Siemens SIRIUS 3SK1 Manual page 207

PFH and PFDavg values of 3SK1 safety relays
The table below shows the values of the:
● Average frequency of a hazardous failure of the safety function per hour (PFH) at a high
demand rate in accordance with IEC 61508.
● Average probability of failure of the safety function upon demand (PFDavg) at a low
demand rate in accordance with IEC 61508.
Safety relay
3SK1111-.AB30
3SK1111-.AW20
3SK1112-.BB40
3SK1121-.AB40
3SK1121-.CB41
3SK1121-.CB42
3SK1121-.CB44
3SK1122-.AB40
3SK1122-.CB41
3SK1122-.CB42
3SK1122-.CB44
3SK1120-.AB40
3SK1211-.BB40
3SK1211-.BB00
3SK1211-.BW20
3SK1213-.AB40
3SK1213-.AJ20
3SK1213-.AL20
3SK1220-.AB40
SIRIUS 3SK1 safety relays
Manual, 06/2018, A5E02526190021A/RS-AD/004
PFH [1/h]
less than
1.7 E
-09
1.5 E
-09
1.0 E
-09
2.5 E
-09
3.7 E
-09
3.7 E
-09
3.7 E
-09
1.3 E
-09
1.5 E
-09
1.5 E
-09
1.5 E
-09
1.3 E
-09
1.7 E
-09
1.7 E
-09
1.7 E
-09
1.0 E
-09
1.0 E
-09
1.0 E
-09
1.0 E
-09
Technical data
13.2 General technical data
PFDavg
less than
1.0 E
-06
1.0 E
-06
7.0 E
-06
7.0 E
-06
7.0 E
-06
7.0 E
-06
7.0 E
-06
7.0 E
-06
7.0 E
-06
7.0 E
-06
7.0 E
-06
7.0 E
-06
1.0 E
-06
1.0 E
-06
1.0 E
-06
1.0 E
-06
1.0 E
-06
1.0 E
-06
7.0 E
-06
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