E2S Warning Signals
Impress House, Mansell Road, Acton, London W3 7QH
www.e2s.com
Tel: +44 (0)208 743 8880
Document No. D210-00-651-IS
Issue 1
13-01-23
Sheet 12 of 13
19) SIL 2 Specific Unit Mounting Requirements
The sounder should be mounted no closer that 5m from a sounder source of similar SPL output. This is to ensure false tone
activation does not occur when the unit is monitoring the tone pulse duration and tone failure.
20) SIL 2 Reliability Data
Reliability and Functional safety IEC/EN61508 which has been assessed and is considered suitable for use in low demand safety
function:
1. Random Hardware Failures and Architectural constraints (route 1
H
)
2. As an unvoted item (i.e. hardware fault tolerance of 0) at SIL 2
The product was assessed against failure modes:
•
Failure respond to an input with a correct tone.
•
Failure to respond to an input even with an alternative tone.
•
Spurious sound output despite no input.
BExS110D-SIL (Failure to Sound)
Integrity in respect of failure to release
SIL 2
Total Failure rate
0.304 pmh
“hazardous” failure rate (revealed)
0.233 pmh
“hazardous” failure rate (unrevealed)
0.017 pmh
“safe”
failure rate (revealed)
0
“safe”
failure rate (unrevealed)
0
Diagnostic Coverage
93%
System type
B
Hardware Fault Tolerance
0
Safe Failure Fraction
>93%
PFD (hazardous failure)
9.4 x 10-5
Proof Test Interval
Up to 1 week
BExS110D-SIL (Failure to Sound or Incorrect tone)
Integrity in respect of failure to release
SIL 2
Total Failure rate
0.304 pmh
“hazardous” failure rate (revealed)
0.235 pmh
“hazardous” failure rate (unrevealed)
0.005 pmh
“safe” failure rate (revealed)
0.01
“safe” failure rat
e (unrevealed)
0
Diagnostic Coverage
98%
System type
B
Hardware Fault Tolerance
0
Safe Failure Fraction
>98%
PFD (hazardous failure)
2.0 x 10
-5
Proof Test Interval
Up to 1 week
Table 4: SIL 2 Failure Rate
21) Synchronised Operation
All BExS110D-SIL alarm horn sounders connected to the same power supply and set to the same alarm tone will provide a
synchronised output when activated.
