Siemens SIPART PS2 PA 6DR55 Series, Руководство по эксплуатации

Страница: 111 / 292

Functional safety
8.2 Device-specific safety notes
SIPART PS2 with PROFIBUS communication
Operating Instructions, 09/2007, A5E00127926-07
111
● The electrical auxiliary power supply from the PROFIBUS PA or the FOUNDATION
fieldbus connection fails
● Failure of auxiliary pneumatic power
The safety function is not effected by other device functions, particularly the microcontroller,
software and communication interface. The positioners SIPART PS2 PA and
SIPART PS2 FF must therefore be considered as a type A subsystem as per EN 61508-2 as
far as this safety function is concerned.
If the valve actuator cannot be depressurized on demand or in case of a fault, this represents
a dangerous failure.
WARNING
The binding settings and conditions are listed in the "Settings" and "Safety characteristics"
sections.
These conditions must be met in order to fulfill the safety function.
When the safety function has been executed, safety-instrumented systems with no self-
locking function should be brought to a monitored or otherwise safe state within the Mean
Time To Restoration (MTTR). The MTTR is 8 hours.
The calculated Mean Time Between Failures (MTBF) for the positioners SIPART PS2 PA
and SIPART PS2 FF is 73 years. The MTBF for the basic electronics module is 187 years in
line with SN29500.
The characteristic service life of the valve block depends on the load. On average it is
approx. 200 million switching operations for each of the two pilot valves with symmetrical
load. The actual number of switching operations performed can be recalled in the local
display or by means of the PROFIBUS PA or the FOUNDATION fieldbus communication.
See diagnostics parameters "40.VENT1" and "41.VENT2" under the following also-see link
for this purpose.
See also
Meaning of diagnostics values (Page 225)
8.2.3 Settings
The coding bridge on the basic electronic system must be plugged without fail on to the left
position facing the terminals ("safe pos.") or removed completely for the safety function to
work properly.
Special parameter settings are not necessary.
Protection against configuration changes
You should attach the housing cover so that the device is protected against unwanted and
unauthorized changes/operation.