User Documentation

Scope and standards
1373930000/02/06-2017 5
1. Scope and standards
1.1 Scope
This safety manual applies to SIL3 relays from
Weidmüller's SAFESERIES for the following items
produced after 03/2012:
SCS 24VDC P1SIL3DS 1303890000
SCS 24VDC P1SIL3DS M 1303760000
SCS 24VDC P1SIL3DS MG3 1304040000
SIL3 relays in the SCS 24VDC P1SIL3DS series
from
Weidmüller Interface GmbH & Co KG
Klingenbergstrasse 16
32758 Detmold
Germany
have been certified by
TÜV NORD CERT GmbH
Am TÜV 1
30519 Hannover
Germany
according to EN 61508 SIL3. They are certified as
“Safety Approved” for use in “low demand mode”
and “high demand mode” systems.
Certificate Registration No:
44 207 12 405992
1.2 Abbreviations
Safety Integrity Level (SIL):
Four discrete levels (SIL1 to SIL4). The higher the
SIL of a safety-related system, the lower the
probability that it will not perform the required
safety functions.
Average Probability of Failure on Demand
(PFD
avg
):
Average probability of failure of a safety function
working in low demand mode of operation.
Probability of Failure per Hour (PFH):
Average probability of failure of a safety function
working in high demand or continuous mode of
operation.
Safe Failure Fraction (SFF):
Percentage part of safe failures and dangerous
detected failures of a safety function or a sub-
system related to all failures.
Hardware Fault Tolerance (HFT):
HFT = n means, that n+1 faults could cause a loss
of the safety function.
Low demand mode of operation:
Frequency of demands on a safety-related system
no greater than one per year and no greater than
twice the proof-test frequency.
High demand or continuous mode of
operation:
Frequency of demands on a safety-related system
greater than one per year or greater than twice
the proof-test frequency.
Device type A (simple subsystem):
The failure modes of all constituent components
are well defined and the behaviour under fault
conditions can be completely determined.