Safety Characteristics; Maintenance/Check - Siemens SIPART PS2 Series Operating Instructions Manual

See also
Safety function (Page 191)
9.5

Safety characteristics

The safety characteristics necessary for use of the system are listed in the SIL declaration of
conformity. These values apply under the following conditions:
● The positioner is only used in applications with low demand rate for the "Low demand mode".
● The positioner is blocked against unwanted and unauthorized changes/operation.
● The signal source with 0 mA or the power supply source with 0 V for the SIPART PS2
positioner is generated by a safe system that fulfills SIL 2 for single-channel operation.
● The connected actuator must be single-acting and return the process valve to the safe end
position by spring force in the following scenarios:
– With a chamber pressure (Y1 connection) up to a third of the maximum available supply
● The air outlet does not contain any additional cross-sectional contractions leading to an
increased dynamic pressure. In particular, a silencer is only allowed if icing or other
contamination is ruled out.
● The restrictor in the Y1 circuit may not be completely closed during operation.
● According to ISO 8573-1, the air quality is Class 3 maximum and free of oil, water and dirt.
● The average temperature viewed over a long period is 40 °C.
● Fault rates are calculated on the basis of a mean time to repair (MTTR) of 8 hours.
● In case of a fault, the pneumatic outlet of the positioner is depressurized. A spring in the
pneumatic actuator must move the process valve to the pre-defined, safe end position.
● A dangerous failure of the positioner is one in which the pressure outlet is not depressurized
or the safety position is not reached when the signal source is 0 mA or the power supply
source is 0 V.
See also
Settings (Page 194)
9.6

Maintenance/check

Interval
We recommend that the functioning of the positioner is checked at regular intervals of one
year.
SIPART PS2 with 4 to 20 mA/HART
Operating Instructions, 11/2019, A5E00074631-AE
pressure (PZ connection)
Functional safety
9.6 Maintenance/check
195