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A
A
Assessment of Functional Safety
s
e s
s s
m
e
t n
f o
f o
F
u F
n
t c
i
o i
n
l a
This sounder is intended for use in a safety system conforming to the requirements of IEC61508.
h T
s i
o s
u
n
d
er
s i
t n i
n e
d
ed
Si
Sira Test & certification Ltd has conducted a Failure Modes Effect and Diagnostic Analysis (FMEDA) of the DC
a r
T
es
t
&
c
er
i t
c i f
t a
o i
n
L
v
version of DB3 sounder against the requirements of IEC 61508-2 using a Proof Test Interval of 8760hrs.
er
s
o i
n
f o
D
B
B
3
o s
u
n
d
er
T
The DC version of the sounder was considered to be the worst case. The results are shown below and are based on
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t f
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Route 1
R
o
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1
H
H
T
The sounder is classed as a Type B device.
e h
s
o
u
n
d
r e
s i
c
a l
s s
ed
s a
Architectural constraints:
A
c r
t i h
ec
u t
ur
l a
o c
n
t s
a r
Random hardware failures:
R
a
n
d
o
m
h
h
a
d r
w
a
e r
f
l i a
Probability of failure on demand:
P
o r
b
a
b
t i l i
y t t y
y
f o
a f
l i
ur
e
P
P
Probability of Dangerous failure on safety
o r
b
b
a
b
b
t i l i
t i l i
y t t y
t
f o
f
D
D
a
n
e g
u f
function:
n
t c
o i
: n
H
Hardware safety integrity compliance
a
d r
w
a
e r
e
s
f a
et t y
y
y
t n i
eg
Sy
Systematic safety integrity compliance
y
s
e t
m
a
i t
c
s
f a
et t y
y
y
t n i
g eg
Systematic Capability
Sy
s
e t
m
a
i t
c
C
a
p
a
b
l i
y t t y i
Overall SIL-capability achieved
O
v
r e
l l a
S
L I -
a c
p
a
l i b
y t t y i
© MEDC 2014
l
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ty
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ty
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em
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g
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r
eq
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m
en
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d
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w
s a
o c
s n
d i
er
ed
o t
a
y T
e p
B
d
ev
c i
e.
.
Safety Function of DB3 Sounder:
S
Sa
f
et t y
y
'
'To provide a pre-described audible warning sound when required'
o T T o
p
o r r o
i v v i
e d d e
a
p
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-
-
de
es
c
r r i
b i i b
n i
: s t
ur
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:
o
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m
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n
: d
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us
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g t t y i
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y
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p
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c a
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ed
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f n
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t
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r
eq
q
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o
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E
f
f
f
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ec
t
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D
D
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C
6
1
5
0
8
-
2
us
n i
g
g
a
b
t e
e h
w
o
s r
c t
s a
e.
T
h
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e
DB3 SOUNDER
D
B
3
S
O
U
N
D
ER
F
un
t c
o i
n
f o
D
B
3
S
u o
n
d :
d
r e
ed
a
u
d d i
b i i b
e l l e
w w a
a
n r r n
n i
g
o s
o
u
y T
Type B
e p
B
Proof Test Interval
P
o r
o
o
T f
H
HFT=0
F
= T
0
=
=8760Hrs
8
7
6
6
0
SF
SFF =
F
=
MTTR = 8 Hrs
M
T T
R
7
74.00%
4
0 .
0
%
λ
λ
= 3.25E-06
=
3
2 .
5
E
-06
DD
DD
λ
λ
= 2.15E-06
=
2
1 .
5
E
-06
DU
D
U
PFD
F P
D
=9.44E-03
=
9
4 .
4
E
-
03
AVG
A
VG
(
(Low Demand Mode)
o L
w
D
e
m
a
n
d
M
M
F P
F P
PFH = 2.15E-06
H
H
=
2
2
1 .
1
5
5
E
E
-06
06
6
6
(High Demand Mode)
H (
g i
h
D
e
m
a
n
d
M
SC
SC 2 (Ref to 56A24816B)
e r
m
n e
s t
f o
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C
6
1
5
0
. 8
g
n
s o
c i t
A
n
a
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s i s
F (
M
E
D
P
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o
T f
es
t
n I
e t
v r
rv
l a
f o
8
7
r
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ul
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o
w
n
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w
n
d
w w h
h
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r r e
eq
i u
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ed
d'
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es
t
t n I
er
rv
v
l a
[
[4]
] 4
H
s r
[
[4]
] 4
=
8
H
s r
λ
λ
=
= 2.20E-08
2
2 .
0
E
-08
S
SD
D
λ
λ
=
= 2.81E-06
2
8 .
1
E
-06
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Route 1
R
o
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e
1
H
H
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Route 1
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ut
e
1
S
S
2
R (
f e
o t
5
6
A
2
4
8
1
6
) B
SIL 1 (Low Demand)
SI
L
1
(
o L
w
D
e
m
a
n
) d
SI
SIL 1 (High Demand)
L
1
H (
g i
h
D
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m
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) d
) A
o
o
t f
e h
D
C
6
0
h
h
. s r
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n
d
d
a
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b
s a
ed
o
n
SI
SIL 1
L
1
SIL 2
SI
L
2
SI
SIL 1
SI
L
L
1
1
07/14
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