Functional Safety - MEDC Xénon XB15 Manuel Technique

8.0 FUNCTIONAL SAFETY

Introduction
The XB15 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 spherical visual warning light when the correct voltage is
applied to the unit. The DC versions of the Beacon are designed to operate on a supply voltage tolerance of +/- 20%;
the AC versions of the beacon are designed to operate on a supply voltage tolerance of +/- 10%.
The telephone initiate versions of the Beacon are not included in this safety manual.
Under No fault (Normal) Operating conditions the XB15 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
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 DC version of
XB15 Xenon Beacon against the requirements of IEC 61508-2 using a Proof Test Interval of 8760hrs.
The DC version of the Beacon was considered to be the worst case.
The results are shown below and are based on Route 1
The Beacon is classed as a Type B device
Architectural constraints
Safe Failure Fraction (SFF)
DD
Random
DU
hardware
-1
failures: [h ] SD
SU
Diagnostic coverage (DC)
PFD @ PTI = 730Hrs,MTTR = 8Hrs
Probability of Dangerous failure
(High Demand – PFH) [h
Hardware safety integrity compliance
Systematic safety integrity compliance
Systematic Capability
(SC1, SC2, SC3, SC4)
Hardware safety integrity achieved
© MEDC 2014
XB15 Xenon Beacon
Safety Function of XB15 Xenon Beacon:
'To provide a cycled visual warning light when energized'
-1
]
H.
HFT = 0
62%
0.00E+00
5.85E-06
0.00E+00
9.35E-06
0
2.18E-03
5.85E-06
Route 1
See report R56A24816B
SC2 (R56A24816B)
Type B
SIL 1
SIL 2
SIL 1
H
SIL 1
09/14