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Zeichnungsnr./ Drwg-no.: 30007-008-12f
4.4.2.1. Use as acoustic warning system without test function
The safety function – generating a warning signal – is realised via a one-channel system (1oo1 according to
IEC/EN61508) without taking account of the diagnosis function, as also described in section 4.2.
The low and high demand mode is useable in the system without the automatic test function.
Evaluation for applications with high requirement rate or continuous requirement (high demand) and low
requirement rate (low demand) without automatic test release of the monitoring equipment.
T
ProofTest
1
4
Years
PFD
mean
1,1 x 10
-3
4,4 x 10
-3
(1/requirement)
PFH
G
2,5 x 10
-7
2,4 x 10
-7
(1/h)
SFF 96,8
96,8
%
DC 0
0
%
MTTR 48
h
λ
DU
Complete
251
Fit
λ
S
Complete
7535
Fit
HFT 0
Suitability of the system for use in safety chains until
SIL 2
The monitoring of the function of the sounder is used during the 'proof test'. The 'proof test' is described in
section 4.9 of the operating instructions/safety manual.
4.4.2.2. Use as acoustic warning system with test function
This monitoring can only be used with systems in low demand mode. The test function, as described in sec-
tion 4.7, is taken into account. This must be automated and must take place at least ten to one hundred
times more often than the expected requirement rate. The system with test function, including the diagnosis
and respective measures in the fault message, must be in accordance with the requirements of the function
safety according to IEC/EN61508.
In the following, a requirement rate less frequent than once a year is assumed (low demand).
Daily test interval (24h)
PFD
mean
3,0 x 10
-4
(1/requirement)
T
ProofTest
= 1 year
SFF
90,5%
%
MTTR = 48 h
DC
73%
%
Weekly test interval (168h)
PFD
mean
3,1 x 10
-4
(1/requirement)
T
ProofTest
= 1 year
SFF
90%
%
MTTR = 48 h
DC
72%
%
Monthly test interval (672h)
PFD
mean
3,6 x 10
-4
(1/requirement)
T
ProofTest
= 1 year
SFF
88,6%
%
MTTR = 48 h
DC
67%
%
Monthly test interval (672h)
PFD
mean
4,5 x 10
-3
(1/requirement)
T
ProofTest
= 15 years
SFF
90,5%
%
MTTR = 48 h
DC
73%
%
λ
DU
Complete
251
Fit
λ
S
Complete
7535
Fit
HFT 0
Suitability of the system for use in safety chains until
SIL 2
