MEDC LD15 UL, Техническое руководство

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8.0 FUNCTIONAL SAFETY
Introduction
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%.
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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.
The DC version of the Beacon is designed to operate on a supply voltage of 11-58Vdc,
the AC version of the beacon is designed to operate on a supply voltage of 110-254Vac.
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 61508-2 using a Proof Test Interval of 8760hrs.
The results are shown below and are based on Route 1H.
The Beacon is classed as a Type B device
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 Beacon
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.
- LD15 DC