MEDC LD15 - Manual (Page 8)

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The LD15 Beacon 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 Beacon is to provide an intermittent or permanent spherical visual
warning light when the correct voltage is applied to the unit. The Beacon is designed to operate
on a supply voltage of 24vDC with a tolerance of +/- 20%.
Under No fault (Normal) Operating conditions the LD15 Beacon will provide a spherical visual
warning light when required by the system, with no time delay or other faults
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
This Beacon is intended for use in a safety system conforming to the requirements of IEC61508.
Sira Test & certification Ltd has conducted a Failure Modes Effect and Diagnostic Analysis
(FMEDA) of the LD15 Xenon Beacon against the requirements of IEC 6150
The results are shown below and are based on Route 1
H.
The Beacon is classed as a Type B device
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8-2 using a Proof
Test Interval of 8760hrs.
Safety Function:
‘To provide an intermittent or permanent spherical visual warning light upon demand’.
Summary of Clauses
2/7.4.2 and 2/7.4.4
LD15 LED Beacon
Single Mode (1oo1)
LD15 LED Bea con
Redundant Mode (1oo2)
Verdict
HFT=0 HFT=1 Type B
Architectural constraints
Safe Failure Fraction (SFF) 60% 60% SIL 1
Random hardware
failures:
[h -1 ]
!
DD
!
DU
0.00E+00
3.44E-08
0.00E+00
3.45E-09
!
Random hardware
failures:
[h -1 ]
!
SD
!
SU
0.00E+00
5.16E-08
0.00E+00
5.19E-09
!
Diagnostic coverage (DC) 0.00% 0.00%
!
PFD @ PTI = 8760Hrs
MTTR = 8 Hrs
1.51E-04 1.51E-05 !
Average freq. of dangerous failure
(high demand-PFH)[h
-1 ]
3.44E-08 3.45E-09
SIL 3
SIL 3
!
Hardware safety integrity
compliance
[
Route 1
H
Systematic safety integrity
compliance
See report R56A31253B
Systematic Capability
(SC1, SC2, SC3, SC4)
SC2 (R56A31253B)
Hardware safety integrity achieved Limited to: SIL 1 (1oo1) & SIL 2 (1oo2) due to SFF value.
04/15 © MEDC 2015