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The horn – DB3B UL
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8.0 Functional safety
Introduction
The DB3B Sounder has been designed for use
in potentially explosive atmospheres and harsh
environmental conditions. 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 Sounder is to provide a
pre-determined audible warning sound when required if
the correct voltage is applied to the unit. The DC version
of the Sounder is designed to operate on a supply voltage
between 12-48v dc.
Under No fault (Normal) Operating conditions the DB3B
Sounder will provide an audible warning sound when
required by the system.
Summary of clauses
2/7.4.2 And 2/7.4.4
Architectural constraints
Safe Failure Fraction (SFF)
λ
Random hardware
DD
λ
failures: [h
]
-1
DU
λ
Random hardware
SD
λ
failures: [h
]
-1
SU
PFD @ PTI = 8760Hrs
MTTR = 8 Hrs
Average freq. of dangerous failure (high
demand-PFH)[h
]
-1
Hardware safety integrity compliance
Systematic safety integrity compliance
Systematic Capability
(SC1, SC2, SC3, SC4)
Hardware safety integrity achieved
10
The horn – DB3B UL TM261 April 2020 www.eaton.com
DB3B Sounder
Safety Function of DB3B Sounder:
To provide a pre-described audible warning sound when required'
DB3B Sounder
Single mode (1oo1)
HFT=0
65.9%
6.5E+09
1.16E-07
0.00E+00
2.18E-07
5.09E-04
1.16E-07
Limited to: SIL 1 (1oo1) & SIL 2 (1oo2) due to SFF value.
Under fault conditions the failure mode of the Sounder
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 Sounder 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 DB3B Sounder 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 Sounder is classed as a Type B device.
DB3B Sounder
Redundant mode (1oo2)
HFT=1
65.9%
6.5E+10
1.16E-08
0.00E+00
2.18E-08
5.09E-05
1.16E-08
Route 1
H
Route 1
s
SC2
.
H
Verdict
Type B
SIL 1(1oo1)
SIL 2 (1oo2)
SIL 3(1oo1)
SIL 2(1oo1)
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