Medc XB15 User Manual download pdf (Page 7)

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%.

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

XB15 Xenon Beacon

Safety Function of XB15 Xenon Beacon:

‘To provide a cycled visual warning light when energized’

HFT = 0

Type B

Architectural constraints

Safe Failure Fraction (SFF)

62%

SIL 1

0.00E+00

5.85E-06

Random

hardware

failures: [h

-1

]

0.00E+00

9.35E-06

Diagnostic coverage (DC)

PFD @ PTI = 730Hrs,MTTR = 8Hrs

2.18E-03

SIL 2

Probability of Dangerous failure

(High Demand – PFH) [h

-1

]

5.85E-06

SIL 1

Hardware safety integrity compliance

Route 1

Systematic safety integrity compliance

See report R56A24816B

Systematic Capability

(SC1, SC2, SC3, SC4)

SC2 (R56A24816B)

Hardware safety integrity achieved

SIL 1

01/15

1 2 3 4 5 6 7 8 9 10 11 12 ... 15 16

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