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Functional safety
8.2 Device-specific safety notes
SFF
< 60%
60 to 90%
90 to 99%
> 99%
8.2
Device-specific safety notes
8.2.1
Application range for functional safety
The SIPART PS2 positioner is also suitable for control valves that satisfy the special
requirements in terms of function safety to SIL 2 in accordance with IEC 61508 or IEC
61511-1. The device versions SIPART PS2 PA (6DR551*) and SIPART PS2 FF (6DR561*)
are available for applications with PROFIBUS PA and for the FOUNDATION field bus
respectively.
These are single-acting, depressurizing positioners for installation on pneumatic actuators
with spring return.
The positioner depressurizes the valve actuator when faults occur or on demand by means
of the separate input for the safety shutdown. The valve actuator thus switches the valve to
the specified safety position. Except for the valve control, all other device functions including
position and status signals and the communication via PROFIBUS PA or FOUNDATION field
bus remain unrestricted.
These positioners meet the following requirements:
● Functional safety to SIL 2 in accordance with IEC 61508 and IEC 61511-1 regarding the
● Explosion protection on 6DR5***-*E*** variations
● Electromagnetic compatibility in accordance with EN 61326/A1, Appendix A.1
8.2.2
Safety function
Safety function on positioner
Depressurizing the connected valve actuator can be referred to as a safety function on the
positioner SIPART PS2 PA and SIPART PS2 FF. The built-in spring brings the valve into the
required safety position - this is known as tight closing. Depending on the direction of action
of this spring, the valve is completely opened or closed.
The safety function is triggered if the following occurs:
● The signal at the input for the safety shutdown (terminals 81 and 82) is less than 4.5 V.
110
HFT (for type A sub-systems)
0
SIL 1
SIL 2
SIL 3
SIL 3
safety shutdown
This function is likewise referred to as "safety shutdown" in the device documentation.
1
SIL 2
SIL 3
SIL 4
SIL 4
SIPART PS2 with PROFIBUS communication
Operating Instructions, 09/2007, A5E00127926-07
2
SIL 3
SIL 4
SIL 4
SIL 4
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