
4
…
20
m A / HART
F unctional safety
31338
-
EN
-
070510