European Safety Systems Ltd.
Impress House, Mansell Road, Acton, London W3 7QH
www.e2s.com
Tel: +44 (0)208 743 8880
Document No. D190-00-671-IS
Issue 2
06-03-2023
Sheet 14 of 15
17) 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.
18) 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.
D1xS2FDC024-S/D1xS2HDC024-S (Failure to Sound)
Integrity in respect of failure to release
SIL 2
Total Failure rate
0.447 pmh
“hazardous” failure rate (revealed)
0.443 pmh
“hazardous” failure rate (unrevealed)
0.004 pmh
“safe” failure rate (revealed)
0.002 pmh
“safe”
failure rate (unrevealed)
0
Diagnostic Coverage
99%
System type
B
Hardware Fault Tolerance
0
Safe Failure Fraction
>99%
PFD (hazardous failure)
3.3 x 10
-5
Proof Test Interval
Up to 1 year
D1xS2FDC024-S/D1xS2HDC024-S (Failure to Sound or Incorrect tone)
Integrity in respect of failure to release
SIL 2
Total Failure rate
0.464 pmh
“hazardous” failure rate (revealed)
0.455 pmh
“hazardous” failure rate (unrevealed)
0.009pmh
“safe” failure rate (revealed)
0.002 pmh
“safe” failure rate (unrevealed)
0
Diagnostic Coverage
98%
System type
B
Hardware Fault Tolerance
0
Safe Failure Fraction
>97%
PFD (hazardous failure)
5.2 x 10
-5
Proof Test Interval
Up to 1 year
Table 6: SIL 2 Failure Rate
19) Synchronised Operation
All D1xS2FDC024-S/D1xS2HDC024-S alarm horn sounders connected to the same power supply and set to the same alarm tone will provide a
synchronised output when activated.
