Functional safety
9
9.1 Range of applications for functional safety
The positioner is suitable for use on valves that satisfy the special requirements in terms of
functional safety up to SIL 2 in accordance with IEC 61508 or IEC 61511. The 6DR5.1.-0....-....-
Z C20 versions are available for this.
These are single-acting positioners for mounting on pneumatic actuators with spring return.
The positioner automatically depressurizes the actuator on demand or in case of faults. The
actuator brings the process valve to the specified safety position in this way.
This positioner meets the following requirement:
● Functional safety up to SIL 2 in accordance with IEC 61508 or IEC 61511 for safe venting
See also
Functional safety in process instrumentation (http://www.siemens.com/SIL)
9.2 Safety function
Depressurizing of the connected actuator is the safety function for the SIPART PS2 positioner.
The built-in spring brings the process valve to the required safety position. Depending on the
direction of action of this spring, the process valve is completely opened or closed.
The positioner starts the depressurizing process of the connected pneumatic actuator at the
latest 100 ms after the request. The progress of the depressurizing process depends on the
connections and properties of the pneumatic actuator.
This safety function can be triggered by:
● With 2-wire connection: a signal source with 0 mA.
● With 3/4-wire connection: a power supply source with 0 V.
The safety function is not affected by other device functions, particularly the microcontroller,
software and communication interface. With respect to this safety function, the positioner must
therefore be considered as a type A subsystem in accordance with IEC 61508-2.
SIPART PS2 with 4 to 20 mA/HART
Operating Instructions, 11/2019, A5E00074631-AE 191
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