MEDC BG - Manual (Page 8)

11/13 © MEDC 2013
Assessment of Functional Safety
The BG Call Point 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 BG Break Glass unit against the requirements of IEC61508-2 using a proof test interval of 8760hrs.
The Call Point is classed as a Type A device.
BG BREAKGLASS UNIT
Safety Function of BG Break Glass Unit:
‘To raise the alarm upon breaking the glass’
Architectural constraints:
Type A
HFT=0
SFF= 97%
Proof Test Interval
=8760Hrs
MTTR = 8 Hrs
SIL3
Random hardware failures:
DD
= 0
DU
= 5.72E-07
SD
= 0
SU
= 2.04E-05
Probability of failure on demand:
PFD
AVG
=2.51E-03
(Low Demand Mode)
SIL2
Probability of Dangerous failure on
safety function:
PFH = 5.72E-07
(High Demand Mode)
SIL2
Hardware safety integrity compliance [1] Route 1
H
Systematic safety integrity compliance Route 1
S
Systematic Capability SC2
Overall SIL-capability achieved
SIL 2 (Low Demand)
SIL 2 (High Demand)