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The horn – DB3B UL
TM261 April 2020 www.eaton.com
The horn – DB3B UL
English
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.
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
H
.
The Sounder is classed as a Type B device.
DB3B Sounder
Safety Function of DB3B Sounder:
To provide a pre-described audible warning sound when required’
Summary of clauses
2/7.4.2 And 2/7.4.4
DB3B Sounder
Single mode (1oo1)
DB3B Sounder
Redundant mode (1oo2)
Verdict
Architectural constraints
Safe Failure Fraction (SFF)
HFT=0
HFT=1
Type B
65.9%
65.9%
SIL 1(1oo1)
SIL 2 (1oo2)
Random hardware
failures: [h
-1
]
λ
DD
λ
DU
6.5E+09
1.16E-07
6.5E+10
1.16E-08
Random hardware
failures: [h
-1
]
λ
SD
λ
SU
0.00E+00
2.18E-07
0.00E+00
2.18E-08
PFD @ PTI = 8760Hrs
MTTR = 8 Hrs
5.09E-04
5.09E-05
SIL 3(1oo1)
Average freq. of dangerous failure (high
demand-PFH)[h
-1
]
1.16E-07
1.16E-08
SIL 2(1oo1)
Hardware safety integrity compliance
Route 1
H
Systematic safety integrity compliance
Route 1
s
Systematic Capability
(SC1, SC2, SC3, SC4)
SC2
Hardware safety integrity achieved
Limited to: SIL 1 (1oo1) & SIL 2 (1oo2) due to SFF value.
