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6.0 FUNCTION L S FETY
Introduction
The SM87LED Beacon has been designed for use in potentially explosive atmospheres
and harsh environmental conditions. The marine grade alloy or stainless steel enclosures
are suitable for use offshore or onshore, where light weight combined with corrosion
resistance and strength is required.
The safety function of the Beacon is to provide an intermittent spherical visual warning light
when the correct voltage is applied to the unit. The Beacon is designed to operate on a
supply voltage tolerance of +/- 20
The telephone initiate versions of the Beacon are not included in this safety manual.
Under No fault (Normal) Operating conditions the SM87LED Beacon will provide a
spherical visual warning light when required by the system.
Under fault conditions the failure mode of the Beacon is a failure to provide a spherical
visual warning light. For the failure rate associated with this failure mode please refer to
the table below.
Assessment of Functional Safety
The SM87LED Call Point 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
SM87LED Beacon against the requirements of IEC61508-2 using a proof test interval of
8760hrs.
The results are shown below and are based on Route 1
The Beacon is classed as a Type A device.
'To provide a spherical visual warning light when energised'
Architectural constraints:
Random hardware failures:
Probability of failure on demand:
Probability of Dangerous failure on
safety function:
Hardware safety integrity
!
[1]
compliance
Systematic safety integrity
compliance!
Systematic Capability
Overall SIL-capability achieved
05/17
SM87LED Beacon
Safety Function of SM87LED Beacon:
Type A
HFT=0
SFF= 66%
!
= 0
DD
!
= 1.96E-08
DU
PFD
=8.62E-05
AVG
(Low Demand Mode)
PFH = 1.96E-08
(High Demand Mode)
*Limited to SIL 2 due to SFF value
H
Proof Test Interval
=8760Hrs
MTTR = 8 Hrs
!
= 0
SD
!
= 3.92E-08
SU
SIL4
SIL3
!
Route 1
H
!
Route 1
S
SC2
SIL 2 (Low Demand)*
SIL 2 (High Demand)*
SIL2
© Eaton MEDC Ltd 2017
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