6 safety manual – JUMO 701150 14597 safetyM STB/STW - Safety Temperature Limiter and Safety Temperature Monitor Operating Manual User Manual
Page 44
6 Safety Manual
44
Table Low Demand PFD
The sensor, logic unit, and actuator together form a safety-related system that performs a safety function. The "average proba-
bility of dangerous failures of the entire safety-related system" (PFD
avg
) is usually divided up into the sensor, logic unit, and ac-
tuator subsystems according to the following diagram.
Typical subdivision of the "average probability of dangerous failures of a safety function on demand" (PFD
avg
) into subsystems
The specifications related to functional safety in this Safety Manual include sensor systems (resistance temperature sensors,
thermocouples), logic unit (701150), and (as signal contact) the relay output in the 701150 system.
The actuator (for example a power contactor) is system-related and must be taken into consideration separately according to
the standard for the safety loop.
Safety Integrity Level
(SIL)
Operating mode with low demand rate
PFD
av
(low demand mode)
4
≥
10
-5
to <10
-4
3
≥
10
-4
to <10
-3
2
≥
10
-3
to <10
-2
1
≥
10
-2
to <10
-1