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Loudspeaker - DB4B
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8.0 Functional safety
Introduction
The DB4B Loudspeaker has been designed for use in potentially explosive atmospheres and harsh environmental condi-
tions. The glass reinforced polyester enclosures are suitable for use offshore or onshore, where light weight combined
with corrosion resistance is required.
The safety function of the Speaker is to provide an audible warning when required.
Under No fault (Normal) Operating conditions the DB4B Speaker will provide an audible warning sound when required by
the system.
Under fault conditions the failure mode of the Speaker is a failure to provide an audible warning sound. For the failure
rate associated with this failure mode please refer to the table below.
Assessment of Functional Safety
This Loudspeaker is intended for use in a safety system conforming to the requirements of IEC61508.
UL has conducted a Failure Modes Effect and Diagnostic Analysis (FMEDA) of the DB4B Loudspeaker against the
requirements of IEC 61508-2 using a Proof Test Interval of 8760hrs.
The results are shown below and are based on Route 1
The Speaker is classed as a Type A device.
Architectural constraints:
Random hardware failures:
Probability of failure on demand:
Probability of Dangerous failure on
safety function:
Hardware safety integrity
compliance
[1]
Systematic safety integrity
compliance
Systematic Capability
Overall SIL-capability achieved
8
8
Loudspeaker - dB4B
.
H
dB4B speaker
Safety Function of the DB4B Speaker:
'To raise an audible warning sound when required
Type A
HFT=0
SFF= 71.5%
λ
= 0
DD
λ
= 2.88E-08
DU
PFD
=1.26E-04
AVG
(Low Demand Mode)
PFH = 2.88E-08
(High Demand Mode)
*Limited to SIL 2 due to SFF value
TM252 November 2023 www.eaton.com
Proof Test Interval
=8760Hrs
MTTR = 8 Hrs
λ
= 0
SD
λ
= 7.22E-08
SU
SIL3
SIL3
Route 1
H
Route 1
S
SC2
SIL 2 (Low Demand)*
SIL 2 (High Demand)*
SIL2
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