Siemens SIPART Series Operating Instructions Manual page 143

Functional safety
8.1 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 valve actuator on demand or in case of faults,
which thus switches the valve to the specified safety position.
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)
8.2 Safety function
Depressurizing of the connected actuator is the safety function for the SIPART PS2
positioner. The built-in spring brings the valve to the required safety position. Depending on
the direction of action of this spring, the 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.
Situations in which it is not possible to depressurize the actuator on demand or in the case of
a fault represent a dangerous failure.
Disregarding conditions for fulfilling the safety function
Disregard can result in a malfunction of the process plant or application, e.g. process
pressure too high, maximum level exceeded.
The mandatory settings and conditions are listed in chapters "Settings (Page 144)" and
"Safety characteristics (Page 144)".
• These conditions must be met in order to fulfill the safety function.
SIPART PS2 with and without HART
Operating Instructions, 10/2013, A5E00074631-11
WARNING
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